import unittest
import sys
from StringIO import StringIO


class TaskHandler(object):

    def __init__(self):

        """
        Ships must dock first, then vessel can be unloaded, then a truck can
        load a container, and lastly it needs to go through a customs check.
        The refueling process can happen anytime after a ship docks.
        """

        self._task_order = {'RE-FUELING SHIP': ['SHIP DOCKING'],
                            'UNLOADING VESSEL': ['SHIP DOCKING'],
                            'TRUCK LOADING CONTAINER': ['UNLOADING VESSEL'],
                            'CUSTOMS CHECK': ['TRUCK LOADING CONTAINER']
                           }


        self.task_list = {'SHIP DOCKING': 0,
                          'RE-FUELING SHIP': 0,
                          'UNLOADING VESSEL': 0,
                          'TRUCK LOADING CONTAINER': 0,
                          'CUSTOMS CHECK': 0
                         }


    def tasks_remaining(self):
        """ Gets total number of tasks remaining. """

        return sum(self.task_list.values())


    def add_task(self, tasks_array):
        """ Adds an array of tasks to existing task list. """

        for task_file in tasks_array:
            task = open(task_file).read().rstrip()
            self.task_list[task] = self.task_list.get(task) + 1


    def execute_tasks(self):
        """ Executes tasks in sensible order. """

        for task in self.task_list.keys():

            if task not in self._task_order:
                while self.task_list[task] > 0:
                    print task + ' COMPLETED'
                    self.remove_task(task)

            else:
                while self.task_list[task] > 0:
                    self.check_dependencies(task)
                    print task + ' COMPLETED'
                    self.remove_task(task)



    def check_dependencies(self, task):
        """ Checks for any task dependencies. """

        dependencies_remaining = []

        if task in self._task_order:
            dependencies = self._task_order[task]

            for dependency in dependencies:
                dependencies_remaining.append(dependency)

        if dependencies_remaining == []:
            return
        else:
            for dependency in dependencies_remaining:
                self.check_dependencies(dependency)



    def remove_task(self, task):
        """ Removes a task from the task list once it has been completed. """

        self.task_list[task] -= 1


    def __repr__(self):

        return '<{} tasks remaining>'.format(self.tasks_remaining())



class TestingTaskHandler(unittest.TestCase):

    def setUp(self):
        self.job = TaskHandler()
        self.job.add_task(['task0.py', 'task1.py', 'task4.py', 'task2.py', 'task3.py', 'task3.py', 'task4.py', 'task2.py', 'task1.py'])
        self.held = sys.stdout
        sys.stdout = StringIO()

    def test_add_tasks(self):
        self.assertEqual(self.job.tasks_remaining(), 9)
        self.assertEqual(self.job.task_list, {'SHIP DOCKING': 1, 'UNLOADING VESSEL': 2, 'CUSTOMS CHECK': 2, 'TRUCK LOADING CONTAINER': 2, 'RE-FUELING SHIP': 2})

    def test_remove_task(self):
        self.job.remove_task('SHIP DOCKING')
        self.assertEqual(self.job.tasks_remaining(), 8)
        self.assertEqual(self.job.task_list, {'SHIP DOCKING': 0, 'UNLOADING VESSEL': 2, 'CUSTOMS CHECK': 2, 'TRUCK LOADING CONTAINER': 2, 'RE-FUELING SHIP': 2})

    def test_execute_tasks(self):
        self.job.execute_tasks()
        self.assertEqual(self.job.tasks_remaining(), 0)
        self.assertEqual(sys.stdout.getvalue(),
            'SHIP DOCKING COMPLETED\nUNLOADING VESSEL COMPLETED\nUNLOADING VESSEL COMPLETED\nCUSTOMS CHECK COMPLETED\nCUSTOMS CHECK COMPLETED\nTRUCK LOADING CONTAINER COMPLETED\nTRUCK LOADING CONTAINER COMPLETED\nRE-FUELING SHIP COMPLETED\nRE-FUELING SHIP COMPLETED\n')



if __name__ == '__main__':
    unittest.main()