define(['../lang/isObject', '../date/now'], function(isObject, now) {

  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
  var undefined;

  /** Used as the `TypeError` message for "Functions" methods. */
  var FUNC_ERROR_TEXT = 'Expected a function';

  /* Native method references for those with the same name as other `lodash` methods. */
  var nativeMax = Math.max;

  /**
   * Creates a debounced function that delays invoking `func` until after `wait`
   * milliseconds have elapsed since the last time the debounced function was
   * invoked. The debounced function comes with a `cancel` method to cancel
   * delayed invocations. Provide an options object to indicate that `func`
   * should be invoked on the leading and/or trailing edge of the `wait` timeout.
   * Subsequent calls to the debounced function return the result of the last
   * `func` invocation.
   *
   * **Note:** If `leading` and `trailing` options are `true`, `func` is invoked
   * on the trailing edge of the timeout only if the the debounced function is
   * invoked more than once during the `wait` timeout.
   *
   * See [David Corbacho's article](http://drupalmotion.com/article/debounce-and-throttle-visual-explanation)
   * for details over the differences between `_.debounce` and `_.throttle`.
   *
   * @static
   * @memberOf _
   * @category Function
   * @param {Function} func The function to debounce.
   * @param {number} [wait=0] The number of milliseconds to delay.
   * @param {Object} [options] The options object.
   * @param {boolean} [options.leading=false] Specify invoking on the leading
   *  edge of the timeout.
   * @param {number} [options.maxWait] The maximum time `func` is allowed to be
   *  delayed before it's invoked.
   * @param {boolean} [options.trailing=true] Specify invoking on the trailing
   *  edge of the timeout.
   * @returns {Function} Returns the new debounced function.
   * @example
   *
   * // avoid costly calculations while the window size is in flux
   * jQuery(window).on('resize', _.debounce(calculateLayout, 150));
   *
   * // invoke `sendMail` when the click event is fired, debouncing subsequent calls
   * jQuery('#postbox').on('click', _.debounce(sendMail, 300, {
   *   'leading': true,
   *   'trailing': false
   * }));
   *
   * // ensure `batchLog` is invoked once after 1 second of debounced calls
   * var source = new EventSource('/stream');
   * jQuery(source).on('message', _.debounce(batchLog, 250, {
   *   'maxWait': 1000
   * }));
   *
   * // cancel a debounced call
   * var todoChanges = _.debounce(batchLog, 1000);
   * Object.observe(models.todo, todoChanges);
   *
   * Object.observe(models, function(changes) {
   *   if (_.find(changes, { 'user': 'todo', 'type': 'delete'})) {
   *     todoChanges.cancel();
   *   }
   * }, ['delete']);
   *
   * // ...at some point `models.todo` is changed
   * models.todo.completed = true;
   *
   * // ...before 1 second has passed `models.todo` is deleted
   * // which cancels the debounced `todoChanges` call
   * delete models.todo;
   */
  function debounce(func, wait, options) {
    var args,
        maxTimeoutId,
        result,
        stamp,
        thisArg,
        timeoutId,
        trailingCall,
        lastCalled = 0,
        maxWait = false,
        trailing = true;

    if (typeof func != 'function') {
      throw new TypeError(FUNC_ERROR_TEXT);
    }
    wait = wait < 0 ? 0 : (+wait || 0);
    if (options === true) {
      var leading = true;
      trailing = false;
    } else if (isObject(options)) {
      leading = !!options.leading;
      maxWait = 'maxWait' in options && nativeMax(+options.maxWait || 0, wait);
      trailing = 'trailing' in options ? !!options.trailing : trailing;
    }

    function cancel() {
      if (timeoutId) {
        clearTimeout(timeoutId);
      }
      if (maxTimeoutId) {
        clearTimeout(maxTimeoutId);
      }
      lastCalled = 0;
      maxTimeoutId = timeoutId = trailingCall = undefined;
    }

    function complete(isCalled, id) {
      if (id) {
        clearTimeout(id);
      }
      maxTimeoutId = timeoutId = trailingCall = undefined;
      if (isCalled) {
        lastCalled = now();
        result = func.apply(thisArg, args);
        if (!timeoutId && !maxTimeoutId) {
          args = thisArg = undefined;
        }
      }
    }

    function delayed() {
      var remaining = wait - (now() - stamp);
      if (remaining <= 0 || remaining > wait) {
        complete(trailingCall, maxTimeoutId);
      } else {
        timeoutId = setTimeout(delayed, remaining);
      }
    }

    function maxDelayed() {
      complete(trailing, timeoutId);
    }

    function debounced() {
      args = arguments;
      stamp = now();
      thisArg = this;
      trailingCall = trailing && (timeoutId || !leading);

      if (maxWait === false) {
        var leadingCall = leading && !timeoutId;
      } else {
        if (!maxTimeoutId && !leading) {
          lastCalled = stamp;
        }
        var remaining = maxWait - (stamp - lastCalled),
            isCalled = remaining <= 0 || remaining > maxWait;

        if (isCalled) {
          if (maxTimeoutId) {
            maxTimeoutId = clearTimeout(maxTimeoutId);
          }
          lastCalled = stamp;
          result = func.apply(thisArg, args);
        }
        else if (!maxTimeoutId) {
          maxTimeoutId = setTimeout(maxDelayed, remaining);
        }
      }
      if (isCalled && timeoutId) {
        timeoutId = clearTimeout(timeoutId);
      }
      else if (!timeoutId && wait !== maxWait) {
        timeoutId = setTimeout(delayed, wait);
      }
      if (leadingCall) {
        isCalled = true;
        result = func.apply(thisArg, args);
      }
      if (isCalled && !timeoutId && !maxTimeoutId) {
        args = thisArg = undefined;
      }
      return result;
    }
    debounced.cancel = cancel;
    return debounced;
  }

  return debounce;
});