# A WavPack reader/tagger
#
# Copyright 2006 Joe Wreschnig
#           2014 Christoph Reiter
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.

"""WavPack reading and writing.

WavPack is a lossless format that uses APEv2 tags. Read

* http://www.wavpack.com/
* http://www.wavpack.com/file_format.txt

for more information.
"""

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

from mutagen import StreamInfo
from mutagen.apev2 import APEv2File, error, delete
from mutagen._util import cdata


class WavPackHeaderError(error):
    pass

RATES = [6000, 8000, 9600, 11025, 12000, 16000, 22050, 24000, 32000, 44100,
         48000, 64000, 88200, 96000, 192000]


class _WavPackHeader(object):

    def __init__(self, block_size, version, track_no, index_no, total_samples,
                 block_index, block_samples, flags, crc):

        self.block_size = block_size
        self.version = version
        self.track_no = track_no
        self.index_no = index_no
        self.total_samples = total_samples
        self.block_index = block_index
        self.block_samples = block_samples
        self.flags = flags
        self.crc = crc

    @classmethod
    def from_fileobj(cls, fileobj):
        """A new _WavPackHeader or raises WavPackHeaderError"""

        header = fileobj.read(32)
        if len(header) != 32 or not header.startswith(b"wvpk"):
            raise WavPackHeaderError("not a WavPack header: %r" % header)

        block_size = cdata.uint_le(header[4:8])
        version = cdata.ushort_le(header[8:10])
        track_no = ord(header[10:11])
        index_no = ord(header[11:12])
        samples = cdata.uint_le(header[12:16])
        if samples == 2**32 - 1:
            samples = -1
        block_index = cdata.uint_le(header[16:20])
        block_samples = cdata.uint_le(header[20:24])
        flags = cdata.uint_le(header[24:28])
        crc = cdata.uint_le(header[28:32])

        return _WavPackHeader(block_size, version, track_no, index_no,
                              samples, block_index, block_samples, flags, crc)


class WavPackInfo(StreamInfo):
    """WavPack stream information.

    Attributes:

    * channels - number of audio channels (1 or 2)
    * length - file length in seconds, as a float
    * sample_rate - audio sampling rate in Hz
    * version - WavPack stream version
    """

    def __init__(self, fileobj):
        try:
            header = _WavPackHeader.from_fileobj(fileobj)
        except WavPackHeaderError:
            raise WavPackHeaderError("not a WavPack file")

        self.version = header.version
        self.channels = bool(header.flags & 4) or 2
        self.sample_rate = RATES[(header.flags >> 23) & 0xF]

        if header.total_samples == -1 or header.block_index != 0:
            # TODO: we could make this faster by using the tag size
            # and search backwards for the last block, then do
            # last.block_index + last.block_samples - initial.block_index
            samples = header.block_samples
            while 1:
                fileobj.seek(header.block_size - 32 + 8, 1)
                try:
                    header = _WavPackHeader.from_fileobj(fileobj)
                except WavPackHeaderError:
                    break
                samples += header.block_samples
        else:
            samples = header.total_samples

        self.length = float(samples) / self.sample_rate

    def pprint(self):
        return "WavPack, %.2f seconds, %d Hz" % (self.length, self.sample_rate)


class WavPack(APEv2File):
    _Info = WavPackInfo
    _mimes = ["audio/x-wavpack"]

    @staticmethod
    def score(filename, fileobj, header):
        return header.startswith(b"wvpk") * 2


Open = WavPack
