Merge branch '1.8-path-segments' into 1.8

src/main/java/com/replaymod/simplepathing/InterpolatorType.java

@@ -0,0 +1,54 @@
+package com.replaymod.simplepathing;
+
+import com.replaymod.replaystudio.pathing.interpolation.CatmullRomSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.CubicSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
+import com.replaymod.replaystudio.pathing.interpolation.LinearInterpolator;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+import java.util.function.Supplier;
+
+@AllArgsConstructor
+public enum InterpolatorType {
+    DEFAULT("default", null, null),
+    CATMULL_ROM("catmullrom", CatmullRomSplineInterpolator.class, () -> new CatmullRomSplineInterpolator(0.5)),
+    CUBIC("cubic", CubicSplineInterpolator.class, CubicSplineInterpolator::new),
+    LINEAR("linear", LinearInterpolator.class, LinearInterpolator::new);
+
+    @Getter
+    private String localizationKey;
+
+    @Getter
+    private Class<? extends Interpolator> interpolatorClass;
+
+    private Supplier<Interpolator> interpolatorConstructor;
+
+    public String getI18nName() {
+        return String.format("replaymod.gui.editkeyframe.interpolator.%1$s.name", localizationKey);
+    }
+
+    public String getI18nDescription() {
+        return String.format("replaymod.gui.editkeyframe.interpolator.%1$s.desc", localizationKey);
+    }
+
+    public static InterpolatorType fromString(String string) {
+        for (InterpolatorType t : values()) {
+            if (t.getI18nName().equals(string)) return t;
+        }
+        return CATMULL_ROM; //the default
+    }
+
+    public static InterpolatorType fromClass(Class<? extends Interpolator> cls) {
+        for (InterpolatorType type : values()) {
+            if (cls.equals(type.getInterpolatorClass())) {
+                return type;
+            }
+        }
+        return DEFAULT;
+    }
+
+    public Interpolator newInstance() {
+        return interpolatorConstructor.get();
+    }
+}

src/main/java/com/replaymod/simplepathing/ReplayModSimplePathing.java

@@ -1,36 +1,25 @@
 package com.replaymod.simplepathing;
 
-import com.google.gson.stream.JsonReader;
-import com.google.gson.stream.JsonWriter;
 import com.replaymod.core.ReplayMod;
 import com.replaymod.core.events.SettingsChangedEvent;
-import com.replaymod.pathing.properties.CameraProperties;
-import com.replaymod.pathing.properties.SpectatorProperty;
-import com.replaymod.pathing.properties.TimestampProperty;
 import com.replaymod.replay.events.ReplayCloseEvent;
 import com.replaymod.replay.events.ReplayOpenEvent;
-import com.replaymod.replaystudio.pathing.PathingRegistry;
-import com.replaymod.replaystudio.pathing.impl.TimelineImpl;
-import com.replaymod.replaystudio.pathing.interpolation.CubicSplineInterpolator;
-import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
-import com.replaymod.replaystudio.pathing.interpolation.LinearInterpolator;
 import com.replaymod.replaystudio.pathing.path.Keyframe;
-import com.replaymod.replaystudio.pathing.path.Timeline;
+import com.replaymod.simplepathing.SPTimeline.SPPath;
 import com.replaymod.simplepathing.gui.GuiPathing;
 import com.replaymod.simplepathing.preview.PathPreview;
+import lombok.Getter;
 import net.minecraftforge.fml.common.FMLCommonHandler;
 import net.minecraftforge.fml.common.Mod;
 import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import org.apache.logging.log4j.Logger;
 
-import java.io.IOException;
-
 @Mod(modid = ReplayModSimplePathing.MOD_ID,
         version = "@MOD_VERSION@",
         acceptedMinecraftVersions = "@MC_VERSION@",
         useMetadata = true)
-public class ReplayModSimplePathing implements PathingRegistry {
+public class ReplayModSimplePathing {
     public static final String MOD_ID = "replaymod-simplepathing";
 
     private ReplayMod core;
@@ -54,84 +43,60 @@ public class ReplayModSimplePathing implements PathingRegistry {
 
     @SubscribeEvent
     public void postReplayOpen(ReplayOpenEvent.Post event) {
+        currentTimeline = new SPTimeline();
         guiPathing = new GuiPathing(core, this, event.getReplayHandler());
     }
 
     @SubscribeEvent
     public void onReplayClose(ReplayCloseEvent.Post event) {
+        currentTimeline = null;
         guiPathing = null;
-        currentTimeline = createTimeline();
+        selectedPath = null;
-        currentTimeline.createPath();
-        currentTimeline.createPath();
-        selectedKeyframe = null;
     }
 
     @SubscribeEvent
     public void onSettingsChanged(SettingsChangedEvent event) {
-        if (event.getKey() == Setting.LINEAR_INTERPOLATION) {
+        if (event.getKey() == Setting.DEFAULT_INTERPOLATION) {
             if (currentTimeline != null && guiPathing != null) {
-                currentTimeline.applyChange(guiPathing.updateInterpolators());
+                updateDefaultInterpolatorType();
             }
         }
     }
 
-    private Timeline currentTimeline = createTimeline(); { currentTimeline.createPath(); currentTimeline.createPath(); }
+    private SPTimeline currentTimeline;
-    private Keyframe selectedKeyframe;
 
-    public Keyframe getSelectedKeyframe() {
+    @Getter
-        return selectedKeyframe;
+    private SPPath selectedPath;
+    @Getter
+    private long selectedTime;
+
+    public boolean isSelected(Keyframe keyframe) {
+        return selectedPath != null && currentTimeline.getKeyframe(selectedPath, selectedTime) == keyframe;
     }
 
-    public void setSelectedKeyframe(Keyframe selected) {
+    public void setSelected(SPPath path, long time) {
-        this.selectedKeyframe = selected;
+        selectedPath = path;
+        selectedTime = time;
     }
 
-    public void setCurrentTimeline(Timeline currentTimeline) {
+    public void setCurrentTimeline(SPTimeline newTimeline) {
-        if (this.currentTimeline != currentTimeline) {
+        selectedPath = null;
-            selectedKeyframe = null;
+        currentTimeline = newTimeline;
-        }
-        this.currentTimeline = currentTimeline;
     }
 
-    public Timeline getCurrentTimeline() {
+    public void clearCurrentTimeline() {
+        setCurrentTimeline(new SPTimeline());
+        updateDefaultInterpolatorType();
+    }
+
+    public SPTimeline getCurrentTimeline() {
         return currentTimeline;
     }
 
-    @Override
+    private void updateDefaultInterpolatorType() {
-    public Timeline createTimeline() {
+        InterpolatorType newDefaultType =
-        Timeline timeline = new TimelineImpl();
+                InterpolatorType.fromString(core.getSettingsRegistry().get(Setting.DEFAULT_INTERPOLATION));
-
+        currentTimeline.setDefaultInterpolatorType(newDefaultType);
-        timeline.registerProperty(TimestampProperty.PROPERTY);
-        timeline.registerProperty(CameraProperties.POSITION);
-        timeline.registerProperty(CameraProperties.ROTATION);
-        timeline.registerProperty(SpectatorProperty.PROPERTY);
-
-        return timeline;
-    }
-
-    @Override
-    public void serializeInterpolator(JsonWriter writer, Interpolator interpolator) throws IOException {
-        if (interpolator instanceof LinearInterpolator) {
-            writer.value("linear");
-        } else if (interpolator instanceof CubicSplineInterpolator) {
-            writer.value("cubic-spline");
-        } else {
-            throw new IOException("Unknown interpolator type: " + interpolator);
-        }
-    }
-
-    @Override
-    public Interpolator deserializeInterpolator(JsonReader reader) throws IOException {
-        String type = reader.nextString();
-        switch (type) {
-            case "linear":
-                return new LinearInterpolator();
-            case "cubic-spline":
-                return new CubicSplineInterpolator();
-            default:
-                throw new IOException("Unknown interpolation type: " + type);
-
-        }
     }
 
     public ReplayMod getCore() {

src/main/java/com/replaymod/simplepathing/SPTimeline.java

@@ -0,0 +1,669 @@
+package com.replaymod.simplepathing;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Iterables;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import com.replaymod.pathing.properties.CameraProperties;
+import com.replaymod.pathing.properties.SpectatorProperty;
+import com.replaymod.pathing.properties.TimestampProperty;
+import com.replaymod.replaystudio.pathing.PathingRegistry;
+import com.replaymod.replaystudio.pathing.change.AddKeyframe;
+import com.replaymod.replaystudio.pathing.change.Change;
+import com.replaymod.replaystudio.pathing.change.CombinedChange;
+import com.replaymod.replaystudio.pathing.change.SetInterpolator;
+import com.replaymod.replaystudio.pathing.change.UpdateKeyframeProperties;
+import com.replaymod.replaystudio.pathing.impl.TimelineImpl;
+import com.replaymod.replaystudio.pathing.interpolation.CatmullRomSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.CubicSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
+import com.replaymod.replaystudio.pathing.interpolation.LinearInterpolator;
+import com.replaymod.replaystudio.pathing.path.Keyframe;
+import com.replaymod.replaystudio.pathing.path.Path;
+import com.replaymod.replaystudio.pathing.path.PathSegment;
+import com.replaymod.replaystudio.pathing.path.Timeline;
+import com.replaymod.replaystudio.pathing.property.Property;
+import com.replaymod.replaystudio.util.EntityPositionTracker;
+import com.replaymod.replaystudio.util.Location;
+import com.replaymod.simplepathing.properties.ExplicitInterpolationProperty;
+import lombok.Getter;
+import net.minecraft.crash.CrashReport;
+import net.minecraft.crash.CrashReportCategory;
+import net.minecraft.util.ReportedException;
+import org.apache.commons.lang3.ObjectUtils;
+import org.apache.commons.lang3.Validate;
+import org.apache.commons.lang3.tuple.Triple;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringReader;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+
+import static com.replaymod.replaystudio.pathing.change.RemoveKeyframe.create;
+import static com.replaymod.simplepathing.ReplayModSimplePathing.LOGGER;
+
+/**
+ * Simplified timeline abstraction used in the SimplePathing module.
+ */
+public class SPTimeline implements PathingRegistry {
+    public enum SPPath {
+        TIME,
+        POSITION,
+    }
+
+    @Getter
+    private final Timeline timeline;
+    @Getter
+    private final Path timePath;
+    @Getter
+    private final Path positionPath;
+
+    @Getter
+    private EntityPositionTracker entityTracker;
+    private InterpolatorType defaultInterpolatorType = InterpolatorType.fromString("invalid string returns default");
+
+    public SPTimeline() {
+        this(createInitialTimeline());
+    }
+
+    public SPTimeline(Timeline timeline) {
+        this.timeline = timeline;
+        this.timePath = timeline.getPaths().get(SPPath.TIME.ordinal());
+        this.positionPath = timeline.getPaths().get(SPPath.POSITION.ordinal());
+    }
+
+    public Path getPath(SPPath path) {
+        switch (path) {
+            case TIME:
+                return getTimePath();
+            case POSITION:
+                return getPositionPath();
+        }
+        throw new IllegalArgumentException("Unknown path " + path);
+    }
+
+    public Keyframe getKeyframe(SPPath path, long keyframe) {
+        return getPath(path).getKeyframe(keyframe);
+    }
+
+    public void setEntityTracker(EntityPositionTracker entityTracker) {
+        Preconditions.checkState(this.entityTracker == null, "Entity tracker already set");
+        this.entityTracker = entityTracker;
+    }
+
+    public void setDefaultInterpolatorType(InterpolatorType defaultInterpolatorType) {
+        Validate.isTrue(defaultInterpolatorType != InterpolatorType.DEFAULT, "Must not be DEFAULT");
+        this.defaultInterpolatorType = Validate.notNull(defaultInterpolatorType);
+
+        if (entityTracker != null) {
+            timeline.pushChange(updateInterpolators());
+        }
+    }
+
+    public Change setDefaultInterpolator(Interpolator interpolator) {
+        Preconditions.checkState(defaultInterpolatorType != null, "Default interpolator type not set.");
+        Validate.isInstanceOf(defaultInterpolatorType.getInterpolatorClass(), interpolator);
+
+        registerPositionInterpolatorProperties(interpolator);
+
+        Change change = CombinedChange.create(
+                positionPath.getSegments().stream()
+                        // Ignore explicitly set segments
+                        .filter(s -> !s.getStartKeyframe().getValue(ExplicitInterpolationProperty.PROPERTY).isPresent())
+                        // Ignore spectator segments
+                        .filter(s -> !isSpectatorSegment(s))
+                        // Update interpolator for every remaining segment
+                        // This will create a fragmented interpolator which is split by the updateInterpolators call
+                        .map(s -> SetInterpolator.create(s, interpolator)).toArray(Change[]::new)
+        );
+        change.apply(timeline);
+        return CombinedChange.createFromApplied(change, updateInterpolators());
+    }
+
+    public boolean isTimeKeyframe(long time) {
+        return timePath.getKeyframe(time) != null;
+    }
+
+    public boolean isPositionKeyframe(long time) {
+        return positionPath.getKeyframe(time) != null;
+    }
+
+    public boolean isSpectatorKeyframe(long time) {
+        Keyframe keyframe = positionPath.getKeyframe(time);
+        return keyframe != null && keyframe.getValue(SpectatorProperty.PROPERTY).isPresent();
+    }
+
+    public void addPositionKeyframe(long time, double posX, double posY, double posZ,
+                                    float yaw, float pitch, float roll, int spectated) {
+        LOGGER.debug("Adding position keyframe at {} pos {}/{}/{} rot {}/{}/{} entId {}",
+                time, posX, posY, posZ, yaw, pitch, roll, spectated);
+
+        Path path = positionPath;
+
+        Preconditions.checkState(positionPath.getKeyframe(time) == null, "Keyframe already exists");
+
+        Change change = AddKeyframe.create(path, time);
+        change.apply(timeline);
+        Keyframe keyframe = path.getKeyframe(time);
+
+        UpdateKeyframeProperties.Builder builder = UpdateKeyframeProperties.create(path, keyframe);
+        builder.setValue(CameraProperties.POSITION, Triple.of(posX, posY, posZ));
+        builder.setValue(CameraProperties.ROTATION, Triple.of(yaw, pitch, roll));
+        if (spectated != -1) {
+            builder.setValue(SpectatorProperty.PROPERTY, spectated);
+        }
+        UpdateKeyframeProperties updateChange = builder.done();
+        updateChange.apply(timeline);
+        change = CombinedChange.createFromApplied(change, updateChange);
+
+        // If this new keyframe formed the first segment of the path
+        if (path.getSegments().size() == 1) {
+            // then create an initial interpolator of default type
+            PathSegment segment = path.getSegments().iterator().next();
+            Interpolator interpolator = createDefaultInterpolator();
+            SetInterpolator setInterpolator = SetInterpolator.create(segment, interpolator);
+            setInterpolator.apply(timeline);
+            change = CombinedChange.createFromApplied(change, setInterpolator);
+        }
+
+        // Update interpolators for spectator keyframes
+        // while this is overkill, it is far simpler than updating differently for every possible case
+        change = CombinedChange.createFromApplied(change, updateInterpolators());
+
+        Change specPosUpdate = updateSpectatorPositions();
+        specPosUpdate.apply(timeline);
+        change = CombinedChange.createFromApplied(change, specPosUpdate);
+
+        timeline.pushChange(change);
+    }
+
+    public Change updatePositionKeyframe(long time, double posX, double posY, double posZ,
+                                    float yaw, float pitch, float roll) {
+        LOGGER.debug("Updating position keyframe at {} to pos {}/{}/{} rot {}/{}/{}",
+                time, posX, posY, posZ, yaw, pitch, roll);
+
+        Keyframe keyframe = positionPath.getKeyframe(time);
+
+        Preconditions.checkState(keyframe != null, "Keyframe does not exists");
+        Preconditions.checkState(!keyframe.getValue(SpectatorProperty.PROPERTY).isPresent(), "Cannot update spectator keyframe");
+
+        Change change = UpdateKeyframeProperties.create(positionPath, keyframe)
+                .setValue(CameraProperties.POSITION, Triple.of(posX, posY, posZ))
+                .setValue(CameraProperties.ROTATION, Triple.of(yaw, pitch, roll))
+                .done();
+        change.apply(timeline);
+        return change;
+    }
+
+    public void removePositionKeyframe(long time) {
+        LOGGER.debug("Removing position keyframe at {}", time);
+
+        Path path = positionPath;
+        Keyframe keyframe = path.getKeyframe(time);
+
+        Preconditions.checkState(keyframe != null, "No keyframe at that time");
+
+        Change change = create(path, keyframe);
+        change.apply(timeline);
+
+        // Update interpolators for spectator keyframes
+        // while this is overkill, it is far simpler than updating differently for every possible case
+        change = CombinedChange.createFromApplied(change, updateInterpolators());
+
+        Change specPosUpdate = updateSpectatorPositions();
+        specPosUpdate.apply(timeline);
+        change = CombinedChange.createFromApplied(change, specPosUpdate);
+
+        timeline.pushChange(change);
+    }
+
+    public void addTimeKeyframe(long time, int replayTime) {
+        LOGGER.debug("Adding time keyframe at {} time {}", time, replayTime);
+
+        Path path = timePath;
+
+        Preconditions.checkState(path.getKeyframe(time) == null, "Keyframe already exists");
+
+        Change change = AddKeyframe.create(path, time);
+        change.apply(timeline);
+        Keyframe keyframe = path.getKeyframe(time);
+
+        UpdateKeyframeProperties updateChange = UpdateKeyframeProperties.create(path, keyframe)
+                .setValue(TimestampProperty.PROPERTY, replayTime)
+                .done();
+        updateChange.apply(timeline);
+        change = CombinedChange.createFromApplied(change, updateChange);
+
+        // If this new keyframe formed the first segment of the path
+        if (path.getSegments().size() == 1) {
+            // then create an initial interpolator
+            PathSegment segment = path.getSegments().iterator().next();
+            Interpolator interpolator = new LinearInterpolator();
+            interpolator.registerProperty(TimestampProperty.PROPERTY);
+            SetInterpolator setInterpolator = SetInterpolator.create(segment, interpolator);
+            setInterpolator.apply(timeline);
+            change = CombinedChange.createFromApplied(change, setInterpolator);
+        }
+
+        Change specPosUpdate = updateSpectatorPositions();
+        specPosUpdate.apply(timeline);
+        change = CombinedChange.createFromApplied(change, specPosUpdate);
+
+        timeline.pushChange(change);
+    }
+
+    public Change updateTimeKeyframe(long time, int replayTime) {
+        LOGGER.debug("Updating time keyframe at {} to time {}", time, replayTime);
+
+        Keyframe keyframe = timePath.getKeyframe(time);
+
+        Preconditions.checkState(keyframe != null, "Keyframe does not exists");
+
+        Change change = UpdateKeyframeProperties.create(timePath, keyframe)
+                .setValue(TimestampProperty.PROPERTY, replayTime)
+                .done();
+        change.apply(timeline);
+        return change;
+    }
+
+    public void removeTimeKeyframe(long time) {
+        LOGGER.debug("Removing time keyframe at {}", time);
+
+        Path path = timePath;
+        Keyframe keyframe = path.getKeyframe(time);
+
+        Preconditions.checkState(keyframe != null, "No keyframe at that time");
+
+        Change change = create(path, keyframe);
+        change.apply(timeline);
+
+        Change specPosUpdate = updateSpectatorPositions();
+        specPosUpdate.apply(timeline);
+        change = CombinedChange.createFromApplied(change, specPosUpdate);
+
+        timeline.pushChange(change);
+    }
+
+    public Change setInterpolatorToDefault(long time) {
+        LOGGER.debug("Setting interpolator of position keyframe at {} to the default", time);
+
+        Keyframe keyframe = positionPath.getKeyframe(time);
+
+        Preconditions.checkState(keyframe != null, "Keyframe does not exists");
+
+        Change change = UpdateKeyframeProperties.create(positionPath, keyframe)
+                .removeProperty(ExplicitInterpolationProperty.PROPERTY)
+                .done();
+        change.apply(timeline);
+        return CombinedChange.createFromApplied(change, updateInterpolators());
+    }
+
+    public Change setInterpolator(long time, Interpolator interpolator) {
+        LOGGER.debug("Setting interpolator of position keyframe at {} to {}", time, interpolator);
+
+        Keyframe keyframe = positionPath.getKeyframe(time);
+        Preconditions.checkState(keyframe != null, "Keyframe does not exists");
+        PathSegment segment = positionPath.getSegments().stream().filter(s -> s.getStartKeyframe() == keyframe)
+                .findFirst().orElseThrow(() -> new IllegalStateException("Keyframe has no following segment."));
+
+        registerPositionInterpolatorProperties(interpolator);
+
+        Change change = CombinedChange.create(
+                UpdateKeyframeProperties.create(positionPath, keyframe)
+                        .setValue(ExplicitInterpolationProperty.PROPERTY, ObjectUtils.NULL)
+                        .done(),
+                SetInterpolator.create(segment, interpolator)
+        );
+        change.apply(timeline);
+        return CombinedChange.createFromApplied(change, updateInterpolators());
+    }
+
+    public Change moveKeyframe(SPPath spPath, long oldTime, long newTime) {
+        LOGGER.debug("Moving keyframe on {} from {} to {}", spPath, oldTime, newTime);
+        Path path = getPath(spPath);
+        Keyframe keyframe = path.getKeyframe(oldTime);
+
+        Preconditions.checkState(keyframe != null, "No keyframe at specified time");
+
+        // Interpolator of the first segment might be required later if it is the only one
+        Optional<Interpolator> firstInterpolator =
+                path.getSegments().stream().findFirst().map(PathSegment::getInterpolator);
+
+        // The interpolator of the previous segment
+        Optional<Interpolator> interpolatorBefore =
+                path.getSegments().stream().filter(s -> s.getEndKeyframe() == keyframe).findFirst().map(PathSegment::getInterpolator);
+
+        // The interpolator of the following segment
+        Optional<Interpolator> interpolatorAfter =
+                path.getSegments().stream().filter(s -> s.getStartKeyframe() == keyframe).findFirst().map(PathSegment::getInterpolator);
+
+        // First remove the old keyframe
+        Change removeChange = create(path, keyframe);
+        removeChange.apply(timeline);
+
+        // and add a new one at the correct time
+        Change addChange = AddKeyframe.create(path, newTime);
+        addChange.apply(timeline);
+
+        // Then copy over all properties
+        UpdateKeyframeProperties.Builder builder = UpdateKeyframeProperties.create(path, path.getKeyframe(newTime));
+        for (Property property : keyframe.getProperties()) {
+            copyProperty(property, keyframe, builder);
+        }
+        Change propertyChange = builder.done();
+        propertyChange.apply(timeline);
+
+
+        Change restoreInterpolatorChange;
+        Keyframe newKf = path.getKeyframe(newTime);
+        if (Iterables.getLast(path.getKeyframes()) != newKf) { // Unless this is the last keyframe
+            // the interpolator of the following segment has been lost and needs to be restored
+            restoreInterpolatorChange = interpolatorAfter.<Change>flatMap(interpolator ->
+                    path.getSegments().stream().filter(s -> s.getStartKeyframe() == newKf).findFirst().map(segment ->
+                            SetInterpolator.create(segment, interpolator)
+                    )
+            ).orElseGet(CombinedChange::create);
+        } else { // If it is the last keyframe however,
+            // the interpolator of the previous segment has been lost and needs to be restored
+            restoreInterpolatorChange = interpolatorBefore.<Change>flatMap(interpolator ->
+                    path.getSegments().stream().filter(s -> s.getEndKeyframe() == newKf).findFirst().map(segment ->
+                            SetInterpolator.create(segment, interpolator)
+                    )
+            ).orElseGet(CombinedChange::create);
+        }
+        restoreInterpolatorChange.apply(timeline);
+
+        // Finally update the interpolators
+        Change interpolatorUpdateChange;
+        if (spPath == SPPath.POSITION) {
+            // Position / Spectator keyframes need special handling
+            interpolatorUpdateChange = updateInterpolators();
+        } else {
+            // Time keyframes only need updating when only one segment of them exists
+            if (path.getSegments().size() == 1) {
+                assert firstInterpolator.isPresent() : "One segment should have existed before as well";
+                interpolatorUpdateChange = SetInterpolator.create(path.getSegments().iterator().next(), firstInterpolator.get());
+            } else {
+                interpolatorUpdateChange = CombinedChange.create(); // Noop change
+            }
+            interpolatorUpdateChange.apply(timeline);
+        }
+
+        // and update spectator positions
+        Change spectatorChange = updateSpectatorPositions();
+        spectatorChange.apply(timeline);
+
+        return CombinedChange.createFromApplied(removeChange, addChange, propertyChange,
+                restoreInterpolatorChange, interpolatorUpdateChange, spectatorChange);
+    }
+
+    // Helper method because generics cannot be defined on blocks
+    private <T> void copyProperty(Property<T> property, Keyframe from, UpdateKeyframeProperties.Builder to) {
+        from.getValue(property).ifPresent(value -> to.setValue(property, value));
+    }
+
+    private Change updateInterpolators() {
+        Collection<PathSegment> pathSegments = positionPath.getSegments();
+        // Contains updated pathsegment-interpolator mappings, may be changed multiple times over the course of this method
+        Map<PathSegment, Interpolator> updates = new HashMap<>();
+
+        // First, setup spectator interpolators
+        Interpolator interpolator = null;
+        // Iterate through all segments
+        for (PathSegment segment : pathSegments) {
+            if (isSpectatorSegment(segment)) {
+                // If the last segment was a spectator segment, then use its interpolator for this segment as well
+                if (interpolator == null) {
+                    // otherwise create a new interpolator
+                    interpolator = new LinearInterpolator();
+                    interpolator.registerProperty(SpectatorProperty.PROPERTY);
+                }
+                // Now that we have an interpolator, set it for the current segment
+                updates.put(segment, interpolator);
+            } else {
+                // Not a spectator segment, make sure we don't re-use the last interpolator (it would not be continuous)
+                interpolator = null;
+            }
+        }
+
+        // Then, if required, replace old default interpolators with new ones
+        pathSegments.stream()
+                // Ignore explicitly set segments
+                .filter(s -> !s.getStartKeyframe().getValue(ExplicitInterpolationProperty.PROPERTY).isPresent())
+                // Ignore spectator segments
+                .filter(s -> !isSpectatorSegment(s))
+                // Ignore already correct segments, should ignore all if default hasn't changed
+                .filter(s -> !s.getInterpolator().getClass().equals(defaultInterpolatorType.getInterpolatorClass()))
+                // Finally, set the interpolators
+                // This will create one interpolator per segment, they will be merged later
+                .forEach(segment -> updates.put(segment, createDefaultInterpolator()));
+
+        // All interpolators should now be set appropriately but may still be fragmented.
+        // Cleaning that up is a two step process
+
+        // Firstly, all interpolators that are not continuous need to be split up
+        Interpolator lastInterpolator = null;
+        Set<Interpolator> used = Collections.newSetFromMap(new IdentityHashMap<>());
+        for (PathSegment segment : pathSegments) {
+            if (isSpectatorSegment(segment)) {
+                lastInterpolator = null;
+                continue; // Chain broken by spectator segment
+            }
+
+            Interpolator currentInterpolator = updates.getOrDefault(segment, segment.getInterpolator());
+            if (lastInterpolator == currentInterpolator) {
+                continue; // All fine, interpolator is still continuous
+            }
+
+            // New interpolator, make sure it hasn't been used before
+            if (!used.add(interpolator)) {
+                // It has been used before, we need to clone it and use the clone instead
+                // This will create a new interpolator for each segment which will be merged later
+                currentInterpolator = cloneInterpolator(currentInterpolator);
+                updates.put(segment, currentInterpolator);
+            }
+            lastInterpolator = currentInterpolator;
+        }
+
+        // Secondly, all neighbouring interpolators that are equal need to be merged
+        lastInterpolator = null;
+        String lastInterpolatorSerialized = null;
+        for (PathSegment segment : pathSegments) {
+            if (isSpectatorSegment(segment)) {
+                lastInterpolator = null;
+                lastInterpolatorSerialized = null;
+                continue; // Spectator segments are continuous by construction
+            }
+            Interpolator currentInterpolator = updates.getOrDefault(segment, segment.getInterpolator());
+            String serialized = serializeInterpolator(currentInterpolator);
+            if (lastInterpolator != currentInterpolator && serialized.equals(lastInterpolatorSerialized)) {
+                // This interpolator is equal to the last one but not the same, needs merging
+                updates.put(segment, lastInterpolator);
+                continue;
+            }
+            // New interpolator, not related to the previous one, merged by definition
+            lastInterpolator = currentInterpolator;
+            lastInterpolatorSerialized = serialized;
+        }
+
+        Change change = CombinedChange.create(updates.entrySet().stream()
+                .map(e -> SetInterpolator.create(e.getKey(), e.getValue())).toArray(Change[]::new));
+        change.apply(timeline);
+        return change;
+    }
+
+    private boolean isSpectatorSegment(PathSegment segment) {
+        return segment.getStartKeyframe().getValue(SpectatorProperty.PROPERTY).isPresent()
+                && segment.getEndKeyframe().getValue(SpectatorProperty.PROPERTY).isPresent();
+    }
+
+    private Change updateSpectatorPositions() {
+        List<Change> changes = new ArrayList<>();
+        timePath.updateAll();
+        for (Keyframe keyframe : positionPath.getKeyframes()) {
+            Optional<Integer> spectator = keyframe.getValue(SpectatorProperty.PROPERTY);
+            if (spectator.isPresent()) {
+                Optional<Integer> time = timePath.getValue(TimestampProperty.PROPERTY, keyframe.getTime());
+                if (!time.isPresent()) {
+                    continue; // No time keyframes set at this video time, cannot determine replay time
+                }
+                Location expected = entityTracker.getEntityPositionAtTimestamp(spectator.get(), time.get());
+                if (expected == null) {
+                    continue; // We don't have any data on this entity for some reason
+                }
+                Triple<Double, Double, Double> pos = keyframe.getValue(CameraProperties.POSITION).orElse(Triple.of(0D, 0D, 0D));
+                Triple<Float, Float, Float> rot = keyframe.getValue(CameraProperties.ROTATION).orElse(Triple.of(0F, 0F, 0F));
+                Location actual = new Location(pos.getLeft(), pos.getMiddle(), pos.getRight(), rot.getLeft(), rot.getRight());
+                if (!expected.equals(actual)) {
+                    changes.add(UpdateKeyframeProperties.create(positionPath, keyframe)
+                            .setValue(CameraProperties.POSITION, Triple.of(expected.getX(), expected.getY(), expected.getZ()))
+                            .setValue(CameraProperties.ROTATION, Triple.of(expected.getYaw(), expected.getPitch(), 0f)).done()
+                    );
+                }
+            }
+        }
+        return CombinedChange.create(changes.toArray(new Change[changes.size()]));
+    }
+
+    private Interpolator createDefaultInterpolator() {
+        return registerPositionInterpolatorProperties(defaultInterpolatorType.newInstance());
+    }
+
+    private Interpolator registerPositionInterpolatorProperties(Interpolator interpolator) {
+        interpolator.registerProperty(CameraProperties.POSITION);
+        interpolator.registerProperty(CameraProperties.ROTATION);
+        return interpolator;
+    }
+
+    @Override
+    public Timeline createTimeline() {
+        return createTimelineStatic();
+    }
+
+    private static Timeline createInitialTimeline() {
+        Timeline timeline = createTimelineStatic();
+        timeline.createPath();
+        timeline.createPath();
+        return timeline;
+    }
+
+    private static Timeline createTimelineStatic() {
+        Timeline timeline = new TimelineImpl();
+
+        timeline.registerProperty(TimestampProperty.PROPERTY);
+        timeline.registerProperty(CameraProperties.POSITION);
+        timeline.registerProperty(CameraProperties.ROTATION);
+        timeline.registerProperty(SpectatorProperty.PROPERTY);
+        timeline.registerProperty(ExplicitInterpolationProperty.PROPERTY);
+
+        return timeline;
+    }
+
+    @Override
+    public void serializeInterpolator(JsonWriter writer, Interpolator interpolator) throws IOException {
+        if (interpolator instanceof LinearInterpolator) {
+            writer.value("linear");
+        } else if (interpolator instanceof CubicSplineInterpolator) {
+            writer.value("cubic-spline");
+        } else if (interpolator instanceof CatmullRomSplineInterpolator) {
+            writer.beginObject();
+            writer.name("type").value("catmull-rom-spline");
+            writer.name("alpha").value(((CatmullRomSplineInterpolator) interpolator).getAlpha());
+            writer.endObject();
+        } else {
+            throw new IOException("Unknown interpolator type: " + interpolator);
+        }
+    }
+
+    @Override
+    public Interpolator deserializeInterpolator(JsonReader reader) throws IOException {
+        String type;
+        JsonObject args;
+        switch (reader.peek()) {
+            case STRING:
+                type = reader.nextString();
+                args = null;
+                break;
+            case BEGIN_OBJECT:
+                args = new JsonParser().parse(reader).getAsJsonObject();
+                type = args.get("type").getAsString();
+                break;
+            default:
+                throw new IOException("Unexpected token: " + reader.peek());
+        }
+        switch (type) {
+            case "linear":
+                return new LinearInterpolator();
+            case "cubic-spline":
+                return new CubicSplineInterpolator();
+            case "catmull-rom-spline":
+                if (args == null || !args.has("alpha")) {
+                    throw new IOException("Missing alpha value for catmull-rom-spline.");
+                }
+                return new CatmullRomSplineInterpolator(args.get("alpha").getAsDouble());
+            default:
+                throw new IOException("Unknown interpolation type: " + type);
+
+        }
+    }
+
+    /**
+     * Clones an interpolator by de- and re-serializing it.
+     * @param interpolator The interpolator to clone
+     * @return The cloned interpolator
+     */
+    private Interpolator cloneInterpolator(Interpolator interpolator) {
+        Interpolator cloned = deserializeInterpolator(serializeInterpolator(interpolator));
+        interpolator.getKeyframeProperties().forEach(cloned::registerProperty);
+        return cloned;
+    }
+
+    /**
+     * Serializes the specific interpolator to String.
+     * Does <b>not</b> serialize the registered keyframe properties.
+     * @param interpolator The interpolator to serialize.
+     * @return The serialized interpolator
+     */
+    private String serializeInterpolator(Interpolator interpolator) {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+
+        JsonWriter jsonWriter = new JsonWriter(new PrintWriter(baos));
+        try {
+            jsonWriter.beginArray();
+            serializeInterpolator(jsonWriter, interpolator);
+            jsonWriter.endArray();
+            jsonWriter.flush();
+        } catch (IOException e) {
+            CrashReport crash = CrashReport.makeCrashReport(e, "Serializing interpolator");
+            CrashReportCategory category = crash.makeCategory("Serializing interpolator");
+            category.addCrashSectionCallable("Interpolator", interpolator::toString);
+            throw new ReportedException(crash);
+        }
+
+        return baos.toString();
+    }
+
+    private Interpolator deserializeInterpolator(String json) {
+        JsonReader jsonReader = new JsonReader(new StringReader(json));
+        try {
+            jsonReader.beginArray();
+            return deserializeInterpolator(jsonReader);
+        } catch (IOException e) {
+            CrashReport crash = CrashReport.makeCrashReport(e, "De-serializing interpolator");
+            CrashReportCategory category = crash.makeCategory("De-serializing interpolator");
+            category.addCrashSection("Interpolator", json);
+            throw new ReportedException(crash);
+        }
+    }
+}

src/main/java/com/replaymod/simplepathing/Setting.java

@@ -2,9 +2,25 @@ package com.replaymod.simplepathing;
 
 import com.replaymod.core.SettingsRegistry;
 
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
 public final class Setting<T> extends SettingsRegistry.SettingKeys<T> {
     public static final Setting<Boolean> PATH_PREVIEW = make("pathpreview", "pathpreview", true);
-    public static final Setting<Boolean> LINEAR_INTERPOLATION = make("linear_interpolation", "linearinterpolation", false);
+    public static final SettingsRegistry.MultipleChoiceSettingKeys<String> DEFAULT_INTERPOLATION;
+
+    static {
+        String format = "replaymod.gui.editkeyframe.interpolator.%s.name";
+        DEFAULT_INTERPOLATION = new SettingsRegistry.MultipleChoiceSettingKeys<>(
+                "simplepathing", "interpolator", "replaymod.gui.settings.interpolator",
+                String.format(format, InterpolatorType.fromString("invalid returns default").getLocalizationKey())
+        );
+        DEFAULT_INTERPOLATION.setChoices(
+                Arrays.stream(InterpolatorType.values()).filter(i -> i != InterpolatorType.DEFAULT)
+                        .map(i -> String.format(format, i.getLocalizationKey()))
+                        .collect(Collectors.toList())
+        );
+    }
 
     private static <T> Setting<T> make(String key, String displayName, T defaultValue) {
         return new Setting<>(key, displayName, defaultValue);

src/main/java/com/replaymod/simplepathing/gui/GuiEditKeyframe.java

@@ -5,14 +5,27 @@ import com.replaymod.pathing.properties.TimestampProperty;
 import com.replaymod.replay.ReplayModReplay;
 import com.replaymod.replaystudio.pathing.change.Change;
 import com.replaymod.replaystudio.pathing.change.CombinedChange;
-import com.replaymod.replaystudio.pathing.change.UpdateKeyframeProperties;
+import com.replaymod.replaystudio.pathing.interpolation.CatmullRomSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.CubicSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
+import com.replaymod.replaystudio.pathing.interpolation.LinearInterpolator;
 import com.replaymod.replaystudio.pathing.path.Keyframe;
 import com.replaymod.replaystudio.pathing.path.Path;
+import com.replaymod.replaystudio.pathing.path.PathSegment;
+import com.replaymod.simplepathing.InterpolatorType;
+import com.replaymod.simplepathing.SPTimeline;
+import com.replaymod.simplepathing.SPTimeline.SPPath;
+import com.replaymod.simplepathing.Setting;
+import com.replaymod.simplepathing.properties.ExplicitInterpolationProperty;
+import de.johni0702.minecraft.gui.container.AbstractGuiContainer;
 import de.johni0702.minecraft.gui.container.GuiPanel;
 import de.johni0702.minecraft.gui.element.GuiButton;
 import de.johni0702.minecraft.gui.element.GuiLabel;
 import de.johni0702.minecraft.gui.element.GuiNumberField;
+import de.johni0702.minecraft.gui.element.GuiTooltip;
+import de.johni0702.minecraft.gui.element.IGuiClickable;
 import de.johni0702.minecraft.gui.element.IGuiLabel;
+import de.johni0702.minecraft.gui.element.advanced.GuiDropdownMenu;
 import de.johni0702.minecraft.gui.function.Typeable;
 import de.johni0702.minecraft.gui.layout.GridLayout;
 import de.johni0702.minecraft.gui.layout.HorizontalLayout;
@@ -20,10 +33,16 @@ import de.johni0702.minecraft.gui.layout.VerticalLayout;
 import de.johni0702.minecraft.gui.popup.AbstractGuiPopup;
 import de.johni0702.minecraft.gui.utils.Colors;
 import de.johni0702.minecraft.gui.utils.Consumer;
-import org.apache.commons.lang3.tuple.Triple;
+import lombok.Getter;
+import net.minecraft.client.resources.I18n;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
 import org.lwjgl.input.Keyboard;
 import org.lwjgl.util.ReadablePoint;
 
+import java.util.Map;
+import java.util.Optional;
+
 import static de.johni0702.minecraft.gui.utils.Utils.link;
 
 public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends AbstractGuiPopup<T> implements Typeable {
@@ -31,6 +50,11 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
         return new GuiNumberField().setPrecision(0).setValidateOnFocusChange(true);
     }
 
+    protected static final Logger logger = LogManager.getLogger();
+
+    protected final GuiPathing guiPathing;
+
+    protected final long time;
     protected final Keyframe keyframe;
     protected final Path path;
 
@@ -66,12 +90,13 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
                 .addElements(new VerticalLayout.Data(0.5, false), title, inputs, timePanel, buttons);
     }
 
-    public GuiEditKeyframe(GuiPathing gui, Path path, Keyframe keyframe, String type) {
+    public GuiEditKeyframe(GuiPathing gui, SPPath path, long time, String type) {
         super(ReplayModReplay.instance.getReplayHandler().getOverlay());
-        this.keyframe = keyframe;
+        this.guiPathing = gui;
-        this.path = path;
+        this.time = time;
+        this.path = gui.getMod().getCurrentTimeline().getPath(path);
+        this.keyframe = this.path.getKeyframe(time);
 
-        long time = keyframe.getTime();
         Consumer<String> updateSaveButtonState = s -> saveButton.setEnabled(canSave());
         timeMinField.setValue(time / 1000 / 60).onTextChanged(updateSaveButtonState);
         timeSecField.setValue(time / 1000 % 60).onTextChanged(updateSaveButtonState);
@@ -81,10 +106,11 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
         saveButton.onClick(() -> {
             Change change = save();
             long newTime = (timeMinField.getInteger() * 60 + timeSecField.getInteger()) * 1000 + timeMSecField.getInteger();
-            if (newTime != keyframe.getTime()) {
+            if (newTime != time) {
-                change = CombinedChange.createFromApplied(change, gui.moveKeyframe(path, keyframe, newTime));
+                change = CombinedChange.createFromApplied(change,
+                        gui.getMod().getCurrentTimeline().moveKeyframe(path, time, newTime));
             }
-            path.getTimeline().pushChange(change);
+            gui.getMod().getCurrentTimeline().getTimeline().pushChange(change);
             close();
         });
     }
@@ -114,7 +140,7 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
     protected abstract Change save();
 
     public static class Spectator extends GuiEditKeyframe<Spectator> {
-        public Spectator(GuiPathing gui, Path path, Keyframe keyframe) {
+        public Spectator(GuiPathing gui, SPPath path, long keyframe) {
             super(gui, path, keyframe, "spec");
 
             link(timeMinField, timeSecField, timeMSecField);
@@ -147,10 +173,10 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
                             timestampMSecField, new GuiLabel().setI18nText("replaymod.gui.milliseconds"));
         }
 
-        public Time(GuiPathing gui, Path path, Keyframe keyframe) {
+        public Time(GuiPathing gui, SPPath path, long keyframe) {
             super(gui, path, keyframe, "time");
 
-            keyframe.getValue(TimestampProperty.PROPERTY).ifPresent(time -> {
+            this.keyframe.getValue(TimestampProperty.PROPERTY).ifPresent(time -> {
                 timestampMinField.setValue(time / 1000 / 60);
                 timestampSecField.setValue(time / 1000 % 60);
                 timestampMSecField.setValue(time % 1000);
@@ -165,11 +191,7 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
         protected Change save() {
             int time = (timestampMinField.getInteger() * 60 + timestampSecField.getInteger()) * 1000
                     + timestampMSecField.getInteger();
-            Change change = UpdateKeyframeProperties.create(path, keyframe)
+            return guiPathing.getMod().getCurrentTimeline().updateTimeKeyframe(keyframe.getTime(), time);
-                    .setValue(TimestampProperty.PROPERTY, time)
-                    .done();
-            change.apply(path.getTimeline());
-            return change;
         }
 
         @Override
@@ -187,8 +209,11 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
         public final GuiNumberField pitchField = newGuiNumberField().setSize(60, 20).setPrecision(5);
         public final GuiNumberField rollField = newGuiNumberField().setSize(60, 20).setPrecision(5);
 
+        public final InterpolationPanel interpolationPanel = new InterpolationPanel();
+
         {
-            inputs.setLayout(new GridLayout().setCellsEqualSize(false).setColumns(4).setSpacingX(3).setSpacingY(5))
+            GuiPanel positionInputs = new GuiPanel()
+                    .setLayout(new GridLayout().setCellsEqualSize(false).setColumns(4).setSpacingX(3).setSpacingY(5))
                     .addElements(new GridLayout.Data(1, 0.5),
                             new GuiLabel().setI18nText("replaymod.gui.editkeyframe.xpos"), xField,
                             new GuiLabel().setI18nText("replaymod.gui.editkeyframe.camyaw"), yawField,
@@ -196,17 +221,20 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
                             new GuiLabel().setI18nText("replaymod.gui.editkeyframe.campitch"), pitchField,
                             new GuiLabel().setI18nText("replaymod.gui.editkeyframe.zpos"), zField,
                             new GuiLabel().setI18nText("replaymod.gui.editkeyframe.camroll"), rollField);
+
+            inputs.setLayout(new VerticalLayout().setSpacing(10)).addElements(new VerticalLayout.Data(0.5, false),
+                    positionInputs, interpolationPanel);
         }
 
-        public Position(GuiPathing gui, Path path, Keyframe keyframe) {
+        public Position(GuiPathing gui, SPPath path, long keyframe) {
             super(gui, path, keyframe, "pos");
 
-            keyframe.getValue(CameraProperties.POSITION).ifPresent(pos -> {
+            this.keyframe.getValue(CameraProperties.POSITION).ifPresent(pos -> {
                 xField.setValue(pos.getLeft());
                 yField.setValue(pos.getMiddle());
                 zField.setValue(pos.getRight());
             });
-            keyframe.getValue(CameraProperties.ROTATION).ifPresent(rot -> {
+            this.keyframe.getValue(CameraProperties.ROTATION).ifPresent(rot -> {
                 yawField.setValue(rot.getLeft());
                 pitchField.setValue(rot.getMiddle());
                 rollField.setValue(rot.getRight());
@@ -219,17 +247,176 @@ public abstract class GuiEditKeyframe<T extends GuiEditKeyframe<T>> extends Abst
 
         @Override
         protected Change save() {
-            Change change = UpdateKeyframeProperties.create(path, keyframe)
+            SPTimeline timeline = guiPathing.getMod().getCurrentTimeline();
-                    .setValue(CameraProperties.POSITION, Triple.of(xField.getDouble(), yField.getDouble(), zField.getDouble()))
+            Change positionChange = timeline.updatePositionKeyframe(time,
-                    .setValue(CameraProperties.ROTATION, Triple.of(yawField.getFloat(), pitchField.getFloat(), rollField.getFloat()))
+                    xField.getDouble(), yField.getDouble(), zField.getDouble(),
-                    .done();
+                    yawField.getFloat(), pitchField.getFloat(), rollField.getFloat()
-            change.apply(path.getTimeline());
+            );
-            return change;
+            Interpolator interpolator = interpolationPanel.getSettingsPanel().createInterpolator();
+            if (interpolationPanel.getInterpolatorType() == InterpolatorType.DEFAULT) {
+                return CombinedChange.createFromApplied(positionChange, timeline.setInterpolatorToDefault(time),
+                        timeline.setDefaultInterpolator(interpolator));
+            } else {
+                return CombinedChange.createFromApplied(positionChange, timeline.setInterpolator(time, interpolator));
+            }
         }
 
         @Override
         protected Position getThis() {
             return this;
         }
+
+        public class InterpolationPanel extends AbstractGuiContainer<InterpolationPanel> {
+
+            @Getter
+            private SettingsPanel settingsPanel;
+
+            private GuiDropdownMenu<InterpolatorType> dropdown;
+
+            public InterpolationPanel() {
+                setLayout(new VerticalLayout());
+
+                dropdown = new GuiDropdownMenu<InterpolatorType>()
+                        .setToString(s -> I18n.format(s.getI18nName()))
+                        .setValues(InterpolatorType.values()).setHeight(20)
+                        .onSelection(i -> setSettingsPanel(dropdown.getSelectedValue()));
+
+                // set hover tooltips
+                for (Map.Entry<InterpolatorType, IGuiClickable> e : dropdown.getDropdownEntries().entrySet()) {
+                    e.getValue().setTooltip(new GuiTooltip().setI18nText(e.getKey().getI18nDescription()));
+                }
+
+                GuiPanel dropdownPanel = new GuiPanel()
+                        .setLayout(new GridLayout().setCellsEqualSize(false).setColumns(2).setSpacingX(3).setSpacingY(5))
+                        .addElements(new GridLayout.Data(1, 0.5),
+                                new GuiLabel().setI18nText("replaymod.gui.editkeyframe.interpolator"), dropdown);
+
+
+                addElements(new VerticalLayout.Data(0.5, false), dropdownPanel);
+
+                Optional<PathSegment> segment = path.getSegments().stream()
+                        .filter(s -> s.getStartKeyframe() == keyframe).findFirst();
+                if (segment.isPresent()) {
+                    Interpolator interpolator = segment.get().getInterpolator();
+                    InterpolatorType type = InterpolatorType.fromClass(interpolator.getClass());
+                    if (keyframe.getValue(ExplicitInterpolationProperty.PROPERTY).isPresent()) {
+                        dropdown.setSelected(type); // trigger the callback once to display settings panel
+                    } else {
+                        setSettingsPanel(InterpolatorType.DEFAULT);
+                    }
+                    if (getInterpolatorTypeNoDefault(type).getInterpolatorClass().isInstance(interpolator)) {
+                        //noinspection unchecked
+                        settingsPanel.loadSettings(interpolator);
+                    }
+                } else {
+                    // Disable dropdown if this is the last keyframe
+                    dropdown.setDisabled();
+                }
+            }
+
+            public void setSettingsPanel(InterpolatorType type) {
+                removeElement(this.settingsPanel);
+
+                switch (getInterpolatorTypeNoDefault(type)) {
+                    case CATMULL_ROM:
+                        settingsPanel = new CatmullRomSettingsPanel();
+                        break;
+                    case CUBIC:
+                        settingsPanel = new CubicSettingsPanel();
+                        break;
+                    case LINEAR:
+                        settingsPanel = new LinearSettingsPanel();
+                        break;
+                }
+
+                addElements(new GridLayout.Data(0.5, 0.5), settingsPanel);
+            }
+
+            protected InterpolatorType getInterpolatorTypeNoDefault(InterpolatorType interpolatorType) {
+                if (interpolatorType == InterpolatorType.DEFAULT || interpolatorType == null) {
+                    InterpolatorType defaultType = InterpolatorType.fromString(
+                            guiPathing.getMod().getCore().getSettingsRegistry().get(Setting.DEFAULT_INTERPOLATION));
+                    return defaultType;
+                }
+                return interpolatorType;
+            }
+
+            public InterpolatorType getInterpolatorType() {
+                return dropdown.getSelectedValue();
+            }
+
+            @Override
+            protected InterpolationPanel getThis() {
+                return this;
+            }
+
+            public abstract class SettingsPanel<I extends Interpolator, T extends SettingsPanel<I, T>> extends AbstractGuiContainer<T> {
+
+                public abstract void loadSettings(I interpolator);
+
+                public abstract I createInterpolator();
+            }
+
+            public class CatmullRomSettingsPanel extends SettingsPanel<CatmullRomSplineInterpolator, CatmullRomSettingsPanel> {
+                public final GuiLabel alphaLabel = new GuiLabel().setColor(Colors.BLACK)
+                        .setI18nText("replaymod.gui.editkeyframe.interpolator.catmullrom.alpha");
+                public final GuiNumberField alphaField = new GuiNumberField().setSize(100, 20).setPrecision(5)
+                        .setMinValue(0).setValidateOnFocusChange(true);
+
+                {
+                    setLayout(new HorizontalLayout(HorizontalLayout.Alignment.CENTER));
+                    addElements(new HorizontalLayout.Data(0.5), alphaLabel, alphaField);
+                }
+
+                @Override
+                public void loadSettings(CatmullRomSplineInterpolator interpolator) {
+                    alphaField.setValue(interpolator.getAlpha());
+                }
+
+                @Override
+                public CatmullRomSplineInterpolator createInterpolator() {
+                    return new CatmullRomSplineInterpolator(alphaField.getDouble());
+                }
+
+                @Override
+                protected CatmullRomSettingsPanel getThis() {
+                    return this;
+                }
+            }
+
+            public class CubicSettingsPanel extends SettingsPanel<CubicSplineInterpolator, CubicSettingsPanel> {
+
+                @Override
+                public void loadSettings(CubicSplineInterpolator interpolator) {
+                }
+
+                @Override
+                public CubicSplineInterpolator createInterpolator() {
+                    return new CubicSplineInterpolator();
+                }
+
+                @Override
+                protected CubicSettingsPanel getThis() {
+                    return this;
+                }
+            }
+
+            public class LinearSettingsPanel extends SettingsPanel<LinearInterpolator, LinearSettingsPanel> {
+
+                @Override
+                public void loadSettings(LinearInterpolator interpolator) {
+                }
+
+                @Override
+                public LinearInterpolator createInterpolator() {
+                    return new LinearInterpolator();
+                }
+
+                @Override
+                protected LinearSettingsPanel getThis() {
+                    return this;
+                }
+            }
+        }
     }
 }

src/main/java/com/replaymod/simplepathing/gui/GuiKeyframeTimeline.java

@@ -1,7 +1,5 @@
 package com.replaymod.simplepathing.gui;
 
-import com.google.common.base.Function;
-import com.google.common.collect.Iterables;
 import com.replaymod.core.ReplayMod;
 import com.replaymod.pathing.properties.CameraProperties;
 import com.replaymod.pathing.properties.SpectatorProperty;
@@ -11,9 +9,10 @@ import com.replaymod.replaystudio.pathing.change.Change;
 import com.replaymod.replaystudio.pathing.path.Keyframe;
 import com.replaymod.replaystudio.pathing.path.Path;
 import com.replaymod.replaystudio.pathing.path.PathSegment;
-import com.replaymod.replaystudio.pathing.path.Timeline;
 import com.replaymod.replaystudio.pathing.property.Property;
 import com.replaymod.simplepathing.ReplayModSimplePathing;
+import com.replaymod.simplepathing.SPTimeline;
+import com.replaymod.simplepathing.SPTimeline.SPPath;
 import de.johni0702.minecraft.gui.GuiRenderer;
 import de.johni0702.minecraft.gui.element.advanced.AbstractGuiTimeline;
 import de.johni0702.minecraft.gui.function.Draggable;
@@ -23,7 +22,6 @@ import org.lwjgl.util.Point;
 import org.lwjgl.util.ReadableDimension;
 import org.lwjgl.util.ReadablePoint;
 
-import javax.annotation.Nullable;
 import java.util.Comparator;
 import java.util.Optional;
 
@@ -37,14 +35,14 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
     private final GuiPathing gui;
 
     /**
-     * The keyframe that was last clicked on using the left mouse button.
+     * The keyframe (time on timeline) that was last clicked on using the left mouse button.
      */
-    private Keyframe lastClickedKeyframe;
+    private long lastClickedKeyframe;
 
     /**
-     * Id of the path of {@link #lastClickedKeyframe}.
+     * Path of {@link #lastClickedKeyframe}.
      */
-    private int lastClickedPath;
+    private SPPath lastClickedPath;
 
     /**
      * The time at which {@link #lastClickedKeyframe} was updated.
@@ -89,18 +87,13 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
 
         renderer.bindTexture(ReplayMod.TEXTURE);
 
-        for (Keyframe keyframe : Iterables.concat(Iterables.transform(mod.getCurrentTimeline().getPaths(), new Function<Path, Iterable<Keyframe>>() {
+        SPTimeline timeline = mod.getCurrentTimeline();
-            @Nullable
+
-            @Override
+        timeline.getTimeline().getPaths().stream().flatMap(path -> path.getKeyframes().stream()).forEach(keyframe -> {
-            public Iterable<Keyframe> apply(@Nullable Path input) {
-                assert input != null;
-                return input.getKeyframes();
-            }
-        }))) {
             if (keyframe.getTime() >= startTime && keyframe.getTime() <= endTime) {
                 double relativeTime = keyframe.getTime() - startTime;
                 int positonX = BORDER_LEFT + (int) (relativeTime / visibleTime * visibleWidth) - KEYFRAME_SIZE / 2;
-                int u = KEYFRAME_TEXTURE_X + (mod.getSelectedKeyframe() == keyframe ? KEYFRAME_SIZE : 0);
+                int u = KEYFRAME_TEXTURE_X + (mod.isSelected(keyframe) ? KEYFRAME_SIZE : 0);
                 int v = KEYFRAME_TEXTURE_Y;
                 if (keyframe.getValue(CameraProperties.POSITION).isPresent()) {
                     if (keyframe.getValue(SpectatorProperty.PROPERTY).isPresent()) {
@@ -113,10 +106,10 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
                     renderer.drawTexturedRect(positonX, BORDER_TOP + KEYFRAME_SIZE, u, v, KEYFRAME_SIZE, KEYFRAME_SIZE);
                 }
             }
-        }
+        });
 
         // Draw colored quads on spectator path segments
-        for (PathSegment segment : mod.getCurrentTimeline().getPaths().get(GuiPathing.POSITION_PATH).getSegments()) {
+        for (PathSegment segment : timeline.getPositionPath().getSegments()) {
             if (segment.getInterpolator() == null
                     || !segment.getInterpolator().getKeyframeProperties().contains(SpectatorProperty.PROPERTY)) {
                 continue; // Not a spectator segment
@@ -125,7 +118,7 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
         }
 
         // Draw red quads on time path segments that would require time going backwards
-        for (PathSegment segment : mod.getCurrentTimeline().getPaths().get(GuiPathing.TIME_PATH).getSegments()) {
+        for (PathSegment segment : timeline.getTimePath().getSegments()) {
             long startTimestamp = segment.getStartKeyframe().getValue(TimestampProperty.PROPERTY).orElseThrow(IllegalStateException::new);
             long endTimestamp = segment.getEndKeyframe().getValue(TimestampProperty.PROPERTY).orElseThrow(IllegalStateException::new);
             if (endTimestamp >= startTimestamp) {
@@ -162,29 +155,28 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
      * @param position The raw position
      * @return Pair of path id and keyframe or null when no keyframe was clicked
      */
-    private Pair<Integer, Keyframe> getKeyframe(ReadablePoint position) {
+    private Pair<SPPath, Long> getKeyframe(ReadablePoint position) {
         int time = getTimeAt(position.getX(), position.getY());
         if (time != -1) {
             Point mouse = new Point(position);
             getContainer().convertFor(this, mouse);
             int mouseY = mouse.getY();
             if (mouseY > BORDER_TOP && mouseY < BORDER_TOP + 2 * KEYFRAME_SIZE) {
-                Timeline timeline = gui.getMod().getCurrentTimeline();
+                SPPath path;
-                int path;
                 if (mouseY <= BORDER_TOP + KEYFRAME_SIZE) {
                     // Position keyframe
-                    path = GuiPathing.POSITION_PATH;
+                    path = SPPath.POSITION;
                 } else {
                     // Time keyframe
-                    path = GuiPathing.TIME_PATH;
+                    path = SPPath.TIME;
                 }
                 int visibleTime = (int) (getZoom() * getLength());
-                int tolerance = visibleTime * KEYFRAME_SIZE / (size.getWidth() - BORDER_LEFT - BORDER_RIGHT) / 2;
+                int tolerance = visibleTime * KEYFRAME_SIZE / (getLastSize().getWidth() - BORDER_LEFT - BORDER_RIGHT) / 2;
-                Optional<Keyframe> keyframe = timeline.getPaths().get(path).getKeyframes().stream()
+                Optional<Keyframe> keyframe = gui.getMod().getCurrentTimeline().getPath(path).getKeyframes().stream()
                         .filter(k -> Math.abs(k.getTime() - time) <= tolerance)
                         .sorted(Comparator.comparing(k -> Math.abs(k.getTime() - time)))
                         .findFirst();
-                return Pair.of(path, keyframe.orElse(null));
+                return Pair.of(path, keyframe.map(Keyframe::getTime).orElse(null));
             }
         }
         return Pair.of(null, null);
@@ -193,30 +185,31 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
     @Override
     public boolean mouseClick(ReadablePoint position, int button) {
         int time = getTimeAt(position.getX(), position.getY());
-        Pair<Integer, Keyframe> pathKeyframePair = getKeyframe(position);
+        Pair<SPPath, Long> pathKeyframePair = getKeyframe(position);
         if (pathKeyframePair.getRight() != null) {
+            SPPath path = pathKeyframePair.getLeft();
             // Clicked on keyframe
-            Keyframe keyframe = pathKeyframePair.getRight();
+            long keyframeTime = pathKeyframePair.getRight();
             if (button == 0) { // Left click
                 long now = Minecraft.getSystemTime();
-                if (lastClickedKeyframe == keyframe) {
+                if (lastClickedKeyframe == keyframeTime) {
                     // Clicked the same keyframe again, potentially a double click
                     if (now - lastClickedTime < DOUBLE_CLICK_INTERVAL) {
                         // Yup, double click, open the edit keyframe gui
-                        Path path = gui.getMod().getCurrentTimeline().getPaths().get(pathKeyframePair.getLeft());
+                        gui.openEditKeyframePopup(path, keyframeTime);
-                        gui.openEditKeyframePopup(path, keyframe);
                         return true;
                     }
                 }
                 // Not a double click, just update the click time and selection
                 lastClickedTime = now;
-                lastClickedKeyframe = keyframe;
+                lastClickedKeyframe = keyframeTime;
-                lastClickedPath = pathKeyframePair.getLeft();
+                lastClickedPath = path;
-                gui.getMod().setSelectedKeyframe(lastClickedKeyframe);
+                gui.getMod().setSelected(lastClickedPath, lastClickedKeyframe);
                 // We might be dragging
                 draggingStartX = position.getX();
                 dragging = true;
             } else if (button == 1) { // Right click
+                Keyframe keyframe = gui.getMod().getCurrentTimeline().getKeyframe(path, keyframeTime);
                 for (Property property : keyframe.getProperties()) {
                     applyPropertyToGame(property, keyframe);
                 }
@@ -226,12 +219,11 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
             // Clicked on timeline but not on any keyframe
             if (button == 0) { // Left click
                 setCursorPosition(time);
-                gui.getMod().setSelectedKeyframe(null);
+                gui.getMod().setSelected(null, 0);
             } else if (button == 1) { // Right click
                 if (pathKeyframePair.getLeft() != null) {
                     // Apply the value of the clicked path at the clicked position
-                    Timeline timeline = gui.getMod().getCurrentTimeline();
+                    Path path = gui.getMod().getCurrentTimeline().getPath(pathKeyframePair.getLeft());
-                    Path path = timeline.getPaths().get(pathKeyframePair.getLeft());
                     path.getKeyframes().stream().flatMap(k -> k.getProperties().stream()).distinct().forEach(
                             p -> applyPropertyToGame(p, path, time));
                 }
@@ -280,12 +272,13 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
             }
         }
         if (actuallyDragging) {
+            if (!gui.ensureEntityTracker(() -> mouseDrag(position, button, timeSinceLastCall))) return true;
             // Threshold passed
-            Path path = gui.getMod().getCurrentTimeline().getPaths().get(lastClickedPath);
+            SPTimeline timeline = gui.getMod().getCurrentTimeline();
             Point mouse = new Point(position);
             getContainer().convertFor(this, mouse);
             int mouseX = mouse.getX();
-            int width = size.getWidth();
+            int width = getLastSize().getWidth();
             int bodyWidth = width - BORDER_LEFT - BORDER_RIGHT;
             double segmentLength = getLength() * getZoom();
             double segmentTime =  segmentLength * (mouseX - BORDER_LEFT) / bodyWidth;
@@ -295,24 +288,21 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
             }
 
             // If there already is a keyframe at the target time, then increase the time by one until there is none
-            while (path.getKeyframe(newTime) != null) {
+            while (timeline.getKeyframe(lastClickedPath, newTime) != null) {
                 newTime++;
             }
 
             // First undo any previous changes
             if (draggingChange != null) {
-                draggingChange.undo(gui.getMod().getCurrentTimeline());
+                draggingChange.undo(timeline.getTimeline());
             }
 
             // Move keyframe to new position and
             // store change for later undoing / pushing to history
-            draggingChange = gui.moveKeyframe(path, lastClickedKeyframe, newTime);
+            draggingChange = timeline.moveKeyframe(lastClickedPath, lastClickedKeyframe, newTime);
 
             // Selected keyframe has been replaced
-            gui.getMod().setSelectedKeyframe(path.getKeyframe(newTime));
+            gui.getMod().setSelected(lastClickedPath, newTime);
-
-            // Path has been changed
-            path.updateAll();
         }
         return true;
     }
@@ -321,7 +311,7 @@ public class GuiKeyframeTimeline extends AbstractGuiTimeline<GuiKeyframeTimeline
     public boolean mouseRelease(ReadablePoint position, int button) {
         if (dragging) {
             if (actuallyDragging) {
-                gui.getMod().getCurrentTimeline().pushChange(draggingChange);
+                gui.getMod().getCurrentTimeline().getTimeline().pushChange(draggingChange);
                 draggingChange = null;
                 actuallyDragging = false;
             }

src/main/java/com/replaymod/simplepathing/gui/GuiPathing.java

@@ -14,25 +14,26 @@ import com.replaymod.render.gui.GuiRenderSettings;
 import com.replaymod.replay.ReplayHandler;
 import com.replaymod.replay.camera.CameraEntity;
 import com.replaymod.replay.gui.overlay.GuiReplayOverlay;
-import com.replaymod.replaystudio.pathing.change.*;
-import com.replaymod.replaystudio.pathing.interpolation.CubicSplineInterpolator;
-import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
-import com.replaymod.replaystudio.pathing.interpolation.LinearInterpolator;
 import com.replaymod.replaystudio.pathing.path.Keyframe;
 import com.replaymod.replaystudio.pathing.path.Path;
-import com.replaymod.replaystudio.pathing.path.PathSegment;
 import com.replaymod.replaystudio.pathing.path.Timeline;
-import com.replaymod.replaystudio.pathing.property.Property;
 import com.replaymod.replaystudio.pathing.serialize.TimelineSerialization;
 import com.replaymod.replaystudio.util.EntityPositionTracker;
-import com.replaymod.replaystudio.util.Location;
 import com.replaymod.simplepathing.ReplayModSimplePathing;
-import com.replaymod.simplepathing.Setting;
+import com.replaymod.simplepathing.SPTimeline;
+import com.replaymod.simplepathing.SPTimeline.SPPath;
 import de.johni0702.minecraft.gui.GuiRenderer;
 import de.johni0702.minecraft.gui.RenderInfo;
 import de.johni0702.minecraft.gui.container.GuiContainer;
 import de.johni0702.minecraft.gui.container.GuiPanel;
-import de.johni0702.minecraft.gui.element.*;
+import de.johni0702.minecraft.gui.element.AbstractGuiClickable;
+import de.johni0702.minecraft.gui.element.AbstractGuiElement;
+import de.johni0702.minecraft.gui.element.GuiElement;
+import de.johni0702.minecraft.gui.element.GuiHorizontalScrollbar;
+import de.johni0702.minecraft.gui.element.GuiLabel;
+import de.johni0702.minecraft.gui.element.GuiTexturedButton;
+import de.johni0702.minecraft.gui.element.GuiTooltip;
+import de.johni0702.minecraft.gui.element.IGuiClickable;
 import de.johni0702.minecraft.gui.element.advanced.GuiProgressBar;
 import de.johni0702.minecraft.gui.element.advanced.GuiTimelineTime;
 import de.johni0702.minecraft.gui.layout.CustomLayout;
@@ -43,9 +44,7 @@ import de.johni0702.minecraft.gui.popup.GuiInfoPopup;
 import de.johni0702.minecraft.gui.popup.GuiYesNoPopup;
 import de.johni0702.minecraft.gui.utils.Colors;
 import net.minecraft.crash.CrashReport;
-import net.minecraft.entity.Entity;
 import net.minecraftforge.fml.common.Loader;
-import org.apache.commons.lang3.tuple.Triple;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.lwjgl.input.Keyboard;
@@ -57,10 +56,7 @@ import org.lwjgl.util.WritablePoint;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collections;
-import java.util.List;
-import java.util.Optional;
 import java.util.function.Consumer;
 
 import static com.replaymod.core.utils.Utils.error;
@@ -71,9 +67,6 @@ import static com.replaymod.simplepathing.ReplayModSimplePathing.LOGGER;
  * Gui plug-in to the GuiReplayOverlay for simple pathing.
  */
 public class GuiPathing {
-    public static final int TIME_PATH = 0;
-    public static final int POSITION_PATH = 1;
-
     private static final Logger logger = LogManager.getLogger();
 
     public final GuiTexturedButton playPauseButton = new GuiTexturedButton() {
@@ -99,10 +92,11 @@ public class GuiPathing {
             if (!preparePathsForPlayback()) return;
 
             // Clone the timeline passed to the settings gui as it may be stored for later rendering in a queue
-            Timeline timeline = mod.getCurrentTimeline();
+            SPTimeline spTimeline = mod.getCurrentTimeline();
+            Timeline timeline;
             try {
-                TimelineSerialization serialization = new TimelineSerialization(mod, null);
+                TimelineSerialization serialization = new TimelineSerialization(spTimeline, null);
-                String serialized = serialization.serialize(Collections.singletonMap("", timeline));
+                String serialized = serialization.serialize(Collections.singletonMap("", spTimeline.getTimeline()));
                 timeline = serialization.deserialize(serialized).get("");
             } catch (Throwable t) {
                 error(LOGGER, replayHandler.getOverlay(), CrashReport.makeCrashReport(t, "Cloning timeline"), () -> {});
@@ -296,15 +290,14 @@ public class GuiPathing {
                 if (player.isActive()) {
                     player.getFuture().cancel(false);
                 } else {
-                    Timeline timeline = mod.getCurrentTimeline();
+                    Path timePath = mod.getCurrentTimeline().getTimePath();
-                    Path timePath = timeline.getPaths().get(TIME_PATH);
 
                     if (!preparePathsForPlayback()) return;
 
                     timePath.setActive(!Keyboard.isKeyDown(Keyboard.KEY_LSHIFT));
                     // Start from cursor time unless the control key is pressed (then start from beginning)
                     int startTime = Keyboard.isKeyDown(Keyboard.KEY_LCONTROL)? 0 : GuiPathing.this.timeline.getCursorPosition();
-                    ListenableFuture<Void> future = player.start(timeline, startTime);
+                    ListenableFuture<Void> future = player.start(mod.getCurrentTimeline().getTimeline(), startTime);
                     overlay.setCloseable(false);
                     overlay.setMouseVisible(true);
                     Futures.addCallback(future, new FutureCallback<Void>() {
@@ -328,26 +321,28 @@ public class GuiPathing {
         positionKeyframeButton.setTexturePosH(new ReadablePoint() {
             @Override
             public int getX() {
-                Keyframe keyframe = mod.getSelectedKeyframe();
+                SPPath keyframePath = mod.getSelectedPath();
-                if (keyframe == null || !keyframe.getValue(CameraProperties.POSITION).isPresent()) {
+                long keyframeTime = mod.getSelectedTime();
+                if (keyframePath != SPPath.POSITION) {
                     // No keyframe or wrong path
-                    keyframe = mod.getCurrentTimeline().getPaths().get(POSITION_PATH).getKeyframe(timeline.getCursorPosition());
+                    keyframeTime = timeline.getCursorPosition();
+                    keyframePath = mod.getCurrentTimeline().isPositionKeyframe(keyframeTime) ? SPPath.POSITION : null;
                 }
-                if (keyframe == null) {
+                if (keyframePath != SPPath.POSITION) {
                     return replayHandler.isCameraView() ? 0 : 40;
                 } else {
-                    return keyframe.getValue(SpectatorProperty.PROPERTY).isPresent() ? 40 : 0;
+                    return mod.getCurrentTimeline().isSpectatorKeyframe(keyframeTime) ? 40 : 0;
                 }
             }
 
             @Override
             public int getY() {
-                Keyframe keyframe = mod.getSelectedKeyframe();
+                SPPath keyframePath = mod.getSelectedPath();
-                if (keyframe == null || !keyframe.getValue(CameraProperties.POSITION).isPresent()) {
+                if (keyframePath != SPPath.POSITION) {
                     // No keyframe selected but there might be one at exactly the position of the cursor
-                    keyframe = mod.getCurrentTimeline().getPaths().get(POSITION_PATH).getKeyframe(timeline.getCursorPosition());
+                    keyframePath = mod.getCurrentTimeline().isPositionKeyframe(timeline.getCursorPosition()) ? SPPath.POSITION : null;
                 }
-                return keyframe != null && keyframe.getValue(CameraProperties.POSITION).isPresent() ? 60 : 40;
+                return keyframePath == SPPath.POSITION ? 60 : 40;
             }
 
             @Override
@@ -357,7 +352,7 @@ public class GuiPathing {
         }).onClick(new Runnable() {
             @Override
             public void run() {
-                updateKeyframe(false);
+                updateKeyframe(SPPath.POSITION);
             }
         });
 
@@ -369,12 +364,12 @@ public class GuiPathing {
 
             @Override
             public int getY() {
-                Keyframe keyframe = mod.getSelectedKeyframe();
+                SPPath keyframePath = mod.getSelectedPath();
-                if (keyframe == null || !keyframe.getValue(TimestampProperty.PROPERTY).isPresent()) {
+                if (keyframePath != SPPath.TIME) {
                     // No keyframe selected but there might be one at exactly the position of the cursor
-                    keyframe = mod.getCurrentTimeline().getPaths().get(TIME_PATH).getKeyframe(timeline.getCursorPosition());
+                    keyframePath = mod.getCurrentTimeline().isTimeKeyframe(timeline.getCursorPosition()) ? SPPath.TIME : null;
                 }
-                return keyframe != null && keyframe.getValue(TimestampProperty.PROPERTY).isPresent() ? 100 : 80;
+                return keyframePath == SPPath.TIME ? 100 : 80;
             }
 
             @Override
@@ -384,7 +379,7 @@ public class GuiPathing {
         }).onClick(new Runnable() {
             @Override
             public void run() {
-                updateKeyframe(true);
+                updateKeyframe(SPPath.TIME);
             }
         });
 
@@ -406,12 +401,12 @@ public class GuiPathing {
                 }
                 try {
                     GuiKeyframeRepository gui = new GuiKeyframeRepository(
-                            mod, replayHandler.getReplayFile(), mod.getCurrentTimeline());
+                            mod.getCurrentTimeline(), replayHandler.getReplayFile(), mod.getCurrentTimeline().getTimeline());
                     Futures.addCallback(gui.getFuture(), new FutureCallback<Timeline>() {
                         @Override
                         public void onSuccess(Timeline result) {
                             if (result != null) {
-                                mod.setCurrentTimeline(result);
+                                mod.setCurrentTimeline(new SPTimeline(result));
                             }
                         }
 
@@ -437,10 +432,10 @@ public class GuiPathing {
                 @Override
                 public void onSuccess(Boolean delete) {
                     if (delete) {
-                        Timeline timeline = mod.createTimeline();
+                        mod.clearCurrentTimeline();
-                        timeline.createPath();
+                        if (entityTracker != null) {
-                        timeline.createPath();
+                            mod.getCurrentTimeline().setEntityTracker(entityTracker);
-                        mod.setCurrentTimeline(timeline);
+                        }
                     }
                 }
 
@@ -457,7 +452,7 @@ public class GuiPathing {
             // Position of the cursor
             int cursor = timeline.getCursorPosition();
             // Get the last time keyframe before the cursor
-            mod.getCurrentTimeline().getPaths().get(TIME_PATH).getKeyframes().stream()
+            mod.getCurrentTimeline().getTimePath().getKeyframes().stream()
                     .filter(it -> it.getTime() <= cursor).reduce((__, last) -> last).ifPresent(keyframe -> {
                 // Cursor position at the keyframe
                 int keyframeCursor = (int) keyframe.getTime();
@@ -473,7 +468,7 @@ public class GuiPathing {
                 // Move cursor to new position
                 timeline.setCursorPosition(keyframeCursor + cursorPassed);
                 // Deselect keyframe to allow the user to add a new one right away
-                mod.setSelectedKeyframe(null);
+                mod.setSelected(null, 0);
             });
         });
 
@@ -481,8 +476,8 @@ public class GuiPathing {
             if (!overlay.isVisible()) {
                 return;
             }
-            if (mod.getSelectedKeyframe() != null) {
+            if (mod.getSelectedPath() != null) {
-                updateKeyframe(mod.getSelectedKeyframe().getValue(TimestampProperty.PROPERTY).isPresent());
+                updateKeyframe(mod.getSelectedPath());
             }
         });
 
@@ -513,13 +508,12 @@ public class GuiPathing {
     }
 
     private boolean preparePathsForPlayback() {
-        Timeline timeline = mod.getCurrentTimeline();
+        SPTimeline timeline = mod.getCurrentTimeline();
-        timeline.getPaths().get(TIME_PATH).updateAll();
+        timeline.getTimeline().getPaths().forEach(Path::updateAll);
-        timeline.getPaths().get(POSITION_PATH).updateAll();
 
         // Make sure time keyframes's values are monotonically increasing
         int lastTime = 0;
-        for (Keyframe keyframe : timeline.getPaths().get(TIME_PATH).getKeyframes()) {
+        for (Keyframe keyframe : timeline.getTimePath().getKeyframes()) {
             int time = keyframe.getValue(TimestampProperty.PROPERTY).orElseThrow(IllegalStateException::new);
             if (time < lastTime) {
                 // We are going backwards in time
@@ -533,8 +527,8 @@ public class GuiPathing {
         }
 
         // Make sure there are at least two position- and two time-keyframes
-        if (timeline.getPaths().get(POSITION_PATH).getSegments().isEmpty()
+        if (timeline.getPositionPath().getSegments().isEmpty()
-                || timeline.getPaths().get(TIME_PATH).getSegments().isEmpty()) {
+                || timeline.getTimePath().getSegments().isEmpty()) {
             GuiInfoPopup.open(replayHandler.getOverlay(), "replaymod.chat.morekeyframes");
             return false;
         }
@@ -546,19 +540,19 @@ public class GuiPathing {
         scrollbar.setZoom(scrollbar.getZoom() * factor);
     }
 
-    /**
+    public boolean ensureEntityTracker(Runnable withDelayedTracker) {
-     * Called when either one of the property buttons is pressed.
-     * @param isTime {@code true} for the time property button, {@code false} for the place property button
-     */
-    private void updateKeyframe(final boolean isTime) {
         if (entityTracker == null) {
+            LOGGER.debug("Entity tracker not yet loaded, delaying...");
             LoadEntityTrackerPopup popup = new LoadEntityTrackerPopup(replayHandler.getOverlay());
             entityTrackerLoadingProgress = p -> popup.progressBar.setProgress(p.floatValue());
             Futures.addCallback(entityTrackerFuture, new FutureCallback<Void>() {
                 @Override
                 public void onSuccess(@Nullable Void result) {
                     popup.close();
-                    updateKeyframe(isTime);
+                    if (mod.getCurrentTimeline().getEntityTracker() == null) {
+                        mod.getCurrentTimeline().setEntityTracker(entityTracker);
+                    }
+                    withDelayedTracker.run();
                 }
 
                 @Override
@@ -566,186 +560,65 @@ public class GuiPathing {
                     popup.close();
                 }
             });
-            return;
+            return false;
         }
+        if (mod.getCurrentTimeline().getEntityTracker() == null) {
+            mod.getCurrentTimeline().setEntityTracker(entityTracker);
+        }
+        return true;
+    }
+
+    /**
+     * Called when either one of the property buttons is pressed.
+     * @param path {@code TIME} for the time property button, {@code POSITION} for the place property button
+     */
+    private void updateKeyframe(SPPath path) {
+        LOGGER.debug("Updating keyframe on path {}" + path);
+        if (!ensureEntityTracker(() -> updateKeyframe(path))) return;
 
         int time = timeline.getCursorPosition();
-        Timeline timeline = mod.getCurrentTimeline();
+        SPTimeline timeline = mod.getCurrentTimeline();
-        Path path = timeline.getPaths().get(isTime ? TIME_PATH : POSITION_PATH);
 
-        Keyframe keyframe = mod.getSelectedKeyframe();
+        switch (path) {
-        if (keyframe != null && keyframe.getValue(TimestampProperty.PROPERTY).isPresent() ^ isTime) {
+            case TIME:
-            // Keyframe is on the wrong timeline
+                if (mod.getSelectedPath() == path) {
-            keyframe = null;
+                    LOGGER.debug("Selected keyframe is time keyframe -> removing keyframe");
-        }
+                    timeline.removeTimeKeyframe(mod.getSelectedTime());
-        if (keyframe == null) {
+                    mod.setSelected(null, 0);
-            // No keyframe selected but there may still be one at this exact time
+                } else if (timeline.isTimeKeyframe(time)) {
-            keyframe = path.getKeyframe(time);
+                    LOGGER.debug("Keyframe at cursor position is time keyframe -> removing keyframe");
-        }
+                    timeline.removeTimeKeyframe(time);
-        Change change;
+                    mod.setSelected(null, 0);
-        if (keyframe == null) {
-            change = AddKeyframe.create(path, time);
-            change.apply(timeline);
-            keyframe = path.getKeyframe(time);
                 } else {
-            change = RemoveKeyframe.create(path, keyframe);
+                    LOGGER.debug("No time keyframe found -> adding new keyframe");
-            change.apply(timeline);
+                    timeline.addTimeKeyframe(time, replayHandler.getReplaySender().currentTimeStamp());
-            keyframe = null;
+                    mod.setSelected(path, time);
                 }
-
+                break;
-        if (keyframe != null) {
+            case POSITION:
-            UpdateKeyframeProperties.Builder builder = UpdateKeyframeProperties.create(path, keyframe);
+                if (mod.getSelectedPath() == path) {
-            if (isTime) {
+                    LOGGER.debug("Selected keyframe is position keyframe -> removing keyframe");
-                builder.setValue(TimestampProperty.PROPERTY, replayHandler.getReplaySender().currentTimeStamp());
+                    timeline.removePositionKeyframe(mod.getSelectedTime());
+                    mod.setSelected(null, 0);
+                } else if (timeline.isPositionKeyframe(time)) {
+                    LOGGER.debug("Keyframe at cursor position is position keyframe -> removing keyframe");
+                    timeline.removePositionKeyframe(time);
+                    mod.setSelected(null, 0);
                 } else {
+                    LOGGER.debug("No position keyframe found -> adding new keyframe");
                     CameraEntity camera = replayHandler.getCameraEntity();
-                builder.setValue(CameraProperties.POSITION, Triple.of(camera.posX, camera.posY, camera.posZ));
+                    int spectatedId = -1;
-                builder.setValue(CameraProperties.ROTATION, Triple.of(camera.rotationYaw, camera.rotationPitch, camera.roll));
                     if (!replayHandler.isCameraView()) {
-                    Entity spectated = replayHandler.getOverlay().getMinecraft().getRenderViewEntity();
+                        spectatedId = replayHandler.getOverlay().getMinecraft().getRenderViewEntity().getEntityId();
-                    builder.setValue(SpectatorProperty.PROPERTY, spectated.getEntityId());
                     }
+                    timeline.addPositionKeyframe(time, camera.posX, camera.posY, camera.posZ,
+                            camera.rotationYaw, camera.rotationPitch, camera.roll, spectatedId);
+                    mod.setSelected(path, time);
                 }
-            UpdateKeyframeProperties updateChange = builder.done();
+                break;
-            updateChange.apply(timeline);
-            change = CombinedChange.createFromApplied(change, updateChange);
-
-            // If this new keyframe formed the first segment of the time path
-            if (isTime && path.getSegments().size() == 1) {
-                PathSegment segment = path.getSegments().iterator().next();
-                Interpolator interpolator = new LinearInterpolator();
-                interpolator.registerProperty(TimestampProperty.PROPERTY);
-                SetInterpolator setInterpolator = SetInterpolator.create(segment, interpolator);
-                setInterpolator.apply(timeline);
-                change = CombinedChange.createFromApplied(change, setInterpolator);
         }
     }
 
-        // Update interpolators for spectator keyframes
-        // while this is overkill, it is far simpler than updating differently for every possible case
-        if (!isTime) {
-            Change interpolators = updateInterpolators();
-            interpolators.apply(timeline);
-            change = CombinedChange.createFromApplied(change, interpolators);
-        }
-
-        Change specPosUpdate = updateSpectatorPositions();
-        specPosUpdate.apply(timeline);
-        change = CombinedChange.createFromApplied(change, specPosUpdate);
-
-        timeline.pushChange(change);
-
-        mod.setSelectedKeyframe(keyframe);
-    }
-
-    public Change updateInterpolators() {
-        boolean linearInterpolation = mod.getCore().getSettingsRegistry().get(Setting.LINEAR_INTERPOLATION);
-        List<Change> changes = new ArrayList<>();
-        Interpolator interpolator = null;
-        boolean isSpectatorInterpolator = false;
-        for (PathSegment segment : mod.getCurrentTimeline().getPaths().get(POSITION_PATH).getSegments()) {
-            if (segment.getStartKeyframe().getValue(SpectatorProperty.PROPERTY).isPresent()
-                    && segment.getEndKeyframe().getValue(SpectatorProperty.PROPERTY).isPresent()) {
-                // Spectator segment
-                if (!isSpectatorInterpolator) {
-                    isSpectatorInterpolator = true;
-                    interpolator = new LinearInterpolator();
-                    interpolator.registerProperty(SpectatorProperty.PROPERTY);
-                }
-                changes.add(SetInterpolator.create(segment, interpolator));
-            } else {
-                // Normal segment
-                if (isSpectatorInterpolator || interpolator == null) {
-                    isSpectatorInterpolator = false;
-                    interpolator = linearInterpolation ? new LinearInterpolator() : new CubicSplineInterpolator();
-                    interpolator.registerProperty(CameraProperties.POSITION);
-                    interpolator.registerProperty(CameraProperties.ROTATION);
-                }
-                changes.add(SetInterpolator.create(segment, interpolator));
-            }
-        }
-        return CombinedChange.create(changes.toArray(new Change[changes.size()]));
-    }
-
-    public Change updateSpectatorPositions() {
-        List<Change> changes = new ArrayList<>();
-        Path positionPath = mod.getCurrentTimeline().getPaths().get(POSITION_PATH);
-        Path timePath = mod.getCurrentTimeline().getPaths().get(TIME_PATH);
-        timePath.updateAll();
-        for (Keyframe keyframe : positionPath.getKeyframes()) {
-            Optional<Integer> spectator = keyframe.getValue(SpectatorProperty.PROPERTY);
-            if (spectator.isPresent()) {
-                Optional<Integer> time = timePath.getValue(TimestampProperty.PROPERTY, keyframe.getTime());
-                if (!time.isPresent()) {
-                    continue; // No time keyframes set at this video time, cannot determine replay time
-                }
-                Location expected = entityTracker.getEntityPositionAtTimestamp(spectator.get(), time.get());
-                if (expected == null) {
-                    continue; // We don't have any data on this entity for some reason
-                }
-                Triple<Double, Double, Double> pos = keyframe.getValue(CameraProperties.POSITION).orElse(Triple.of(0D, 0D, 0D));
-                Triple<Float, Float, Float> rot = keyframe.getValue(CameraProperties.ROTATION).orElse(Triple.of(0F, 0F, 0F));
-                Location actual = new Location(pos.getLeft(), pos.getMiddle(), pos.getRight(), rot.getLeft(), rot.getRight());
-                if (!expected.equals(actual)) {
-                    changes.add(UpdateKeyframeProperties.create(positionPath, keyframe)
-                            .setValue(CameraProperties.POSITION, Triple.of(expected.getX(), expected.getY(), expected.getZ()))
-                            .setValue(CameraProperties.ROTATION, Triple.of(expected.getYaw(), expected.getPitch(), 0f)).done()
-                    );
-                }
-            }
-        }
-        return CombinedChange.create(changes.toArray(new Change[changes.size()]));
-    }
-
-    public Change moveKeyframe(Path path, Keyframe keyframe, long newTime) {
-        Timeline timeline = mod.getCurrentTimeline();
-        // Interpolator might be required later (only if path is the time path)
-        Optional<Interpolator> interpolator =
-                path.getSegments().stream().findFirst().map(PathSegment::getInterpolator);
-
-        // First remove the old keyframe
-        Change removeChange = RemoveKeyframe.create(path, keyframe);
-        removeChange.apply(timeline);
-
-        // and add a new one at the correct time
-        Change addChange = AddKeyframe.create(path, newTime);
-        addChange.apply(timeline);
-        path.getKeyframe(newTime);
-
-        // Then copy over all properties
-        UpdateKeyframeProperties.Builder builder = UpdateKeyframeProperties.create(path, path.getKeyframe(newTime));
-        for (Property property : keyframe.getProperties()) {
-            copyProperty(property, keyframe, builder);
-        }
-        Change propertyChange = builder.done();
-        propertyChange.apply(timeline);
-
-        // Finally set the interpolators
-        Change interpolatorChange;
-        if (path.getTimeline().getPaths().indexOf(path) == GuiPathing.POSITION_PATH) {
-            // Position / Spectator keyframes need special handling
-            interpolatorChange = updateInterpolators();
-        } else {
-            // Time keyframes only need updating when only one segment of them exists
-            if (path.getSegments().size() == 1) {
-                interpolatorChange = SetInterpolator.create(path.getSegments().iterator().next(), interpolator.get());
-            } else {
-                interpolatorChange = CombinedChange.create(); // Noop change
-            }
-        }
-        interpolatorChange.apply(timeline);
-        // and update spectator positions
-        Change spectatorChange = updateSpectatorPositions();
-        spectatorChange.apply(timeline);
-
-        return CombinedChange.createFromApplied(removeChange, addChange, propertyChange, interpolatorChange, spectatorChange);
-    }
-
-    // Helper method because generics cannot be defined on blocks
-    private <T> void copyProperty(Property<T> property, Keyframe from, UpdateKeyframeProperties.Builder to) {
-        from.getValue(property).ifPresent(value -> to.setValue(property, value));
-    }
-
     public ReplayModSimplePathing getMod() {
         return mod;
     }
@@ -754,13 +627,15 @@ public class GuiPathing {
         return entityTracker;
     }
 
-    public void openEditKeyframePopup(Path path, Keyframe keyframe) {
+    public void openEditKeyframePopup(SPPath path, long time) {
+        if (!ensureEntityTracker(() -> openEditKeyframePopup(path, time))) return;
+        Keyframe keyframe = mod.getCurrentTimeline().getKeyframe(path, time);
         if (keyframe.getProperties().contains(SpectatorProperty.PROPERTY)) {
-            new GuiEditKeyframe.Spectator(this, path, keyframe).open();
+            new GuiEditKeyframe.Spectator(this, path, keyframe.getTime()).open();
         } else if (keyframe.getProperties().contains(CameraProperties.POSITION)) {
-            new GuiEditKeyframe.Position(this, path, keyframe).open();
+            new GuiEditKeyframe.Position(this, path, keyframe.getTime()).open();
         } else {
-            new GuiEditKeyframe.Time(this, path, keyframe).open();
+            new GuiEditKeyframe.Time(this, path, keyframe.getTime()).open();
         }
     }
 

src/main/java/com/replaymod/simplepathing/preview/PathPreviewRenderer.java

@@ -9,10 +9,10 @@ import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
 import com.replaymod.replaystudio.pathing.path.Keyframe;
 import com.replaymod.replaystudio.pathing.path.Path;
 import com.replaymod.replaystudio.pathing.path.PathSegment;
-import com.replaymod.replaystudio.pathing.path.Timeline;
 import com.replaymod.replaystudio.util.EntityPositionTracker;
 import com.replaymod.replaystudio.util.Location;
 import com.replaymod.simplepathing.ReplayModSimplePathing;
+import com.replaymod.simplepathing.SPTimeline;
 import com.replaymod.simplepathing.gui.GuiPathing;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.renderer.GlStateManager;
@@ -67,11 +67,11 @@ public class PathPreviewRenderer {
         if (guiPathing == null) return;
         EntityPositionTracker entityTracker = guiPathing.getEntityTracker();
 
-        Timeline timeline = mod.getCurrentTimeline();
+        SPTimeline timeline = mod.getCurrentTimeline();
         if (timeline == null) return;
-        Path path = timeline.getPaths().get(GuiPathing.POSITION_PATH);
+        Path path = timeline.getPositionPath();
         if (path.getKeyframes().isEmpty()) return;
-        Path timePath = timeline.getPaths().get(GuiPathing.TIME_PATH);
+        Path timePath = timeline.getTimePath();
 
         path.update();
 
@@ -230,7 +230,7 @@ public class PathPreviewRenderer {
         float posY = 0f;
         float size = 10f / ReplayMod.TEXTURE_SIZE;
 
-        if (keyframe == mod.getSelectedKeyframe()) {
+        if (mod.isSelected(keyframe)) {
             posY += size;
         }
 

src/main/java/com/replaymod/simplepathing/properties/ExplicitInterpolationProperty.java

@@ -0,0 +1,44 @@
+package com.replaymod.simplepathing.properties;
+
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import com.replaymod.replaystudio.pathing.property.AbstractProperty;
+import com.replaymod.replaystudio.pathing.property.PropertyPart;
+import lombok.NonNull;
+import org.apache.commons.lang3.ObjectUtils;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Collections;
+
+/**
+ * Property indicating that the next path segment's interpolator is fixed
+ */
+public class ExplicitInterpolationProperty extends AbstractProperty<Object> {
+    public static final ExplicitInterpolationProperty PROPERTY = new ExplicitInterpolationProperty();
+
+    private ExplicitInterpolationProperty() {
+        super("interpolationFixed", "<internal>", null, new Object());
+    }
+
+    @Override
+    public Collection<PropertyPart<Object>> getParts() {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public void applyToGame(Object value, @NonNull Object replayHandler) {
+        // dummy property, do nothing
+    }
+
+    @Override
+    public void toJson(JsonWriter writer, Object value) throws IOException {
+        writer.nullValue();
+    }
+
+    @Override
+    public Object fromJson(JsonReader reader) throws IOException {
+        reader.nextNull();
+        return ObjectUtils.NULL;
+    }
+}

src/main/resources/assets/replaymod/lang/en_US.lang

@@ -292,6 +292,7 @@ replaymod.gui.settings.title=Replay Mod Settings
 
 replaymod.gui.settings.interpolation.linear=Linear
 replaymod.gui.settings.interpolation.cubic=Cubic
+replaymod.gui.settings.interpolation.catmullrom=Catmull Rom
 
 replaymod.gui.settings.bitrate=Video Bitrate
 replaymod.gui.settings.framerate=Video Framerate
@@ -309,6 +310,7 @@ replaymod.gui.settings.keyframecleancallback=Clear Confirmation
 replaymod.gui.settings.renderinvisible=Render invisible Entities
 replaymod.gui.settings.camera=Camera
 replaymod.gui.settings.showchat=Show Chat
+replaymod.gui.settings.interpolator=Default Interpolator
 
 replaymod.gui.settings.warning.linea=WARNING: Recording settings will be
 replaymod.gui.settings.warning.lineb=applied the next time you join a world.
@@ -372,6 +374,17 @@ replaymod.gui.editkeyframe.spec.method.shoulder.pitch=Pitch Offset
 replaymod.gui.editkeyframe.spec.method.shoulder.yaw=Rotation Angle
 replaymod.gui.editkeyframe.spec.method.shoulder.smoothness=Path Smoothness
 
+replaymod.gui.editkeyframe.interpolator=Interpolator
+replaymod.gui.editkeyframe.interpolator.default.name=Default Interpolator
+replaymod.gui.editkeyframe.interpolator.default.desc=Uses the default interpolator defined in the Replay Mod Settings.
+replaymod.gui.editkeyframe.interpolator.catmullrom.name=Catmull Rom Spline Interpolator
+replaymod.gui.editkeyframe.interpolator.catmullrom.desc=Calculates a catmull rom spline with customizable alpha value for precise tightness and smoothness of the camera path.
+replaymod.gui.editkeyframe.interpolator.catmullrom.alpha=Alpha:
+replaymod.gui.editkeyframe.interpolator.cubic.name=Cubic Spline Interpolator
+replaymod.gui.editkeyframe.interpolator.cubic.desc=Calculates a cubic equation matrix for all points for a smooth camera path.
+replaymod.gui.editkeyframe.interpolator.linear.name=Linear Interpolator
+replaymod.gui.editkeyframe.interpolator.linear.desc=Draws straight lines between the keyframes.
+
 #Render Settings GUI
 replaymod.gui.rendersettings.title=Rendering Options
 replaymod.gui.rendersettings.renderer=Rendering Method

src/test/java/com/replaymod/simplepathing/SPTimelineTest.java

@@ -0,0 +1,626 @@
+package com.replaymod.simplepathing;
+
+import com.google.common.collect.Iterables;
+import com.replaymod.pathing.properties.CameraProperties;
+import com.replaymod.pathing.properties.SpectatorProperty;
+import com.replaymod.pathing.properties.TimestampProperty;
+import com.replaymod.replaystudio.pathing.change.Change;
+import com.replaymod.replaystudio.pathing.interpolation.CatmullRomSplineInterpolator;
+import com.replaymod.replaystudio.pathing.interpolation.Interpolator;
+import com.replaymod.replaystudio.pathing.interpolation.LinearInterpolator;
+import com.replaymod.replaystudio.pathing.path.Keyframe;
+import com.replaymod.replaystudio.pathing.path.Path;
+import com.replaymod.replaystudio.pathing.path.PathSegment;
+import com.replaymod.replaystudio.pathing.path.Timeline;
+import com.replaymod.replaystudio.util.EntityPositionTracker;
+import com.replaymod.replaystudio.util.Location;
+import com.replaymod.simplepathing.SPTimeline.SPPath;
+import org.apache.commons.lang3.tuple.Triple;
+import org.apache.logging.log4j.LogManager;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+
+public class SPTimelineTest {
+    private SPTimeline impl;
+    private Timeline timeline;
+
+    @BeforeClass
+    public static void setupLogger() {
+        ReplayModSimplePathing.LOGGER = LogManager.getLogger();
+    }
+
+    @Before
+    public void setup() {
+        impl = new SPTimeline();
+        impl.setDefaultInterpolatorType(InterpolatorType.CUBIC);
+        impl.setEntityTracker(new EntityPositionTrackerMock());
+        timeline = impl.getTimeline();
+    }
+
+    @Test
+    public void testGetPath() {
+        assertSame(impl.getTimeline().getPaths().get(0), impl.getTimePath());
+        assertSame(impl.getTimeline().getPaths().get(0), impl.getPath(SPPath.TIME));
+        assertSame(impl.getTimeline().getPaths().get(1), impl.getPositionPath());
+        assertSame(impl.getTimeline().getPaths().get(1), impl.getPath(SPPath.POSITION));
+    }
+
+    @Test
+    public void testGetKeyframe() {
+        assertSame(timeline.getPaths().get(0).insert(123), impl.getKeyframe(SPPath.TIME, 123));
+        assertSame(timeline.getPaths().get(1).insert(456), impl.getKeyframe(SPPath.POSITION, 456));
+    }
+
+    @Test
+    public void testIsTimeKeyframe() {
+        impl.getTimePath().insert(123);
+        impl.getPositionPath().insert(456);
+        impl.getPositionPath().insert(42).setValue(SpectatorProperty.PROPERTY, 42);
+        assertTrue(impl.isTimeKeyframe(123));
+        assertFalse(impl.isTimeKeyframe(456));
+        assertFalse(impl.isTimeKeyframe(789));
+        assertFalse(impl.isTimeKeyframe(42));
+    }
+
+    @Test
+    public void testIsPositionKeyframe() {
+        impl.getTimePath().insert(123);
+        impl.getPositionPath().insert(456);
+        impl.getPositionPath().insert(42).setValue(SpectatorProperty.PROPERTY, 42);
+        assertFalse(impl.isPositionKeyframe(123));
+        assertTrue(impl.isPositionKeyframe(456));
+        assertFalse(impl.isPositionKeyframe(789));
+        assertTrue(impl.isSpectatorKeyframe(42));
+    }
+
+    @Test
+    public void testIsSpectatorKeyframe() {
+        impl.getTimePath().insert(123);
+        impl.getPositionPath().insert(456);
+        impl.getPositionPath().insert(42).setValue(SpectatorProperty.PROPERTY, 42);
+        assertFalse(impl.isSpectatorKeyframe(123));
+        assertFalse(impl.isSpectatorKeyframe(456));
+        assertFalse(impl.isSpectatorKeyframe(789));
+        assertTrue(impl.isSpectatorKeyframe(42));
+    }
+
+    @Test
+    public void testAddPositionKeyframe() {
+        assertNull(timeline.peekUndoStack());
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, -1);
+        assertNotNull(timeline.peekUndoStack());
+        Keyframe keyframe = impl.getKeyframe(SPPath.POSITION, 0);
+        assertNotNull(keyframe);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(1d, 2d, 3d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(4f, 5f, 6f)));
+        assertFalse(keyframe.getValue(SpectatorProperty.PROPERTY).isPresent());
+        timeline.undoLastChange();
+        assertNull(timeline.peekUndoStack());
+        assertNull(impl.getKeyframe(SPPath.POSITION, 0));
+    }
+
+    @Test
+    public void testAddPositionKeyframeSpectator() {
+        assertNull(timeline.peekUndoStack());
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, 7);
+        assertNotNull(timeline.peekUndoStack());
+        Keyframe keyframe = impl.getKeyframe(SPPath.POSITION, 0);
+        assertNotNull(keyframe);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(1d, 2d, 3d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(4f, 5f, 6f)));
+        assertEquals(keyframe.getValue(SpectatorProperty.PROPERTY), Optional.of(7));
+        timeline.undoLastChange();
+        assertNull(timeline.peekUndoStack());
+        assertNull(impl.getKeyframe(SPPath.POSITION, 0));
+    }
+
+    @Test
+    public void testPositionKeyframeSpectatorPosition() {
+        Keyframe keyframe;
+        impl.addTimeKeyframe(0, 0);
+        impl.addTimeKeyframe(9, 9);
+
+        impl.addPositionKeyframe(4, 1, 2, 3, 4, 5, 6, 1);
+        keyframe = impl.getKeyframe(SPPath.POSITION, 4);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(1d, 2d, 3d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(4f, 5f, 6f)));
+
+        impl.addPositionKeyframe(6, 1, 2, 3, 4, 5, 6, 42);
+        keyframe = impl.getKeyframe(SPPath.POSITION, 6);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(12d, 0d, 0d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(0f, 0f, 0f)));
+
+        impl.addPositionKeyframe(8, 1, 2, 3, 4, 5, 6, 42);
+        keyframe = impl.getKeyframe(SPPath.POSITION, 8);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(16d, 0d, 0d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(0f, 0f, 0f)));
+
+        impl.addPositionKeyframe(10, 1, 2, 3, 4, 5, 6, 42);
+        keyframe = impl.getKeyframe(SPPath.POSITION, 10);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(1d, 2d, 3d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(4f, 5f, 6f)));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testAddPositionKeyframeDuplicate() {
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, -1);
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, -1);
+    }
+
+    @Test
+    public void testUpdatePositionKeyframe() {
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, -1);
+        Change change = impl.updatePositionKeyframe(0, 7, 8, 9, 10, 11, 12);
+        assertNotNull(change);
+        Keyframe keyframe = impl.getKeyframe(SPPath.POSITION, 0);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(7d, 8d, 9d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(10f, 11f, 12f)));
+        assertFalse(keyframe.getValue(SpectatorProperty.PROPERTY).isPresent());
+        change.undo(timeline);
+        keyframe = impl.getKeyframe(SPPath.POSITION, 0);
+        assertEquals(keyframe.getValue(CameraProperties.POSITION), Optional.of(Triple.of(1d, 2d, 3d)));
+        assertEquals(keyframe.getValue(CameraProperties.ROTATION), Optional.of(Triple.of(4f, 5f, 6f)));
+        assertFalse(keyframe.getValue(SpectatorProperty.PROPERTY).isPresent());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testUpdatePositionKeyframeNoKeyframe() {
+        impl.updatePositionKeyframe(0, 1, 2, 3, 4, 5, 6);
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testUpdatePositionKeyframeSpectatorKeyframe() {
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, 7);
+        impl.updatePositionKeyframe(0, 1, 2, 3, 4, 5, 6);
+    }
+
+    @Test
+    public void testRemovePositionKeyframe() {
+        impl.addPositionKeyframe(0, 1, 2, 3, 4, 5, 6, -1);
+        impl.removePositionKeyframe(0);
+        assertNull(impl.getKeyframe(SPPath.POSITION, 0));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testRemovePositionKeyframeNoKeyframe() {
+        impl.removePositionKeyframe(0);
+    }
+
+    @Test
+    public void testAddTimeKeyframe() {
+        assertNull(timeline.peekUndoStack());
+        impl.addTimeKeyframe(0, 1);
+        assertNotNull(timeline.peekUndoStack());
+        Keyframe keyframe = impl.getKeyframe(SPPath.TIME, 0);
+        assertNotNull(keyframe);
+        assertEquals(keyframe.getValue(TimestampProperty.PROPERTY), Optional.of(1));
+        timeline.undoLastChange();
+        assertNull(timeline.peekUndoStack());
+        assertNull(impl.getKeyframe(SPPath.TIME, 0));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testAddTimeKeyframeDuplicate() {
+        impl.addTimeKeyframe(0, 1);
+        impl.addTimeKeyframe(0, 1);
+    }
+
+    @Test
+    public void testUpdateTimeKeyframe() {
+        impl.addTimeKeyframe(0, 1);
+        Change change = impl.updateTimeKeyframe(0, 2);
+        assertNotNull(change);
+        assertEquals(impl.getKeyframe(SPPath.TIME, 0).getValue(TimestampProperty.PROPERTY), Optional.of(2));
+        change.undo(timeline);
+        assertEquals(impl.getKeyframe(SPPath.TIME, 0).getValue(TimestampProperty.PROPERTY), Optional.of(1));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testUpdateTimeKeyframeNoKeyframe() {
+        impl.updateTimeKeyframe(0, 1);
+    }
+
+    @Test
+    public void testRemoveTimeKeyframe() {
+        impl.addTimeKeyframe(0, 1);
+        impl.removeTimeKeyframe(0);
+        assertNull(impl.getKeyframe(SPPath.TIME, 0));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testRemoveTimeKeyframeNoKeyframe() {
+        impl.removeTimeKeyframe(0);
+    }
+
+    /**
+     * Checks all interpolators to make sure that they are continuous and not fragmented.
+     */
+    private void assertValidInterpolators(SPPath path, int expectedNumberOfInterpolators) {
+        String str = prettyPrintInterpolators(impl, path);
+        List<Interpolator> interpolators = impl.getPath(path).getSegments().stream().map(PathSegment::getInterpolator)
+                .distinct().collect(Collectors.toList());
+        assertFalse("Not all interpolators set: " + str, interpolators.contains(null));
+        assertEquals("Mismatched interpolator number: " + str, expectedNumberOfInterpolators, interpolators.size());
+        int i = 0;
+        for (Interpolator interpolator : interpolators) {
+            Keyframe lastKeyframe = null;
+            for (PathSegment segment : interpolator.getSegments().stream()
+                    .sorted(Comparator.comparing(s -> s.getStartKeyframe().getTime())).collect(Collectors.toList())) {
+                String message = "Fragmentation in interpolator " + i + ": " + str;
+                assertTrue(message, lastKeyframe == null || segment.getStartKeyframe() == lastKeyframe);
+                lastKeyframe = segment.getEndKeyframe();
+            }
+            i++;
+        }
+    }
+
+    @Test
+    public void testAddPositionKeyframeAppend() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        addPosition(2, 1);
+        addPosition(3, 1);
+        addPosition(4, 1);
+    }
+
+    @Test
+    public void testAddPositionKeyframePrepend() {
+        addPosition(4, 0);
+        addPosition(3, 1);
+        addPosition(2, 1);
+        addPosition(1, 1);
+        addPosition(0, 1);
+    }
+
+    @Test
+    public void testAddPositionKeyframeMixed() {
+        addPosition(2, 0);
+        addPosition(4, 1);
+        addPosition(3, 1);
+        addPosition(0, 1);
+        addPosition(1, 1);
+    }
+
+    @Test
+    public void testAddPositionSpectatorKeyframe() {
+        addPosition(0, 0);
+        addSpectator(1, 1);
+        addSpectator(2, 2);
+        addPosition(4, 3);
+        addPosition(7, 3);
+        addPosition(8, 3);
+        addSpectator(3, 3);
+        addSpectator(5, 3);
+        addSpectator(6, 5);
+    }
+
+    @Test
+    public void testRemovePositionKeyframeFromStart() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        addPosition(2, 1);
+        addPosition(3, 1);
+        removePosition(0, 1);
+        removePosition(1, 1);
+        removePosition(2, 0);
+        removePosition(3, 0);
+    }
+
+    @Test
+    public void testRemovePositionKeyframeFromEnd() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        addPosition(2, 1);
+        addPosition(3, 1);
+        removePosition(3, 1);
+        removePosition(2, 1);
+        removePosition(1, 0);
+        removePosition(0, 0);
+    }
+
+    @Test
+    public void testRemovePositionKeyframeFromMiddle() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        addPosition(2, 1);
+        addPosition(3, 1);
+        removePosition(1, 1);
+        removePosition(2, 1);
+        removePosition(0, 0);
+        removePosition(3, 0);
+    }
+
+    @Test
+    public void testRemovePositionSpectatorKeyframe() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        addPosition(2, 1);
+        addSpectator(3, 1);
+        addSpectator(4, 2);
+        addSpectator(5, 2);
+        addPosition(6, 3);
+        addPosition(7, 3);
+        addSpectator(8, 3);
+        addSpectator(9, 4);
+        removePosition(4, 4);
+        removePosition(9, 3);
+        removePosition(6, 3);
+        removePosition(7, 2);
+        removePosition(0, 2);
+        removePosition(1, 2);
+        removePosition(3, 2);
+        removePosition(2, 1);
+        removePosition(5, 0);
+        removePosition(8, 0);
+    }
+
+    @Test
+    public void testAddTimeKeyframeAppend() {
+        addTime(0, 0);
+        addTime(1, 1);
+        addTime(2, 1);
+        addTime(3, 1);
+        addTime(4, 1);
+    }
+
+    @Test
+    public void testAddTimeKeyframePrepend() {
+        addTime(4, 0);
+        addTime(3, 1);
+        addTime(2, 1);
+        addTime(1, 1);
+        addTime(0, 1);
+    }
+
+    @Test
+    public void testAddTimeKeyframeMixed() {
+        addTime(2, 0);
+        addTime(4, 1);
+        addTime(3, 1);
+        addTime(0, 1);
+        addTime(1, 1);
+    }
+
+    @Test
+    public void testRemoveTimeKeyframeFromStart() {
+        addTime(0, 0);
+        addTime(1, 1);
+        addTime(2, 1);
+        addTime(3, 1);
+        removeTime(0, 1);
+        removeTime(1, 1);
+        removeTime(2, 0);
+        removeTime(3, 0);
+    }
+
+    @Test
+    public void testRemoveTimeKeyframeFromEnd() {
+        addTime(0, 0);
+        addTime(1, 1);
+        addTime(2, 1);
+        addTime(3, 1);
+        removeTime(3, 1);
+        removeTime(2, 1);
+        removeTime(1, 0);
+        removeTime(0, 0);
+    }
+
+    @Test
+    public void testRemoveTimeKeyframeFromMiddle() {
+        addTime(0, 0);
+        addTime(1, 1);
+        addTime(2, 1);
+        addTime(3, 1);
+        removeTime(1, 1);
+        removeTime(2, 1);
+        removeTime(0, 0);
+        removeTime(3, 0);
+    }
+
+    @Test
+    public void testSetInterpolator() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        addPosition(2, 1);
+        setInterpolator(1, new LinearInterpolator(), 2);
+        assertIsLinear(1);
+        Interpolator interpolator = Iterables.get(impl.getPositionPath().getSegments(), 1).getInterpolator();
+        assertTrue(interpolator.getKeyframeProperties().contains(CameraProperties.POSITION));
+        assertTrue(interpolator.getKeyframeProperties().contains(CameraProperties.ROTATION));
+        addPosition(3, 3);
+        addPosition(4, 3);
+        addPosition(5, 3);
+        setInterpolator(3, new LinearInterpolator(), 5);
+        assertIsLinear(3);
+        removePosition(2, 3);
+        removePosition(3, 3);
+        removePosition(0, 2);
+        removePosition(1, 1);
+        removePosition(4, 0);
+        removePosition(5, 0);
+    }
+
+    private void assertIsLinear(int index) {
+        assertTrue("Expected segment " + index + " to have linear interpolator: " + prettyPrintInterpolators(impl, SPPath.POSITION),
+                Iterables.get(impl.getPositionPath().getSegments(), index).getInterpolator() instanceof LinearInterpolator);
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testSetInterpolatorNoKeyframe() {
+        addTime(0, 0);
+        impl.setInterpolator(0, new LinearInterpolator());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testSetInterpolatorToDefaultNoKeyframe() {
+        addTime(0, 0);
+        impl.setInterpolatorToDefault(0);
+    }
+
+    @Test
+    public void testMoveKeyframe() {
+        addPosition(1, 0);
+        addPosition(3, 1);
+        addPosition(5, 1);
+        addPosition(7, 1);
+        addSpectator(9, 1);
+        addSpectator(11, 2);
+        addSpectator(13, 2);
+        addPosition(15, 3);
+        addPosition(17, 3);
+        addPosition(19, 3);
+        setInterpolator(3, new LinearInterpolator(), 5);
+        assertIsLinear(1);
+        setInterpolator(5, new LinearInterpolator(), 5);
+        assertIsLinear(2);
+        // [P 1] C0 [P 3] L1 [P 5] L1 [P 7] C2 [S 9] L3 [S 11] L3 [S 13] C4 [P 15] C4 [P 17] C4 [P 19]
+
+        impl.moveKeyframe(SPPath.POSITION, 5, 0);
+        assertValidInterpolators(SPPath.POSITION, 6);
+        assertIsLinear(0);
+        impl.moveKeyframe(SPPath.POSITION, 0, 5);
+        assertValidInterpolators(SPPath.POSITION, 5);
+        assertIsLinear(2);
+
+        impl.moveKeyframe(SPPath.POSITION, 3, 12);
+        assertValidInterpolators(SPPath.POSITION, 7);
+        assertIsLinear(5);
+        impl.moveKeyframe(SPPath.POSITION, 12, 3);
+        assertValidInterpolators(SPPath.POSITION, 5);
+        assertIsLinear(1);
+
+        impl.moveKeyframe(SPPath.POSITION, 7, 14);
+        assertValidInterpolators(SPPath.POSITION, 4);
+        impl.moveKeyframe(SPPath.POSITION, 14, 20);
+        assertValidInterpolators(SPPath.POSITION, 4);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testSetDefaultInterpolatorDifferentType() {
+        addPosition(0, 0);
+        addPosition(1, 1);
+        impl.setDefaultInterpolator(new CatmullRomSplineInterpolator(42));
+    }
+
+    @Test
+    public void testSetDefaultInterpolatorSameType() {
+        impl.setDefaultInterpolatorType(InterpolatorType.CATMULL_ROM);
+        addPosition(0, 0);
+        addSpectator(1, 1);
+        addSpectator(2, 2);
+        addPosition(3, 3);
+        addPosition(4, 3);
+        impl.setDefaultInterpolator(new CatmullRomSplineInterpolator(42));
+        assertValidInterpolators(SPPath.POSITION, 3);
+        assertIsCatmullRom(0, 42);
+        assertIsCatmullRom(2, 42);
+        assertIsCatmullRom(3, 42);
+    }
+
+    private void assertIsCatmullRom(int index, double alpha) {
+        String str = prettyPrintInterpolators(impl, SPPath.POSITION);
+        Interpolator interpolator = Iterables.get(impl.getPositionPath().getSegments(), index).getInterpolator();
+        assertTrue("Expected segment " + index + " to be catmull rom interpolator: " + str,
+                 interpolator instanceof CatmullRomSplineInterpolator);
+        assertTrue("Expected interpolator of segment segment " + index + " to have alpha " + alpha + ": " + str,
+                ((CatmullRomSplineInterpolator) interpolator).getAlpha() == 42);
+    }
+
+    private void addPosition(int time, int expectedNumberOfInterpolators) {
+        impl.addPositionKeyframe(time, 1, 2, 3, 4, 5, 6, -1);
+        assertNotNull(impl.getKeyframe(SPPath.POSITION, time));
+        assertValidInterpolators(SPPath.POSITION, expectedNumberOfInterpolators);
+    }
+
+    private void addSpectator(int time, int expectedNumberOfInterpolators) {
+        impl.addPositionKeyframe(time, 1, 2, 3, 4, 5, 6, 42);
+        assertNotNull(impl.getKeyframe(SPPath.POSITION, time));
+        assertTrue(impl.isSpectatorKeyframe(time));
+        assertValidInterpolators(SPPath.POSITION, expectedNumberOfInterpolators);
+    }
+
+    private void addTime(int time, int expectedNumberOfInterpolators) {
+        impl.addTimeKeyframe(time, 1);
+        assertNotNull(impl.getKeyframe(SPPath.TIME, time));
+        assertValidInterpolators(SPPath.TIME, expectedNumberOfInterpolators);
+    }
+
+    private void removePosition(int time, int expectedNumberOfInterpolators) {
+        impl.removePositionKeyframe(time);
+        assertNull(impl.getKeyframe(SPPath.POSITION, time));
+        assertValidInterpolators(SPPath.POSITION, expectedNumberOfInterpolators);
+    }
+
+    private void removeTime(int time, int expectedNumberOfInterpolators) {
+        impl.removeTimeKeyframe(time);
+        assertNull(impl.getKeyframe(SPPath.TIME, time));
+        assertValidInterpolators(SPPath.TIME, expectedNumberOfInterpolators);
+    }
+
+    private void setInterpolator(int time, Interpolator interpolator, int expectedNumberOfInterpolators) {
+        impl.setInterpolator(time, interpolator);
+        assertValidInterpolators(SPPath.POSITION, expectedNumberOfInterpolators);
+    }
+
+    private void assertPositionState(String expected) {
+        assertEquals(expected, prettyPrintInterpolators(impl, SPPath.POSITION));
+    }
+
+    // Tracks only entity 42 which always is at x=time*2, y,z=0
+    private class EntityPositionTrackerMock extends EntityPositionTracker {
+        public EntityPositionTrackerMock() {
+            super(null);
+        }
+
+        @Override
+        public Location getEntityPositionAtTimestamp(int entityID, long timestamp) {
+            if (entityID == 42) {
+                return new Location(timestamp * 2, 0 ,0, 0, 0);
+            } else {
+                return null;
+            }
+        }
+    }
+
+    public static String prettyPrintInterpolators(SPTimeline timeline, SPPath spPath) {
+        return prettyPrintInterpolators(timeline, spPath, Collections.emptyMap());
+    }
+
+    public static String prettyPrintInterpolators(SPTimeline timeline, SPPath spPath, Map<PathSegment, Interpolator> updates) {
+        Map<Interpolator, String> interpolatorIdMap = new IdentityHashMap<>();
+        Path path = timeline.getPath(spPath);
+        StringBuilder sb = new StringBuilder();
+        for (Keyframe keyframe : path.getKeyframes()) {
+            if (spPath == SPPath.TIME) {
+                sb.append("[T ").append(keyframe.getTime()).append("]");
+            } else if (keyframe.getValue(SpectatorProperty.PROPERTY).isPresent()) {
+                sb.append("[S ").append(keyframe.getTime()).append("]");
+            } else {
+                sb.append("[P ").append(keyframe.getTime()).append("]");
+            }
+            path.getSegments().stream().filter(s -> s.getStartKeyframe() == keyframe).findFirst().ifPresent(segment -> {
+                Interpolator interpolator = updates.getOrDefault(segment, segment.getInterpolator());
+                String id = interpolatorIdMap.computeIfAbsent(interpolator, i ->
+                        (i instanceof LinearInterpolator ? "L" : "C") + interpolatorIdMap.size());
+                sb.append(' ').append(id).append(' ');
+            });
+        }
+        return sb.toString();
+    }
+}