# Ultralytics 🚀 AGPL-3.0 License - https://ultralytics.com/license
"""Monkey patches to update/extend functionality of existing functions."""

from __future__ import annotations

import time
from contextlib import contextmanager
from copy import copy
from pathlib import Path
from typing import Any

import cv2
import numpy as np
import torch
from PIL import Image

# OpenCV Multilanguage-friendly functions ------------------------------------------------------------------------------
_imshow = cv2.imshow  # copy to avoid recursion errors


def imread(filename: str, flags: int = cv2.IMREAD_COLOR) -> np.ndarray | None:
    """Read an image from a file with multilanguage filename support.

    Args:
        filename (str): Path to the file to read.
        flags (int, optional): Flag that can take values of cv2.IMREAD_*. Controls how the image is read.

    Returns:
        (np.ndarray | None): The read image array, or None if reading fails.

    Examples:
        >>> img = imread("path/to/image.jpg")
        >>> img = imread("path/to/image.jpg", cv2.IMREAD_GRAYSCALE)
    """
    file_bytes = np.fromfile(filename, np.uint8)
    if filename.endswith((".tiff", ".tif")):
        success, frames = cv2.imdecodemulti(file_bytes, cv2.IMREAD_UNCHANGED)
        if success:
            # Handle multi-frame TIFFs and color images
            return frames[0] if len(frames) == 1 and frames[0].ndim == 3 else np.stack(frames, axis=2)
        return None
    else:
        im = cv2.imdecode(file_bytes, flags)
        # Fallback for formats OpenCV imdecode may not support (AVIF, HEIC)
        if im is None and filename.lower().endswith((".avif", ".heic")):
            im = _imread_pil(filename, flags)
        return im[..., None] if im is not None and im.ndim == 2 else im  # Always ensure 3 dimensions


# PIL patches ---------------------------------------------------------------------------------------------------------
_image_open = Image.open  # copy to avoid recursion errors
_pil_plugins_registered = False


def image_open(filename, *args, **kwargs):
    """Open an image with PIL, lazily registering the HEIF plugin on first failure.

    This monkey-patches PIL.Image.open to add HEIC/HEIF support via pi-heif (lightweight, decode-only), avoiding the
    ~800ms startup cost of importing the package unless actually needed. AVIF is supported natively by Pillow 12+ and
    does not require a plugin.

    Args:
        filename (str): Path to the image file.
        *args (Any): Additional positional arguments passed to PIL.Image.open.
        **kwargs (Any): Additional keyword arguments passed to PIL.Image.open.

    Returns:
        (PIL.Image.Image): The opened PIL image.
    """
    global _pil_plugins_registered
    if _pil_plugins_registered:
        return _image_open(filename, *args, **kwargs)
    try:
        return _image_open(filename, *args, **kwargs)
    except Exception as e:
        suffix = Path(filename).suffix.lower() if isinstance(filename, (str, Path)) else ""
        if suffix not in {".heic", ".heif", ".hif"}:
            raise e
        from ultralytics.utils.checks import check_requirements

        check_requirements("pi-heif")
        from pi_heif import register_heif_opener

        register_heif_opener()
        _pil_plugins_registered = True
        return _image_open(filename, *args, **kwargs)


Image.open = image_open  # apply patch


def _imread_pil(filename: str, flags: int = cv2.IMREAD_COLOR) -> np.ndarray | None:
    """Read an image using PIL as fallback for formats not supported by OpenCV.

    Args:
        filename (str): Path to the file to read.
        flags (int, optional): OpenCV imread flags (used to determine grayscale conversion).

    Returns:
        (np.ndarray | None): The read image array in BGR format, or None if reading fails.
    """
    try:
        with Image.open(filename) as img:
            if flags == cv2.IMREAD_GRAYSCALE:
                return np.asarray(img.convert("L"))
            return cv2.cvtColor(np.asarray(img.convert("RGB")), cv2.COLOR_RGB2BGR)
    except Exception:
        return None


def imwrite(filename: str, img: np.ndarray, params: list[int] | None = None) -> bool:
    """Write an image to a file with multilanguage filename support.

    Args:
        filename (str): Path to the file to write.
        img (np.ndarray): Image to write.
        params (list[int], optional): Additional parameters for image encoding.

    Returns:
        (bool): True if the file was written successfully, False otherwise.

    Examples:
        >>> import numpy as np
        >>> img = np.zeros((100, 100, 3), dtype=np.uint8)  # Create a black image
        >>> success = imwrite("output.jpg", img)  # Write image to file
        >>> print(success)
        True
    """
    try:
        cv2.imencode(Path(filename).suffix, img, params)[1].tofile(filename)
        return True
    except Exception:
        return False


def imshow(winname: str, mat: np.ndarray) -> None:
    """Display an image in the specified window with multilanguage window name support.

    This function is a wrapper around OpenCV's imshow function that displays an image in a named window. It handles
    multilanguage window names by encoding them properly for OpenCV compatibility.

    Args:
        winname (str): Name of the window where the image will be displayed. If a window with this name already exists,
            the image will be displayed in that window.
        mat (np.ndarray): Image to be shown. Should be a valid numpy array representing an image.

    Examples:
        >>> import numpy as np
        >>> img = np.zeros((300, 300, 3), dtype=np.uint8)  # Create a black image
        >>> img[:100, :100] = [255, 0, 0]  # Add a blue square
        >>> imshow("Example Window", img)  # Display the image
    """
    _imshow(winname.encode("unicode_escape").decode(), mat)


# PyTorch functions ----------------------------------------------------------------------------------------------------
_torch_save = torch.save


def torch_load(*args, **kwargs):
    """Load a PyTorch model with updated arguments to avoid warnings.

    This function wraps torch.load and adds the 'weights_only' argument for PyTorch 1.13.0+ to prevent warnings.

    Args:
        *args (Any): Variable length argument list to pass to torch.load.
        **kwargs (Any): Arbitrary keyword arguments to pass to torch.load.

    Returns:
        (Any): The loaded PyTorch object.

    Notes:
        For PyTorch versions 1.13 and above, this function automatically sets `weights_only=False` if the argument is
        not provided, to avoid deprecation warnings.
    """
    from ultralytics.utils.torch_utils import TORCH_1_13

    if TORCH_1_13 and "weights_only" not in kwargs:
        kwargs["weights_only"] = False

    return torch.load(*args, **kwargs)


def torch_save(*args, **kwargs):
    """Save PyTorch objects with retry mechanism for robustness.

    This function wraps torch.save with 3 retries and exponential backoff in case of save failures, which can occur due
    to device flushing delays or antivirus scanning.

    Args:
        *args (Any): Positional arguments to pass to torch.save.
        **kwargs (Any): Keyword arguments to pass to torch.save.

    Examples:
        >>> model = torch.nn.Linear(10, 1)
        >>> torch_save(model.state_dict(), "model.pt")
    """
    for i in range(4):  # 3 retries
        try:
            return _torch_save(*args, **kwargs)
        except RuntimeError as e:  # Unable to save, possibly waiting for device to flush or antivirus scan
            if i == 3:
                raise e
            time.sleep((2**i) / 2)  # Exponential backoff: 0.5s, 1.0s, 2.0s


@contextmanager
def arange_patch(args):
    """Workaround for ONNX torch.arange incompatibility with FP16.

    https://github.com/pytorch/pytorch/issues/148041.
    """
    if args.dynamic and args.half and args.format == "onnx":
        func = torch.arange

        def arange(*args, dtype=None, **kwargs):
            """Wrap torch.arange to cast dtype after creation instead of passing it directly."""
            return func(*args, **kwargs).to(dtype)  # cast to dtype instead of passing dtype

        torch.arange = arange  # patch
        yield
        torch.arange = func  # unpatch
    else:
        yield


@contextmanager
def onnx_export_patch():
    """Workaround for ONNX export issues in PyTorch 2.9+ with Dynamo enabled."""
    from ultralytics.utils.torch_utils import TORCH_2_9

    if TORCH_2_9:
        func = torch.onnx.export

        def torch_export(*args, **kwargs):
            """Export model to ONNX format with Dynamo disabled for compatibility."""
            return func(*args, **kwargs, dynamo=False)

        torch.onnx.export = torch_export  # patch
        yield
        torch.onnx.export = func  # unpatch
    else:
        yield


@contextmanager
def override_configs(args, overrides: dict[str, Any] | None = None):
    """Context manager to temporarily override configurations in args.

    Args:
        args (IterableSimpleNamespace): Original configuration arguments.
        overrides (dict[str, Any] | None): Dictionary of overrides to apply.

    Yields:
        (IterableSimpleNamespace): Configuration arguments with overrides applied.
    """
    if overrides:
        original_args = copy(args)
        for key, value in overrides.items():
            setattr(args, key, value)
        try:
            yield args
        finally:
            args.__dict__.update(original_args.__dict__)
    else:
        yield args
