var isObject = require('./isObject'),

now = require('./now'),
toNumber = require('./toNumber');

/** Error message constants. */ var FUNC_ERROR_TEXT = 'Expected a function';

/* Built-in method references for those with the same name as other `lodash` methods. */ var nativeMax = Math.max,

nativeMin = Math.min;

/**

* 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 `func` invocations and a `flush` method to immediately invoke them.
* Provide `options` to indicate whether `func` should be invoked on the
* leading and/or trailing edge of the `wait` timeout. The `func` is invoked
* with the last arguments provided to the debounced function. 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 debounced function
* is invoked more than once during the `wait` timeout.
*
* If `wait` is `0` and `leading` is `false`, `func` invocation is deferred
* until to the next tick, similar to `setTimeout` with a timeout of `0`.
*
* See [David Corbacho's article](https://css-tricks.com/debouncing-throttling-explained-examples/)
* for details over the differences between `_.debounce` and `_.throttle`.
*
* @static
* @memberOf _
* @since 0.1.0
* @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 clicked, debouncing subsequent calls.
* jQuery(element).on('click', _.debounce(sendMail, 300, {
*   'leading': true,
*   'trailing': false
* }));
*
* // Ensure `batchLog` is invoked once after 1 second of debounced calls.
* var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
* var source = new EventSource('/stream');
* jQuery(source).on('message', debounced);
*
* // Cancel the trailing debounced invocation.
* jQuery(window).on('popstate', debounced.cancel);
*/

function debounce(func, wait, options) {

var lastArgs,
    lastThis,
    maxWait,
    result,
    timerId,
    lastCallTime,
    lastInvokeTime = 0,
    leading = false,
    maxing = false,
    trailing = true;

if (typeof func != 'function') {
  throw new TypeError(FUNC_ERROR_TEXT);
}
wait = toNumber(wait) || 0;
if (isObject(options)) {
  leading = !!options.leading;
  maxing = 'maxWait' in options;
  maxWait = maxing ? nativeMax(toNumber(options.maxWait) || 0, wait) : maxWait;
  trailing = 'trailing' in options ? !!options.trailing : trailing;
}

function invokeFunc(time) {
  var args = lastArgs,
      thisArg = lastThis;

  lastArgs = lastThis = undefined;
  lastInvokeTime = time;
  result = func.apply(thisArg, args);
  return result;
}

function leadingEdge(time) {
  // Reset any `maxWait` timer.
  lastInvokeTime = time;
  // Start the timer for the trailing edge.
  timerId = setTimeout(timerExpired, wait);
  // Invoke the leading edge.
  return leading ? invokeFunc(time) : result;
}

function remainingWait(time) {
  var timeSinceLastCall = time - lastCallTime,
      timeSinceLastInvoke = time - lastInvokeTime,
      timeWaiting = wait - timeSinceLastCall;

  return maxing
    ? nativeMin(timeWaiting, maxWait - timeSinceLastInvoke)
    : timeWaiting;
}

function shouldInvoke(time) {
  var timeSinceLastCall = time - lastCallTime,
      timeSinceLastInvoke = time - lastInvokeTime;

  // Either this is the first call, activity has stopped and we're at the
  // trailing edge, the system time has gone backwards and we're treating
  // it as the trailing edge, or we've hit the `maxWait` limit.
  return (lastCallTime === undefined || (timeSinceLastCall >= wait) ||
    (timeSinceLastCall < 0) || (maxing && timeSinceLastInvoke >= maxWait));
}

function timerExpired() {
  var time = now();
  if (shouldInvoke(time)) {
    return trailingEdge(time);
  }
  // Restart the timer.
  timerId = setTimeout(timerExpired, remainingWait(time));
}

function trailingEdge(time) {
  timerId = undefined;

  // Only invoke if we have `lastArgs` which means `func` has been
  // debounced at least once.
  if (trailing && lastArgs) {
    return invokeFunc(time);
  }
  lastArgs = lastThis = undefined;
  return result;
}

function cancel() {
  if (timerId !== undefined) {
    clearTimeout(timerId);
  }
  lastInvokeTime = 0;
  lastArgs = lastCallTime = lastThis = timerId = undefined;
}

function flush() {
  return timerId === undefined ? result : trailingEdge(now());
}

function debounced() {
  var time = now(),
      isInvoking = shouldInvoke(time);

  lastArgs = arguments;
  lastThis = this;
  lastCallTime = time;

  if (isInvoking) {
    if (timerId === undefined) {
      return leadingEdge(lastCallTime);
    }
    if (maxing) {
      // Handle invocations in a tight loop.
      clearTimeout(timerId);
      timerId = setTimeout(timerExpired, wait);
      return invokeFunc(lastCallTime);
    }
  }
  if (timerId === undefined) {
    timerId = setTimeout(timerExpired, wait);
  }
  return result;
}
debounced.cancel = cancel;
debounced.flush = flush;
return debounced;

}

module.exports = debounce;