Gradient generator

gradient.ts

type GradientGenerator = {
  generate: (seed: string) => string
}

const colors = ['c051e9', '578ce6', '8cacf5', 'd8fb9f']

// Simple PRNG using Mulberry32 algorithm
function mulberry32(seed: number) {
  return function () {
    let temp = (seed += 0x6d2b79f5)
    temp = Math.imul(temp ^ (temp >>> 15), temp | 1)
    temp ^= temp + Math.imul(temp ^ (temp >>> 7), temp | 61)
    return ((temp ^ (temp >>> 14)) >>> 0) / 4294967296
  }
}
const GradientGenerator: GradientGenerator = {
  generate(seed: string) {
    // Convert seed string to seed number
    let seedNumber = 0
    for (let i = 0; i < seed.length; i++) {
      seedNumber += seed.charCodeAt(i)
    }

    const rng = mulberry32(seedNumber)
    const gradients = []
    const numGradients = Math.floor(rng() * 9) + 2

    for (let i = 0; i < numGradients; i++) {
      const x = Math.floor(rng() * 201) - 50
      const y = Math.floor(rng() * 201) - 50
      const start = Math.floor(rng() * 101)
      const end = start + Math.floor(rng() * (101 - start))
      const color = colors[Math.floor(rng() * colors.length)]
      gradients.push(
        `radial-gradient(at ${x}% ${y}%, #${color} ${start}%, transparent ${end}%)`
      )
    }

    return gradients.join()
  },
}

console.log(`
Usage looks like this in a css style:
backgroundImage: GradientGenerator.generate(id || ''),
backgroundImage: ${GradientGenerator.generate('meow')}
`)