# coding=utf-8

from operator import itemgetter
import prolog.engine
import server.problems

id = 119
number = 26
visible = True
facts = None

solution = '''\
len([], 0).
len([_|T], Len) :-
  len(T, LenT),
  Len is LenT + 1.
'''

test_cases = [
    ('len([8, 3, 5, 1], X)',
        [{'X': '4'}]),
    ('len([2, -3, 5, 0, 3], X)',
        [{'X': '5'}]),
    ('len([], X)',
        [{'X': '0'}]),
]

def test(program, solved_problems):
    code = (program + '\n' +
            server.problems.solutions_for_problems('prolog', solved_problems))

    n_correct = 0
    engine_id = None
    try:
        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
        if engine_id is not None and 'error' not in map(itemgetter(0), output):
            # Engine successfully created, and no syntax error in program.
            for query, answers in test_cases:
                # Limit inferences for each solution to curb unbounded recursion.
                limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
                if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
                    n_correct += 1
    finally:
        if engine_id:
            prolog.engine.destroy(engine_id)

    passed = n_correct == len(test_cases)
    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
    return passed, hints

def hint(program, solved_problems):
    # TODO
    return []