class Rng

# Rng provides the random/Rng standard library API.
class Rng
  # Rng.state stores instance state.
  # @type Int
  state: 1

  # Rng.initialize provides the random/Rng standard library operation.
  # @param seed Any seed value.
  # @return Self the initialized object.
  initialize: seed ->
    self.state = 1
    if seed.class != Number or seed != seed
      raise error("random.Rng.seed: seed must be a number")
    self.state = seed.to_i() % 2147483647
    if self.state <= 0
      self.state = self.state + 2147483646

  # Rng.bool provides the random/Rng standard library operation.
  # @param probability Any probability value.
  # @return Any the resulting value.
  bool: probability ->
    if probability == nil
      probability = 0.5
    self.check_probability(probability)
    self.float() < probability

  # Rng.check_probability provides the random/Rng standard library operation.
  # @param probability Any probability value.
  # @return Any the resulting value.
  check_probability: probability ->
    if (
      probability.class != Number or probability != probability or probability < 0 or probability > 1
    )
      raise error("random.Rng.bool: probability must be between 0.0 and 1.0")

  # Rng.check_sample_count provides the random/Rng standard library operation.
  # @param items Array items value.
  # @param count Int count value.
  # @return Int the resulting value.
  check_sample_count: items, count ->
    if count.class != Number or count != count.to_i() or count != count
      raise error("random.Rng.sample: count must be an integer")
    if count < 0 or count > items.len()
      raise error("random.Rng.sample: count out of range")

  # Rng.choice provides the random/Rng standard library operation.
  # @param items Array items value.
  # @return Any the resulting value.
  choice: items ->
    n = items.len()
    if n == 0
      raise error("random.Rng.choice: empty array")
    items[self.int(0, n - 1)]

  # Rng.copy_array provides the random/Rng standard library operation.
  # @param items Array items value.
  # @return Array the resulting value.
  copy_array: items ->
    out = []
    i = 0
    while i < items.len()
      out.push(items[i])
      i = i + 1
    out

  # Rng.float provides the random/Rng standard library operation.
  # @return Any the resulting value.
  float: ->
    self.next_int() / 2147483647

  # Rng.int provides the random/Rng standard library operation.
  # @param min Any min value.
  # @param max Any max value.
  # @return Any the resulting value.
  int: min, max ->
    if (
      min.class != Number or max.class != Number or min != min.to_i() or max != max.to_i()
    )
      raise error("random.Rng.int: bounds must be integers")
    if max < min
      raise error("random.Rng.int: max < min")
    span = max - min + 1
    min + self.next_int() % span

  # Rng.new provides the random/Rng standard library operation.
  # @param seed Any seed value.
  # @return Self the resulting value.
  new: seed ->
    Rng(seed)

  # Rng.next_int provides the random/Rng standard library operation.
  # @return Any the resulting value.
  next_int: ->
    self.state = self.state * 48271 % 2147483647
    self.state

  # Rng.sample provides the random/Rng standard library operation.
  # @param items Array items value.
  # @param count Int count value.
  # @return Any the resulting value.
  sample: items, count ->
    self.check_sample_count(items, count)
    shuffled = self.shuffle_copy(items)
    out = []
    i = 0
    while i < count
      out.push(shuffled[i])
      i = i + 1
    out

  # Rng.seed provides the random/Rng standard library operation.
  # @param value String value value.
  # @return Any the resulting value.
  seed: value ->
    if value.class != Number or value != value
      raise error("random.Rng.seed: seed must be a number")
    self.state = value.to_i() % 2147483647
    if self.state <= 0
      self.state = self.state + 2147483646
    self

  # Rng.shuffle provides the random/Rng standard library operation.
  # @param items Array items value.
  # @return Any the resulting value.
  shuffle: items ->
    n = items.len()
    i = n - 1
    while i > 0
      j = self.int(0, i)
      tmp = items[i]
      items[i] = items[j]
      items[j] = tmp
      i = i - 1
    nil

  # Rng.shuffle_copy provides the random/Rng standard library operation.
  # @param items Array items value.
  # @return Any the resulting value.
  shuffle_copy: items ->
    copy = self.copy_array(items)
    self.shuffle(copy)
    copy

  # Rng.weight_total provides the random/Rng standard library operation.
  # @param weights Any weights value.
  # @param label Any label value.
  # @return Any the resulting value.
  weight_total: weights, label ->
    if weights.len() == 0
      raise error(label + ": empty weights")
    total = 0
    i = 0
    while i < weights.len()
      weight = weights[i]
      if weight.class != Number or weight != weight or weight < 0
        raise error(label + ": weights must be finite non-negative numbers")
      total = total + weight
      i = i + 1
    if total <= 0
      raise error(label + ": at least one weight must be positive")
    total

  # Rng.weighted_choice provides the random/Rng standard library operation.
  # @param items Array items value.
  # @param weights Any weights value.
  # @return Any the resulting value.
  weighted_choice: items, weights ->
    if items.len() != weights.len()
      raise error("random.Rng.weighted_choice: items and weights length mismatch")
    items[self.weighted_index(weights)]

  # Rng.weighted_index provides the random/Rng standard library operation.
  # @param weights Any weights value.
  # @return Int the resulting value.
  weighted_index: weights ->
    total = self.weight_total(weights, "random.Rng.weighted_index")
    pick = self.float() * total
    sum = 0
    i = 0
    while i < weights.len()
      sum = sum + weights[i]
      if pick < sum
        return i
      i = i + 1
    weights.len() - 1