const startPrice = 100;
const maxDailyPriceChange = 5;
const maxRangeDelta = 1;

function sfc32(a: number, b: number, c: number, d: number) {
  return function () {
    a >>>= 0;
    b >>>= 0;
    c >>>= 0;
    d >>>= 0;
    let t = (a + b) | 0;
    a = b ^ (b >>> 9);
    b = (c + (c << 3)) | 0;
    c = (c << 21) | (c >>> 11);
    d = (d + 1) | 0;
    t = (t + d) | 0;
    c = (c + t) | 0;
    return (t >>> 0) / 4294967296;
  };
}

function seedRandom(seed = 1337): () => number {
  const realSeed = seed ^ 0xdeadbeef; // 32-bit seed with optional XOR value
  // Pad seed with Phi, Pi and E.
  // https://en.wikipedia.org/wiki/Nothing-up-my-sleeve_number
  return sfc32(0x9e3779b9, 0x243f6a88, 0xb7e15162, realSeed);
}

export function getData(days: number) {
  let currentPrice = startPrice;
  const random = seedRandom();
  return Array.from({ length: days }, (_, i) => {
    // Note time is reversed
    const close = currentPrice;
    const open = close + (random() * 2 - 1) * maxDailyPriceChange;
    currentPrice = open;

    const high = Math.max(open, close) + random() * maxRangeDelta;
    const low = Math.min(open, close) - random() * maxRangeDelta;

    const timestamp = new Date(2024, 0, 0 /* End of 2023 */, -i);

    return { timestamp, open, close, high, low };
  }).reverse();
}