Very rudimentary track editor... and headache spaghetti

track/system.ts

@@ -17,6 +17,15 @@ export class TrackSystem {
     return this.segments.values().next().value;
   }
 
+  get lastSegment() {
+    return this.segments.values().toArray().pop();
+  }
+
+  registerSegment(segment: TrackSegment) {
+    segment.setTrack(this);
+    this.segments.set(segment.id, segment);
+  }
+
   draw(showControls = false) {
     for (const segment of this.segments.values()) {
       segment.draw(showControls);
@@ -168,6 +177,54 @@ export class TrackSegment extends PathSegment {
     );
   }
 
+  propagate() {
+    const [_, __, p3, p4] = this.points;
+    const tangent = Vector.sub(p4, p3);
+    for (const fNeighbour of this.frontNeighbours) {
+      fNeighbour.receivePropagation(tangent);
+    }
+  }
+
+  lastHeading?: number;
+
+  receivePropagation(tangent: Vector) {
+    const [p1, p2, p3, p4] = this.points;
+    // const angle = tangent.heading() - (this.lastHeading ?? 0);
+    // this.lastHeading = tangent.heading();
+    // const newP2 = Vector.add(p1, tangent);
+    // const p2ToP3 = Vector.sub(p3, p2);
+    // p2ToP3.rotate(angle);
+    // p3.set(Vector.add(newP2, p2ToP3));
+    // const p2Top4 = Vector.sub(p4, p2);
+    // p2Top4.rotate(angle);
+    // p4.set(Vector.add(newP2, p2Top4));
+    // p2.set(newP2);
+    this.rotate(tangent);
+    this.propagate();
+  }
+
+  // TODO: this duplicates receivePropagation, but for some reason it doesn't work when called from receivePropagation
+  rotate(angle: number | Vector) {
+    const [p1, p2, p3, p4] = this.points;
+    let newP2;
+    if (angle instanceof Vector) {
+      const tan = angle;
+      angle = tan.heading() - (this.lastHeading ?? 0);
+      this.lastHeading = tan.heading();
+      newP2 = Vector.add(p1, tan);
+    } else {
+      const p1ToP2 = Vector.sub(p2, p1);
+      p1ToP2.rotate(angle);
+      newP2 = Vector.add(p1, p1ToP2);
+    }
+    const p2ToP3 = Vector.sub(p3, p2);
+    p2ToP3.rotate(angle);
+    p3.set(Vector.add(newP2, p2ToP3));
+    const p2Top4 = Vector.sub(p4, p2);
+    p2Top4.rotate(angle);
+    p4.set(Vector.add(newP2, p2Top4));
+    p2.set(newP2);
+  }
   static deserialize(data: any) {
     return new TrackSegment(
       data.p.map((p: [number, number, number]) => new Vector(p[0], p[1], p[2])),