trainsim/track.ts

import { PathSegment } from "./math/path.ts";
import { Vector } from "doodler";
import { Train } from "./train.ts";

export class Track extends PathSegment {

  editable = false;

  next: Track;
  prev: Track;

  id: string;

  constructor(points: [Vector, Vector, Vector, Vector], next?: Track, prev?: Track) {
    super(points);
    this.id = crypto.randomUUID();
    this.next = next || this;
    this.prev = prev || this;
  }

  followTrack(train: Train): [Vector, number] {
    const predict = train.velocity.copy();
    predict.normalize();
    predict.mult(1);
    const predictpos = Vector.add(train.position, predict)

    // const leading = train.leadingPoint;
    // let closest = this.points[0];
    // let closestDistance = this.getClosestPoint(leading);
    let [closest, closestDistance, closestT] = this.getClosestPoint(predictpos);
    // deno-lint-ignore no-this-alias
    let mostValid: Track = this;

    if (this.next !== this) {
      const [point, distance, t] = this.next.getClosestPoint(predictpos);
      if (distance < closestDistance) {
        closest = point;
        closestDistance = distance;
        mostValid = this.next;
        closestT = t;
      }
    }
    if (this.prev !== this) {
      const [point, distance, t] = this.next.getClosestPoint(predictpos);
      if (distance < closestDistance) {
        closest = point;
        closestDistance = distance;
        mostValid = this.next;
        closestT = t;
      }
    }

    train.currentTrack = mostValid;
    train.arrive(closest);
    // if (predictpos.dist(closest) > 2) train.arrive(closest);
    return [closest, closestT];
  }

  getNearestPoint(p: Vector) {
    let [closest, closestDistance] = this.getClosestPoint(p);

    if (this.next !== this) {
      const [point, distance, t] = this.next.getClosestPoint(p);
      if (distance < closestDistance) {
        closest = point;
        closestDistance = distance;
      }
    }
    if (this.prev !== this) {
      const [point, distance, t] = this.next.getClosestPoint(p);
      if (distance < closestDistance) {
        closest = point;
        closestDistance = distance;
      }
    }

    return closest;
  }

  getAllPointsInRange(v: Vector, r: number) {
    const points: [number, PathSegment][] = this.getPointsWithinRadius(v, r).concat(this.next.getPointsWithinRadius(v, r), this.prev.getPointsWithinRadius(v, r))

    return points;
  }

  draw(): void {
    super.draw();
    if (this.editable)
      for (const e of this.points) {
        e.drawDot();
      }
  }

  setNext(t: Track) {
    this.next = t;
    this.next.points[0] = this.points[3];
  }

  setPrev(t: Track) {
    this.prev = t;
    this.prev.points[3] = this.points[0];
  }
}

export class Spline<T extends PathSegment = PathSegment> {
  segments: T[] = [];
  ctx?: CanvasRenderingContext2D;

  evenPoints: Vector[];
  constructor(segs: T[]) {
    this.segments = segs;
    this.evenPoints = this.calculateEvenlySpacedPoints(1);
  }

  setContext(ctx: CanvasRenderingContext2D) {
    this.ctx = ctx;
    for (const segment of this.segments) {
      segment.setContext(ctx);
    }
  }

  draw() {
    for (const segment of this.segments) {
      segment.draw();
    }
  }

  calculateEvenlySpacedPoints(spacing: number, resolution = 1) {
    // return this.segments.flatMap(s => s.calculateEvenlySpacedPoints(spacing, resolution));
    const points: Vector[] = []

    points.push(this.segments[0].points[0]);
    let prev = points[0];
    let distSinceLastEvenPoint = 0
    for (const seg of this.segments) {

      let t = 0;

      const div = Math.ceil(seg.length * resolution * 10);
      while (t < 1) {
        t += 1 / div;
        const point = seg.getPointAtT(t);
        distSinceLastEvenPoint += prev.dist(point);


        if (distSinceLastEvenPoint >= spacing) {
          const overshoot = distSinceLastEvenPoint - spacing;
          const evenPoint = Vector.add(point, Vector.sub(point, prev).normalize().mult(overshoot))
          distSinceLastEvenPoint = overshoot;
          points.push(evenPoint);
          prev = evenPoint;
        }

        prev = point
      }
    }

    return points;
  }

  followEvenPoints(t: number) {
    if (t < 0) t+= this.evenPoints.length
    const i = Math.floor(t);
    const a = this.evenPoints[i]
    const b = this.evenPoints[(i + 1) % this.evenPoints.length]

    try {
      return Vector.lerp(a, b, t % 1);

    } catch {
      console.log(t, i, a, b);
    }
  }
}

export const generateSquareTrack = () => {
  const first = new Track([new Vector(20, 40), new Vector(20, 100), new Vector(20, 300), new Vector(20, 360)]);

  const second = new Track([first.points[3], new Vector(20, 370), new Vector(30, 380), new Vector(40, 380)]);

  const third = new Track([second.points[3], new Vector(100, 380), new Vector(300, 380), new Vector(360, 380)]);

  const fourth = new Track([third.points[3], new Vector(370, 380), new Vector(380, 370), new Vector(380, 360)]);

  const fifth = new Track([fourth.points[3], new Vector(380, 300), new Vector(380, 100), new Vector(380, 40)]);

  const sixth = new Track([fifth.points[3], new Vector(380, 30), new Vector(370, 20), new Vector(360, 20)]);

  const seventh = new Track([sixth.points[3], new Vector(300, 20), new Vector(100, 20), new Vector(40, 20)]);

  const eighth = new Track([seventh.points[3], new Vector(30, 20), new Vector(20, 30), first.points[0]]);

  const tracks = [first, second, third, fourth, fifth, sixth, seventh, eighth];
  for (const [i, track] of tracks.entries()) {
    track.next = tracks[(i + 1) % tracks.length];
    track.prev = tracks.at(i - 1)!;
  }
  // first.next = second;
  // first.prev = eighth;
  // second.next = third;
  // second.prev = first;
  // third.

  return new Spline<Track>([first, second, third, fourth, fifth, sixth, seventh, eighth]);
}

export const loadFromJson = () => {
  const json = JSON.parse(localStorage.getItem('railPath') || '');
  if (!json) return generateSquareTrack();
  const segments: Track[] = [];

  for (const {points} of json.segments) {
    segments.push(new Track(points.map((p:{x:number,y:number}) => new Vector(p.x, p.y))));
  }

  for (const [i,s] of segments.entries()) {
    s.setNext(segments[(i+1)%segments.length])
    s.setPrev(segments.at(i-1)!)
  }

  return new Spline<Track>(segments);
}