import pytest

pytest.importorskip("numpy")

import numpy as np

import dask
import dask.array as da
from dask.array.core import getter, getter_nofancy
from dask.array.optimization import (
    fuse_slice,
    getitem,
    optimize,
    optimize_blockwise,
    optimize_slices,
)
from dask.array.utils import assert_eq
from dask.highlevelgraph import HighLevelGraph
from dask.optimization import fuse
from dask.utils import SerializableLock


def test_fuse_getitem():
    pairs = [
        (
            (getter, (getter, "x", slice(1000, 2000)), slice(15, 20)),
            (getter, "x", slice(1015, 1020)),
        ),
        (
            (
                getitem,
                (getter, "x", (slice(1000, 2000), slice(100, 200))),
                (slice(15, 20), slice(50, 60)),
            ),
            (getter, "x", (slice(1015, 1020), slice(150, 160))),
        ),
        (
            (
                getitem,
                (getter_nofancy, "x", (slice(1000, 2000), slice(100, 200))),
                (slice(15, 20), slice(50, 60)),
            ),
            (getter_nofancy, "x", (slice(1015, 1020), slice(150, 160))),
        ),
        ((getter, (getter, "x", slice(1000, 2000)), 10), (getter, "x", 1010)),
        (
            (getitem, (getter, "x", (slice(1000, 2000), 10)), (slice(15, 20),)),
            (getter, "x", (slice(1015, 1020), 10)),
        ),
        (
            (getitem, (getter_nofancy, "x", (slice(1000, 2000), 10)), (slice(15, 20),)),
            (getter_nofancy, "x", (slice(1015, 1020), 10)),
        ),
        (
            (getter, (getter, "x", (10, slice(1000, 2000))), (slice(15, 20),)),
            (getter, "x", (10, slice(1015, 1020))),
        ),
        (
            (
                getter,
                (getter, "x", (slice(1000, 2000), slice(100, 200))),
                (slice(None, None), slice(50, 60)),
            ),
            (getter, "x", (slice(1000, 2000), slice(150, 160))),
        ),
        (
            (getter, (getter, "x", (None, slice(None, None))), (slice(None, None), 5)),
            (getter, "x", (None, 5)),
        ),
        (
            (
                getter,
                (getter, "x", (slice(1000, 2000), slice(10, 20))),
                (slice(5, 10),),
            ),
            (getter, "x", (slice(1005, 1010), slice(10, 20))),
        ),
        (
            (
                getitem,
                (getitem, "x", (slice(1000, 2000),)),
                (slice(5, 10), slice(10, 20)),
            ),
            (getitem, "x", (slice(1005, 1010), slice(10, 20))),
        ),
        (
            (getter, (getter, "x", slice(1000, 2000), False, False), slice(15, 20)),
            (getter, "x", slice(1015, 1020)),
        ),
        (
            (getter, (getter, "x", slice(1000, 2000)), slice(15, 20), False, False),
            (getter, "x", slice(1015, 1020)),
        ),
        (
            (
                getter,
                (getter_nofancy, "x", slice(1000, 2000), False, False),
                slice(15, 20),
                False,
                False,
            ),
            (getter_nofancy, "x", slice(1015, 1020), False, False),
        ),
    ]

    for inp, expected in pairs:
        result = optimize_slices({"y": inp})
        assert result == {"y": expected}


def test_fuse_getitem_lock():
    lock1 = SerializableLock()
    lock2 = SerializableLock()

    pairs = [
        (
            (getter, (getter, "x", slice(1000, 2000), True, lock1), slice(15, 20)),
            (getter, "x", slice(1015, 1020), True, lock1),
        ),
        (
            (
                getitem,
                (getter, "x", (slice(1000, 2000), slice(100, 200)), True, lock1),
                (slice(15, 20), slice(50, 60)),
            ),
            (getter, "x", (slice(1015, 1020), slice(150, 160)), True, lock1),
        ),
        (
            (
                getitem,
                (
                    getter_nofancy,
                    "x",
                    (slice(1000, 2000), slice(100, 200)),
                    True,
                    lock1,
                ),
                (slice(15, 20), slice(50, 60)),
            ),
            (getter_nofancy, "x", (slice(1015, 1020), slice(150, 160)), True, lock1),
        ),
        (
            (
                getter,
                (getter, "x", slice(1000, 2000), True, lock1),
                slice(15, 20),
                True,
                lock2,
            ),
            (
                getter,
                (getter, "x", slice(1000, 2000), True, lock1),
                slice(15, 20),
                True,
                lock2,
            ),
        ),
    ]

    for inp, expected in pairs:
        result = optimize_slices({"y": inp})
        assert result == {"y": expected}


def test_optimize_with_getitem_fusion():
    dsk = {
        "a": "some-array",
        "b": (getter, "a", (slice(10, 20), slice(100, 200))),
        "c": (getter, "b", (5, slice(50, 60))),
    }

    result = optimize(dsk, ["c"])
    expected_task = (getter, "some-array", (15, slice(150, 160)))
    assert any(v == expected_task for v in result.values())
    assert len(result) < len(dsk)


def test_optimize_slicing():
    dsk = {
        "a": (range, 10),
        "b": (getter, "a", (slice(None, None, None),)),
        "c": (getter, "b", (slice(None, None, None),)),
        "d": (getter, "c", (slice(0, 5, None),)),
        "e": (getter, "d", (slice(None, None, None),)),
    }

    expected = {"e": (getter, (range, 10), (slice(0, 5, None),))}
    result = optimize_slices(fuse(dsk, [], rename_keys=False)[0])
    assert result == expected

    # protect output keys
    expected = {
        "c": (getter, (range, 10), (slice(0, None, None),)),
        "d": (getter, "c", (slice(0, 5, None),)),
        "e": (getter, "d", (slice(None, None, None),)),
    }
    result = optimize_slices(fuse(dsk, ["c", "d", "e"], rename_keys=False)[0])

    assert result == expected


def test_fuse_slice():
    assert fuse_slice(slice(10, 15), slice(0, 5, 2)) == slice(10, 15, 2)

    assert fuse_slice((slice(100, 200),), (None, slice(10, 20))) == (
        None,
        slice(110, 120),
    )
    assert fuse_slice((slice(100, 200),), (slice(10, 20), None)) == (
        slice(110, 120),
        None,
    )
    assert fuse_slice((1,), (None,)) == (1, None)
    assert fuse_slice((1, slice(10, 20)), (None, None, 3, None)) == (
        1,
        None,
        None,
        13,
        None,
    )

    with pytest.raises(NotImplementedError):
        fuse_slice(slice(10, 15, 2), -1)
    # Regression test for #3076
    with pytest.raises(NotImplementedError):
        fuse_slice(None, np.array([0, 0]))


def test_fuse_slice_with_lists():
    assert fuse_slice(slice(10, 20, 2), [1, 2, 3]) == [12, 14, 16]
    assert fuse_slice([10, 20, 30, 40, 50], [3, 1, 2]) == [40, 20, 30]
    assert fuse_slice([10, 20, 30, 40, 50], 3) == 40
    assert fuse_slice([10, 20, 30, 40, 50], -1) == 50
    assert fuse_slice([10, 20, 30, 40, 50], slice(1, None, 2)) == [20, 40]
    assert fuse_slice(
        (slice(None), slice(0, 10), [1, 2, 3]), (slice(None), slice(1, 5), slice(None))
    ) == (slice(0, None), slice(1, 5), [1, 2, 3])
    assert fuse_slice(
        (slice(None), slice(None), [1, 2, 3]), (slice(None), slice(1, 5), 1)
    ) == (slice(0, None), slice(1, 5), 2)


def test_nonfusible_fancy_indexing():
    nil = slice(None)
    cases = [  # x[:, list, :][int, :, :]
        ((nil, [1, 2, 3], nil), (0, nil, nil)),
        # x[int, :, :][:, list, :]
        ((0, nil, nil), (nil, [1, 2, 3], nil)),
        # x[:, list, :, :][:, :, :, int]
        ((nil, [1, 2], nil, nil), (nil, nil, nil, 0)),
    ]

    for a, b in cases:
        with pytest.raises(NotImplementedError):
            fuse_slice(a, b)


def test_hard_fuse_slice_cases():
    dsk = {
        "x": (getter, (getter, "x", (None, slice(None, None))), (slice(None, None), 5))
    }
    assert optimize_slices(dsk) == {"x": (getter, "x", (None, 5))}


def test_dont_fuse_numpy_arrays():
    x = np.ones(10)
    for chunks in [(5,), (10,)]:
        y = da.from_array(x, chunks=(10,))

        dsk = y.__dask_optimize__(y.dask, y.__dask_keys__())
        assert sum(isinstance(v, np.ndarray) for v in dsk.values()) == 1


def test_minimize_data_transfer():
    zarr = pytest.importorskip("zarr")
    x = zarr.ones((100,))
    y = da.from_array(x, chunks=25)
    z = y + 1
    dsk = z.__dask_optimize__(z.dask, z.__dask_keys__())

    keys = list(dsk)
    results = dask.get(dsk, keys)
    big_key = [k for k, r in zip(keys, results) if r is x][0]
    dependencies, dependents = dask.core.get_deps(dsk)
    deps = dependents[big_key]

    assert len(deps) == 4
    for dep in deps:
        assert dsk[dep][0] in (getitem, getter)
        assert dsk[dep][1] == big_key


def test_fuse_slices_with_alias():
    dsk = {
        "x": np.arange(16).reshape((4, 4)),
        ("dx", 0, 0): (getter, "x", (slice(0, 4), slice(0, 4))),
        ("alias", 0, 0): ("dx", 0, 0),
        ("dx2", 0): (getitem, ("alias", 0, 0), (slice(None), 0)),
    }
    keys = [("dx2", 0)]
    dsk2 = optimize(dsk, keys)
    assert len(dsk2) == 3
    fused_key = (dsk2.keys() - {"x", ("dx2", 0)}).pop()
    assert dsk2[fused_key] == (getter, "x", (slice(0, 4), 0))


def test_dont_fuse_fancy_indexing_in_getter_nofancy():
    dsk = {
        "a": (
            getitem,
            (getter_nofancy, "x", (slice(10, 20, None), slice(100, 200, None))),
            ([1, 3], slice(50, 60, None)),
        )
    }
    assert optimize_slices(dsk) == dsk

    dsk = {"a": (getitem, (getter_nofancy, "x", [1, 2, 3]), 0)}
    assert optimize_slices(dsk) == dsk


@pytest.mark.parametrize("chunks", [10, 5, 3])
def test_fuse_getter_with_asarray(chunks):
    x = np.ones(10) * 1234567890
    y = da.ones(10, chunks=chunks)
    z = x + y
    dsk = z.__dask_optimize__(z.dask, z.__dask_keys__())
    assert any(v is x for v in dsk.values())
    for v in dsk.values():
        s = str(v)
        assert s.count("getitem") + s.count("getter") <= 1
        if v is not x:
            assert "1234567890" not in s
    n_getters = len([v for v in dsk.values() if v[0] in (getitem, getter)])
    if y.npartitions > 1:
        assert n_getters == y.npartitions
    else:
        assert n_getters == 0

    assert_eq(z, x + 1)


@pytest.mark.parametrize(
    "get,remove", [(getter, False), (getter_nofancy, False), (getitem, True)]
)
def test_remove_no_op_slices_if_get_is_not_getter_or_getter_nofancy(get, remove):
    # Test that no-op slices are removed as long as get is not getter or
    # getter_nofancy. This ensures that `get` calls are always made in all
    # tasks created by `from_array`, even after optimization
    null = slice(0, None)
    opts = [
        (
            (get, "x", null, False, False),
            "x" if remove else (get, "x", null, False, False),
        ),
        (
            (getitem, (get, "x", null, False, False), null),
            "x" if remove else (get, "x", null, False, False),
        ),
        (
            (getitem, (get, "x", (null, null), False, False), ()),
            "x" if remove else (get, "x", (null, null), False, False),
        ),
    ]
    for orig, final in opts:
        assert optimize_slices({"a": orig}) == {"a": final}


@pytest.mark.xfail(reason="blockwise fusion does not respect this, which is ok")
def test_turn_off_fusion():
    x = da.ones(10, chunks=(5,))
    y = da.sum(x + 1 + 2 + 3)

    a = y.__dask_optimize__(y.dask, y.__dask_keys__())

    with dask.config.set({"optimization.fuse.ave-width": 0}):
        b = y.__dask_optimize__(y.dask, y.__dask_keys__())

    assert dask.get(a, y.__dask_keys__()) == dask.get(b, y.__dask_keys__())
    assert len(a) < len(b)


def test_disable_lowlevel_fusion():
    """Check that by disabling fusion, the HLG survives through optimizations"""

    with dask.config.set({"optimization.fuse.active": False}):
        y = da.ones(3, chunks=(3,), dtype="int")
        optimize = y.__dask_optimize__
        dsk1 = y.__dask_graph__()
        dsk2 = optimize(dsk1, y.__dask_keys__())
        assert isinstance(dsk1, HighLevelGraph)
        assert isinstance(dsk2, HighLevelGraph)
        assert dsk1 == dsk2
        y = y.persist()
        assert isinstance(y.__dask_graph__(), HighLevelGraph)
        assert_eq(y, [1] * 3)


def test_array_creation_blockwise_fusion():
    """
    Check that certain array creation routines work with blockwise and can be
    fused with other blockwise operations.
    """
    x = da.ones(3, chunks=(3,))
    y = da.zeros(3, chunks=(3,))
    z = da.full(3, fill_value=2, chunks=(3,))
    a = x + y + z
    dsk1 = a.__dask_graph__()
    assert len(dsk1) == 5
    dsk2 = optimize_blockwise(dsk1)
    assert len(dsk2) == 1
    assert_eq(a, np.full(3, 3.0))


def test_gh3937():
    # test for github issue #3937
    x = da.from_array([1, 2, 3.0], (2,))
    x = da.concatenate((x, [x[-1]]))
    y = x.rechunk((2,))
    # This will produce Integral type indices that are not ints (np.int64), failing
    # the optimizer
    y = da.coarsen(np.sum, y, {0: 2})
    # How to trigger the optimizer explicitly?
    y.compute()


def test_double_dependencies():
    x = np.arange(56).reshape((7, 8))
    d = da.from_array(x, chunks=(4, 4))
    X = d + 1
    X = da.dot(X, X.T)

    assert_eq(X.compute(optimize_graph=False), X)


def test_fuse_roots():
    x = da.ones(10, chunks=(2,))
    y = da.zeros(10, chunks=(2,))
    z = (x + 1) + (2 * y ** 2)
    (zz,) = dask.optimize(z)
    # assert len(zz.dask) == 5
    assert sum(map(dask.istask, zz.dask.values())) == 5  # there are some aliases
    assert_eq(zz, z)


def test_fuse_roots_annotations():
    x = da.ones(10, chunks=(2,))
    y = da.zeros(10, chunks=(2,))

    with dask.annotate(foo="bar"):
        y = y ** 2

    z = (x + 1) + (2 * y)
    hlg = dask.blockwise.optimize_blockwise(z.dask)
    assert len(hlg.layers) == 3
    assert {"foo": "bar"} in [l.annotations for l in hlg.layers.values()]
    za = da.Array(hlg, z.name, z.chunks, z.dtype)
    assert_eq(za, z)
