Lewerow/Zurvan

'use strict';
var TypeChecks = require('./utils/TypeChecks');
var TimeUnit = require('../TimeUnit');
var assert = require('assert');

function delayByCycling(schedule, cycleCount, f) {
  var cyclesExecuted = 0;
  (function cycle(f) {
    if (++cyclesExecuted < cycleCount) {
      schedule(cycle, f);
    } else {
      f();
    }
  })(f);
}

function TimeForwarder(
  timeServer,
  timerInterceptor,
  immediateInterceptor,
  debugLogger
) {
  this.forwardingStartedSavedStack = undefined;
  this.timerInterceptor = timerInterceptor;
  this.timeServer = timeServer;
  this.immediateInterceptor = immediateInterceptor;
  this.debugLogger = debugLogger;
}

TimeForwarder.prototype.prepareTimeReport = function() {
  var currentTime = this.timeServer.currentTime.toMilliseconds();
  var targetTime = this.timeServer.targetTime.toMilliseconds();

  var timeReport =
    'Cannot release timers during event expiration ' +
    'current time: <<' +
    currentTime +
    '>> ms, target time: <<' +
    targetTime +
    '>> ms. ';

  if (targetTime === currentTime) {
    timeReport =
      timeReport + ' Target time reached, but queue not cleared yet. ';
  }

  return timeReport;
};

TimeForwarder.prototype.stopForwarding = function() {
  var that = this;
  return new that.schedule.Promise(function(resolve, reject) {
    if (that.isExpiringEvents()) {
      return reject(
        new Error(
          that.prepareTimeReport() +
            'Expiring events requested at: ' +
            that.forwardingStartedSavedStack
        )
      );
    }

    return resolve();
  });
};

TimeForwarder.prototype.stopExpiringEvents = function() {
  this.forwardingStartedSavedStack = undefined;
};

TimeForwarder.prototype.enable = function(config) {
  this.schedule = {
    Promise: config.promiseScheduler,
    EndOfQueue: this.immediateInterceptor.endOfQueueScheduler(),
    Internal: this.immediateInterceptor.internalScheduler()
  };
  this.config = config;
};

TimeForwarder.prototype.disable = function() {
  this.schedule = undefined;
};

TimeForwarder.prototype.startExpiringEvents = function() {
  this.forwardingStartedSavedStack = new Error().stack;
};

TimeForwarder.prototype.isExpiringEvents = function() {
  return this.forwardingStartedSavedStack !== undefined;
};

TimeForwarder.prototype.advanceTime = function(timeToForward) {
  var advanceStep = new TimeUnit(timeToForward);
  var that = this;

  return new that.schedule.Promise(function(resolve, reject) {
    if (advanceStep.isShorterThan(TimeUnit.milliseconds(0))) {
      return reject(
        new Error(
          'Zurvan cannot move back in time. Requested step: << ' +
            advanceStep.toMilliseconds() +
            'ms >>'
        )
      );
    }

    if (that.isExpiringEvents()) {
      return reject(
        new Error(
          that.prepareTimeReport() +
            'Forwarding requested from: ' +
            that.forwardingStartedSavedStack
        )
      );
    }

    that.timeServer.targetTime = that.timeServer.currentTime.extended(
      advanceStep
    );
    that.debugLogger(
      'advancing time to ' + that.timeServer.targetTime.toNanoseconds() + 'ns'
    );
    that.startExpiringEvents();

    // that's a workaround - in certain cases I believe this might not work (pathological chains of setImmediate/process.nextTick)
    // but I wasn't able to find out any such scenario, so I'm leaving it here for now - if you find one, file an issue on GitHub
    // or just increase the counter from configuration parameters
    delayByCycling(
      that.schedule.EndOfQueue,
      that.config.requestedCyclesAroundSetImmediateQueue,
      fireTimersOneByOne
    );

    var executionErrors = [];
    var currentSetImmediateBatchSize = 0;
    function fireTimersOneByOne() {
      if (that.immediateInterceptor.areAwaiting()) {
        if (
          ++currentSetImmediateBatchSize >=
          that.config.maxAllowedSetImmediateBatchSize
        ) {
          that.immediateInterceptor.startDroppingImmediates();

          // full cycle is needed to drop the immediates causing infinite loop
          // original immediates used, because fake ones are already being dropped
          delayByCycling(
            that.schedule.Internal,
            that.config.requestedCyclesAroundSetImmediateQueue,
            function() {
              reject(
                new Error(
                  'Possible infinite setImmediate loop detected. ' +
                    currentSetImmediateBatchSize +
                    ' setImmediates in single batch occurred. Dropping all further immediates, global objects are in undefined state.' +
                    ' Forwarding time requested from: ' +
                    that.forwardingStartedSavedStack
                )
              );
            }
          );
          return;
        }

        that.schedule.EndOfQueue(function() {
          fireTimersOneByOne();
        });
        return;
      }

      var closestTimer = that.timerInterceptor.nextTimer();
      if (
        closestTimer &&
        !closestTimer.dueTime.isLongerThan(that.timeServer.targetTime)
      ) {
        closestTimer.clear();
        that.timeServer.currentTime.setTo(closestTimer.dueTime);
        that.schedule.EndOfQueue(function() {
          try {
            closestTimer.expire();
          } catch (err) {
            executionErrors.push({
              failedAt: closestTimer.dueTime,
              error: err,
              timerCallDelay: closestTimer.callDelay.toMilliseconds()
            });
          }
          that.schedule.EndOfQueue(function() {
            fireTimersOneByOne();
          });
        });
      } else {
        that.timeServer.currentTime.setTo(that.timeServer.targetTime);
        that.stopExpiringEvents();
        if (that.config.rejectOnCallbackFailure && executionErrors.length > 0) {
          reject(executionErrors);
        } else {
          resolve(executionErrors);
        }
      }
    }
  });
};

TimeForwarder.prototype.expireAllTimeouts = function() {
  var lastTimeout = this.timerInterceptor.lastTimeout();
  if (lastTimeout) {
    var that = this;
    return this.advanceTime(
      lastTimeout.dueTime.shortened(that.timeServer.currentTime)
    ).then(function() {
      return that.expireAllTimeouts();
    });
  }

  return this.advanceTime(0);
};

TimeForwarder.prototype.forwardTimeToNextTimer = function() {
  var closestTimer = this.timerInterceptor.nextTimer();
  if (closestTimer) {
    return this.advanceTime(
      closestTimer.dueTime.shortened(this.timeServer.currentTime)
    );
  }
  return this.advanceTime(0);
};

TimeForwarder.prototype.fireAllOutdatedTimers = function() {
  var closestTimer = this.timerInterceptor.nextTimer();
  while (
    closestTimer &&
    !closestTimer.dueTime.isLongerThan(this.timeServer.currentTime)
  ) {
    closestTimer.clear();
    this.schedule.EndOfQueue(closestTimer.expire.bind(closestTimer));
    closestTimer = this.timerInterceptor.nextTimer();
  }
};

function assertValidBlockStep(blockStep) {
  if (blockStep.isShorterThan(TimeUnit.milliseconds(0))) {
    throw new Error(
      'Zurvan cannot move back in time. Requested step: << ' +
        blockStep.toMilliseconds() +
        'ms >>'
    );
  }
}

TimeForwarder.prototype.blockSystem = function(timeToBlock) {
  var blockStep = new TimeUnit(timeToBlock);
  assertValidBlockStep(blockStep);

  if (!this.isExpiringEvents()) {
    assert(this.timeServer.targetTime.isEqualTo(this.timeServer.currentTime));
    this.timeServer.targetTime.add(blockStep);
    this.debugLogger(
      'simulating blocking call until ' +
        this.timeServer.targetTime.toNanoseconds() +
        'ns'
    );
  } else if (
    this.timeServer.targetTime.isShorterThan(
      this.timeServer.currentTime.extended(blockStep)
    )
  ) {
    throw new Error(
      'Cannot block system during advancing for longer than requested advance time. Currently at: << ' +
        this.timeServer.currentTime.toMilliseconds() +
        ' >> ms, target: << ' +
        this.timeServer.targetTime.toMilliseconds() +
        ' ms >>, requested step: << ' +
        blockStep.toMilliseconds() +
        ' ms >>. Forwarding requested from: ' +
        this.forwardingStartedSavedStack
    );
  }

  this.timeServer.currentTime.add(blockStep);
  this.fireAllOutdatedTimers();
};

module.exports = TimeForwarder;