Add common pathing code and SimplePathing module

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

@@ -0,0 +1,62 @@
+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.path.Keyframe;
+import com.replaymod.pathing.path.Path;
+import com.replaymod.pathing.path.Timeline;
+import lombok.NonNull;
+
+/**
+ * Adds a new property.
+ */
+public final class AddKeyframe implements Change {
+    @NonNull
+    public static AddKeyframe create(Path path, long time) {
+        return new AddKeyframe(path.getTimeline().getPaths().indexOf(path), time);
+    }
+
+    AddKeyframe(int path, long time) {
+        this.path = path;
+        this.time = time;
+    }
+
+    /**
+     * Path index
+     */
+    private final int path;
+
+    /**
+     * Time at which the property should be injected.
+     */
+    private final long time;
+
+    /**
+     * Index of the newly created property.
+     */
+    private int index;
+
+    private boolean applied;
+
+    @Override
+    public void apply(Timeline timeline) {
+        Preconditions.checkState(!applied, "Already applied!");
+
+        Path path = timeline.getPaths().get(this.path);
+        Keyframe keyframe = path.insert(time);
+        index = Iterables.indexOf(path.getKeyframes(), Predicates.equalTo(keyframe));
+
+        applied = true;
+    }
+
+    @Override
+    public void undo(Timeline timeline) {
+        Preconditions.checkState(applied, "Not yet applied!");
+
+        Path path = timeline.getPaths().get(this.path);
+        path.remove(Iterables.get(path.getKeyframes(), index), true);
+
+        applied = false;
+    }
+}