class Queue

# Queue provides the collections/Queue standard library API.
class Queue
  # Queue.head stores the index of the next item to pop.
  # @type Int
  head: 0

  # Queue.items stores queued values.
  # @type Array
  items: []

  # Queue.initialize provides the collections/Queue standard library operation.
  # @param values Array values value.
  # @return Self the initialized object.
  initialize: values = nil ->
    if values == nil
      self.items = []
    else
      self.items = values.slice(0, values.len())
    self.head = 0

  # Queue.clear provides the collections/Queue standard library operation.
  # @return Nil the resulting value.
  clear: ->
    self.items = []
    self.head = 0
    self

  # Queue.compact provides the collections/Queue standard library operation.
  # @return Any the resulting value.
  compact: ->
    if self.head > 32 and self.head * 2 >= self.items.len()
      self.items = self.to_array()
      self.head = 0

  # Queue.empty? provides the collections/Queue standard library operation.
  # @return Boolean whether the condition is true.
  empty?: ->
    self.len() == 0

  # Queue.from_array provides the collections/Queue standard library operation.
  # @param values Array values value.
  # @return Array the resulting value.
  from_array: values ->
    Queue(values)

  # Queue.len provides the collections/Queue standard library operation.
  # @return Int the resulting value.
  len: ->
    self.items.len() - self.head

  # Queue.peek provides the collections/Queue standard library operation.
  # @return Any the resulting value.
  peek: ->
    if self.empty?()
      raise error("collections.Queue.peek: empty queue")
    self.items[self.head]

  # Queue.pop provides the collections/Queue standard library operation.
  # @return Any the resulting value.
  pop: ->
    if self.empty?()
      raise error("collections.Queue.pop: empty queue")
    value = self.items[self.head]
    self.head = self.head + 1
    self.compact()
    value

  # Queue.push provides the collections/Queue standard library operation.
  # @param value String value value.
  # @return Any the resulting value.
  push: value ->
    self.items.push(value)
    self

  # Queue.to_array provides the collections/Queue standard library operation.
  # @return Array the resulting value.
  to_array: ->
    out = []
    i = self.head
    while i < self.items.len()
      out.push(self.items[i])
      i = i + 1
    out