import contextlib
import functools
import os
import random
import shutil
import tempfile
from distutils.util import strtobool

import numpy as np
import pytest
import torch
from PIL import Image
from torchvision import io

import __main__  # noqa: 401


def get_bool_env_var(name, *, exist_ok=False, default=False):
    value = os.getenv(name)
    if value is None:
        return default
    if exist_ok:
        return True
    return bool(strtobool(value))


IN_CIRCLE_CI = get_bool_env_var("CIRCLECI")
IN_RE_WORKER = get_bool_env_var("INSIDE_RE_WORKER", exist_ok=True)
IN_FBCODE = get_bool_env_var("IN_FBCODE_TORCHVISION")
CUDA_NOT_AVAILABLE_MSG = "CUDA device not available"
CIRCLECI_GPU_NO_CUDA_MSG = "We're in a CircleCI GPU machine, and this test doesn't need cuda."


@contextlib.contextmanager
def get_tmp_dir(src=None, **kwargs):
    tmp_dir = tempfile.mkdtemp(**kwargs)
    if src is not None:
        os.rmdir(tmp_dir)
        shutil.copytree(src, tmp_dir)
    try:
        yield tmp_dir
    finally:
        shutil.rmtree(tmp_dir)


def set_rng_seed(seed):
    torch.manual_seed(seed)
    random.seed(seed)


class MapNestedTensorObjectImpl:
    def __init__(self, tensor_map_fn):
        self.tensor_map_fn = tensor_map_fn

    def __call__(self, object):
        if isinstance(object, torch.Tensor):
            return self.tensor_map_fn(object)

        elif isinstance(object, dict):
            mapped_dict = {}
            for key, value in object.items():
                mapped_dict[self(key)] = self(value)
            return mapped_dict

        elif isinstance(object, (list, tuple)):
            mapped_iter = []
            for iter in object:
                mapped_iter.append(self(iter))
            return mapped_iter if not isinstance(object, tuple) else tuple(mapped_iter)

        else:
            return object


def map_nested_tensor_object(object, tensor_map_fn):
    impl = MapNestedTensorObjectImpl(tensor_map_fn)
    return impl(object)


def is_iterable(obj):
    try:
        iter(obj)
        return True
    except TypeError:
        return False


@contextlib.contextmanager
def freeze_rng_state():
    rng_state = torch.get_rng_state()
    if torch.cuda.is_available():
        cuda_rng_state = torch.cuda.get_rng_state()
    yield
    if torch.cuda.is_available():
        torch.cuda.set_rng_state(cuda_rng_state)
    torch.set_rng_state(rng_state)


def cycle_over(objs):
    for idx, obj1 in enumerate(objs):
        for obj2 in objs[:idx] + objs[idx + 1 :]:
            yield obj1, obj2


def int_dtypes():
    return (torch.uint8, torch.int8, torch.int16, torch.int32, torch.int64)


def float_dtypes():
    return (torch.float32, torch.float64)


@contextlib.contextmanager
def disable_console_output():
    with contextlib.ExitStack() as stack, open(os.devnull, "w") as devnull:
        stack.enter_context(contextlib.redirect_stdout(devnull))
        stack.enter_context(contextlib.redirect_stderr(devnull))
        yield


def cpu_and_gpu():
    import pytest  # noqa

    return ("cpu", pytest.param("cuda", marks=pytest.mark.needs_cuda))


def needs_cuda(test_func):
    import pytest  # noqa

    return pytest.mark.needs_cuda(test_func)


def _create_data(height=3, width=3, channels=3, device="cpu"):
    # TODO: When all relevant tests are ported to pytest, turn this into a module-level fixture
    tensor = torch.randint(0, 256, (channels, height, width), dtype=torch.uint8, device=device)
    data = tensor.permute(1, 2, 0).contiguous().cpu().numpy()
    mode = "RGB"
    if channels == 1:
        mode = "L"
        data = data[..., 0]
    pil_img = Image.fromarray(data, mode=mode)
    return tensor, pil_img


def _create_data_batch(height=3, width=3, channels=3, num_samples=4, device="cpu"):
    # TODO: When all relevant tests are ported to pytest, turn this into a module-level fixture
    batch_tensor = torch.randint(0, 256, (num_samples, channels, height, width), dtype=torch.uint8, device=device)
    return batch_tensor


assert_equal = functools.partial(torch.testing.assert_close, rtol=0, atol=1e-6)


def get_list_of_videos(tmpdir, num_videos=5, sizes=None, fps=None):
    names = []
    for i in range(num_videos):
        if sizes is None:
            size = 5 * (i + 1)
        else:
            size = sizes[i]
        if fps is None:
            f = 5
        else:
            f = fps[i]
        data = torch.randint(0, 256, (size, 300, 400, 3), dtype=torch.uint8)
        name = os.path.join(tmpdir, f"{i}.mp4")
        names.append(name)
        io.write_video(name, data, fps=f)

    return names


def _assert_equal_tensor_to_pil(tensor, pil_image, msg=None):
    np_pil_image = np.array(pil_image)
    if np_pil_image.ndim == 2:
        np_pil_image = np_pil_image[:, :, None]
    pil_tensor = torch.as_tensor(np_pil_image.transpose((2, 0, 1)))
    if msg is None:
        msg = f"tensor:\n{tensor} \ndid not equal PIL tensor:\n{pil_tensor}"
    assert_equal(tensor.cpu(), pil_tensor, msg=msg)


def _assert_approx_equal_tensor_to_pil(
    tensor, pil_image, tol=1e-5, msg=None, agg_method="mean", allowed_percentage_diff=None
):
    # TODO: we could just merge this into _assert_equal_tensor_to_pil
    np_pil_image = np.array(pil_image)
    if np_pil_image.ndim == 2:
        np_pil_image = np_pil_image[:, :, None]
    pil_tensor = torch.as_tensor(np_pil_image.transpose((2, 0, 1))).to(tensor)

    if allowed_percentage_diff is not None:
        # Assert that less than a given %age of pixels are different
        assert (tensor != pil_tensor).to(torch.float).mean() <= allowed_percentage_diff

    # error value can be mean absolute error, max abs error
    # Convert to float to avoid underflow when computing absolute difference
    tensor = tensor.to(torch.float)
    pil_tensor = pil_tensor.to(torch.float)
    err = getattr(torch, agg_method)(torch.abs(tensor - pil_tensor)).item()
    assert err < tol


def _test_fn_on_batch(batch_tensors, fn, scripted_fn_atol=1e-8, **fn_kwargs):
    transformed_batch = fn(batch_tensors, **fn_kwargs)
    for i in range(len(batch_tensors)):
        img_tensor = batch_tensors[i, ...]
        transformed_img = fn(img_tensor, **fn_kwargs)
        assert_equal(transformed_img, transformed_batch[i, ...])

    if scripted_fn_atol >= 0:
        scripted_fn = torch.jit.script(fn)
        # scriptable function test
        s_transformed_batch = scripted_fn(batch_tensors, **fn_kwargs)
        torch.testing.assert_close(transformed_batch, s_transformed_batch, rtol=1e-5, atol=scripted_fn_atol)


def run_on_env_var(name, *, skip_reason=None, exist_ok=False, default=False):
    return pytest.mark.skipif(not get_bool_env_var(name, exist_ok=exist_ok, default=default), reason=skip_reason)
