# coding=utf-8

import threading
import python.engine
from db.models import Problem
from . import problems

__all__ = ['PythonSession']

class PythonSession(object):
    """Abstracts a Python session.
    Only public methods are available to the outside world due to the use of multiprocessing managers.
    Therefore prefix any private methods with an underscore (_).
    No properties are accessible; use getters and setters instead.
    Values are passed by value instead of by reference (deep copy!).
    """
    def __init__(self):
        self._access_lock = threading.Lock()
        self._interpreter = None

    def create(self):
        with self._access_lock:
            if not self._interpreter:
                self._interpreter = python.engine.create()

    def pull(self):
        with self._access_lock:
            if self._interpreter is None:
                return 'Python is not running'
            return python.engine.pull(self._interpreter)

    def push(self, stdin):
        with self._access_lock:
            if self._interpreter is not None:
                python.engine.push(self._interpreter, stdin)

    def destroy(self):
        with self._access_lock:
            if self._interpreter is not None:
                python.engine.destroy(self._interpreter)
                self._interpreter = None

    def __del__(self):
        if hasattr(self, '_interpreter') and self._interpreter is not None:
            python.engine.destroy(self._interpreter)
            self._interpreter = None

    def hint(self, user_id, problem_id, program):
        language, problem_group, problem = Problem.identifier(problem_id)

        # Try problem-specific hints.
        problem_module = problems.load_problem(language, problem_group, problem, 'common')
        if hasattr(problem_module, 'hint'):
            hints = problem_module.hint(program)
            if hints:
                return hints

        # Finally return a generic "try thinking a bit" message.
        return [{'id': 'no_hint'}]

    def test(self, user_id, problem_id, program):
        language, problem_group, problem = Problem.identifier(problem_id)
        problem_module = problems.load_problem(language, problem_group, problem, 'common')
        try:
            n_correct, n_all = problem_module.test(program)
            return [{'id': 'test_results', 'args': {'passed': n_correct, 'total': n_all}}]
        except AttributeError as ex:
            return [{'id': 'test_results', 'args': {'passed': 0, 'total': 0}}]