diablo2d/js/core/util.js

/* ============================================================
 * Diablo2D — util.js : math, RNG, misc helpers
 * ============================================================ */
'use strict';

window.D2 = window.D2 || {};
(function (D2) {

  const TAU = Math.PI * 2;
  const clamp = (v, a, b) => v < a ? a : (v > b ? b : v);
  const lerp = (a, b, t) => a + (b - a) * t;
  const smoothstep = (a, b, x) => { const t = clamp((x - a) / (b - a), 0, 1); return t * t * (3 - 2 * t); };
  const dist2 = (ax, ay, bx, by) => { const dx = ax - bx, dy = ay - by; return dx * dx + dy * dy; };
  const dist = (ax, ay, bx, by) => Math.sqrt(dist2(ax, ay, bx, by));
  const angleTo = (ax, ay, bx, by) => Math.atan2(by - ay, bx - ax);
  const wrapAngle = a => { while (a > Math.PI) a -= TAU; while (a < -Math.PI) a += TAU; return a; };
  const approachAngle = (cur, target, maxStep) => {
    let d = wrapAngle(target - cur);
    if (Math.abs(d) <= maxStep) return target;
    return cur + Math.sign(d) * maxStep;
  };
  const easeOutCubic = t => 1 - Math.pow(1 - t, 3);
  const easeInQuad = t => t * t;

  /* deterministic RNG */
  function mulberry32(seed) {
    let a = seed >>> 0;
    return function () {
      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;
    };
  }

  class RNG {
    constructor(seed) {
      this.seedFn = mulberry32(seed);
      this.seed = seed >>> 0;
    }
    next() { return this.seedFn(); }
    range(a, b) { return a + this.seedFn() * (b - a); }          // float [a,b)
    int(a, b) { return Math.floor(this.range(a, b + 1)); }        // int [a,b]
    chance(p) { return this.seedFn() < p; }
    pick(arr) { return arr[Math.floor(this.seedFn() * arr.length)]; }
    weighted(entries) {                                           // [{v,w}] or [[val,weight]]
      let total = 0;
      for (const e of entries) total += e.w !== undefined ? e.w : e[1];
      let roll = this.seedFn() * total;
      for (const e of entries) {
        roll -= e.w !== undefined ? e.w : e[1];
        if (roll <= 0) return e.v !== undefined ? e.v : e[0];
      }
      const last = entries[entries.length - 1];
      return last.v !== undefined ? last.v : last[0];
    }
    shuffle(arr) {
      for (let i = arr.length - 1; i > 0; i--) {
        const j = Math.floor(this.seedFn() * (i + 1));
        [arr[i], arr[j]] = [arr[j], arr[i]];
      }
      return arr;
    }
  }

  let _uid = 1;
  const uid = () => _uid++;

  function fmtNum(n) {
    n = Math.round(n);
    if (Math.abs(n) >= 1000000) return (n / 1000000).toFixed(1) + 'M';
    if (Math.abs(n) >= 10000) return (n / 1000).toFixed(1) + 'k';
    return String(n);
  }

  function roman(n) {
    if (n <= 0) return '0';
    const map = [[1000,'M'],[900,'CM'],[500,'D'],[400,'CD'],[100,'C'],[90,'XC'],[50,'L'],[40,'XL'],[10,'X'],[9,'IX'],[5,'V'],[4,'IV'],[1,'I']];
    let out = '';
    for (const [v, s] of map) while (n >= v) { out += s; n -= v; }
    return out;
  }

  function deepClone(o) { return JSON.parse(JSON.stringify(o)); }

  /* color helpers: '#rrggbb' <-> [r,g,b] */
  function hexToRgb(hex) {
    const h = hex.replace('#', '');
    return [parseInt(h.slice(0, 2), 16), parseInt(h.slice(2, 4), 16), parseInt(h.slice(4, 6), 16)];
  }
  function rgbToHex(r, g, b) {
    const c = v => clamp(Math.round(v), 0, 255).toString(16).padStart(2, '0');
    return '#' + c(r) + c(g) + c(b);
  }
  function lerpColor(c1, c2, t) {
    const a = typeof c1 === 'string' ? hexToRgb(c1) : c1;
    const b = typeof c2 === 'string' ? hexToRgb(c2) : c2;
    return rgbToHex(lerp(a[0], b[0], t), lerp(a[1], b[1], t), lerp(a[2], b[2], t));
  }
  function shade(hex, f) { // f<1 darken, f>1 lighten
    const [r, g, b] = hexToRgb(hex);
    return rgbToHex(r * f, g * f, b * f);
  }
  function rgba(hex, alpha) {
    const [r, g, b] = hexToRgb(hex);
    return `rgba(${r},${g},${b},${alpha})`;
  }

  /* simple event bus */
  class Bus {
    constructor() { this._l = new Map(); }
    on(evt, fn) {
      if (!this._l.has(evt)) this._l.set(evt, []);
      this._l.get(evt).push(fn);
    }
    off(evt, fn) {
      const l = this._l.get(evt);
      if (l) { const i = l.indexOf(fn); if (i >= 0) l.splice(i, 1); }
    }
    emit(evt, ...args) {
      const l = this._l.get(evt);
      if (l) for (const fn of [...l]) fn(...args);
    }
  }

  D2.util = {
    TAU, clamp, lerp, smoothstep, dist, dist2, angleTo, wrapAngle, approachAngle,
    easeOutCubic, easeInQuad,
    mulberry32, RNG, uid,
    fmtNum, roman, deepClone,
    hexToRgb, rgbToHex, lerpColor, shade, rgba,
    Bus,
  };
})(window.D2);