/**
 * SHADES — boot, game loop, phase machine. Lane A owns this file.
 *
 * Nothing is auto-run on import: index.html calls boot(). That keeps createGame()
 * importable from selftest.html, which must never construct a WebGLRenderer.
 *
 * The loop is a fixed-dt accumulator. Sim modules only ever see FIXED_DT, never
 * a real frame delta — that is the whole reason selftest can fast-forward a 90 s
 * storm in a few milliseconds and get the same numbers the player got.
 */

import * as THREE from '../vendor/three.module.js';
import { FIXED_DT, PHASES, STORM_LEN, YARD, Emitter, createStubWind } from './contracts.js';
import { createWorld, heightAt } from './world.js';
import { createCameraRig } from './camera.js';

// ---------------------------------------------------------------------------
// Phase machine
// ---------------------------------------------------------------------------

/**
 * forecast → prep → storm → aftermath → forecast.
 * @returns {import('./contracts.js').Game}
 */
export function createGame() {
  const emitter = new Emitter();
  let phase = 'forecast';
  let phaseT = 0;

  return {
    get phase() { return phase; },
    /** Seconds since this phase began. The storm clock. */
    get phaseT() { return phaseT; },

    on(type, fn) { return emitter.on(type, fn); },

    /** @param {'forecast'|'prep'|'storm'|'aftermath'} next */
    setPhase(next) {
      if (!PHASES.includes(next)) throw new Error(`unknown phase '${next}'`);
      if (next === phase) return;
      const from = phase;
      phase = next;
      phaseT = 0;
      emitter.emit('phaseChange', { from, to: next });
    },

    /** Advance to the next phase in loop order. */
    advance() {
      this.setPhase(PHASES[(PHASES.indexOf(phase) + 1) % PHASES.length]);
    },

    tick(dt) {
      phaseT += dt;
      // The storm is on a timer; every other phase waits for the player.
      if (phase === 'storm' && phaseT >= STORM_LEN) this.setPhase('aftermath');
    },
  };
}

// ---------------------------------------------------------------------------
// M0 placeholder player
// ---------------------------------------------------------------------------

/**
 * A 1.7 m capsule that walks. This exists ONLY so the camera has something to
 * follow and the yard scale is legible before Lane D lands.
 *
 * Lane D: replace the call site in boot() with your player.js factory — the
 * shape you need to satisfy is `Player` in contracts.js ({pos, carrying, busy,
 * update}) — then delete this function. Everything else in this file already
 * talks to you through that contract, so nothing else should need to change.
 */
function createPlaceholderPlayer(scene, world, cameraRig) {
  const WALK = 2.2, RUN = 4.5;   // m/s

  const mesh = new THREE.Mesh(
    new THREE.CapsuleGeometry(0.28, 1.14, 4, 12),
    new THREE.MeshStandardMaterial({ color: 0xffd27a, roughness: 0.7 }),
  );
  mesh.name = 'player_placeholder';
  mesh.castShadow = true;
  scene.add(mesh);

  const keys = new Set();
  const onDown = (e) => {
    keys.add(e.key.toLowerCase());
    if ([' ', 'arrowup', 'arrowdown', 'arrowleft', 'arrowright'].includes(e.key.toLowerCase())) e.preventDefault();
  };
  const onUp = (e) => keys.delete(e.key.toLowerCase());
  addEventListener('keydown', onDown);
  addEventListener('keyup', onUp);

  const pos = new THREE.Vector3(0, heightAt(0, 6), 6);
  const move = new THREE.Vector3();
  const fwd = new THREE.Vector3();
  const right = new THREE.Vector3();
  let facing = 0;

  const hx = YARD.width / 2 - 0.5, hz = YARD.depth / 2 - 0.5;

  return {
    pos,
    carrying: null,
    busy: false,
    mesh,

    update(dt) {
      const yaw = cameraRig.yaw;
      // Camera-relative: forward is where the camera is looking, flattened.
      fwd.set(-Math.sin(yaw), 0, -Math.cos(yaw));
      right.set(Math.cos(yaw), 0, -Math.sin(yaw));

      move.set(0, 0, 0);
      if (keys.has('w') || keys.has('arrowup')) move.add(fwd);
      if (keys.has('s') || keys.has('arrowdown')) move.sub(fwd);
      if (keys.has('d') || keys.has('arrowright')) move.add(right);
      if (keys.has('a') || keys.has('arrowleft')) move.sub(right);

      if (move.lengthSq() > 0) {
        move.normalize().multiplyScalar((keys.has('shift') ? RUN : WALK) * dt);
        pos.x = Math.max(-hx, Math.min(hx, pos.x + move.x));
        pos.z = Math.max(-hz, Math.min(hz, pos.z + move.z));
        facing = Math.atan2(move.x, move.z);
      }
      pos.y = world.heightAt(pos.x, pos.z);

      mesh.position.set(pos.x, pos.y + 0.85, pos.z);   // capsule centre
      mesh.rotation.y = facing;
    },

    dispose() {
      removeEventListener('keydown', onDown);
      removeEventListener('keyup', onUp);
    },
  };
}

// ---------------------------------------------------------------------------
// Boot
// ---------------------------------------------------------------------------

/**
 * @param {object} [opts]
 * @param {HTMLCanvasElement} [opts.canvas]
 */
export function boot(opts = {}) {
  const canvas = opts.canvas ?? document.getElementById('c');

  const renderer = new THREE.WebGLRenderer({ canvas, antialias: true });
  renderer.setPixelRatio(Math.min(devicePixelRatio, 2));
  renderer.shadowMap.enabled = true;
  renderer.shadowMap.type = THREE.PCFSoftShadowMap;
  renderer.toneMapping = THREE.ACESFilmicToneMapping;
  renderer.toneMappingExposure = 1.0;

  const scene = new THREE.Scene();

  // Lane C: swap createStubWind() for your createWeather(). Everything that
  // moves reads this one object, so that swap is the whole integration.
  const wind = createStubWind({ calm: true });

  const world = createWorld(scene, { wind });
  const cameraRig = createCameraRig(canvas);
  cameraRig.setSolids(world.solids);
  cameraRig.setGround(world.heightAt);

  const player = createPlaceholderPlayer(scene, world, cameraRig);
  const game = createGame();

  // --- dev overlay (temporary — Lane A's hud.js replaces it after M0) ----
  const hud = document.getElementById('dev');
  const banner = document.getElementById('banner');
  game.on('phaseChange', ({ to }) => {
    if (banner) {
      banner.textContent = to.toUpperCase();
      banner.style.opacity = '1';
      setTimeout(() => { banner.style.opacity = '0'; }, 1400);
    }
  });
  addEventListener('keydown', (e) => {
    if (e.key === 'Enter') game.advance();
  });

  // --- resize ------------------------------------------------------------
  function resize() {
    const w = canvas.clientWidth || innerWidth;
    const h = canvas.clientHeight || innerHeight;
    renderer.setSize(w, h, false);
    cameraRig.resize(w, h);
  }
  addEventListener('resize', resize);
  resize();

  // --- loop --------------------------------------------------------------
  const clock = new THREE.Clock();
  let acc = 0;
  let simT = 0;
  let frames = 0, fpsT = 0, fps = 0;

  function step(dt, t) {
    game.tick(dt);
    world.update(dt, t);
    player.update(dt, t);
    // Lane B: sailRig.step(dt, wind, t) goes here.
    // Lane C: debris.step(dt, wind, t) goes here.
  }

  function frame() {
    // Clamped so a background tab or a breakpoint doesn't make the sim try to
    // catch up over thousands of steps and lock the page.
    const raw = Math.min(0.25, clock.getDelta());
    acc += raw;
    let guard = 0;
    while (acc >= FIXED_DT && guard++ < 60) {
      step(FIXED_DT, simT);
      simT += FIXED_DT;
      acc -= FIXED_DT;
    }

    cameraRig.update(raw, player.pos);
    renderer.render(scene, cameraRig.object);

    frames++; fpsT += raw;
    if (fpsT >= 0.5) { fps = frames / fpsT; frames = 0; fpsT = 0; }
    if (hud) {
      const w = wind.sample(player.pos, simT);
      hud.textContent =
        `${fps.toFixed(0)} fps | phase ${game.phase} ${game.phaseT.toFixed(1)}s | ` +
        `wind ${w.length().toFixed(1)} m/s | t ${simT.toFixed(1)}s`;
    }
    requestAnimationFrame(frame);
  }
  requestAnimationFrame(frame);

  // Handy for poking at the world from the console.
  const api = { renderer, scene, world, cameraRig, player, game, wind, get simT() { return simT; } };
  globalThis.SHADES = api;
  return api;
}