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'use strict'

// Hacked https://github.com/felixge/node-measured

// Based on http://en.wikipedia.org/wiki/Binary_Heap
// as well as http://eloquentjavascript.net/appendix2.html
module.exports = BinaryHeap
function BinaryHeap (options) {
  options = options || {}

  this._elements = options.elements || []
  this._score = options.score || this._score
}

BinaryHeap.prototype.add = function (/* elements */) {
  for (var i = 0; i < arguments.length; i++) {
    var element = arguments[i]

    this._elements.push(element)
    this._bubble(this._elements.length - 1)
  }
}

BinaryHeap.prototype.first = function () {
  return this._elements[0]
}

BinaryHeap.prototype.removeFirst = function () {
  var root = this._elements[0]
  var last = this._elements.pop()

  if (this._elements.length > 0) {
    this._elements[0] = last
    this._sink(0)
  }

  return root
}

BinaryHeap.prototype.clone = function () {
  return new BinaryHeap({
    elements: this.toArray(),
    score: this._score
  })
}

BinaryHeap.prototype.toSortedArray = function () {
  var array = []
  var clone = this.clone()

  while (true) {
    var element = clone.removeFirst()
    if (element === undefined) break

    array.push(element)
  }

  return array
}

BinaryHeap.prototype.toArray = function () {
  return [].concat(this._elements)
}

BinaryHeap.prototype.size = function () {
  return this._elements.length
}

BinaryHeap.prototype._bubble = function (bubbleIndex) {
  var bubbleElement = this._elements[bubbleIndex]
  var bubbleScore = this._score(bubbleElement)

  while (bubbleIndex > 0) {
    var parentIndex = this._parentIndex(bubbleIndex)
    var parentElement = this._elements[parentIndex]
    var parentScore = this._score(parentElement)

    if (bubbleScore <= parentScore) break

    this._elements[parentIndex] = bubbleElement
    this._elements[bubbleIndex] = parentElement
    bubbleIndex = parentIndex
  }
}

BinaryHeap.prototype._sink = function (sinkIndex) {
  var sinkElement = this._elements[sinkIndex]
  var sinkScore = this._score(sinkElement)
  var length = this._elements.length

  while (true) {
    var swapIndex = null
    var swapScore = null
    var swapElement = null
    var childIndexes = this._childIndexes(sinkIndex)

    for (var i = 0; i < childIndexes.length; i++) {
      var childIndex = childIndexes[i]

      if (childIndex >= length) break

      var childElement = this._elements[childIndex]
      var childScore = this._score(childElement)

      if (childScore > sinkScore) {
        if (swapScore === null || swapScore < childScore) {
          swapIndex = childIndex
          swapScore = childScore
          swapElement = childElement
        }
      }
    }

    if (swapIndex === null) break

    this._elements[swapIndex] = sinkElement
    this._elements[sinkIndex] = swapElement
    sinkIndex = swapIndex
  }
}

BinaryHeap.prototype._parentIndex = function (index) {
  return Math.floor((index - 1) / 2)
}

BinaryHeap.prototype._childIndexes = function (index) {
  return [
    2 * index + 1,
    2 * index + 2
  ]
}

BinaryHeap.prototype._score = function (element) {
  return element.valueOf()
}