/*!
 * lunr.SortedSet
 * Copyright (C) @YEAR Oliver Nightingale
 */

/**
 * lunr.SortedSets are used to maintain an array of uniq values in a sorted
 * order.
 *
 * @constructor
 */
lunr.SortedSet = function () {
  this.length = 0
  this.elements = []
}

/**
 * Loads a previously serialised sorted set.
 *
 * @param {Array} serialisedData The serialised set to load.
 * @returns {lunr.SortedSet}
 * @memberOf SortedSet
 */
lunr.SortedSet.load = function (serialisedData) {
  var set = new this

  set.elements = serialisedData
  set.length = serialisedData.length

  return set
}

/**
 * Inserts new items into the set in the correct position to maintain the
 * order.
 *
 * @param {Object} The objects to add to this set.
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.add = function () {
  var i, element

  for (i = 0; i < arguments.length; i++) {
    element = arguments[i]
    if (~this.indexOf(element)) continue
    this.elements.splice(this.locationFor(element), 0, element)
  }

  this.length = this.elements.length
}

/**
 * Converts this sorted set into an array.
 *
 * @returns {Array}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.toArray = function () {
  return this.elements.slice()
}

/**
 * Creates a new array with the results of calling a provided function on every
 * element in this sorted set.
 *
 * Delegates to Array.prototype.map and has the same signature.
 *
 * @param {Function} fn The function that is called on each element of the
 * set.
 * @param {Object} ctx An optional object that can be used as the context
 * for the function fn.
 * @returns {Array}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.map = function (fn, ctx) {
  return this.elements.map(fn, ctx)
}

/**
 * Executes a provided function once per sorted set element.
 *
 * Delegates to Array.prototype.forEach and has the same signature.
 *
 * @param {Function} fn The function that is called on each element of the
 * set.
 * @param {Object} ctx An optional object that can be used as the context
 * @memberOf SortedSet
 * for the function fn.
 */
lunr.SortedSet.prototype.forEach = function (fn, ctx) {
  return this.elements.forEach(fn, ctx)
}

/**
 * Returns the index at which a given element can be found in the
 * sorted set, or -1 if it is not present.
 *
 * @param {Object} elem The object to locate in the sorted set.
 * @returns {Number}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.indexOf = function (elem) {
  var start = 0,
      end = this.elements.length,
      sectionLength = end - start,
      pivot = start + Math.floor(sectionLength / 2),
      pivotElem = this.elements[pivot]

  while (sectionLength > 1) {
    if (pivotElem === elem) return pivot

    if (pivotElem < elem) start = pivot
    if (pivotElem > elem) end = pivot

    sectionLength = end - start
    pivot = start + Math.floor(sectionLength / 2)
    pivotElem = this.elements[pivot]
  }

  if (pivotElem === elem) return pivot

  return -1
}

/**
 * Returns the position within the sorted set that an element should be
 * inserted at to maintain the current order of the set.
 *
 * This function assumes that the element to search for does not already exist
 * in the sorted set.
 *
 * @param {Object} elem The elem to find the position for in the set
 * @returns {Number}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.locationFor = function (elem) {
  var start = 0,
      end = this.elements.length,
      sectionLength = end - start,
      pivot = start + Math.floor(sectionLength / 2),
      pivotElem = this.elements[pivot]

  while (sectionLength > 1) {
    if (pivotElem < elem) start = pivot
    if (pivotElem > elem) end = pivot

    sectionLength = end - start
    pivot = start + Math.floor(sectionLength / 2)
    pivotElem = this.elements[pivot]
  }

  if (pivotElem > elem) return pivot
  if (pivotElem < elem) return pivot + 1
}

/**
 * Creates a new lunr.SortedSet that contains the elements in the intersection
 * of this set and the passed set.
 *
 * @param {lunr.SortedSet} otherSet The set to intersect with this set.
 * @returns {lunr.SortedSet}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.intersect = function (otherSet) {
  var intersectSet = new lunr.SortedSet,
      i = 0, j = 0,
      a_len = this.length, b_len = otherSet.length,
      a = this.elements, b = otherSet.elements

  while (true) {
    if (i > a_len - 1 || j > b_len - 1) break

    if (a[i] === b[j]) {
      intersectSet.add(a[i])
      i++, j++
      continue
    }

    if (a[i] < b[j]) {
      i++
      continue
    }

    if (a[i] > b[j]) {
      j++
      continue
    }
  };

  return intersectSet
}

/**
 * Makes a copy of this set
 *
 * @returns {lunr.SortedSet}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.clone = function () {
  var clone = new lunr.SortedSet

  clone.elements = this.toArray()
  clone.length = clone.elements.length

  return clone
}

/**
 * Creates a new lunr.SortedSet that contains the elements in the union
 * of this set and the passed set.
 *
 * @param {lunr.SortedSet} otherSet The set to union with this set.
 * @returns {lunr.SortedSet}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.union = function (otherSet) {
  var longSet, shortSet, unionSet

  if (this.length >= otherSet.length) {
    longSet = this, shortSet = otherSet
  } else {
    longSet = otherSet, shortSet = this
  }

  unionSet = longSet.clone()

  unionSet.add.apply(unionSet, shortSet.toArray())

  return unionSet
}

/**
 * Returns a representation of the sorted set ready for serialisation.
 *
 * @returns {Array}
 * @memberOf SortedSet
 */
lunr.SortedSet.prototype.toJSON = function () {
  return this.toArray()
}
