// A port of an algorithm by Johannes Baagøe <baagoe@baagoe.com>, 2010
// http://baagoe.com/en/RandomMusings/javascript/
// https://github.com/nquinlan/better-random-numbers-for-javascript-mirror

export interface AleaState {
   s0: number;
   s1: number;
   s2: number;
   c: number;
}

export function Mash() {
   let n = 0xefc8249d;

   const mash = function (data: string) {
      for (let i = 0; i < data.length; i++) {
         n += data.charCodeAt(i);
         let h = 0.02519603282416938 * n;
         n = h >>> 0;
         h -= n;
         h *= n;
         n = h >>> 0;
         h -= n;
         n += h * 0x100000000; // 2^32
      }
      return (n >>> 0) * 2.3283064365386963e-10; // 2^-32
   };

   return mash;
}

export class Alea {
   private mash: (data: string) => number = undefined as any;
   public s0: number = undefined as any;
   public s1: number = undefined as any;
   public s2: number = undefined as any;
   public c: number = undefined as any;

   constructor(seed: string) {
      this.setSeed(seed);
   }

   setSeed(seed: string) {
      this.mash = Mash();

      this.s0 = this.mash(" ");
      this.s1 = this.mash(" ");
      this.s2 = this.mash(" ");
      this.c = 1;

      this.s0 -= this.mash(seed);

      if (this.s0 < 0) {
         this.s0 += 1;
      }

      this.s1 -= this.mash(seed);

      if (this.s1 < 0) {
         this.s1 += 1;
      }

      this.s2 -= this.mash(seed);

      if (this.s2 < 0) {
         this.s2 += 1;
      }
   }

   next() {
      const t = 2091639 * this.s0 + this.c * 2.3283064365386963e-10; // 2^-32
      this.s0 = this.s1;
      this.s1 = this.s2;
      return (this.s2 = t - (this.c = t | 0));
   }
}

export class PRNG {
   readonly xg: Alea;

   constructor(seed: string) {
      this.xg = new Alea(seed);
   }

   setSeed(seed: string) {
      this.xg.setSeed(seed);
   }

   next() {
      return this.xg.next();
   }

   int32() {
      return (this.xg.next() * 0x100000000) | 0;
   }

   double() {
      return this.next() + ((this.next() * 0x200000) | 0) * 1.1102230246251565e-16;
   }
}