// Code adapted from https://github.com/macmcmeans/aleaPRNG

import { type PRNG } from "./types.js";

// 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
// Original work is under MIT license -

// Copyright (C) 2010 by Johannes Baagøe <baagoe@baagoe.org>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

function getMash() {
  let n = 0xefc8249d;

  return (data: string): number => {
    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
  };
}

type State = {
  c: number;
  s0: number;
  s1: number;
  s2: number;
};

function getInitialState(seed: string): State {
  const mash = getMash();

  // Apply the seeding algorithm from Baagoe.
  let s0 = mash(" ");
  let s1 = mash(" ");
  let s2 = mash(" ");
  s0 -= mash(seed);
  if (s0 < 0) {
    s0 += 1;
  }
  s1 -= mash(seed);
  if (s1 < 0) {
    s1 += 1;
  }
  s2 -= mash(seed);
  if (s2 < 0) {
    s2 += 1;
  }

  return { s0, s1, s2, c: 1 };
}

export function getAleaRng(seed?: string): PRNG {
  const state = getInitialState(seed ?? "undefined");

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