import multiprocessing
import signal
from PIL import Image  # type: ignore
from typing import Any, List, Optional, Sequence

from .types.generic import Color, Matrix, Point


# If we compiled the faster cython code, we can use it instead!
try:
    from .blendalt import affine_composite
except ImportError:
    def clamp(color: float) -> int:
        return min(max(0, round(color)), 255)

    def blend_normal(
        # RGBA color tuple representing what's already at the dest.
        dest: Sequence[int],
        # RGBA color tuple representing the source we want to blend to the dest.
        src: Sequence[int],
    ) -> Sequence[int]:
        # "Normal" blend mode, which is just alpha blending. Various games use the DX
        # equation Src * As + Dst * (1 - As). We premultiply Dst by Ad as well, since
        # we are blitting onto a destination that could have transparency. Once we are
        # done, we divide out the premultiplied Ad in order to put the pixes back to
        # their full blended values since we are not setting the destination alpha to 1.0.
        # This enables partial transparent backgrounds to work properly.

        # Short circuit for speed.
        if src[3] == 0:
            return dest
        if src[3] == 255:
            return src

        # Calculate alpha blending.
        srcpercent = src[3] / 255.0
        destpercent = dest[3] / 255.0
        srcremainder = 1.0 - srcpercent
        new_alpha = max(min(0.0, srcpercent + destpercent * srcremainder), 1.0)
        return (
            clamp(((dest[0] * destpercent * srcremainder) + (src[0] * srcpercent)) / new_alpha),
            clamp(((dest[1] * destpercent * srcremainder) + (src[1] * srcpercent)) / new_alpha),
            clamp(((dest[2] * destpercent * srcremainder) + (src[2] * srcpercent)) / new_alpha),
            clamp(255 * new_alpha)
        )

    def blend_addition(
        # RGBA color tuple representing what's already at the dest.
        dest: Sequence[int],
        # RGBA color tuple representing the source we want to blend to the dest.
        src: Sequence[int],
    ) -> Sequence[int]:
        # "Addition" blend mode, which is used for fog/clouds/etc. Various games use the DX
        # equation Src * As + Dst * 1. It appears jubeat does not premultiply the source
        # by its alpha component.

        # Short circuit for speed.
        if src[3] == 0:
            return dest

        # Calculate final color blending.
        srcpercent = src[3] / 255.0
        return (
            clamp(dest[0] + (src[0] * srcpercent)),
            clamp(dest[1] + (src[1] * srcpercent)),
            clamp(dest[2] + (src[2] * srcpercent)),
            # Additive blending doesn't actually make sense on semi-transparent destinations,
            # as that implies that the semi-transparent pixel will be later displayed on top
            # of something else. That doesn't work since additive blending needs to non-linearly
            # mix with the destination. So, in reality, we should be doing what subtractive
            # blending does and keeping the destination alpha (which should always be 255),
            # but if somebody renders an animation with additive blending meant to go over a
            # background onto a transparent or semi-transparent background this will make the
            # resulting graphic look more correct.
            clamp(dest[3] + (255 * srcpercent)),
        )

    def blend_subtraction(
        # RGBA color tuple representing what's already at the dest.
        dest: Sequence[int],
        # RGBA color tuple representing the source we want to blend to the dest.
        src: Sequence[int],
    ) -> Sequence[int]:
        # "Subtraction" blend mode, used for darkening an image. Various games use the DX
        # equation Dst * 1 - Src * As. It appears jubeat does not premultiply the source
        # by its alpha component much like the "additive" blend above..

        # Short circuit for speed.
        if src[3] == 0:
            return dest

        # Calculate final color blending.
        srcpercent = src[3] / 255.0
        return (
            clamp(dest[0] - (src[0] * srcpercent)),
            clamp(dest[1] - (src[1] * srcpercent)),
            clamp(dest[2] - (src[2] * srcpercent)),
            dest[3],
        )

    def blend_multiply(
        # RGBA color tuple representing what's already at the dest.
        dest: Sequence[int],
        # RGBA color tuple representing the source we want to blend to the dest.
        src: Sequence[int],
    ) -> Sequence[int]:
        # "Multiply" blend mode, used for darkening an image. Various games use the DX
        # equation Src * 0 + Dst * Src. It appears jubeat uses the alternative formula
        # Src * Dst + Dst * (1 - As) which reduces to the first equation as long as the
        # source alpha is always 255.

        # Calculate final color blending.
        return (
            clamp(255 * ((dest[0] / 255.0) * (src[0] / 255.0))),
            clamp(255 * ((dest[1] / 255.0) * (src[1] / 255.0))),
            clamp(255 * ((dest[2] / 255.0) * (src[2] / 255.0))),
            dest[3],
        )

    def affine_composite(
        img: Image.Image,
        add_color: Color,
        mult_color: Color,
        transform: Matrix,
        mask: Optional[Image.Image],
        blendfunc: int,
        texture: Image.Image,
        single_threaded: bool = False,
    ) -> Image.Image:
        # Calculate the inverse so we can map canvas space back to texture space.
        try:
            inverse = transform.inverse()
        except ZeroDivisionError:
            # If this happens, that means one of the scaling factors was zero, making
            # this object invisible. We can ignore this since the object should not
            # be drawn.
            return img

        # Warn if we have an unsupported blend.
        if blendfunc not in {0, 1, 2, 3, 8, 9, 70, 256, 257}:
            print(f"WARNING: Unsupported blend {blendfunc}")
            return img

        # These are calculated properties and caching them outside of the loop
        # speeds things up a bit.
        imgwidth = img.width
        imgheight = img.height
        texwidth = texture.width
        texheight = texture.height

        # Calculate the maximum range of update this texture can possibly reside in.
        pix1 = transform.multiply_point(Point.identity())
        pix2 = transform.multiply_point(Point.identity().add(Point(texwidth, 0)))
        pix3 = transform.multiply_point(Point.identity().add(Point(0, texheight)))
        pix4 = transform.multiply_point(Point.identity().add(Point(texwidth, texheight)))

        # Map this to the rectangle we need to sweep in the rendering image.
        minx = max(int(min(pix1.x, pix2.x, pix3.x, pix4.x)), 0)
        maxx = min(int(max(pix1.x, pix2.x, pix3.x, pix4.x)) + 1, imgwidth)
        miny = max(int(min(pix1.y, pix2.y, pix3.y, pix4.y)), 0)
        maxy = min(int(max(pix1.y, pix2.y, pix3.y, pix4.y)) + 1, imgheight)

        if maxx <= minx or maxy <= miny:
            # This image is entirely off the screen!
            return img

        cores = multiprocessing.cpu_count()
        if single_threaded or cores < 2:
            # Get the data in an easier to manipulate and faster to update fashion.
            imgmap = list(img.getdata())
            texmap = list(texture.getdata())
            if mask:
                alpha = mask.split()[-1]
                maskmap = alpha.tobytes('raw', 'L')
            else:
                maskmap = None

            # We don't have enough CPU cores to bother multiprocessing.
            for imgy in range(miny, maxy):
                for imgx in range(minx, maxx):
                    # Determine offset
                    imgoff = imgx + (imgy * imgwidth)

                    # Calculate what texture pixel data goes here.
                    texloc = inverse.multiply_point(Point(float(imgx + 0.5), float(imgy + 0.5)))
                    texx, texy = texloc.as_tuple()

                    # If we're out of bounds, don't update.
                    if texx < 0 or texy < 0 or texx >= texwidth or texy >= texheight:
                        continue

                    # Blend it.
                    texoff = texx + (texy * texwidth)
                    if maskmap is not None and maskmap[imgoff] == 0:
                        # This pixel is masked off!
                        continue
                    imgmap[imgoff] = blend_point(add_color, mult_color, texmap[texoff], imgmap[imgoff], blendfunc)

            img.putdata(imgmap)
        else:
            imgbytes = img.tobytes('raw', 'RGBA')
            texbytes = texture.tobytes('raw', 'RGBA')
            if mask:
                alpha = mask.split()[-1]
                maskbytes = alpha.tobytes('raw', 'L')
            else:
                maskbytes = None

            # Let's spread the load across multiple processors.
            procs: List[multiprocessing.Process] = []
            work: multiprocessing.Queue = multiprocessing.Queue()
            results: multiprocessing.Queue = multiprocessing.Queue()
            expected: int = 0
            interrupted: bool = False

            def ctrlc(sig: Any, frame: Any) -> None:
                nonlocal interrupted
                interrupted = True

            previous_handler = signal.getsignal(signal.SIGINT)
            signal.signal(signal.SIGINT, ctrlc)

            for _ in range(cores):
                proc = multiprocessing.Process(
                    target=pixel_renderer,
                    args=(
                        work,
                        results,
                        minx,
                        maxx,
                        imgwidth,
                        texwidth,
                        texheight,
                        inverse,
                        add_color,
                        mult_color,
                        blendfunc,
                        imgbytes,
                        texbytes,
                        maskbytes,
                    ),
                )
                procs.append(proc)
                proc.start()

            for imgy in range(miny, maxy):
                work.put(imgy)
                expected += 1

            lines: List[bytes] = [
                imgbytes[x:(x + (imgwidth * 4))]
                for x in range(
                    0,
                    imgwidth * imgheight * 4,
                    imgwidth * 4,
                )
            ]
            for _ in range(expected):
                imgy, result = results.get()
                lines[imgy] = result

            for proc in procs:
                work.put(None)
            for proc in procs:
                proc.join()

            signal.signal(signal.SIGINT, previous_handler)
            if interrupted:
                raise KeyboardInterrupt()

            img = Image.frombytes('RGBA', (imgwidth, imgheight), b''.join(lines))
        return img

    def blend_mask_create(
        # RGBA color tuple representing what's already at the dest.
        dest: Sequence[int],
        # RGBA color tuple representing the source we want to blend to the dest.
        src: Sequence[int],
    ) -> Sequence[int]:
        # Mask creating just allows a pixel to be drawn if the source image has a nonzero
        # alpha, according to the SWF spec.
        if src[3] != 0:
            return (255, 0, 0, 255)
        else:
            return (0, 0, 0, 0)

    def blend_mask_combine(
        # RGBA color tuple representing what's already at the dest.
        dest: Sequence[int],
        # RGBA color tuple representing the source we want to blend to the dest.
        src: Sequence[int],
    ) -> Sequence[int]:
        # Mask blending just takes the source and destination and ands them together, making
        # a final mask that is the intersection of the original mask and the new mask. The
        # reason we even have a color component to this is for debugging visibility.
        if dest[3] != 0 and src[3] != 0:
            return (255, 0, 0, 255)
        else:
            return (0, 0, 0, 0)

    def pixel_renderer(
        work: multiprocessing.Queue,
        results: multiprocessing.Queue,
        minx: int,
        maxx: int,
        imgwidth: int,
        texwidth: int,
        texheight: int,
        inverse: Matrix,
        add_color: Color,
        mult_color: Color,
        blendfunc: int,
        imgbytes: bytes,
        texbytes: bytes,
        maskbytes: Optional[bytes],
    ) -> None:
        while True:
            imgy = work.get()
            if imgy is None:
                return

            result: List[Sequence[int]] = []
            for imgx in range(imgwidth):
                # Determine offset
                imgoff = imgx + (imgy * imgwidth)
                if imgx < minx or imgx >= maxx:
                    result.append(imgbytes[(imgoff * 4):((imgoff + 1) * 4)])
                    continue

                # Calculate what texture pixel data goes here.
                texloc = inverse.multiply_point(Point(float(imgx + 0.5), float(imgy + 0.5)))
                texx, texy = texloc.as_tuple()

                # If we're out of bounds, don't update.
                if texx < 0 or texy < 0 or texx >= texwidth or texy >= texheight:
                    result.append(imgbytes[(imgoff * 4):((imgoff + 1) * 4)])
                    continue

                # Blend it.
                texoff = texx + (texy * texwidth)
                if maskbytes is not None and maskbytes[imgoff] == 0:
                    # This pixel is masked off!
                    result.append(imgbytes[(imgoff * 4):((imgoff + 1) * 4)])
                    continue
                result.append(blend_point(add_color, mult_color, texbytes[(texoff * 4):((texoff + 1) * 4)], imgbytes[(imgoff * 4):((imgoff + 1) * 4)], blendfunc))

            linebytes = bytes([channel for pixel in result for channel in pixel])
            results.put((imgy, linebytes))

    def blend_point(
        add_color: Color,
        mult_color: Color,
        # This should be a sequence of exactly 4 values, either bytes or a tuple.
        src_color: Sequence[int],
        # This should be a sequence of exactly 4 values, either bytes or a tuple.
        dest_color: Sequence[int],
        blendfunc: int,
    ) -> Sequence[int]:
        # Calculate multiplicative and additive colors against the source.
        src_color = (
            clamp((src_color[0] * mult_color.r) + (255 * add_color.r)),
            clamp((src_color[1] * mult_color.g) + (255 * add_color.g)),
            clamp((src_color[2] * mult_color.b) + (255 * add_color.b)),
            clamp((src_color[3] * mult_color.a) + (255 * add_color.a)),
        )

        if blendfunc == 3:
            return blend_multiply(dest_color, src_color)
        # TODO: blend mode 4, which is "screen" blending according to SWF references. I've only seen this
        # in Jubeat and it implements it using OpenGL equation Src * (1 - Dst) + Dst * 1.
        # TODO: blend mode 5, which is "lighten" blending according to SWF references. Jubeat does not
        # premultiply by alpha, but the GL/DX equation is max(Src * As, Dst * 1).
        # TODO: blend mode 6, which is "darken" blending according to SWF references. Jubeat does not
        # premultiply by alpha, but the GL/DX equation is min(Src * As, Dst * 1).
        # TODO: blend mode 10, which is "invert" according to SWF references. The only game I could find
        # that implemented this had equation Src * (1 - Dst) + Dst * (1 - As).
        # TODO: blend mode 13, which is "overlay" according to SWF references. The equation seems to be
        # Src * Dst + Dst * Src but Jubeat thinks it should be Src * Dst + Dst * (1 - As).
        elif blendfunc == 8:
            return blend_addition(dest_color, src_color)
        elif blendfunc == 9 or blendfunc == 70:
            return blend_subtraction(dest_color, src_color)
        # TODO: blend mode 75, which is not in the SWF spec and appears to have the equation
        # Src * (1 - Dst) + Dst * (1 - Src).
        elif blendfunc == 256:
            # Dummy blend function for calculating masks.
            return blend_mask_combine(dest_color, src_color)
        elif blendfunc == 257:
            # Dummy blend function for calculating masks.
            return blend_mask_create(dest_color, src_color)
        else:
            return blend_normal(dest_color, src_color)