wongjiahau/ttap-web

function colorhash(seed: number) {
  return new (require("color-hash") as any)({
    // lightness: 0.75,
    // saturation: 0.5,
    hash: (x: string) => customHashFunction(x, seed),
  });
}

// Memoization to improve performance
const memo: { [key: string]: string } = {};
export function ColorHash(
  input: string,
  seed: number = 32,
  memoize = true
): string {
  // why the default seed is 32?
  // it is based on heuristics, a test is run to try numbers between 1 - 999
  // and the number 32 resulted in the least duplciated hashes
  // that's why the seed is defaulted to 32
  // refer seedThatResultedInTheLeastHashesDuplicates from _colorhash.test.ts
  const result = memo[input];
  if (memoize && result) {
    return result;
  } else {
    const temp = colorhash(seed).hex(input); // eslint-disable-line no-undef
    memo[input] = temp;
    return temp;
  }
}

export function customHashFunction(input: string, seed: number): number {
  const seed2 = 137;
  let hash = 0;
  // make hash more sensitive for short string like 'a', 'b', 'c'
  const str = input;
  for (let i = 0; i < str.length; i++) {
    if (hash > Number.MAX_SAFE_INTEGER) {
      hash = hash / seed2 + (hash % seed2);
    } else {
      hash = hash * seed + str.charCodeAt(i);
    }
  }
  return hash;
}