# Copyright 2006 Joe Wreschnig
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.

"""Read and write Ogg Theora comments.

This module handles Theora files wrapped in an Ogg bitstream. The
first Theora stream found is used.

Based on the specification at http://theora.org/doc/Theora_I_spec.pdf.
"""

__all__ = ["OggTheora", "Open", "delete"]

import struct

from mutagen import StreamInfo
from mutagen._vorbis import VCommentDict
from mutagen._util import cdata, get_size, loadfile, convert_error
from mutagen._tags import PaddingInfo
from mutagen.ogg import OggPage, OggFileType, error as OggError


class error(OggError):
    pass


class OggTheoraHeaderError(error):
    pass


class OggTheoraInfo(StreamInfo):
    """OggTheoraInfo()

    Ogg Theora stream information.

    Attributes:
        length (`float`): File length in seconds, as a float
        fps (`float`): Video frames per second, as a float
        bitrate (`int`): Bitrate in bps (int)
    """

    length = 0
    fps = 0
    bitrate = 0

    def __init__(self, fileobj):
        page = OggPage(fileobj)
        while not page.packets or \
                not page.packets[0].startswith(b"\x80theora"):
            page = OggPage(fileobj)
        if not page.first:
            raise OggTheoraHeaderError(
                "page has ID header, but doesn't start a stream")
        data = page.packets[0]
        if len(data) < 42:
            raise OggTheoraHeaderError("Truncated header")
        vmaj, vmin = struct.unpack("2B", data[7:9])
        if (vmaj, vmin) != (3, 2):
            raise OggTheoraHeaderError(
                "found Theora version %d.%d != 3.2" % (vmaj, vmin))
        fps_num, fps_den = struct.unpack(">2I", data[22:30])
        if not fps_den or not fps_num:
            raise OggTheoraHeaderError("FRN or FRD is equal to zero")
        self.fps = fps_num / float(fps_den)
        self.bitrate = cdata.uint_be(b"\x00" + data[37:40])
        self.granule_shift = (cdata.ushort_be(data[40:42]) >> 5) & 0x1F
        self.serial = page.serial

    def _post_tags(self, fileobj):
        page = OggPage.find_last(fileobj, self.serial, finishing=True)
        if page is None:
            raise OggTheoraHeaderError
        position = page.position
        mask = (1 << self.granule_shift) - 1
        frames = (position >> self.granule_shift) + (position & mask)
        assert self.fps
        self.length = frames / float(self.fps)

    def pprint(self):
        return u"Ogg Theora, %.2f seconds, %d bps" % (self.length,
                                                      self.bitrate)


class OggTheoraCommentDict(VCommentDict):
    """Theora comments embedded in an Ogg bitstream."""

    def __init__(self, fileobj, info):
        pages = []
        complete = False
        while not complete:
            page = OggPage(fileobj)
            if page.serial == info.serial:
                pages.append(page)
                complete = page.complete or (len(page.packets) > 1)
        packets = OggPage.to_packets(pages)
        if not packets:
            raise error("Missing metadata packet")
        data = packets[0][7:]
        super(OggTheoraCommentDict, self).__init__(data, framing=False)
        self._padding = len(data) - self._size

    def _inject(self, fileobj, padding_func):
        """Write tag data into the Theora comment packet/page."""

        fileobj.seek(0)
        page = OggPage(fileobj)
        while not page.packets or \
                not page.packets[0].startswith(b"\x81theora"):
            page = OggPage(fileobj)

        old_pages = [page]
        while not (old_pages[-1].complete or len(old_pages[-1].packets) > 1):
            page = OggPage(fileobj)
            if page.serial == old_pages[0].serial:
                old_pages.append(page)

        packets = OggPage.to_packets(old_pages, strict=False)

        content_size = get_size(fileobj) - len(packets[0])  # approx
        vcomment_data = b"\x81theora" + self.write(framing=False)
        padding_left = len(packets[0]) - len(vcomment_data)

        info = PaddingInfo(padding_left, content_size)
        new_padding = info._get_padding(padding_func)

        packets[0] = vcomment_data + b"\x00" * new_padding

        new_pages = OggPage._from_packets_try_preserve(packets, old_pages)
        OggPage.replace(fileobj, old_pages, new_pages)


class OggTheora(OggFileType):
    """OggTheora(filething)

    An Ogg Theora file.

    Arguments:
        filething (filething)

    Attributes:
        info (`OggTheoraInfo`)
        tags (`mutagen._vorbis.VCommentDict`)
    """

    _Info = OggTheoraInfo
    _Tags = OggTheoraCommentDict
    _Error = OggTheoraHeaderError
    _mimes = ["video/x-theora"]

    info = None
    tags = None

    @staticmethod
    def score(filename, fileobj, header):
        return (header.startswith(b"OggS") *
                ((b"\x80theora" in header) + (b"\x81theora" in header)) * 2)


Open = OggTheora


@convert_error(IOError, error)
@loadfile(method=False, writable=True)
def delete(filething):
    """ delete(filething)

    Arguments:
        filething (filething)
    Raises:
        mutagen.MutagenError

    Remove tags from a file.
    """

    t = OggTheora(filething)
    filething.fileobj.seek(0)
    t.delete(filething)