slaguru666andClaude Opus 4.8
100e514c4d
Buildings (modern/fantasy, multi-floor, footprint shapes), caves, outdoor biomes, and town/village + city-block settlements. Auto-places Foundry walls, doors, windows, lighting; furniture as locked tiles; live preview. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
89 lines
2.3 KiB
JavaScript
89 lines
2.3 KiB
JavaScript
/**
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* Seeded pseudo-random number generation.
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*
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* Pure, dependency-free, and Foundry-agnostic so it can be unit-tested in Node.
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* Same seed string always produces the same map.
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*/
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/** Hash an arbitrary string into a 32-bit unsigned integer seed (xfnv1a). */
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export function hashSeed(input) {
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const str = String(input ?? "");
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let h = 2166136261 >>> 0;
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for (let i = 0; i < str.length; i += 1) {
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h ^= str.charCodeAt(i);
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h = Math.imul(h, 16777619);
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}
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// Final avalanche so similar strings diverge.
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h += h << 13; h ^= h >>> 7;
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h += h << 3; h ^= h >>> 17;
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h += h << 5;
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return h >>> 0;
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}
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/** mulberry32 — small, fast, good-enough PRNG. Returns a function -> float in [0,1). */
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export function mulberry32(seed) {
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let a = seed >>> 0;
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return function next() {
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a |= 0;
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a = (a + 0x6d2b79f5) | 0;
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let t = Math.imul(a ^ (a >>> 15), 1 | a);
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t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
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return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
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};
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}
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/**
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* Convenience wrapper around a raw float generator with the helpers a
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* generator actually needs.
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*/
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export class Rng {
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constructor(seed) {
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this._next = mulberry32(typeof seed === "number" ? seed : hashSeed(seed));
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}
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/** Float in [0, 1). */
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float() {
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return this._next();
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}
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/** Float in [min, max). */
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range(min, max) {
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return min + this._next() * (max - min);
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}
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/** Integer in [min, max] inclusive. */
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int(min, max) {
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return Math.floor(min + this._next() * (max - min + 1));
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}
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/** True with probability p (0..1). */
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chance(p) {
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return this._next() < p;
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}
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/** Pick a uniformly random element from a non-empty array. */
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pick(arr) {
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return arr[Math.floor(this._next() * arr.length)];
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}
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/** Pick by weight. items: [{weight, ...}] -> returns one item. */
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weighted(items) {
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const total = items.reduce((sum, it) => sum + (it.weight ?? 1), 0);
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let roll = this._next() * total;
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for (const it of items) {
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roll -= it.weight ?? 1;
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if (roll < 0) return it;
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}
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return items[items.length - 1];
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}
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/** In-place Fisher–Yates shuffle, returns the same array. */
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shuffle(arr) {
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for (let i = arr.length - 1; i > 0; i -= 1) {
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const j = Math.floor(this._next() * (i + 1));
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[arr[i], arr[j]] = [arr[j], arr[i]];
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}
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return arr;
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}
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}
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