import * as THREE from "three";

export const ROAD_WIDTH = 16;

export const trackCurve = new THREE.CatmullRomCurve3(
  [
    // מסלול אובלי קצר: שתי ישורות ושתי פניות רחבות בלבד.
    new THREE.Vector3(-58, 0, -48), // קו הזינוק באמצע הישורת
    new THREE.Vector3(-54, 0, -88),
    new THREE.Vector3(-32, 0, -112),
    new THREE.Vector3(0, 0, -116),
    new THREE.Vector3(32, 0, -112),
    new THREE.Vector3(54, 0, -88),
    new THREE.Vector3(58, 0, -48),
    new THREE.Vector3(58, 0, -12),
    new THREE.Vector3(32, 0, 12),
    new THREE.Vector3(0, 0, 18),
    new THREE.Vector3(-32, 0, 12),
    new THREE.Vector3(-58, 0, -12),
  ],
  true,
  "catmullrom",
  0.5,
);

const SAMPLES = 700;

export const trackSamples: { p: THREE.Vector3; t: number }[] = Array.from(
  { length: SAMPLES },
  (_, i) => {
    const t = i / SAMPLES;
    return { p: trackCurve.getPointAt(t), t };
  },
);

/** Nearest normalized position (0..1) along the track and distance from centerline. */
export function nearestOnTrack(pos: THREE.Vector3) {
  let best = 0;
  let bestDist = Infinity;
  for (const s of trackSamples) {
    const dx = s.p.x - pos.x;
    const dz = s.p.z - pos.z;
    const d = dx * dx + dz * dz;
    if (d < bestDist) {
      bestDist = d;
      best = s.t;
    }
  }
  return { t: best, distance: Math.sqrt(bestDist) };
}

/** Flat ribbon geometry following the curve. */
export function buildRoadGeometry(width = ROAD_WIDTH, segments = 700) {
  const positions: number[] = [];
  const uvs: number[] = [];
  const indices: number[] = [];
  const up = new THREE.Vector3(0, 1, 0);
  const side = new THREE.Vector3();

  for (let i = 0; i <= segments; i++) {
    const t = i / segments;
    const p = trackCurve.getPointAt(t % 1);
    const tan = trackCurve.getTangentAt(t % 1);
    side.crossVectors(tan, up).normalize().multiplyScalar(width / 2);
    positions.push(p.x - side.x, 0.02, p.z - side.z);
    positions.push(p.x + side.x, 0.02, p.z + side.z);
    uvs.push(0, t * 60, 1, t * 60);
    if (i < segments) {
      const a = i * 2;
      indices.push(a, a + 1, a + 2, a + 1, a + 3, a + 2);
    }
  }

  const geo = new THREE.BufferGeometry();
  geo.setAttribute("position", new THREE.Float32BufferAttribute(positions, 3));
  geo.setAttribute("uv", new THREE.Float32BufferAttribute(uvs, 2));
  geo.setIndex(indices);
  geo.computeVertexNormals();
  return geo;
}

/** Thin colored strip along one edge of the road (kerb). */
export function buildEdgeGeometry(offset: number, thickness = 0.9, segments = 700) {
  const positions: number[] = [];
  const indices: number[] = [];
  const up = new THREE.Vector3(0, 1, 0);
  const side = new THREE.Vector3();

  for (let i = 0; i <= segments; i++) {
    const t = i / segments;
    const p = trackCurve.getPointAt(t % 1);
    const tan = trackCurve.getTangentAt(t % 1);
    side.crossVectors(tan, up).normalize();
    const inner = offset - thickness / 2;
    const outer = offset + thickness / 2;
    positions.push(p.x + side.x * inner, 0.05, p.z + side.z * inner);
    positions.push(p.x + side.x * outer, 0.05, p.z + side.z * outer);
    if (i < segments) {
      const a = i * 2;
      indices.push(a, a + 1, a + 2, a + 1, a + 3, a + 2);
    }
  }

  const geo = new THREE.BufferGeometry();
  geo.setAttribute("position", new THREE.Float32BufferAttribute(positions, 3));
  geo.setIndex(indices);
  geo.computeVertexNormals();
  return geo;
}

export const startPoint = trackCurve.getPointAt(0);
export const startTangent = trackCurve.getTangentAt(0);
export const startHeading = Math.atan2(startTangent.x, startTangent.z);