# This file is part of Hypothesis, which may be found at
# https://github.com/HypothesisWorks/hypothesis/
#
# Most of this work is copyright (C) 2013-2020 David R. MacIver
# (david@drmaciver.com), but it contains contributions by others. See
# CONTRIBUTING.rst for a full list of people who may hold copyright, and
# consult the git log if you need to determine who owns an individual
# contribution.
#
# This Source Code Form is subject to the terms of the Mozilla Public License,
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at https://mozilla.org/MPL/2.0/.
#
# END HEADER

import itertools
import math
from math import inf

import pytest

from hypothesis import assume, example, given, note, reject, settings, strategies as st
from hypothesis.internal.conjecture.dfa import DEAD, ConcreteDFA


def test_enumeration_when_sizes_do_not_agree():
    dfa = ConcreteDFA([{0: 1, 1: 2}, {}, {1: 3}, {}], {1, 3})  # 0  # 1  # 2  # 3

    assert list(dfa.all_matching_strings()) == [b"\0", b"\1\1"]


def test_enumeration_of_very_long_strings():
    """This test is mainly testing that it terminates. If we were
    to use a naive breadth first search for this it would take
    forever to run because it would run in time roughly 256 ** 50.
    """
    size = 50
    dfa = ConcreteDFA(
        [{c: n + 1 for c in range(256)} for n in range(100)] + [{}], {size}
    )

    for i, s in enumerate(dfa.all_matching_strings()):
        assert len(s) == size
        assert int.from_bytes(s, "big") == i
        if i >= 1000:
            break


def test_is_dead_with_cache_reuse():
    dfa = ConcreteDFA([{0: i + 1, 1: 11} for i in range(10)] + [{}, {}], {10})
    for n in range(10, -1, -1):
        assert not dfa.is_dead(n)


def test_max_length_of_empty_dfa_is_zero():
    dfa = ConcreteDFA([{}], {0})
    assert dfa.max_length(dfa.start) == 0


def test_mixed_dfa_initialization():
    d = ConcreteDFA([[(2, 1)], [(0, 5, 2)], {4: 0, 3: 1}], {0})

    assert d.transition(0, 2) == 1
    assert d.transition(0, 3) == DEAD

    for n in range(6):
        assert d.transition(1, n) == 2
    assert d.transition(1, 6) == DEAD

    assert d.transition(2, 4) == 0
    assert d.transition(2, 3) == 1
    assert d.transition(2, 5) == DEAD


@st.composite
def dfas(draw):
    states = draw(st.integers(1, 20))

    a_state = st.integers(0, states - 1)
    a_byte = st.integers(0, 255)

    start = draw(a_state)
    accepting = draw(st.sets(a_state, min_size=1))

    transitions = [draw(st.dictionaries(a_byte, a_state)) for _ in range(states)]

    return ConcreteDFA(transitions, accepting, start)


@settings(max_examples=20)
@given(dfas(), st.booleans())
def test_canonicalised_matches_same_strings(dfa, via_repr):
    canon = dfa.canonicalise()
    note(canon)

    if via_repr:
        canon = eval(repr(canon))

    assert dfa.max_length(dfa.start) == canon.max_length(canon.start)

    try:
        minimal = next(dfa.all_matching_strings())
    except StopIteration:
        reject()

    assert minimal == next(canon.all_matching_strings())

    assert dfa.count_strings(dfa.start, len(minimal)) == canon.count_strings(
        canon.start, len(minimal)
    )


@settings(max_examples=20)
@given(dfas())
def test_has_string_of_max_length(dfa):
    length = dfa.max_length(dfa.start)
    assume(math.isfinite(length))
    assume(not dfa.is_dead(dfa.start))

    assert dfa.count_strings(dfa.start, length) > 0


def test_converts_long_tables_to_dicts():
    dfa = ConcreteDFA(
        [[(0, 0), (1, 1), (2, 2), (3, 1), (4, 0), (7, 10, 1)], [(0, 0)], []], {2}
    )
    assert dfa.transition(0, 2) == 2
    assert dfa.transition(1, 0) == 0

    assert isinstance(dfa._ConcreteDFA__transitions[0], dict)
    assert isinstance(dfa._ConcreteDFA__transitions[1], list)


@settings(max_examples=20)
@given(dfas(), dfas())
def test_dfa_with_different_string_is_not_equivalent(x, y):
    assume(not x.is_dead(x.start))

    s = next(x.all_matching_strings())
    assume(not y.matches(s))

    assert not x.equivalent(y)


@example(x=b"", y=b"\0", z=b"\0")
@given(x=st.binary(), y=st.binary(min_size=1), z=st.binary())
def test_all_matching_regions_include_all_matches(x, y, z):
    y_matcher = ConcreteDFA([{c: i + 1} for i, c in enumerate(y)] + [[]], {len(y)})
    assert y_matcher.matches(y)

    s = x + y + z

    assert (len(x), len(x) + len(y)) in y_matcher.all_matching_regions(s)


@pytest.mark.parametrize("n", [1, 10, 100, 1000])
def test_max_length_of_long_dfa(n):
    dfa = ConcreteDFA([{0: i + 1} for i in range(n)] + [{}], {n})
    assert not dfa.is_dead(dfa.start)
    assert dfa.max_length(dfa.start) == n


def test_dfa_with_cached_dead():
    dfa = ConcreteDFA([[{0: 1, 1: 2}], [], []], {2})

    assert dfa.is_dead(1)
    assert dfa.is_dead(0)


@pytest.mark.parametrize("order", itertools.permutations((0, 1, 2)))
def test_dead_nodes(order):
    dfa = ConcreteDFA([{0: 1, 1: 2}, {}, {}], {2})
    for i in order:
        assert dfa.is_dead(i) == (i == 1)


@given(st.permutations(range(5)))
def test_max_length_of_recursive_dfa(order):
    dfa = ConcreteDFA([{0: 1, 1: 2, 2: 3}, {0: 2}, {0: 1}, {0: 0, 1: 4}, {}], {4})
    for i in order:
        dfa.max_length(i)

    assert dfa.max_length(0) == inf
    assert dfa.max_length(1) == 0
    assert dfa.max_length(2) == 0
    assert dfa.max_length(3) == inf
    assert dfa.max_length(4) == 0


def test_transitions_out_of_dead_are_empty():
    dfa = ConcreteDFA([{}], {0})
    assert list(dfa.raw_transitions(DEAD)) == []


def test_can_transition_from_dead():
    dfa = ConcreteDFA([{}], {0})
    assert dfa.transition(DEAD, 0) == DEAD