/**
 * binary companion star — a distant "other star" wandering slowly.
 *
 * Content layer (two world-space sprites: a bright core + a soft halo),
 * NOT a filter: Canvas-safe and immune to the HUD. It sits FAR away
 * (very low parallax ~0.08, so it barely moves as you fly — a distant
 * light source) and drifts along a slow elliptical arc, seeded per system
 * so each binary's companion wanders its own way. Both sprites use
 * additive blend — it is a source of light, so it glows, never occludes.
 * Depth 3 keeps it behind the art (planets 5, ship 10).
 *
 * Config: data/systems.json → types.binary.effect.wanderer.
 */
import Phaser from '../vendor/phaser.js';
import { canvasTexture } from '../utils/Textures.js';
import { toColor } from '../utils/Color.js';

const DEPTH = 3; // behind the art, in front of the starfield

/** A tight, bright core — the star's body. White (tint gives the color). */
function drawCore(ctx, size) {
  const c = size / 2;
  const g = ctx.createRadialGradient(c, c, 0, c, c, c);
  g.addColorStop(0.0, 'rgba(255,255,255,1.0)');
  g.addColorStop(0.5, 'rgba(255,255,255,0.9)');
  g.addColorStop(1.0, 'rgba(255,255,255,0.0)');
  ctx.fillStyle = g;
  ctx.fillRect(0, 0, size, size);
}

/** A wide, soft halo — the star's corona. White (tint gives the color). */
function drawHalo(ctx, size) {
  const c = size / 2;
  const g = ctx.createRadialGradient(c, c, 0, c, c, c);
  g.addColorStop(0.0, 'rgba(255,255,255,0.55)');
  g.addColorStop(0.4, 'rgba(255,255,255,0.28)');
  g.addColorStop(1.0, 'rgba(255,255,255,0.0)');
  ctx.fillStyle = g;
  ctx.fillRect(0, 0, size, size);
}

/**
 * The companion star (core + halo) wandering a slow seeded arc.
 *
 * @param {object} scene Phaser scene
 * @param {string} color star color (CSS hex)
 * @param {object} cfg data/systems.json → effect.wanderer
 * @param {{phase?:number, angle?:number, drift?:number}} fx per-system seeded 0..1 variation
 */
export class WandererStar {
  constructor(scene, color, cfg, fx = {}) {
    this.scene = scene;
    this.color = toColor(color, 0x9fd0ff);
    this.cfg = cfg ?? {};
    this.fx = fx ?? {};
    this.core = null;
    this.halo = null;
    this.tSec = 0;
  }

  /** Build the core + halo (idempotent). */
  create() {
    const scene = this.scene;
    if (this.core) return;
    const {
      coreSize = [40, 70],
      haloSize = [120, 200],
      parallax = 0.08,
      speed = [3, 8],
    } = this.cfg;

    const coreKey = canvasTexture(scene, 'fx-wanderer-core', 64, 64, (ctx) => drawCore(ctx, 64));
    const haloKey = canvasTexture(scene, 'fx-wanderer-halo', 128, 128, (ctx) => drawHalo(ctx, 128));

    // Seeded starting point (upper third of the view — a star in the sky)
    // and a slow elliptical arc (the "wander").
    const fx = this.fx;
    const phase = fx.phase ?? 0.5;
    const angle = fx.angle ?? 0.5;
    const drift = fx.drift ?? 0.5;
    const w = scene.scale.width;
    const h = scene.scale.height;
    const baseX = w * (0.2 + 0.6 * phase);
    const baseY = h * (0.15 + 0.3 * angle);
    const ampX = w * (0.05 + 0.12 * drift);
    const ampY = h * (0.04 + 0.10 * drift);
    const omega = ((speed[0] + (speed[1] - speed[0]) * drift) / w) * Math.PI * 2; // rad/s (slow)

    this.core = scene.add
      .image(baseX, baseY, coreKey)
      .setDepth(DEPTH)
      .setTint(this.color)
      .setAlpha(0.95)
      .setBlendMode(Phaser.BlendModes.ADD);
    const cs = coreSize[0] + (coreSize[1] - coreSize[0]) * drift;
    this.core.setScale(cs / 64);

    this.halo = scene.add
      .image(baseX, baseY, haloKey)
      .setDepth(DEPTH)
      .setTint(this.color)
      .setAlpha(0.8)
      .setBlendMode(Phaser.BlendModes.ADD);
    const hs = haloSize[0] + (haloSize[1] - haloSize[0]) * drift;
    this.halo.setScale(hs / 128);

    this.baseX = baseX;
    this.baseY = baseY;
    this.ampX = ampX;
    this.ampY = ampY;
    this.omega = omega;
    this.phase0 = angle * Math.PI * 2;
    this.p = parallax;
  }

  /** Per-frame: slow elliptical wander + camera parallax. */
  update(nowMs, dtMs) {
    if (!this.core) return;
    this.tSec += (dtMs || 0) / 1000;
    const t = this.tSec;
    const a = this.omega * t + this.phase0;
    let x = this.baseX + this.ampX * Math.cos(a);
    let y = this.baseY + this.ampY * Math.sin(a);
    // very low parallax (distant): shifts a little as the camera flies
    const cam = this.scene.cameras.main;
    const camX = cam?.worldView?.x ?? 0;
    const camY = cam?.worldView?.y ?? 0;
    x += (camX - this.scene.scale.width / 2) * this.p;
    y += (camY - this.scene.scale.height / 2) * this.p;
    this.core.setPosition(x, y);
    this.halo.setPosition(x, y);
  }

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