A small timer directive for AngularJS

directive.coffee

# assumes there's already a window.timer = {}

app.directive 'callTimer', ->
    opts =
      restrict: 'E'
      controller: ($scope, $rootScope)->
        $scope.minutes = (window.timer?.state.minutes || 0)
        $scope.seconds = (window.timer?.state.seconds || 0)

        $scope.$on 'start-timer', -> $scope.startTimer()
        $scope.$on 'stop-timer', -> $scope.stopTimer()

        $scope.startTimer = ->
          incrementTimer = ->
            $scope.seconds += 1
            if $scope.seconds >= 60
              $scope.seconds = 0
              $scope.minutes += 1
            window.timer.state =
              minutes: $scope.minutes
              seconds: $scope.seconds
            $rootScope.setTimeDisplay($scope.minutes, $scope.seconds)
            $rootScope.$digest()

          window.timer =
            interval: window.setInterval(incrementTimer, 1000)
            state:
              minutes: $scope.minutes
              seconds: $scope.seconds

        $scope.stopTimer = ->
          $scope.$emit('timer-stopped', window.timer.state)
          $scope.minutes = 0
          $scope.seconds = 0
          window.clearInterval(window.timer.interval)
          $rootScope.setTimeDisplay($scope.minutes, $scope.seconds)
          window.timer = null

        $rootScope.setTimeDisplay = (m, s)->
          $scope.minDisplay = String(m).padLeft('0', 2)
          $scope.secDisplay = String(s).padLeft('0', 2)

        $rootScope.setTimeDisplay($scope.minutes, $scope.seconds)
        
# use with <call-timer>{{minDisplay}}:{{secDisplay}}</call-timer>