import type { RandomGenerator } from "@tsplus/stdlib/io/Random/Generator/RandomGenerator"

/**
 * Uniformly generate an integer in the range [0, rangeSize].
 *
 * @internal
 */
export function uniformIntDistributionInternal(rangeSize: number, rng: RandomGenerator): number {
  const MinRng = rng.min()
  const NumValues = rng.max() - rng.min() + 1

  // Range provided by the RandomGenerator is large enough
  if (rangeSize <= NumValues) {
    const MaxAllowed = NumValues - (NumValues % rangeSize)
    // eslint-disable-next-line no-constant-condition
    while (true) {
      const out = rng.next()
      const deltaV = out - MinRng
      if (deltaV < MaxAllowed) {
        return deltaV % rangeSize // Warning: we expect NumValues <= 2**32, so diff too
      }
    }
  }

  // Compute number of iterations required to have enough random
  // to build uniform entries in the asked range
  let FinalNumValues = NumValues * NumValues
  let NumIterations = 2 // At least 2 (at this point in the code)
  while (FinalNumValues < rangeSize) {
    FinalNumValues *= NumValues
    ;++NumIterations
  }
  const MaxAcceptedRandom = rangeSize * Math.floor((1 * FinalNumValues) / rangeSize)

  // eslint-disable-next-line no-constant-condition
  while (true) {
    // Aggregate mutiple calls to next() into a single random value
    let value = 0
    for (let num = 0; num !== NumIterations; ++num) {
      const out = rng.next()
      value = NumValues * value + (out - MinRng) // Warning: we overflow may when diff > max_safe (eg: =max_safe-min_safe+1)
    }
    if (value < MaxAcceptedRandom) {
      const inDiff = value - rangeSize * Math.floor((1 * value) / rangeSize)
      return inDiff
    }
  }
}