// TURNCRAFT — Lane S (SIDE B). Dust bunnies: 4 fist-sized fluff-balls that
// drift around the under-table PCB floor (y≈3), flee when the player gets
// close, and settle again. Purely cosmetic — no colliders, no game effect.
//
// Consumes only core contracts (IVoxelWorld / IPlayerView / WORLD_DEFS) — the
// world + player views are injected by the integrator via
// `FxSystem.attachAmbience`. All per-tick math is scalar on preallocated
// per-bunny records: zero steady-state allocations. The only allocation a
// bunny ever causes after construction is the `machine:interact
// {action:'bunny_flee'}` payload, rate-limited to at most 1/s globally
// (Lane E2 maps it to a squeak).

import * as THREE from 'three';
import { bus } from '../core/events';
import { LAYOUT } from '../core/constants';
import { WORLD_DEFS, WORLD_KEYS } from '../core/worlds';
import type { IVoxelWorld, IPlayerView } from '../core/types';

// ── keep-out zones (bunnies never wander in; fleeing steers around) ─────────
// The three portal rings (WORLD_DEFS[k].portalStand ± 6) and the two quest
// spots in the fuse room. The parts-bin / fuse-box centres mirror the
// arithmetic in worldgen/anchors.ts (UNDER.partsBin / UNDER.fuseBox) the same
// way fx/layout.ts mirrors the VU towers — derived from LAYOUT, never imported
// (worldgen is another lane's directory).
interface Zone { x: number; z: number; r2: number; }
const M = LAYOUT.mixer;
const KEEP_OUT: Zone[] = [
  ...WORLD_KEYS.map((k) => {
    const s = WORLD_DEFS[k].portalStand;
    return { x: s[0] + 0.5, z: s[2] + 0.5, r2: 6 * 6 };
  }),
  { x: M.minX + 15.5, z: M.minZ + 10.5, r2: 6 * 6 }, // parts bin tray (stylus + fuse pickups)
  { x: M.minX + 24.5, z: M.maxZ - 7.5, r2: 6 * 6 },  // fuse box wall spot (reset ritual ground)
];

// Home points on the under-table floor: two in the record-crate area (where
// SIDE B pulls players), one in the mixer PCB room, one under deck A. Each
// bunny is leashed to its home so it stays findable.
const RIM = LAYOUT.rimThickness;
const HOMES: [number, number][] = [
  [RIM + 18, RIM + 9],                                   // crate floor, in front of the discs
  [WORLD_DEFS.disco.portalStand[0] + 8, RIM + 8],        // crate floor, gap past the last discs
  [(M.minX + M.maxX) / 2 + 6, (M.minZ + M.maxZ) / 2 + 8],// mixer PCB room
  [LAYOUT.deckA.spindleX, LAYOUT.deckA.spindleZ],        // deck A PCB room
];

const BUNNY_COUNT = 4;
const LEASH = 14;          // max wander radius from home (voxels)
const SPOOK_DIST2 = 5 * 5; // player within 5 → flee
const FLEE_DIST = 8;       // voxels of flight
const EMIT_COOLDOWN = 1.0; // machine:interact {bunny_flee} at most 1/s (global)

const enum Mode { Wander, Flee, Settle }

interface Bunny {
  mesh: THREE.Mesh;
  x: number; y: number; z: number;
  ground: number;          // y of the standing surface (top face) under the bunny
  heading: number;         // radians, horizontal
  speed: number;
  mode: Mode;
  timer: number;           // mode-specific countdown (wander re-aim / settle)
  fleeLeft: number;        // voxels of flight remaining
  phase: number;           // bob/breathe animation phase
  spin: number;            // idle tumble rate (rad/s)
  turnSign: number;        // alternate deflection direction on blocked moves
  homeX: number; homeZ: number;
}

/** One fluff-ball: 8–12 soft grey quads jittered into a ball, one draw call. */
function makeFluffGeometry(rng: () => number): THREE.BufferGeometry {
  const quads = 8 + Math.floor(rng() * 5); // 8..12
  const pos = new Float32Array(quads * 4 * 3);
  const col = new Float32Array(quads * 4 * 3);
  const uv = new Float32Array(quads * 4 * 2);
  const idx = new Uint16Array(quads * 6);
  const a = new THREE.Vector3(), b = new THREE.Vector3(), n = new THREE.Vector3();
  for (let q = 0; q < quads; q++) {
    // random centre inside the ball + random plane orientation
    const cx = (rng() * 2 - 1) * 0.34;
    const cy = (rng() * 2 - 1) * 0.26;
    const cz = (rng() * 2 - 1) * 0.34;
    n.set(rng() * 2 - 1, rng() * 2 - 1, rng() * 2 - 1).normalize();
    a.set(rng() * 2 - 1, rng() * 2 - 1, rng() * 2 - 1).cross(n).normalize();
    b.crossVectors(n, a);
    const s = 0.26 + rng() * 0.16; // quad half-size → puffs 0.5..0.85 across
    // dust tone (matches the `dust` block tint 120,116,110) with per-quad jitter
    const shade = 0.30 + rng() * 0.17;
    const r = shade * 1.02, g = shade * 0.99, bcol = shade * 0.94;
    for (let corner = 0; corner < 4; corner++) {
      const su = corner === 1 || corner === 2 ? s : -s;
      const sv = corner >= 2 ? s : -s;
      const i3 = (q * 4 + corner) * 3;
      pos[i3] = cx + a.x * su + b.x * sv;
      pos[i3 + 1] = cy + a.y * su + b.y * sv;
      pos[i3 + 2] = cz + a.z * su + b.z * sv;
      col[i3] = r; col[i3 + 1] = g; col[i3 + 2] = bcol;
      const i2 = (q * 4 + corner) * 2;
      uv[i2] = corner === 1 || corner === 2 ? 1 : 0;
      uv[i2 + 1] = corner >= 2 ? 1 : 0;
    }
    const v0 = q * 4, ii = q * 6;
    idx[ii] = v0; idx[ii + 1] = v0 + 1; idx[ii + 2] = v0 + 2;
    idx[ii + 3] = v0; idx[ii + 4] = v0 + 2; idx[ii + 5] = v0 + 3;
  }
  const geo = new THREE.BufferGeometry();
  geo.setAttribute('position', new THREE.BufferAttribute(pos, 3));
  geo.setAttribute('color', new THREE.BufferAttribute(col, 3));
  geo.setAttribute('uv', new THREE.BufferAttribute(uv, 2));
  geo.setIndex(new THREE.BufferAttribute(idx, 1));
  return geo;
}

export class DustBunnies {
  readonly group: THREE.Group;
  private world: IVoxelWorld;
  private player: IPlayerView;
  private bunnies: Bunny[] = [];
  private material: THREE.MeshBasicMaterial;
  private emitCooldown = 0;

  constructor(world: IVoxelWorld, player: IPlayerView, tex: THREE.Texture) {
    this.world = world;
    this.player = player;
    this.group = new THREE.Group();
    // soft round alpha from the shared glow canvas, normal blending so the
    // fluff reads as matte dust, not light
    this.material = new THREE.MeshBasicMaterial({
      map: tex, transparent: true, depthWrite: false,
      vertexColors: true, side: THREE.DoubleSide,
    });
    // deterministic-ish per-session fluff (visual only; Math.random is fine
    // for FX per CONTRACTS — worldgen determinism doesn't apply here)
    for (let i = 0; i < BUNNY_COUNT; i++) {
      const [hx, hz] = HOMES[i % HOMES.length];
      const mesh = new THREE.Mesh(makeFluffGeometry(Math.random), this.material);
      mesh.frustumCulled = true; // tiny sphere, fine to cull
      this.group.add(mesh);
      const bunny: Bunny = {
        mesh,
        x: hx + 0.5, y: 0, z: hz + 0.5,
        ground: 3,
        heading: Math.random() * Math.PI * 2,
        speed: 0.5,
        mode: Mode.Wander,
        timer: 1 + Math.random() * 3,
        fleeLeft: 0,
        phase: Math.random() * Math.PI * 2,
        spin: 0.5 + Math.random() * 0.7,
        turnSign: i & 1 ? 1 : -1,
        homeX: hx + 0.5, homeZ: hz + 0.5,
      };
      bunny.ground = this.groundTopAt(bunny.x, bunny.z);
      bunny.y = bunny.ground + 0.42;
      this.bunnies.push(bunny);
    }
  }

  /** Spawn-only: standing surface at a known-flat home point (top face of the
   *  highest floor block in the under-table band). */
  private groundTopAt(x: number, z: number): number {
    const xi = Math.floor(x), zi = Math.floor(z);
    for (let y = 5; y >= 0; y--) {
      if (this.world.isSolid(xi, y, zi)) return y + 1;
    }
    return 2; // world floor slab top (should not happen inside the booth)
  }

  /** Standing surface at (x,z) reachable from ground level `from` with at most
   *  a 1-voxel step: a valid surface g has solid under it and air at body
   *  level. Overhangs (e.g. the crate's edge-standing records) are NEVER
   *  ground — that's what keeps bunnies from climbing into geometry. Returns
   *  -1 when nothing within ±1 works (a wall or cliff). */
  private reachableGround(x: number, z: number, from: number): number {
    const xi = Math.floor(x), zi = Math.floor(z);
    // same level first, then step down, then step up
    if (this.world.isSolid(xi, from - 1, zi) && !this.world.isSolid(xi, from, zi)) return from;
    if (this.world.isSolid(xi, from - 2, zi) && !this.world.isSolid(xi, from - 1, zi)) return from - 1;
    if (this.world.isSolid(xi, from, zi) && !this.world.isSolid(xi, from + 1, zi)) return from + 1;
    return -1;
  }

  /** Can a bunny occupy (x,z) coming from ground level `from`? Checks walls
   *  (isSolid lookahead via reachableGround), keep-out zones and the
   *  under-table bounds. Pure scalar math, no allocation. */
  private passable(x: number, z: number, from: number): boolean {
    // hard bounds: stay inside the rim, under the table
    if (x < RIM + 2 || x > this.world.sizeX - RIM - 2) return false;
    if (z < RIM + 2 || z > LAYOUT.backWallZ - 2) return false;
    if (this.reachableGround(x, z, from) < 0) return false;
    for (let i = 0; i < KEEP_OUT.length; i++) {
      const zo = KEEP_OUT[i];
      const dx = x - zo.x, dz = z - zo.z;
      if (dx * dx + dz * dz < zo.r2) return false;
    }
    return true;
  }

  update(dt: number): void {
    if (this.emitCooldown > 0) this.emitCooldown -= dt;
    const pp = this.player.position;
    for (let i = 0; i < this.bunnies.length; i++) {
      this.step(this.bunnies[i], pp[0], pp[1], pp[2], dt);
    }
  }

  private step(b: Bunny, px: number, py: number, pz: number, dt: number): void {
    // escape hatch: if someone builds a block into a bunny, pop it on top
    const bxi = Math.floor(b.x), bzi = Math.floor(b.z);
    if (this.world.isSolid(bxi, b.ground, bzi)) {
      for (let g = b.ground + 1; g <= b.ground + 3; g++) {
        if (!this.world.isSolid(bxi, g, bzi)) { b.ground = g; break; }
      }
    }

    const dx = b.x - px, dz = b.z - pz;
    const d2 = dx * dx + dz * dz;
    const nearY = Math.abs(py - b.y) < 4; // only spooked by a player down here

    // ── spook / re-spook ──
    if (nearY && d2 < SPOOK_DIST2) {
      if (b.mode !== Mode.Flee) {
        b.mode = Mode.Flee;
        b.fleeLeft = FLEE_DIST;
        b.heading = Math.atan2(dz, dx); // straight away from the player
        if (this.emitCooldown <= 0) {
          this.emitCooldown = EMIT_COOLDOWN;
          bus.emit('machine:interact', { machineId: 'bunny', action: 'bunny_flee' });
        }
      } else if (b.fleeLeft < FLEE_DIST * 0.5) {
        b.fleeLeft = FLEE_DIST; // still being chased — keep running
      }
    }

    // ── move ──
    if (b.mode === Mode.Flee) {
      // ease out: fast off the mark, slowing as the 8 voxels run out
      const k = b.fleeLeft / FLEE_DIST;
      b.speed = 0.6 + 6.4 * Math.pow(k, 0.7);
      const stepLen = b.speed * dt;
      if (!this.tryMove(b, stepLen, true)) {
        // cornered — give up early and settle
        b.fleeLeft = 0;
      }
      b.fleeLeft -= stepLen;
      if (b.fleeLeft <= 0) {
        b.mode = Mode.Settle;
        b.timer = 0.8 + Math.random() * 0.8;
      }
    } else if (b.mode === Mode.Settle) {
      b.timer -= dt;
      b.speed = 0;
      if (b.timer <= 0) {
        b.mode = Mode.Wander;
        b.timer = 1 + Math.random() * 3;
      }
    } else {
      // wander: slow drift, heading random-walks; re-aim on a timer
      b.timer -= dt;
      if (b.timer <= 0) {
        b.timer = 2 + Math.random() * 4;
        b.heading = Math.random() * Math.PI * 2;
        b.speed = Math.random() < 0.25 ? 0 : 0.3 + Math.random() * 0.5; // sometimes just sit
      }
      b.heading += (Math.random() - 0.5) * 1.4 * dt;
      // leash: beyond it, ease the heading back toward home
      const hx = b.homeX - b.x, hz = b.homeZ - b.z;
      if (hx * hx + hz * hz > LEASH * LEASH) {
        const want = Math.atan2(hz, hx);
        let delta = want - b.heading;
        while (delta > Math.PI) delta -= Math.PI * 2;
        while (delta < -Math.PI) delta += Math.PI * 2;
        b.heading += delta * Math.min(1, 2.5 * dt);
      }
      if (b.speed > 0) this.tryMove(b, b.speed * dt, false);
    }

    // ── settle onto the floor + dress the mesh (no allocation) ──
    b.phase += dt * (b.mode === Mode.Flee ? 9 : 2.2);
    const bob = b.mode === Mode.Settle
      ? Math.sin(b.phase * 6) * 0.015                   // trembling
      : Math.sin(b.phase) * (b.mode === Mode.Flee ? 0.14 : 0.06);
    b.y = b.ground + 0.42 + Math.abs(bob);
    const m = b.mesh;
    m.position.set(b.x, b.y, b.z);
    m.rotation.y += dt * (b.mode === Mode.Flee ? 7 : b.spin);
    m.rotation.z = Math.sin(b.phase * 0.7) * 0.12;
    const breathe = 1 + Math.sin(b.phase * 1.3) * 0.05;
    m.scale.setScalar(breathe);
  }

  /** Advance along the heading with an isSolid lookahead; on a blocked cell,
   *  deflect (flee tries harder before giving up). Returns false if stuck. */
  private tryMove(b: Bunny, stepLen: number, fleeing: boolean): boolean {
    const look = Math.max(stepLen, 0.35); // look at least a third of a voxel ahead
    const tries = fleeing ? 5 : 2;
    for (let t = 0; t < tries; t++) {
      // deflections: 0, ±45°, ±90° (sign alternates per bunny for variety)
      const deflect = t === 0 ? 0 : b.turnSign * Math.ceil(t / 2) * (Math.PI / 4) * (t & 1 ? 1 : -1);
      const h = b.heading + deflect;
      const cx = Math.cos(h), cz = Math.sin(h);
      if (this.passable(b.x + cx * look, b.z + cz * look, b.ground)) {
        if (deflect !== 0) b.heading = h;
        b.x += cx * stepLen;
        b.z += cz * stepLen;
        // ride 1-voxel bumps (copper traces); keep last ground under overhangs
        const g = this.reachableGround(b.x, b.z, b.ground);
        if (g >= 0) b.ground = g;
        return true;
      }
    }
    // blocked: turn away for next tick
    b.turnSign = -b.turnSign;
    b.heading += b.turnSign * (Math.PI / 2 + Math.random() * (Math.PI / 2));
    return false;
  }

  dispose(): void {
    for (const b of this.bunnies) b.mesh.geometry.dispose();
    this.material.dispose();
    this.group.removeFromParent();
  }
}