from os import PathLike
from typing import Union, BinaryIO, List, Tuple, Optional

from PIL import Image

__all__ = [
    'ImageTyping',
    'load_image',
    'MultiImagesTyping',
    'load_images',
    'add_background_for_rgba',
    'has_alpha_channel',
]


def _is_readable(obj):
    return hasattr(obj, 'read') and hasattr(obj, 'seek')


ImageTyping = Union[str, PathLike, bytes, bytearray, BinaryIO, Image.Image]
MultiImagesTyping = Union[ImageTyping, List[ImageTyping], Tuple[ImageTyping, ...]]


def has_alpha_channel(image: Image.Image) -> bool:
    mode = image.mode
    if mode in ('RGBA', 'LA', 'PA'):
        return True
    if getattr(image, 'palette', None):
        try:
            image.palette.getcolor((0, 0, 0, 0))
            return True
        except Exception:
            pass
    return 'transparency' in image.info


def load_image(image: ImageTyping, mode=None, force_background: Optional[str] = 'white'):
    """
    Minimal loader: supports file paths, bytes, file-like objects and PIL.Image.
    Does NOT perform http/blob downloads to avoid external dependencies.
    """
    if isinstance(image, (str, PathLike, bytes, bytearray)) or _is_readable(image):
        image = Image.open(image)
    elif isinstance(image, Image.Image):
        pass
    else:
        raise TypeError(f'Unknown image type - {image!r}.')

    if has_alpha_channel(image) and force_background is not None:
        image = add_background_for_rgba(image, force_background)

    if mode is not None and image.mode != mode:
        image = image.convert(mode)

    return image


def load_images(images: MultiImagesTyping, mode=None, force_background: Optional[str] = 'white') -> List[Image.Image]:
    if not isinstance(images, (list, tuple)):
        images = [images]
    return [load_image(item, mode, force_background) for item in images]


def add_background_for_rgba(image: ImageTyping, background: str = 'white'):
    image = load_image(image, force_background=None, mode=None)
    try:
        ret_image = Image.new('RGBA', image.size, background)
        ret_image.paste(image, (0, 0), mask=image)
    except Exception:
        ret_image = image
    if ret_image.mode != 'RGB':
        ret_image = ret_image.convert('RGB')
    return ret_image