orbit/js/combat/Fx.js

import Phaser from '../vendor/phaser.js';
import { toColor } from '../utils/Color.js';
import { canvasTexture } from '../utils/Textures.js';

const DOT_KEY = '__combat_dot';
const DOT_SIZE = 64;

function drawSoftDot(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(0.22, 'rgba(255,255,255,0.85)');
  g.addColorStop(0.55, 'rgba(255,255,255,0.26)');
  g.addColorStop(1.0, 'rgba(255,255,255,0.0)');
  ctx.fillStyle = g;
  ctx.fillRect(0, 0, size, size);
}

/**
 * Small hand-rolled FX for the combat range: muzzle flashes, hit glows,
 * spark streams, and the ship-kill burst. Plain additive images stepped
 * in update() — deliberately NOT the particles emitter (this build's
 * emitter velocity semantics are fiddly, see the note in
 * js/visuals/EngineFlare.js), so the look is deterministic, cheap, and
 * needs no tween stepping.
 *
 * All items are world-space (the arena camera is fixed), depths 19–21
 * (above ships (10), under the HUD (100)).
 */
export class Fx {
  /** @param {object} scene the combat scene */
  constructor(scene) {
    this.scene = scene;
    this.items = []; // { img, t0, life, kind, ... }
    Fx.ensureDot(scene);
  }

  /** The shared white soft dot (tint reads as its color). @returns {string} the key */
  static ensureDot(scene) {
    if (scene.textures.exists(DOT_KEY)) return DOT_KEY;
    canvasTexture(scene, DOT_KEY, DOT_SIZE, DOT_SIZE, (ctx, w, h) => drawSoftDot(ctx, Math.min(w, h)));
    return DOT_KEY;
  }

  /** An additive glow: `size` px across at full strength, fading over `life` ms. */
  flash(x, y, color, size = 40, life = 220) {
    const img = this.scene
      .add.image(x, y, DOT_KEY)
      .setTint(toColor(color, 0xffffff))
      .setBlendMode(Phaser.BlendModes.ADD)
      .setDepth(20);
    this.items.push({ img, t0: 0, life, kind: 'flash', grow: size / DOT_SIZE });
    return img;
  }

  /** A growing, fading disc — the shockwave read (a stand-in for a stroke ring). */
  ring(x, y, color, size = 180, life = 450) {
    const img = this.scene
      .add.image(x, y, DOT_KEY)
      .setTint(toColor(color, 0xffffff))
      .setBlendMode(Phaser.BlendModes.ADD)
      .setDepth(19)
      .setScale(6 / DOT_SIZE)
      .setAlpha(0.8);
    this.items.push({ img, t0: 0, life, kind: 'ring', from: 6 / DOT_SIZE, to: size / DOT_SIZE });
    return img;
  }

  /** A burst of sparks (small dots on random headings, decaying). */
  sparks(x, y, color, count = 12, speed = 220, life = 500) {
    for (let i = 0; i < count; i++) {
      const a = Math.random() * Math.PI * 2;
      const sp = speed * (0.4 + Math.random() * 0.8);
      const s = 4 + Math.random() * 5;
      const img = this.scene
        .add.image(x, y, DOT_KEY)
        .setTint(toColor(color, 0xffffff))
        .setBlendMode(Phaser.BlendModes.ADD)
        .setDepth(21)
        .setScale(s / DOT_SIZE);
      this.items.push({
        img,
        t0: 0,
        life: life * (0.6 + Math.random() * 0.6),
        kind: 'spark',
        vx: Math.cos(a) * sp,
        vy: Math.sin(a) * sp,
      });
    }
  }

  /** The big one — a ship's death: core flash + colored bloom + wave + sparks. */
  explode(x, y, color) {
    this.flash(x, y, 0xffffff, 90, 160);
    this.flash(x, y, color, 150, 420);
    this.ring(x, y, color, 200, 480);
    this.sparks(x, y, color, 22, 300, 700);
  }

  /** Step every live item (ms). Dead ones are destroyed. */
  update(deltaMs) {
    const dt = deltaMs / 1000;
    for (let i = this.items.length - 1; i >= 0; i--) {
      const it = this.items[i];
      it.t0 += deltaMs;
      const t = Math.min(1, it.t0 / it.life);
      if (t >= 1) {
        it.img.destroy();
        this.items.splice(i, 1);
        continue;
      }
      if (it.kind === 'flash') {
        it.img.setScale(it.grow * (0.6 + 0.4 * t));
        it.img.setAlpha(1 - t);
      } else if (it.kind === 'ring') {
        it.img.setScale(it.from + (it.to - it.from) * t);
        it.img.setAlpha(0.8 * (1 - t));
      } else if (it.kind === 'spark') {
        it.img.x += it.vx * dt;
        it.img.y += it.vy * dt;
        const decay = Math.max(0, 1 - 2.2 * dt);
        it.vx *= decay;
        it.vy *= decay;
        it.img.setAlpha(1 - t);
      }
    }
  }

  /** Drop everything (a range reset). */
  clear() {
    for (const it of this.items) it.img.destroy();
    this.items.length = 0;
  }
}