Add common pathing code and SimplePathing module

src/main/java/com/replaymod/pathing/change/RemoveKeyframe.java

@@ -0,0 +1,67 @@
+package com.replaymod.pathing.change;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+import com.replaymod.pathing.interpolation.Interpolator;
+import com.replaymod.pathing.path.Keyframe;
+import com.replaymod.pathing.path.Path;
+import com.replaymod.pathing.path.Timeline;
+import lombok.NonNull;
+
+/**
+ * Removes a property.
+ */
+public final class RemoveKeyframe implements Change {
+    @NonNull
+    public static RemoveKeyframe create(@NonNull Path path, @NonNull Keyframe keyframe) {
+        return new RemoveKeyframe(path.getTimeline().getPaths().indexOf(path),
+                Iterables.indexOf(path.getKeyframes(), Predicates.equalTo(keyframe)));
+    }
+
+    RemoveKeyframe(int path, int index) {
+        this.path = path;
+        this.index = index;
+    }
+
+    /**
+     * Path index
+     */
+    private final int path;
+
+    /**
+     * Index of the property to be removed.
+     */
+    private final int index;
+
+    private volatile Keyframe removedKeyframe;
+    private volatile Interpolator removedInterpolator;
+
+    private boolean applied;
+
+    @Override
+    public void apply(Timeline timeline) {
+        Preconditions.checkState(!applied, "Already applied!");
+
+        Path path = timeline.getPaths().get(this.path);
+        if (index < path.getSegments().size()) {
+            removedInterpolator = Iterables.get(path.getSegments(), index).getInterpolator();
+        }
+        path.remove(removedKeyframe = Iterables.get(path.getKeyframes(), index), true);
+
+        applied = true;
+    }
+
+    @Override
+    public void undo(Timeline timeline) {
+        Preconditions.checkState(applied, "Not yet applied!");
+
+        Path path = timeline.getPaths().get(this.path);
+        path.insert(removedKeyframe);
+        if (removedInterpolator != null) {
+            Iterables.get(path.getSegments(), index).setInterpolator(removedInterpolator);
+        }
+
+        applied = false;
+    }
+}