/* -*- Mode: js; js-indent-level: 2; -*- */
/*
 * Copyright 2011 Mozilla Foundation and contributors
 * Licensed under the New BSD license. See LICENSE or:
 * http://opensource.org/licenses/BSD-3-Clause
 */
if (typeof define !== 'function') {
    var define = require('amdefine')(module);
}
define(function (require, exports, module) {

  /**
   * A data structure which is a combination of an array and a set. Adding a new
   * member is O(1), testing for membership is O(1), and finding the index of an
   * element is O(1). Removing elements from the set is not supported. Only
   * strings are supported for membership.
   */
  function ArraySet() {
    this._array = [];
    this._set = {};
  }

  /**
   * Static method for creating ArraySet instances from an existing array.
   */
  ArraySet.fromArray = function ArraySet_fromArray(aArray) {
    var set = new ArraySet();
    for (var i = 0, len = aArray.length; i < len; i++) {
      set.add(aArray[i]);
    }
    return set;
  };

  /**
   * Because behavior goes wacky when you set `__proto__` on `this._set`, we
   * have to prefix all the strings in our set with an arbitrary character.
   *
   * See https://github.com/mozilla/source-map/pull/31 and
   * https://github.com/mozilla/source-map/issues/30
   *
   * @param String aStr
   */
  ArraySet.prototype._toSetString = function ArraySet__toSetString (aStr) {
    return "$" + aStr;
  };

  /**
   * Add the given string to this set.
   *
   * @param String aStr
   */
  ArraySet.prototype.add = function ArraySet_add(aStr) {
    if (this.has(aStr)) {
      // Already a member; nothing to do.
      return;
    }
    var idx = this._array.length;
    this._array.push(aStr);
    this._set[this._toSetString(aStr)] = idx;
  };

  /**
   * Is the given string a member of this set?
   *
   * @param String aStr
   */
  ArraySet.prototype.has = function ArraySet_has(aStr) {
    return Object.prototype.hasOwnProperty.call(this._set,
                                                this._toSetString(aStr));
  };

  /**
   * What is the index of the given string in the array?
   *
   * @param String aStr
   */
  ArraySet.prototype.indexOf = function ArraySet_indexOf(aStr) {
    if (this.has(aStr)) {
      return this._set[this._toSetString(aStr)];
    }
    throw new Error('"' + aStr + '" is not in the set.');
  };

  /**
   * What is the element at the given index?
   *
   * @param Number aIdx
   */
  ArraySet.prototype.at = function ArraySet_at(aIdx) {
    if (aIdx >= 0 && aIdx < this._array.length) {
      return this._array[aIdx];
    }
    throw new Error('No element indexed by ' + aIdx);
  };

  /**
   * Returns the array representation of this set (which has the proper indices
   * indicated by indexOf). Note that this is a copy of the internal array used
   * for storing the members so that no one can mess with internal state.
   */
  ArraySet.prototype.toArray = function ArraySet_toArray() {
    return this._array.slice();
  };

  exports.ArraySet = ArraySet;

});