# This file is part of Hypothesis, which may be found at
# https://github.com/HypothesisWorks/hypothesis/
#
# Copyright the Hypothesis Authors.
# Individual contributors are listed in AUTHORS.rst and the git log.
#
# 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/.

import sys
import time
from itertools import islice

from hypothesis import strategies as st
from hypothesis.internal.intervalsets import IntervalSet
from hypothesis.strategies._internal import SearchStrategy


class _Slow(SearchStrategy):
    def do_draw(self, data):
        time.sleep(1.01)
        data.draw_bytes(2)


SLOW = _Slow()


class HardToShrink(SearchStrategy):
    def __init__(self):
        self.__last = None
        self.accepted = set()

    def do_draw(self, data):
        x = bytes(data.draw_integer(0, 255) for _ in range(100))
        if x in self.accepted:
            return True
        ls = self.__last
        if ls is None:
            if all(x):
                self.__last = x
                self.accepted.add(x)
                return True
            else:
                return False
        diffs = [i for i in range(len(x)) if x[i] != ls[i]]
        if len(diffs) == 1:
            i = diffs[0]
            if x[i] + 1 == ls[i]:
                self.__last = x
                self.accepted.add(x)
                return True
        return False


def build_intervals(intervals):
    it = iter(intervals)
    while batch := tuple(islice(it, 2)):
        # To guarantee we return pairs of 2, drop the last batch if it's
        # unbalanced.
        # Dropping a random element if the list is odd would probably make for
        # a better distribution, but a task for another day.
        if len(batch) < 2:
            continue
        yield batch


def interval_lists(*, min_codepoint=0, max_codepoint=sys.maxunicode, min_size=0):
    return (
        st.lists(
            st.integers(min_codepoint, max_codepoint),
            unique=True,
            min_size=min_size * 2,
        )
        .map(sorted)
        .map(build_intervals)
    )


def intervals(*, min_codepoint=0, max_codepoint=sys.maxunicode, min_size=0):
    return st.builds(
        IntervalSet,
        interval_lists(
            min_codepoint=min_codepoint, max_codepoint=max_codepoint, min_size=min_size
        ),
    )
