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# Source code for PIL.FliImagePlugin

    #
    # The Python Imaging Library.
    # $Id$
    #
    # FLI/FLC file handling.
    #
    # History:
    #       95-09-01 fl     Created
    #       97-01-03 fl     Fixed parser, setup decoder tile
    #       98-07-15 fl     Renamed offset attribute to avoid name clash
    #
    # Copyright (c) Secret Labs AB 1997-98.
    # Copyright (c) Fredrik Lundh 1995-97.
    #
    # See the README file for information on usage and redistribution.
    #
    from __future__ import annotations

    import os

    from . import Image, ImageFile, ImagePalette
    from ._binary import i16le as i16
    from ._binary import i32le as i32
    from ._binary import o8
    from ._util import DeferredError

    #
    # decoder

    def _accept(prefix: bytes) -> bool:
        return (
            len(prefix) >= 16
            and i16(prefix, 4) in [0xAF11, 0xAF12]
            and i16(prefix, 14) in [0, 3]  # flags
        )

    ##
    # Image plugin for the FLI/FLC animation format.  Use the <b>seek</b>
    # method to load individual frames.

    class FliImageFile(ImageFile.ImageFile):
        format = "FLI"
        format_description = "Autodesk FLI/FLC Animation"
        _close_exclusive_fp_after_loading = False

        def _open(self) -> None:
            # HEAD
            assert self.fp is not None
            s = self.fp.read(128)
            if not (
                _accept(s)
                and s[20:22] == b"\x00" * 2
                and s[42:80] == b"\x00" * 38
                and s[88:] == b"\x00" * 40
            ):
                msg = "not an FLI/FLC file"
                raise SyntaxError(msg)

            # frames
            self.n_frames = i16(s, 6)
            self.is_animated = self.n_frames > 1

            # image characteristics
            self._mode = "P"
            self._size = i16(s, 8), i16(s, 10)

            # animation speed
            duration = i32(s, 16)
            magic = i16(s, 4)
            if magic == 0xAF11:
                duration = (duration * 1000) // 70
            self.info["duration"] = duration

            # look for palette
            palette = [(a, a, a) for a in range(256)]

            s = self.fp.read(16)

            self.__offset = 128

            if i16(s, 4) == 0xF100:
                # prefix chunk; ignore it
                self.fp.seek(self.__offset + i32(s))
                s = self.fp.read(16)

            if i16(s, 4) == 0xF1FA:
                # look for palette chunk
                number_of_subchunks = i16(s, 6)
                chunk_size: int | None = None
                for _ in range(number_of_subchunks):
                    if chunk_size is not None:
                        self.fp.seek(chunk_size - 6, os.SEEK_CUR)
                    s = self.fp.read(6)
                    chunk_type = i16(s, 4)
                    if chunk_type in (4, 11):
                        self._palette(palette, 2 if chunk_type == 11 else 0)
                        break
                    chunk_size = i32(s)
                    if not chunk_size:
                        break

            self.palette = ImagePalette.raw(
                "RGB", b"".join(o8(r) + o8(g) + o8(b) for (r, g, b) in palette)
            )

            # set things up to decode first frame
            self.__frame = -1
            self._fp = self.fp
            self.__rewind = self.fp.tell()
            self.seek(0)

        def _palette(self, palette: list[tuple[int, int, int]], shift: int) -> None:
            # load palette

            i = 0
            assert self.fp is not None
            for e in range(i16(self.fp.read(2))):
                s = self.fp.read(2)
                i = i + s[0]
                n = s[1]
                if n == 0:
                    n = 256
                s = self.fp.read(n * 3)
                for n in range(0, len(s), 3):
                    r = s[n] << shift
                    g = s[n + 1] << shift
                    b = s[n + 2] << shift
                    palette[i] = (r, g, b)
                    i += 1

        def seek(self, frame: int) -> None:
            if not self._seek_check(frame):
                return
            if frame < self.__frame:
                self._seek(0)

            for f in range(self.__frame + 1, frame + 1):
                self._seek(f)

        def _seek(self, frame: int) -> None:
            if isinstance(self._fp, DeferredError):
                raise self._fp.ex
            if frame == 0:
                self.__frame = -1
                self._fp.seek(self.__rewind)
                self.__offset = 128
            else:
                # ensure that the previous frame was loaded
                self.load()

            if frame != self.__frame + 1:
                msg = f"cannot seek to frame {frame}"
                raise ValueError(msg)
            self.__frame = frame

            # move to next frame
            self.fp = self._fp
            self.fp.seek(self.__offset)

            s = self.fp.read(4)
            if not s:
                msg = "missing frame size"
                raise EOFError(msg)

            framesize = i32(s)

            self.decodermaxblock = framesize
            self.tile = [ImageFile._Tile("fli", (0, 0) + self.size, self.__offset)]

            self.__offset += framesize

        def tell(self) -> int:
            return self.__frame

    #
    # registry

    Image.register_open(FliImageFile.format, FliImageFile, _accept)

    Image.register_extensions(FliImageFile.format, [".fli", ".flc"])