from __future__ import annotations

import gc
import pickle
import threading
from unittest import mock

import pytest

from xarray.backends.file_manager import CachingFileManager
from xarray.backends.lru_cache import LRUCache
from xarray.core.options import set_options
from xarray.tests import assert_no_warnings


@pytest.fixture(params=[1, 2, 3, None])
def file_cache(request):
    maxsize = request.param
    if maxsize is None:
        yield {}
    else:
        yield LRUCache(maxsize)


def test_file_manager_mock_write(file_cache) -> None:
    mock_file = mock.Mock()
    opener = mock.Mock(spec=open, return_value=mock_file)
    lock = mock.MagicMock(spec=threading.Lock())

    manager = CachingFileManager(opener, "filename", lock=lock, cache=file_cache)
    f = manager.acquire()
    f.write("contents")
    manager.close()

    assert not file_cache
    opener.assert_called_once_with("filename")
    mock_file.write.assert_called_once_with("contents")
    mock_file.close.assert_called_once_with()
    lock.__enter__.assert_has_calls([mock.call(), mock.call()])


@pytest.mark.parametrize("warn_for_unclosed_files", [True, False])
def test_file_manager_autoclose(warn_for_unclosed_files) -> None:
    mock_file = mock.Mock()
    opener = mock.Mock(return_value=mock_file)
    cache: dict = {}

    manager = CachingFileManager(opener, "filename", cache=cache)
    manager.acquire()
    assert cache

    # can no longer use pytest.warns(None)
    if warn_for_unclosed_files:
        ctx = pytest.warns(RuntimeWarning)
    else:
        ctx = assert_no_warnings()  # type: ignore

    with set_options(warn_for_unclosed_files=warn_for_unclosed_files):
        with ctx:
            del manager
            gc.collect()

    assert not cache
    mock_file.close.assert_called_once_with()


def test_file_manager_autoclose_while_locked() -> None:
    opener = mock.Mock()
    lock = threading.Lock()
    cache: dict = {}

    manager = CachingFileManager(opener, "filename", lock=lock, cache=cache)
    manager.acquire()
    assert cache

    lock.acquire()

    with set_options(warn_for_unclosed_files=False):
        del manager
        gc.collect()

    # can't clear the cache while locked, but also don't block in __del__
    assert cache


def test_file_manager_repr() -> None:
    opener = mock.Mock()
    manager = CachingFileManager(opener, "my-file")
    assert "my-file" in repr(manager)


def test_file_manager_cache_and_refcounts() -> None:
    mock_file = mock.Mock()
    opener = mock.Mock(spec=open, return_value=mock_file)
    cache: dict = {}
    ref_counts: dict = {}

    manager = CachingFileManager(opener, "filename", cache=cache, ref_counts=ref_counts)
    assert ref_counts[manager._key] == 1

    assert not cache
    manager.acquire()
    assert len(cache) == 1

    with set_options(warn_for_unclosed_files=False):
        del manager
        gc.collect()

    assert not ref_counts
    assert not cache


def test_file_manager_cache_repeated_open() -> None:
    mock_file = mock.Mock()
    opener = mock.Mock(spec=open, return_value=mock_file)
    cache: dict = {}

    manager = CachingFileManager(opener, "filename", cache=cache)
    manager.acquire()
    assert len(cache) == 1

    manager2 = CachingFileManager(opener, "filename", cache=cache)
    manager2.acquire()
    assert len(cache) == 2

    with set_options(warn_for_unclosed_files=False):
        del manager
        gc.collect()

    assert len(cache) == 1

    with set_options(warn_for_unclosed_files=False):
        del manager2
        gc.collect()

    assert not cache


def test_file_manager_cache_with_pickle(tmpdir) -> None:
    path = str(tmpdir.join("testing.txt"))
    with open(path, "w") as f:
        f.write("data")
    cache: dict = {}

    with mock.patch("xarray.backends.file_manager.FILE_CACHE", cache):
        assert not cache

        manager = CachingFileManager(open, path, mode="r")
        manager.acquire()
        assert len(cache) == 1

        manager2 = pickle.loads(pickle.dumps(manager))
        manager2.acquire()
        assert len(cache) == 1

        with set_options(warn_for_unclosed_files=False):
            del manager
            gc.collect()
        # assert len(cache) == 1

        with set_options(warn_for_unclosed_files=False):
            del manager2
            gc.collect()
        assert not cache


def test_file_manager_write_consecutive(tmpdir, file_cache) -> None:
    path1 = str(tmpdir.join("testing1.txt"))
    path2 = str(tmpdir.join("testing2.txt"))
    manager1 = CachingFileManager(open, path1, mode="w", cache=file_cache)
    manager2 = CachingFileManager(open, path2, mode="w", cache=file_cache)
    f1a = manager1.acquire()
    f1a.write("foo")
    f1a.flush()
    f2 = manager2.acquire()
    f2.write("bar")
    f2.flush()
    f1b = manager1.acquire()
    f1b.write("baz")
    assert (getattr(file_cache, "maxsize", float("inf")) > 1) == (f1a is f1b)
    manager1.close()
    manager2.close()

    with open(path1) as f:
        assert f.read() == "foobaz"
    with open(path2) as f:
        assert f.read() == "bar"


def test_file_manager_write_concurrent(tmpdir, file_cache) -> None:
    path = str(tmpdir.join("testing.txt"))
    manager = CachingFileManager(open, path, mode="w", cache=file_cache)
    f1 = manager.acquire()
    f2 = manager.acquire()
    f3 = manager.acquire()
    assert f1 is f2
    assert f2 is f3
    f1.write("foo")
    f1.flush()
    f2.write("bar")
    f2.flush()
    f3.write("baz")
    f3.flush()
    manager.close()

    with open(path) as f:
        assert f.read() == "foobarbaz"


def test_file_manager_write_pickle(tmpdir, file_cache) -> None:
    path = str(tmpdir.join("testing.txt"))
    manager = CachingFileManager(open, path, mode="w", cache=file_cache)
    f = manager.acquire()
    f.write("foo")
    f.flush()
    manager2 = pickle.loads(pickle.dumps(manager))
    f2 = manager2.acquire()
    f2.write("bar")
    manager2.close()
    manager.close()

    with open(path) as f:
        assert f.read() == "foobar"


def test_file_manager_read(tmpdir, file_cache) -> None:
    path = str(tmpdir.join("testing.txt"))

    with open(path, "w") as f:
        f.write("foobar")

    manager = CachingFileManager(open, path, cache=file_cache)
    f = manager.acquire()
    assert f.read() == "foobar"
    manager.close()


def test_file_manager_acquire_context(tmpdir, file_cache) -> None:
    path = str(tmpdir.join("testing.txt"))

    with open(path, "w") as f:
        f.write("foobar")

    class AcquisitionError(Exception):
        pass

    manager = CachingFileManager(open, path, cache=file_cache)
    with pytest.raises(AcquisitionError):
        with manager.acquire_context() as f:
            assert f.read() == "foobar"
            raise AcquisitionError
    assert not file_cache  # file was *not* already open

    with manager.acquire_context() as f:
        assert f.read() == "foobar"

    with pytest.raises(AcquisitionError):
        with manager.acquire_context() as f:
            f.seek(0)
            assert f.read() == "foobar"
            raise AcquisitionError
    assert file_cache  # file *was* already open

    manager.close()
