// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// Javascript preamble, that lets the output of dart2js run on V8's d8 shell.

var setTimeout;
var clearTimeout;
var setInterval;
var clearInterval;
var dartMainRunner;
var scheduleImmediate;

(function() {
  // Event loop.

  // Task queue as cyclic list queue.
  var taskQueue = new Array(8);  // Length is power of 2.
  var head = 0;
  var tail = 0;
  var mask = taskQueue.length - 1;
  function addTask(elem) {
    taskQueue[head] = elem;
    head = (head + 1) & mask;
    if (head == tail) _growTaskQueue();
  }
  function removeTask() {
    if (head == tail) return;
    var result = taskQueue[tail];
    taskQueue[tail] = undefined;
    tail = (tail + 1) & mask;
    return result;
  }
  function _growTaskQueue() {
    // head == tail.
    var length = taskQueue.length;
    var split = head;
    taskQueue.length = length * 2;
    if (split * 2 < length) {  // split < length / 2
      for (var i = 0; i < split; i++) {
        taskQueue[length + i] = taskQueue[i];
        taskQueue[i] = undefined;
      }
      head += length;
    } else {
      for (var i = split; i < length; i++) {
        taskQueue[length + i] = taskQueue[i];
        taskQueue[i] = undefined;
      }
      tail += length;
    }
    mask = taskQueue.length - 1;
  }

  // Mapping from timer id to timer function.
  // The timer id is written on the function as .$timerId.
  // That field is cleared when the timer is cancelled, but it is not returned
  // from the queue until its time comes.
  var timerIds = {};
  var timerIdCounter = 1;  // Counter used to assing ids.

  // Zero-timer queue as simple array queue using push/shift.
  var zeroTimerQueue = [];

  function addTimer(f, ms) {
    var id = timerIdCounter++;
    f.$timerId = id;
    timerIds[id] = f;
    if (ms == 0) {
      zeroTimerQueue.push(f);
    } else {
      addDelayedTimer(f, ms);
    }
    return id;
  }

  function nextZeroTimer() {
    while (zeroTimerQueue.length > 0) {
      var action = zeroTimerQueue.shift();
      if (action.$timerId !== undefined) return action;
    }
  }

  function nextEvent() {
    var action = removeTask();
    if (action) {
      return action;
    }
    do {
      action = nextZeroTimer();
      if (action) break;
      var nextList = nextDelayedTimerQueue();
      if (!nextList) {
        return;
      }
      var newTime = nextList.shift();
      advanceTimeTo(newTime);
      zeroTimerQueue = nextList;
    } while (true)
    var id = action.$timerId;
    clearTimerId(action, id);
    return action;
  }

  // Mocking time.
  var timeOffset = 0;
  var now = function() {
    // Install the mock Date object only once.
    // Following calls to "now" will just use the new (mocked) Date.now
    // method directly.
    installMockDate();
    now = Date.now;
    return Date.now();
  };
  var originalDate = Date;
  var originalNow = originalDate.now;
  function advanceTimeTo(time) {
    timeOffset = time - originalNow();
  }
  function installMockDate() {
    var NewDate = function Date(Y, M, D, h, m, s, ms) {
      if (this instanceof Date) {
        // Assume a construct call.
        switch (arguments.length) {
          case 0:  return new originalDate(originalNow() + timeOffset);
          case 1:  return new originalDate(Y);
          case 2:  return new originalDate(Y, M);
          case 3:  return new originalDate(Y, M, D);
          case 4:  return new originalDate(Y, M, D, h);
          case 5:  return new originalDate(Y, M, D, h, m);
          case 6:  return new originalDate(Y, M, D, h, m, s);
          default: return new originalDate(Y, M, D, h, m, s, ms);
        }
      }
      return new originalDate(originalNow() + timeOffset).toString();
    };
    NewDate.UTC = originalDate.UTC;
    NewDate.parse = originalDate.parse;
    NewDate.now = function now() { return originalNow() + timeOffset; };
    NewDate.prototype = originalDate.prototype;
    originalDate.prototype.constructor = NewDate;
    Date = NewDate;
  }

  // Heap priority queue with key index.
  // Each entry is list of [timeout, callback1 ... callbackn].
  var timerHeap = [];
  var timerIndex = {};
  function addDelayedTimer(f, ms) {
    var timeout = now() + ms;
    var timerList = timerIndex[timeout];
    if (timerList == null) {
      timerList = [timeout, f];
      timerIndex[timeout] = timerList;
      var index = timerHeap.length;
      timerHeap.length += 1;
      bubbleUp(index, timeout, timerList);
    } else {
      timerList.push(f);
    }
  }

  function nextDelayedTimerQueue() {
    if (timerHeap.length == 0) return null;
    var result = timerHeap[0];
    var last = timerHeap.pop();
    if (timerHeap.length > 0) {
      bubbleDown(0, last[0], last);
    }
    return result;
  }

  function bubbleUp(index, key, value) {
    while (index != 0) {
      var parentIndex = (index - 1) >> 1;
      var parent = timerHeap[parentIndex];
      var parentKey = parent[0];
      if (key > parentKey) break;
      timerHeap[index] = parent;
      index = parentIndex;
    }
    timerHeap[index] = value;
  }

  function bubbleDown(index, key, value) {
    while (true) {
      var leftChildIndex = index * 2 + 1;
      if (leftChildIndex >= timerHeap.length) break;
      var minChildIndex = leftChildIndex;
      var minChild = timerHeap[leftChildIndex];
      var minChildKey = minChild[0];
      var rightChildIndex = leftChildIndex + 1;
      if (rightChildIndex < timerHeap.length) {
        var rightChild = timerHeap[rightChildIndex];
        var rightKey = rightChild[0];
        if (rightKey < minChildKey) {
          minChildIndex = rightChildIndex;
          minChild = rightChild;
          minChildKey = rightKey;
        }
      }
      if (minChildKey > key) break;
      timerHeap[index] = minChild;
      index = minChildIndex;
    }
    timerHeap[index] = value;
  }

  function addInterval(f, ms) {
    var id = timerIdCounter++;
    function repeat() {
      // Reactivate with the same id.
      repeat.$timerId = id;
      timerIds[id] = repeat;
      addDelayedTimer(repeat, ms);
      f();
    }
    repeat.$timerId = id;
    timerIds[id] = repeat;
    addDelayedTimer(repeat, ms);
    return id;
  }

  function cancelTimer(id) {
    var f = timerIds[id];
    if (f == null) return;
    clearTimerId(f, id);
  }

  function clearTimerId(f, id) {
    f.$timerId = undefined;
    delete timerIds[id];
  }

  function eventLoop(action) {
    while (action) {
      try {
        action();
      } catch (e) {
        if (typeof onerror == "function") {
          onerror(e, null, -1);
        } else {
          throw e;
        }
      }
      action = nextEvent();
    }
  }

  dartMainRunner = function(main, args) {
    // Initialize.
    var action = function() { main(args); }
    eventLoop(action);
  };
  setTimeout = addTimer;
  clearTimeout = cancelTimer;
  setInterval = addInterval;
  clearInterval = cancelTimer;
  scheduleImmediate = addTask;
})();