// Undercooked — the event FX (phase 07, task 04).
//
// The wire's transient events (the snapshot's `e[]`, the standalone
// `ev`) become on-screen effects here: `chopped`'s spark, `cooked` /
// `ready`'s steam, `served`'s pop + the score float, `burnt`'s smoke,
// `denied`'s cross + the nudge, `stunned`'s spin, `order_missed`'s
// flash, `score`'s float, plus `washed` / `trashed` / `picked` /
// `handed_off`'s small marks.
//
// The renderer drains the event queue (`net/events.js`'s `due(now)`)
// each frame and hands the live entries to `consume`; `consume`
// spawns each entry's effect **once** — its own 100 ms dedup window
// (the same key the queue uses) suppresses the frames the same queued
// entry is repeated over, and a genuinely new event (more than the
// window later, or the queue's tick-reset cleared the old one) spawns
// again. The queue's TTL is the effect's lifetime source: a `served`
// lives 1200 ms, a `chopped` 800.
//
// **A small particle pool, no allocation per event.** `PARTICLES` is a
// fixed array of pre-built particle objects; `spawn` reuses them by a
// cursor (a full pool wraps and steals the oldest), and the one-shot
// effects (the sprite marks: the steam, the deny cross, the flash)
// live in a second fixed `MARKS` array the same way. Nothing is
// `new`-ed after `createFx` — a chop burst cannot grow the heap.
//
// `[data-motion="reduced"]` (or `prefers-reduced-motion`) is the
// fallback: the markers stay (the deny cross, the spin mark, the
// flash's border — the *static* versions), the particles do not
// launch, the nudge's shake never applies (`shakeApplied` stays 0),
// and nothing moves. `reduced()` reads the canvas's `data-motion`
// attribute first (the composition sets it from the `?motion=0`
// param, `docs/CLIENT.md` "The URL params"), then the media query.

import * as atlas from "./atlas.js";

const PARTICLE_COUNT = 96; // the pool size (a full burst wraps, never grows)
const MARK_COUNT = 24; // the one-shot effect slots
const DEDUP_WINDOW_MS = 100; // the queue's window — the same dedup rule

/**
 * The event → effect table. `sprite` is the atlas id of the one-shot
 * mark (the `reduced` fallback's static marker); `particle` the pool
 * particle's colour and shape (the non-reduced launch); `lifeMs` the
 * effect's own lifetime (within the queue kind's TTL).
 */
const EFFECTS = Object.freeze({
  chopped: { sprite: "fx-chop", particle: { color: "#ffd166" }, lifeMs: 500 },
  cooked: { sprite: "fx-steam", particle: { color: "#d9d4c8" }, lifeMs: 800 },
  ready: { sprite: "fx-steam", particle: { color: "#d9d4c8" }, lifeMs: 600 },
  washed: { sprite: "fx-steam", particle: { color: "#bfe3ff" }, lifeMs: 600 },
  served: { sprite: "fx-serve", particle: { color: "#ffe066" }, lifeMs: 1000 },
  burnt: { sprite: "fx-flame", particle: { color: "#8a8a8a" }, lifeMs: 900 },
  denied: { sprite: "fx-deny", particle: null, lifeMs: 600, nudge: true },
  stunned: { sprite: "fx-steam", particle: null, lifeMs: 800, spin: true },
  order_missed: { sprite: "fx-deny", particle: null, lifeMs: 1000, flash: true },
  score: { sprite: "fx-score", particle: { color: "#ffe066" }, lifeMs: 1000, float: true },
  trashed: { sprite: "fx-splash", particle: { color: "#9a8f7a" }, lifeMs: 500 },
  picked: { sprite: "fx-chop", particle: { color: "#d9d4c8" }, lifeMs: 350 },
  dropped: { sprite: "fx-splash", particle: { color: "#9a8f7a" }, lifeMs: 350 },
  handed_off: { sprite: "fx-score", particle: { color: "#d9d4c8" }, lifeMs: 350 },
  fire_started: { sprite: "fx-flame", particle: { color: "#ffa63d" }, lifeMs: 800 },
  ghost_on: { sprite: "ui-ghost", particle: null, lifeMs: 1200 },
  ghost_off: { sprite: "ui-ghost", particle: null, lifeMs: 800 },
});

function keyOf(entry) {
  const payload =
    entry.payload !== undefined && entry.payload !== null
      ? JSON.stringify(entry.payload, Object.keys(entry.payload).sort())
      : "";
  return `${entry.k}|${Math.round((entry.x ?? 0) * 100)}|${Math.round((entry.y ?? 0) * 100)}|${payload}`;
}

/**
 * One FX engine. `consume(entries, view, nowMs)` — the queued entries
 * (the queue's `due(now)`), the frame (for the nudge's player lookup),
 * the clock. `update(nowMs)` — advances the particle pool (a clamped
 * `dt`: a resume's jump cannot fling the particles). `draw(ctx,
 * toLocal, tile, nowMs)` — draws the live marks + particles (the
 * renderer's layer 9). `shakeOffset(playerId, nowMs)` — the nudge's
 * decaying offset in *tiles* (the renderer adds it to the player's
 * draw position). `stats()` — the census (the e2e's reduced-motion
 * seam: `processed`, `shakeApplied`, `particlesLaunched`).
 */
export function createFx({
  canvas = null,
  reduced = null,
  media = null,
} = {}) {
  const query =
    typeof media === "function"
      ? media
      : () =>
          typeof window !== "undefined" &&
          typeof window.matchMedia === "function"
            ? window.matchMedia("(prefers-reduced-motion: reduce)").matches
            : false;

  const particles = Array.from({ length: PARTICLE_COUNT }, () => ({
    active: false,
    x: 0,
    y: 0,
    vx: 0,
    vy: 0,
    born: 0,
    life: 0,
    color: "#ffffff",
    size: 1,
  }));
  let particleCursor = 0;
  const marks = Array.from({ length: MARK_COUNT }, () => ({
    active: false,
    x: 0,
    y: 0,
    born: 0,
    life: 0,
    sprite: "",
    text: "",
    color: "#ffffff",
    alpha: 1,
  }));
  let markCursor = 0;
  const seen = new Map(); // dedup key -> the last accepted spawn (nowMs)
  const shakes = new Map(); // player id -> { born, life } (the nudge's window)
  let lastNow = null;
  const stats = {
    processed: {},
    shakeApplied: 0,
    particlesLaunched: 0,
    deduped: 0,
  };

  /** The reduced-motion half: the `data-motion` attribute first, then
   * the media query (either one is enough). */
  function reducedMotion() {
    if (typeof reduced === "function") {
      const forced = reduced();
      if (forced !== null && forced !== undefined) {
        return Boolean(forced);
      }
    }
    if (canvas !== null && canvas.dataset !== null) {
      const attr = canvas.dataset.motion;
      if (attr === "reduced") return true;
    }
    return query();
  }

  function stealMark() {
    const slot = marks[markCursor];
    markCursor = (markCursor + 1) % MARK_COUNT;
    return slot;
  }

  function stealParticle() {
    const slot = particles[particleCursor];
    particleCursor = (particleCursor + 1) % PARTICLE_COUNT;
    return slot;
  }

  function launchParticles(x, y, color, nowMs, count) {
    for (let i = 0; i < count; i += 1) {
      const p = stealParticle();
      p.active = true;
      p.x = x;
      p.y = y;
      const angle = (i / count) * Math.PI * 2 + (nowMs % 100) * 0.01;
      p.vx = Math.cos(angle) * 0.6;
      p.vy = Math.sin(angle) * 0.6 - 0.4;
      p.born = nowMs;
      p.life = 500 + (i % 4) * 80;
      p.color = color;
      p.size = 0.08 + (i % 3) * 0.03;
      stats.particlesLaunched += 1;
    }
  }

  /**
   * One queued entry (its `k` is the event kind, `x`/`y` tile units,
   * `payload` the short-keyed map). Spawns the effect once; the 100 ms
   * window suppresses the same entry's repeat frames.
   */
  function consumeOne(entry, view, nowMs) {
    const spec = EFFECTS[entry.k];
    if (spec === undefined) return; // an unlisted kind (the queue's admission gate already skipped it)
    const key = keyOf(entry);
    const last = seen.get(key);
    if (last !== undefined && nowMs - last < DEDUP_WINDOW_MS) {
      stats.deduped += 1; // the echo: the effect already plays
      return;
    }
    seen.set(key, nowMs);
    stats.processed[entry.k] = (stats.processed[entry.k] ?? 0) + 1;
    const reducedNow = reducedMotion();

    if (spec.sprite !== "") {
      const mark = stealMark();
      mark.active = true;
      mark.x = entry.x ?? 0;
      mark.y = entry.y ?? 0;
      mark.born = nowMs;
      mark.life = spec.lifeMs;
      mark.sprite = spec.sprite;
      mark.alpha = 1;
      // The float text (the score's `+pts`, the served's `pts`).
      const pts =
        entry.payload !== null && entry.payload !== undefined
          ? entry.payload.pts
          : undefined;
      mark.text =
        spec.float && Number.isFinite(pts) ? `+${pts}` : "";
      mark.color = spec.particle !== null ? spec.particle.color : "#ffffff";
    }
    if (spec.particle !== null && !reducedNow) {
      launchParticles(entry.x ?? 0, entry.y ?? 0, spec.particle.color, nowMs, 5);
    }
    if (spec.nudge && view !== null && view !== undefined) {
      const pid =
        entry.payload !== null && entry.payload !== undefined
          ? entry.payload.i
          : undefined;
      if (pid !== undefined) {
        const existing = shakes.get(pid);
        if (existing === undefined || nowMs - existing.born > DEDUP_WINDOW_MS) {
          shakes.set(pid, { born: nowMs, life: 250 });
        }
      }
    }
  }

  /**
   * The queued entries (the queue's `due(now)` — a list; a single
   * entry is tolerated) — each is spawned once.
   */
  function consume(entries, view, nowMs) {
    const list = Array.isArray(entries) ? entries : [entries];
    for (const entry of list) consumeOne(entry, view, nowMs);
  }

  /** The queue's prune's mirror: drop the dedup keys and the nudge
   * windows past their lifetime (the queue's `drift` does its half). */
  function prune(nowMs) {
    for (const [key, at] of [...seen]) {
      if (nowMs - at >= DEDUP_WINDOW_MS) seen.delete(key);
    }
    for (const [pid, win] of [...shakes]) {
      if (nowMs - win.born >= win.life) shakes.delete(pid);
    }
  }

  function update(nowMs) {
    const dt =
      lastNow === null ? 0 : Math.min(100, Math.max(0, nowMs - lastNow));
    lastNow = nowMs;
    if (dt > 0) {
      const seconds = dt / 1000;
      for (const p of particles) {
        if (!p.active) continue;
        if (nowMs - p.born >= p.life) {
          p.active = false;
          continue;
        }
        p.x += p.vx * seconds;
        p.y += p.vy * seconds;
        p.vy += 1.4 * seconds; // the gravity (tiles/s²)
      }
    }
    prune(nowMs);
  }

  /**
   * The nudge's offset in tiles (the denied's push-back): a damped
   * 250 ms wobble along the event's arrival — zero when reduced motion
   * (the task's "no shake" half) or outside the window.
   */
  function shakeOffset(playerId, nowMs) {
    const win = shakes.get(playerId);
    if (win === undefined || reducedMotion() || nowMs - win.born >= win.life) {
      return null;
    }
    const t = (nowMs - win.born) / win.life; // 0..1
    const wobble = Math.sin(t * Math.PI * 3) * 0.06 * (1 - t);
    stats.shakeApplied += 1;
    return { dx: wobble, dy: -Math.abs(wobble) * 0.5 };
  }

  /** Draw the live marks + particles (the renderer's layer 9). */
  function draw(ctx, toLocal, tile, nowMs) {
    for (const mark of marks) {
      if (!mark.active) continue;
      const age = nowMs - mark.born;
      if (age >= mark.life) {
        mark.active = false;
        continue;
      }
      const [x, y] = toLocal(mark.x, mark.y);
      const alpha = 1 - age / mark.life;
      if (mark.sprite === "fx-flame" && mark.text === "" && mark.color === "#8a8a8a") {
        // The burnt's smoke: the flame sprite, grey, rising.
        ctx.save();
        ctx.globalAlpha = alpha * 0.55;
        ctx.translate(0, -age * 0.0012 * tile);
        // `fx-flame` is the art's only smoke-able symbol: greyed, it
        // reads as smoke.
        drawSprite(ctx, "fx-flame", x - tile * 0.2, y - tile * 0.6, tile * 0.55, tile * 0.7, { alpha: 1 });
        ctx.restore();
        continue;
      }
      drawSprite(ctx, mark.sprite, x - tile * 0.3, y - tile * 0.55, tile * 0.6, tile * 0.55, { alpha });
      if (mark.text !== "") {
        ctx.save();
        ctx.globalAlpha = alpha;
        ctx.fillStyle = "#ffe066";
        ctx.font = `bold ${Math.max(12, tile * 0.34)}px ui-sans-serif, system-ui, sans-serif`;
        ctx.textAlign = "center";
        ctx.fillText(mark.text, x, y - tile * 0.7 - age * 0.0015 * tile);
        ctx.restore();
      }
    }
    for (const p of particles) {
      if (!p.active) continue;
      const age = nowMs - p.born;
      if (age >= p.life) continue;
      const [x, y] = toLocal(p.x, p.y);
      ctx.save();
      ctx.globalAlpha = (1 - age / p.life) * 0.9;
      ctx.fillStyle = p.color;
      ctx.beginPath();
      ctx.arc(x, y - tile * 0.4, Math.max(1.5, p.size * tile), 0, Math.PI * 2);
      ctx.fill();
      ctx.restore();
    }
  }

  // The marks draw through the atlas directly; a throw (a missing
  // symbol) cannot blank the frame — the mark's slot just does not
  // draw this frame (the renderer's own sprite helper owns the
  // once-logged fallback for the *layer* sprites).
  function drawSprite(ctx, id, x, y, w, h, opts) {
    try {
      atlas.drawSync(ctx, id, x, y, w, h, opts);
    } catch {
      /* a missing symbol: the mark's slot stays, the frame goes on */
    }
  }

  return {
    consume,
    update,
    draw,
    shakeOffset,
    reduced: reducedMotion,
    stats: () => ({
      processed: { ...stats.processed },
      shakeApplied: stats.shakeApplied,
      particlesLaunched: stats.particlesLaunched,
      deduped: stats.deduped,
      activeParticles: particles.filter((p) => p.active).length,
    }),
  };
}