/**
 * redDwarf "red haze" — a thin, gritty red cast over the DARKNESS of space
 * behind the stars.
 *
 * The darkness is the renderer's background (config backgroundColor), which
 * a camera filter does NOT reach (the clear color bypasses the composite).
 * So this is a CONTENT layer, not a filter: one large, canvas-generated
 * gritty red-haze texture drawn at depth -1 (BEHIND the starfield's 0–2),
 * recentered on the camera each frame so it always fills the view. The
 * white stars and all the art sit in front and stay bright — only the void
 * turns a dusty red.
 *
 * The texture (generated once, seeded per system) is: a dark warm-red base
 * + a few large soft blotches (the "haze") + fine per-pixel grain (the
 * "grit"). It is a plain sprite, so it is Canvas-safe and can never touch
 * the HUD (it is world-space, behind everything, independent of the UI split).
 *
 * Config: data/systems.json → types.redDwarf.effect.haze.
 */
import Phaser from '../vendor/phaser.js';
import { canvasTexture } from '../utils/Textures.js';
import { hexToRgb01 } from './SystemEffectsMath.js';

const DEPTH = -1; // behind the starfield (0–2) — the very back
const MARGIN = 320; // the haze extends this far past the viewport (covers drift)

/** A seeded 32-bit PRNG (mulberry32) so a system's haze is stable per run. */
function makeRng(seedNum) {
  let a = (seedNum >>> 0) || 0x9e3779b9;
  return () => {
    a |= 0; a = (a + 0x6d2b79f5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

/**
 * Paint one haze tile (SIZE×SIZE): dark base + soft blotches + fine grain.
 * All from the config; deterministic under `rng`.
 */
function paintHaze(ctx, size, cfg, rng) {
  const [br, bg, bb] = hexToRgb01(cfg.base ?? '#160b09');
  const [tr, tg, tb] = hexToRgb01(cfg.tint ?? '#c0392b');
  const to255 = (v) => Math.max(0, Math.min(255, Math.round(v * 255)));

  // 1. dark warm-red base (this IS the "darkness", so it reads as space).
  ctx.fillStyle = `rgb(${to255(br)}, ${to255(bg)}, ${to255(bb)})`;
  ctx.fillRect(0, 0, size, size);

  // 2. soft atmospheric blotches — the "haze" (large, low-contrast).
  const blobs = Math.max(3, Math.round(cfg.blobs ?? 9));
  const [sMin, sMax] = Array.isArray(cfg.scale) ? cfg.scale : [0.18, 0.42];
  for (let i = 0; i < blobs; i++) {
    const x = rng() * size;
    const y = rng() * size;
    const r = size * (sMin + (sMax - sMin) * rng());
    const warm = 0.55 + 0.45 * rng();
    const a = 0.10 + 0.16 * rng();
    const g = ctx.createRadialGradient(x, y, 0, x, y, r);
    g.addColorStop(0, `rgba(${to255(tr * warm)}, ${to255(tg * warm)}, ${to255(tb * warm)}, ${a.toFixed(3)})`);
    g.addColorStop(1, 'rgba(0,0,0,0)');
    ctx.fillStyle = g;
    ctx.fillRect(0, 0, size, size);
  }

  // 3. fine grain — the "grit" (per-pixel, warm-biased).
  const amp = Math.max(0, cfg.grain ?? 20);
  if (amp > 0) {
    const img = ctx.getImageData(0, 0, size, size);
    const d = img.data;
    for (let i = 0; i < d.length; i += 4) {
      const n = (rng() - 0.5) * 2 * amp;
      d[i] = Math.max(0, Math.min(255, d[i] + n));
      d[i + 1] = Math.max(0, Math.min(255, d[i + 1] + n * 0.62));
      d[i + 2] = Math.max(0, Math.min(255, d[i + 2] + n * 0.46));
    }
    ctx.putImageData(img, 0, 0);
  }
}

/**
 * The red-haze layer (a single full-screen sprite behind the stars).
 *
 * @param {object} scene Phaser scene (add / camera / scale / textures)
 * @param {object} cfg data/systems.json → effect.haze
 * @param {{phase?:number, angle?:number, drift?:number}} fx per-system seeded 0..1 variation
 */
export class RedHaze {
  constructor(scene, cfg, fx = {}) {
    this.scene = scene;
    this.cfg = cfg ?? {};
    this.fx = fx ?? {};
    this.sp = null;
    this.tSec = 0;
  }

  /** Build the texture + sprite (idempotent). */
  create() {
    const scene = this.scene;
    if (this.sp) return;
    const SIZE = 1024;
    // Fixed seed: the haze is a shared, subtle background, so it is
    // consistent across systems and runs (the texture is cached by key).
    const texKey = canvasTexture(scene, 'fx-redhaze', SIZE, SIZE, (ctx) => {
      paintHaze(ctx, SIZE, this.cfg, makeRng(0x51ab1234));
    });
    const w = scene.scale.width;
    const h = scene.scale.height;
    const cam = scene.cameras.main;
    // One large sprite, viewport + margin, centered on the camera.
    this.sp = scene.add
      .image(cam.scrollX + w / 2, cam.scrollY + h / 2, texKey)
      .setDepth(DEPTH)
      .setAlpha(this.cfg.alpha ?? 0.9)
      .setScale((w + 2 * MARGIN) / SIZE, (h + 2 * MARGIN) / SIZE);
  }

  /** Per-frame: keep the haze centered on the camera (with a slow drift). */
  update(nowMs, dtMs) {
    if (!this.sp) return;
    this.tSec += (dtMs || 0) / 1000;
    const cam = this.scene.cameras.main;
    const w = this.scene.scale.width;
    const h = this.scene.scale.height;
    const t = this.tSec;
    // A very slow drift so the haze feels alive (amplitude < MARGIN, so it
    // always still covers the view).
    const dx = Math.sin(t * 0.05 + this.fx.phase * 6.28) * 120;
    const dy = Math.cos(t * 0.04 + this.fx.drift * 6.28) * 120;
    this.sp.x = cam.scrollX + w / 2 + dx;
    this.sp.y = cam.scrollY + h / 2 + dy;
  }

  /** Tear down. */
  destroy() {
    this.sp?.destroy();
    this.sp = null;
  }
}