#
# The Python Imaging Library.
# $Id$
#
# GIF file handling
#
# History:
# 1995-09-01 fl   Created
# 1996-12-14 fl   Added interlace support
# 1996-12-30 fl   Added animation support
# 1997-01-05 fl   Added write support, fixed local colour map bug
# 1997-02-23 fl   Make sure to load raster data in getdata()
# 1997-07-05 fl   Support external decoder (0.4)
# 1998-07-09 fl   Handle all modes when saving (0.5)
# 1998-07-15 fl   Renamed offset attribute to avoid name clash
# 2001-04-16 fl   Added rewind support (seek to frame 0) (0.6)
# 2001-04-17 fl   Added palette optimization (0.7)
# 2002-06-06 fl   Added transparency support for save (0.8)
# 2004-02-24 fl   Disable interlacing for small images
#
# Copyright (c) 1997-2004 by Secret Labs AB
# Copyright (c) 1995-2004 by Fredrik Lundh
#
# See the README file for information on usage and redistribution.
#

from . import Image, ImageFile, ImagePalette, ImageChops, ImageSequence
from ._binary import i8, i16le as i16, o8, o16le as o16

import itertools

# __version__ is deprecated and will be removed in a future version. Use
# PIL.__version__ instead.
__version__ = "0.9"


# --------------------------------------------------------------------
# Identify/read GIF files


def _accept(prefix):
    return prefix[:6] in [b"GIF87a", b"GIF89a"]


##
# Image plugin for GIF images.  This plugin supports both GIF87 and
# GIF89 images.


class GifImageFile(ImageFile.ImageFile):

    format = "GIF"
    format_description = "Compuserve GIF"
    _close_exclusive_fp_after_loading = False

    global_palette = None

    def data(self):
        s = self.fp.read(1)
        if s and i8(s):
            return self.fp.read(i8(s))
        return None

    def _open(self):

        # Screen
        s = self.fp.read(13)
        if s[:6] not in [b"GIF87a", b"GIF89a"]:
            raise SyntaxError("not a GIF file")

        self.info["version"] = s[:6]
        self._size = i16(s[6:]), i16(s[8:])
        self.tile = []
        flags = i8(s[10])
        bits = (flags & 7) + 1

        if flags & 128:
            # get global palette
            self.info["background"] = i8(s[11])
            # check if palette contains colour indices
            p = self.fp.read(3 << bits)
            for i in range(0, len(p), 3):
                if not (i // 3 == i8(p[i]) == i8(p[i + 1]) == i8(p[i + 2])):
                    p = ImagePalette.raw("RGB", p)
                    self.global_palette = self.palette = p
                    break

        self.__fp = self.fp  # FIXME: hack
        self.__rewind = self.fp.tell()
        self._n_frames = None
        self._is_animated = None
        self._seek(0)  # get ready to read first frame

    @property
    def n_frames(self):
        if self._n_frames is None:
            current = self.tell()
            try:
                while True:
                    self.seek(self.tell() + 1)
            except EOFError:
                self._n_frames = self.tell() + 1
            self.seek(current)
        return self._n_frames

    @property
    def is_animated(self):
        if self._is_animated is None:
            if self._n_frames is not None:
                self._is_animated = self._n_frames != 1
            else:
                current = self.tell()

                try:
                    self.seek(1)
                    self._is_animated = True
                except EOFError:
                    self._is_animated = False

                self.seek(current)
        return self._is_animated

    def seek(self, frame):
        if not self._seek_check(frame):
            return
        if frame < self.__frame:
            if frame != 0:
                self.im = None
            self._seek(0)

        last_frame = self.__frame
        for f in range(self.__frame + 1, frame + 1):
            try:
                self._seek(f)
            except EOFError:
                self.seek(last_frame)
                raise EOFError("no more images in GIF file")

    def _seek(self, frame):

        if frame == 0:
            # rewind
            self.__offset = 0
            self.dispose = None
            self.dispose_extent = [0, 0, 0, 0]  # x0, y0, x1, y1
            self.__frame = -1
            self.__fp.seek(self.__rewind)
            self._prev_im = None
            self.disposal_method = 0
        else:
            # ensure that the previous frame was loaded
            if not self.im:
                self.load()

        if frame != self.__frame + 1:
            raise ValueError("cannot seek to frame %d" % frame)
        self.__frame = frame

        self.tile = []

        self.fp = self.__fp
        if self.__offset:
            # backup to last frame
            self.fp.seek(self.__offset)
            while self.data():
                pass
            self.__offset = 0

        if self.dispose:
            self.im.paste(self.dispose, self.dispose_extent)

        from copy import copy

        self.palette = copy(self.global_palette)

        info = {}
        while True:

            s = self.fp.read(1)
            if not s or s == b";":
                break

            elif s == b"!":
                #
                # extensions
                #
                s = self.fp.read(1)
                block = self.data()
                if i8(s) == 249:
                    #
                    # graphic control extension
                    #
                    flags = i8(block[0])
                    if flags & 1:
                        info["transparency"] = i8(block[3])
                    info["duration"] = i16(block[1:3]) * 10

                    # disposal method - find the value of bits 4 - 6
                    dispose_bits = 0b00011100 & flags
                    dispose_bits = dispose_bits >> 2
                    if dispose_bits:
                        # only set the dispose if it is not
                        # unspecified. I'm not sure if this is
                        # correct, but it seems to prevent the last
                        # frame from looking odd for some animations
                        self.disposal_method = dispose_bits
                elif i8(s) == 254:
                    #
                    # comment extension
                    #
                    while block:
                        if "comment" in info:
                            info["comment"] += block
                        else:
                            info["comment"] = block
                        block = self.data()
                    continue
                elif i8(s) == 255:
                    #
                    # application extension
                    #
                    info["extension"] = block, self.fp.tell()
                    if block[:11] == b"NETSCAPE2.0":
                        block = self.data()
                        if len(block) >= 3 and i8(block[0]) == 1:
                            info["loop"] = i16(block[1:3])
                while self.data():
                    pass

            elif s == b",":
                #
                # local image
                #
                s = self.fp.read(9)

                # extent
                x0, y0 = i16(s[0:]), i16(s[2:])
                x1, y1 = x0 + i16(s[4:]), y0 + i16(s[6:])
                if x1 > self.size[0] or y1 > self.size[1]:
                    self._size = max(x1, self.size[0]), max(y1, self.size[1])
                self.dispose_extent = x0, y0, x1, y1
                flags = i8(s[8])

                interlace = (flags & 64) != 0

                if flags & 128:
                    bits = (flags & 7) + 1
                    self.palette = ImagePalette.raw("RGB", self.fp.read(3 << bits))

                # image data
                bits = i8(self.fp.read(1))
                self.__offset = self.fp.tell()
                self.tile = [
                    ("gif", (x0, y0, x1, y1), self.__offset, (bits, interlace))
                ]
                break

            else:
                pass
                # raise IOError, "illegal GIF tag `%x`" % i8(s)

        try:
            if self.disposal_method < 2:
                # do not dispose or none specified
                self.dispose = None
            elif self.disposal_method == 2:
                # replace with background colour
                self.dispose = Image.core.fill("P", self.size, self.info["background"])
            else:
                # replace with previous contents
                if self.im:
                    self.dispose = self.im.copy()

            # only dispose the extent in this frame
            if self.dispose:
                self.dispose = self._crop(self.dispose, self.dispose_extent)
        except (AttributeError, KeyError):
            pass

        if not self.tile:
            # self.__fp = None
            raise EOFError

        for k in ["transparency", "duration", "comment", "extension", "loop"]:
            if k in info:
                self.info[k] = info[k]
            elif k in self.info:
                del self.info[k]

        self.mode = "L"
        if self.palette:
            self.mode = "P"

    def tell(self):
        return self.__frame

    def load_end(self):
        ImageFile.ImageFile.load_end(self)

        # if the disposal method is 'do not dispose', transparent
        # pixels should show the content of the previous frame
        if self._prev_im and self.disposal_method == 1:
            # we do this by pasting the updated area onto the previous
            # frame which we then use as the current image content
            updated = self._crop(self.im, self.dispose_extent)
            self._prev_im.paste(updated, self.dispose_extent, updated.convert("RGBA"))
            self.im = self._prev_im
        self._prev_im = self.im.copy()

    def _close__fp(self):
        try:
            if self.__fp != self.fp:
                self.__fp.close()
        except AttributeError:
            pass
        finally:
            self.__fp = None


# --------------------------------------------------------------------
# Write GIF files


RAWMODE = {"1": "L", "L": "L", "P": "P"}


def _normalize_mode(im, initial_call=False):
    """
    Takes an image (or frame), returns an image in a mode that is appropriate
    for saving in a Gif.

    It may return the original image, or it may return an image converted to
    palette or 'L' mode.

    UNDONE: What is the point of mucking with the initial call palette, for
    an image that shouldn't have a palette, or it would be a mode 'P' and
    get returned in the RAWMODE clause.

    :param im: Image object
    :param initial_call: Default false, set to true for a single frame.
    :returns: Image object
    """
    if im.mode in RAWMODE:
        im.load()
        return im