# 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 io
import random
from operator import attrgetter

import pytest

from hypothesis import Phase, given, settings, strategies as st
from hypothesis.database import InMemoryExampleDatabase
from hypothesis.internal.conjecture.shrinker import sort_key


@pytest.mark.parametrize(
    "buffer_type",
    [bytes, bytearray, memoryview, io.BytesIO],
    ids=attrgetter("__name__"),
)
def test_fuzz_one_input(buffer_type):
    db = InMemoryExampleDatabase()
    seen = []
    seeds = []

    # This is a standard `@given` test, which we can also use as a fuzz target.
    # Note that we specify the DB so we can make more precise assertions,
    # and tighten the phases so we can be sure the failing examples come from fuzzing.
    @given(st.text())
    @settings(database=db, phases=[Phase.reuse, Phase.shrink])
    def test(s):
        seen.append(s)
        assert "\0" not in s, repr(s)

    # Before running fuzz_one_input, there's nothing in `db`, and so the test passes
    # (because example generation is disabled by the custom settings)
    test()
    assert len(seen) == 0

    # If we run a lot of random bytestrings through fuzz_one_input, we'll eventually
    # find a failing example.
    with pytest.raises(AssertionError):
        for _ in range(1000):
            buf = bytes(random.getrandbits(8) for _ in range(1000))
            seeds.append(buf)
            test.hypothesis.fuzz_one_input(buffer_type(buf))

    # fuzz_one_input returns False for invalid bytestrings, due to e.g. assume(False)
    assert len(seen) <= len(seeds)

    # `db` contains exactly one failing example, which is either the most
    # recent seed that we tried or the pruned-and-canonicalised form of it.
    (saved_examples,) = db.data.values()
    assert len(saved_examples) == 1
    assert sort_key(seeds[-1]) >= sort_key(list(saved_examples)[0])

    # Now that we have a failure in `db`, re-running our test is sufficient to
    # reproduce it, *and shrink to a minimal example*.
    with pytest.raises(AssertionError):
        test()
    assert seen[-1] == "\0"


def test_can_fuzz_with_database_eq_None():
    # This test exists to cover the can't-record-failure branch.

    @given(st.none())
    @settings(database=None)
    def test(s):
        assert False

    with pytest.raises(AssertionError):
        test.hypothesis.fuzz_one_input(b"\x00\x00")


def test_fuzzing_unsatisfiable_test_always_returns_None():
    # There are no examples of `st.none().filter(bool)`, but while the Hypothesis
    # engine would give up, fuzz_one_input will just return None each time.

    @given(st.none().filter(bool))
    @settings(database=None)
    def test(s):
        assert False

    for _ in range(100):
        buf = bytes(random.getrandbits(8) for _ in range(3))
        ret = test.hypothesis.fuzz_one_input(buf)
        assert ret is None


def test_autopruning_of_returned_buffer():
    @given(st.binary(min_size=4, max_size=4))
    @settings(database=None)
    def test(s):
        pass

    # Unused portions of the input buffer are discarded from output.
    # (and canonicalised, but that's a no-op for fixed-length `binary()`)
    assert test.hypothesis.fuzz_one_input(b"deadbeef") == b"dead"


STRAT = st.builds(object)


@given(x=STRAT)
def addx(x, y):
    pass


@given(STRAT)
def addy(x, y):
    pass


def test_can_access_strategy_for_wrapped_test():
    assert addx.hypothesis._given_kwargs == {"x": STRAT}
    assert addy.hypothesis._given_kwargs == {"y": STRAT}


@pytest.mark.parametrize(
    "buffers,db_size",
    [
        ([b"aa", b"bb", b"cc", b"dd"], 1),  # ascending -> only saves first
        ([b"dd", b"cc", b"bb", b"aa"], 4),  # descending -> saves all
        ([b"cc", b"dd", b"aa", b"bb"], 2),  # sawtooth -> saves cc then aa
        ([b"aa", b"bb", b"cc", b"XX"], 2),  # two distinct errors -> saves both
    ],
)
def test_fuzz_one_input_does_not_add_redundant_entries_to_database(buffers, db_size):
    db = InMemoryExampleDatabase()
    seen = []

    @given(st.binary(min_size=2, max_size=2))
    @settings(database=db)
    def test(s):
        seen.append(s)
        assert s != b"XX"
        raise AssertionError

    for buf in buffers:
        with pytest.raises(AssertionError):
            test.hypothesis.fuzz_one_input(buf)

    (saved_examples,) = db.data.values()
    assert seen == buffers
    assert len(saved_examples) == db_size