"""
A Pillow loader for .dds files (S3TC-compressed aka DXTC)
Jerome Leclanche <jerome@leclan.ch>

Documentation:
  https://web.archive.org/web/20170802060935/http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt

The contents of this file are hereby released in the public domain (CC0)
Full text of the CC0 license:
  https://creativecommons.org/publicdomain/zero/1.0/
"""

import struct
from enum import IntFlag, IntEnum
from io import BytesIO

from . import Image, ImageFile
from ._binary import o32le as o32

# Magic ("DDS ")
DDS_MAGIC = 0x20534444


# DDS flags
class DDSD(IntFlag):
    CAPS = 0x1
    HEIGHT = 0x2
    WIDTH = 0x4
    PITCH = 0x8
    PIXELFORMAT = 0x1000
    MIPMAPCOUNT = 0x20000
    LINEARSIZE = 0x80000
    DEPTH = 0x800000


# DDS caps
class DDSCAPS(IntFlag):
    COMPLEX = 0x8
    TEXTURE = 0x1000
    MIPMAP = 0x400000


class DDSCAPS2(IntFlag):
    CUBEMAP = 0x200
    CUBEMAP_POSITIVEX = 0x400
    CUBEMAP_NEGATIVEX = 0x800
    CUBEMAP_POSITIVEY = 0x1000
    CUBEMAP_NEGATIVEY = 0x2000
    CUBEMAP_POSITIVEZ = 0x4000
    CUBEMAP_NEGATIVEZ = 0x8000
    VOLUME = 0x200000


# Pixel Format
class DDPF(IntFlag):
    ALPHAPIXELS = 0x1
    ALPHA = 0x2
    FOURCC = 0x4
    PALETTEINDEXED8 = 0x20
    RGB = 0x40
    LUMINANCE = 0x20000


# DXT1
DXT1_FOURCC = 0x31545844

# DXT3
DXT3_FOURCC = 0x33545844

# DXT5
DXT5_FOURCC = 0x35545844


# dxgiformat.h
class DXGI_FORMAT(IntEnum):
    UNKNOWN = 0,
    R32G32B32A32_TYPELESS = 1,
    R32G32B32A32_FLOAT = 2,
    R32G32B32A32_UINT = 3,
    R32G32B32A32_SINT = 4,
    R32G32B32_TYPELESS = 5,
    R32G32B32_FLOAT = 6,
    R32G32B32_UINT = 7,
    R32G32B32_SINT = 8,
    R16G16B16A16_TYPELESS = 9,
    R16G16B16A16_FLOAT = 10,
    R16G16B16A16_UNORM = 11,
    R16G16B16A16_UINT = 12,
    R16G16B16A16_SNORM = 13,
    R16G16B16A16_SINT = 14,
    R32G32_TYPELESS = 15,
    R32G32_FLOAT = 16,
    R32G32_UINT = 17,
    R32G32_SINT = 18,
    R32G8X24_TYPELESS = 19,
    D32_FLOAT_S8X24_UINT = 20,
    R32_FLOAT_X8X24_TYPELESS = 21,
    X32_TYPELESS_G8X24_UINT = 22,
    R10G10B10A2_TYPELESS = 23,
    R10G10B10A2_UNORM = 24,
    R10G10B10A2_UINT = 25,
    R11G11B10_FLOAT = 26,
    R8G8B8A8_TYPELESS = 27,
    R8G8B8A8_UNORM = 28,
    R8G8B8A8_UNORM_SRGB = 29,
    R8G8B8A8_UINT = 30,
    R8G8B8A8_SNORM = 31,
    R8G8B8A8_SINT = 32,
    R16G16_TYPELESS = 33,
    R16G16_FLOAT = 34,
    R16G16_UNORM = 35,
    R16G16_UINT = 36,
    R16G16_SNORM = 37,
    R16G16_SINT = 38,
    R32_TYPELESS = 39,
    D32_FLOAT = 40,
    R32_FLOAT = 41,
    R32_UINT = 42,
    R32_SINT = 43,
    R24G8_TYPELESS = 44,
    D24_UNORM_S8_UINT = 45,
    R24_UNORM_X8_TYPELESS = 46,
    X24_TYPELESS_G8_UINT = 47,
    R8G8_TYPELESS = 48,
    R8G8_UNORM = 49,
    R8G8_UINT = 50,
    R8G8_SNORM = 51,
    R8G8_SINT = 52,
    R16_TYPELESS = 53,
    R16_FLOAT = 54,
    D16_UNORM = 55,
    R16_UNORM = 56,
    R16_UINT = 57,
    R16_SNORM = 58,
    R16_SINT = 59,
    R8_TYPELESS = 60,
    R8_UNORM = 61,
    R8_UINT = 62,
    R8_SNORM = 63,
    R8_SINT = 64,
    A8_UNORM = 65,
    R1_UNORM = 66,
    R9G9B9E5_SHAREDEXP = 67,
    R8G8_B8G8_UNORM = 68,
    G8R8_G8B8_UNORM = 69,
    BC1_TYPELESS = 70,
    BC1_UNORM = 71,
    BC1_UNORM_SRGB = 72,
    BC2_TYPELESS = 73,
    BC2_UNORM = 74,
    BC2_UNORM_SRGB = 75,
    BC3_TYPELESS = 76,
    BC3_UNORM = 77,
    BC3_UNORM_SRGB = 78,
    BC4_TYPELESS = 79,
    BC4_UNORM = 80,
    BC4_SNORM = 81,
    BC5_TYPELESS = 82,
    BC5_UNORM = 83,
    BC5_SNORM = 84,
    B5G6R5_UNORM = 85,
    B5G5R5A1_UNORM = 86,
    B8G8R8A8_UNORM = 87,
    B8G8R8X8_UNORM = 88,
    R10G10B10_XR_BIAS_A2_UNORM = 89,
    B8G8R8A8_TYPELESS = 90,
    B8G8R8A8_UNORM_SRGB = 91,
    B8G8R8X8_TYPELESS = 92,
    B8G8R8X8_UNORM_SRGB = 93,
    BC6H_TYPELESS = 94,
    BC6H_UF16 = 95,
    BC6H_SF16 = 96,
    BC7_TYPELESS = 97,
    BC7_UNORM = 98,
    BC7_UNORM_SRGB = 99,
    AYUV = 100,
    Y410 = 101,
    Y416 = 102,
    NV12 = 103,
    P010 = 104,
    P016 = 105,
    _420_OPAQUE = 106,
    YUY2 = 107,
    Y210 = 108,
    Y216 = 109,
    NV11 = 110,
    AI44 = 111,
    IA44 = 112,
    P8 = 113,
    A8P8 = 114,
    B4G4R4A4_UNORM = 115,
    P208 = 130,
    V208 = 131,
    V408 = 132,
    SAMPLER_FEEDBACK_MIN_MIP_OPAQUE = 133
    SAMPLER_FEEDBACK_MIP_REGION_USED_OPAQUE = 134
    INVALID = -1

    @classmethod
    def _missing_(cls, value: object):
        return cls.INVALID


def make_fourcc(name):
    return struct.unpack('I', name.encode('ascii'))[0]


class D3DFMT(IntEnum):
    UNKNOWN = 0
    R8G8B8 = 20
    A8R8G8B8 = 21
    X8R8G8B8 = 22
    R5G6B5 = 23
    X1R5G5B5 = 24
    A1R5G5B5 = 25
    A4R4G4B4 = 26
    R3G3B2 = 27
    A8 = 28
    A8R3G3B2 = 29
    X4R4G4B4 = 30
    A2B10G10R10 = 31
    A8B8G8R8 = 32
    X8B8G8R8 = 33
    G16R16 = 34
    A2R10G10B10 = 35
    A16B16G16R16 = 36
    A8P8 = 40
    P8 = 41
    L8 = 50
    A8L8 = 51
    A4L4 = 52
    V8U8 = 60
    L6V5U5 = 61
    X8L8V8U8 = 62
    Q8W8V8U8 = 63
    V16U16 = 64
    A2W10V10U10 = 67
    D16_LOCKABLE = 70
    D32 = 71
    D15S1 = 73
    D24S8 = 75
    D24X8 = 77
    D24X4S4 = 79
    D16 = 80
    D32F_LOCKABLE = 82
    D24FS8 = 83
    D32_LOCKABLE = 84
    S8_LOCKABLE = 85
    L16 = 81
    VERTEXDATA = 100
    INDEX16 = 101
    INDEX32 = 102
    Q16W16V16U16 = 110
    R16F = 111
    G16R16F = 112
    A16B16G16R16F = 113
    R32F = 114
    G32R32F = 115
    A32B32G32R32F = 116
    CxV8U8 = 117
    A1 = 118
    A2B10G10R10_XR_BIAS = 119
    BINARYBUFFER = 199

    UYVY = make_fourcc('UYVY')
    R8G8_B8G8 = make_fourcc('RGBG')
    YUY2 = make_fourcc('YUY2')
    G8R8_G8B8 = make_fourcc('GRGB')
    DXT1 = make_fourcc('DXT1')
    DXT2 = make_fourcc('DXT2')
    DXT3 = make_fourcc('DXT3')
    DXT4 = make_fourcc('DXT4')
    DXT5 = make_fourcc('DXT5')
    DX10 = make_fourcc('DX10')
    BC5S = make_fourcc('BC5S')
    ATI1 = make_fourcc('ATI1')
    ATI2 = make_fourcc('ATI2')
    MULTI2_ARGB8 = make_fourcc('MET1')
    INVALID = -1

    @classmethod
    def _missing_(cls, value: object):
        return cls.INVALID


class DdsImageFile(ImageFile.ImageFile):
    format = "DDS"
    format_description = "DirectDraw Surface"

    def _open(self):
        if not _accept(self.fp.read(4)):
            msg = "not a DDS file"
            raise SyntaxError(msg)
        (header_size,) = struct.unpack("<I", self.fp.read(4))
        if header_size != 124:
            msg = f"Unsupported header size {repr(header_size)}"
            raise OSError(msg)
        header_bytes = self.fp.read(header_size - 4)
        if len(header_bytes) != 120:
            msg = f"Incomplete header: {len(header_bytes)} bytes"
            raise OSError(msg)
        header = BytesIO(header_bytes)

        flags_, height, width = struct.unpack("<3I", header.read(12))
        flags = DDSD(flags_)
        self._size = (width, height)
        self.mode = "RGBA"

        pitch, depth, mipmaps = struct.unpack("<3I", header.read(12))
        struct.unpack("<11I", header.read(44))  # reserved

        # pixel format
        pfsize, pfflags_, fourcc_, bitcount = struct.unpack("<4I", header.read(16))
        pfflags = DDPF(pfflags_)
        fourcc = D3DFMT(fourcc_)
        masks = struct.unpack("<4I", header.read(16))
        if flags & DDSD.CAPS:
            (caps1_, caps2_, caps3, caps4, _,) = struct.unpack("<5I", header.read(20))
        else:
            (caps1_, caps2_, caps3, caps4, _,) = 0, 0, 0, 0, 0
        caps1 = DDSCAPS(caps1_)
        caps2 = DDSCAPS2(caps2_)
        if pfflags & DDPF.LUMINANCE:
            # Texture contains uncompressed L or LA data
            if pfflags & DDPF.ALPHAPIXELS:
                self.mode = "LA"
            else:
                self.mode = "L"

            self.tile = [("raw", (0, 0) + self.size, 0, (self.mode, 0, 1))]
        elif pfflags & DDPF.RGB:
            # Texture contains uncompressed RGB data
            masks = {mask: ["R", "G", "B", "A"][i] for i, mask in enumerate(masks)}
            rawmode = ""
            if bitcount == 32:
                rawmode += masks[0xFF000000]
            else:
                self.mode = "RGB"
            rawmode += masks[0xFF0000] + masks[0xFF00] + masks[0xFF]

            self.tile = [("raw", (0, 0) + self.size, 0, (rawmode[::-1], 0, 1))]
        elif pfflags & DDPF.FOURCC:
            data_start = header_size + 4
            if fourcc == D3DFMT.DXT1:
                self.pixel_format = "DXT1"
                tile = ("bcn", (0, 0) + self.size, data_start, (1, self.pixel_format))
            elif fourcc == D3DFMT.DXT3:
                self.pixel_format = "DXT3"
                tile = ("bcn", (0, 0) + self.size, data_start, (2, self.pixel_format))
            elif fourcc == D3DFMT.DXT5:
                self.pixel_format = "DXT5"
                tile = ("bcn", (0, 0) + self.size, data_start, (3, self.pixel_format))
            elif fourcc == D3DFMT.BC5S:
                self.pixel_format = "BC5S"
                tile = ("bcn", (0, 0) + self.size, data_start, (5, self.pixel_format))
                self.mode = "RGB"
            elif fourcc == D3DFMT.ATI1:
                self.pixel_format = "BC4"
                tile = ("bcn", (0, 0) + self.size, data_start, (4, self.pixel_format))
                self.mode = "L"
            elif fourcc == D3DFMT.ATI2:
                self.pixel_format = "BC5"
                tile = ("bcn", (0, 0) + self.size, data_start, (5, self.pixel_format))
                self.mode = "RGB"
            elif fourcc == D3DFMT.DX10:
                data_start += 20
                # ignoring flags which pertain to volume textures and cubemaps
                (dxgi_format,) = struct.unpack("<I", self.fp.read(4))
                self.fp.read(16)
                if dxgi_format in (DXGI_FORMAT.BC5_TYPELESS, DXGI_FORMAT.BC5_UNORM):
                    self.pixel_format = "BC5"
                    tile = ("bcn", (0, 0) + self.size, data_start, (5, self.pixel_format))
                    self.mode = "RGB"
                elif dxgi_format == DXGI_FORMAT.BC5_SNORM:
                    self.pixel_format = "BC5S"
                    tile = ("bcn", (0, 0) + self.size, data_start, (5, self.pixel_format))
                    self.mode = "RGB"
                elif dxgi_format == DXGI_FORMAT.BC6H_UF16:
                    self.pixel_format = "BC6H"
                    tile = ("bcn", (0, 0) + self.size, data_start, (6, self.pixel_format))
                    self.mode = "RGB"
                elif dxgi_format == DXGI_FORMAT.BC6H_SF16:
                    self.pixel_format = "BC6HS"
                    tile = ("bcn", (0, 0) + self.size, data_start, (6, self.pixel_format))
                    self.mode = "RGB"
                elif dxgi_format in (DXGI_FORMAT.BC7_TYPELESS, DXGI_FORMAT.BC7_UNORM):
                    self.pixel_format = "BC7"
                    tile = ("bcn", (0, 0) + self.size, data_start, (7, self.pixel_format))
                elif dxgi_format == DXGI_FORMAT.BC7_UNORM_SRGB:
                    self.pixel_format = "BC7"
                    self.info["gamma"] = 1 / 2.2
                    tile = ("bcn", (0, 0) + self.size, data_start, (7, self.pixel_format))
                elif dxgi_format in (
                    DXGI_FORMAT.R8G8B8A8_TYPELESS,
                    DXGI_FORMAT.R8G8B8A8_UNORM,
                    DXGI_FORMAT.R8G8B8A8_UNORM_SRGB,
                ):
                    tile = ("raw", (0, 0) + self.size, 0, ("RGBA", 0, 1))
                    if dxgi_format == DXGI_FORMAT.R8G8B8A8_UNORM_SRGB:
                        self.info["gamma"] = 1 / 2.2
                else:
                    msg = f"Unimplemented DXGI format {dxgi_format}"
                    raise NotImplementedError(msg)
            else:
                msg = f"Unimplemented pixel format {repr(fourcc)}"
                raise NotImplementedError(msg)

            self.tile = [tile]
        else:
            raise NotImplementedError(f'Unknown pixel format flags {repr(pfflags)}')

    def load_seek(self, pos):
        pass


def _save(im, fp, filename):
    if im.mode not in ("RGB", "RGBA", "L", "LA"):
        msg = f"cannot write mode {im.mode} as DDS"
        raise OSError(msg)

    rawmode = im.mode
    masks = [0xFF0000, 0xFF00, 0xFF]
    if im.mode in ("L", "LA"):
        pixel_flags = DDPF.LUMINANCE
    else:
        pixel_flags = DDPF.RGB
        rawmode = rawmode[::-1]
    if im.mode in ("LA", "RGBA"):
        pixel_flags |= DDPF.ALPHAPIXELS
        masks.append(0xFF000000)

    bitcount = len(masks) * 8
    while len(masks) < 4:
        masks.append(0)

    fp.write(
        o32(DDS_MAGIC)
        + o32(124)  # header size
        + o32(DDSD.CAPS | DDSD.HEIGHT | DDSD.WIDTH | DDSD.PITCH | DDSD.PIXELFORMAT)  # flags
        + o32(im.height)
        + o32(im.width)
        + o32((im.width * bitcount + 7) // 8)  # pitch
        + o32(0)  # depth
        + o32(0)  # mipmaps
        + o32(0) * 11  # reserved
        + o32(32)  # pfsize
        + o32(pixel_flags)  # pfflags
        + o32(0)  # fourcc
        + o32(bitcount)  # bitcount
        + b"".join(o32(mask) for mask in masks)  # rgbabitmask
        + o32(DDSCAPS.TEXTURE)  # dwCaps
        + o32(0)  # dwCaps2
        + o32(0)  # dwCaps3
        + o32(0)  # dwCaps4
        + o32(0)  # dwReserved2
    )
    if im.mode == "RGBA":
        r, g, b, a = im.split()
        im = Image.merge("RGBA", (a, r, g, b))
    ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, 0, 1))])


def _accept(prefix):
    return prefix[:4] == b"DDS "


Image.register_open(DdsImageFile.format, DdsImageFile, _accept)
Image.register_save(DdsImageFile.format, _save)
Image.register_extension(DdsImageFile.format, ".dds")