# This file is part of audioread.
# Copyright 2011, Adrian Sampson.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

"""Read audio files using CoreAudio on Mac OS X."""
import copy
import ctypes
import ctypes.util
import os
import sys

from .exceptions import DecodeError
from .base import AudioFile


# CoreFoundation and CoreAudio libraries along with their function
# prototypes.

def _load_framework(name):
    return ctypes.cdll.LoadLibrary(ctypes.util.find_library(name))


_coreaudio = _load_framework('AudioToolbox')
_corefoundation = _load_framework('CoreFoundation')

# Convert CFStrings to C strings.
_corefoundation.CFStringGetCStringPtr.restype = ctypes.c_char_p
_corefoundation.CFStringGetCStringPtr.argtypes = [ctypes.c_void_p,
                                                  ctypes.c_int]

# Free memory.
_corefoundation.CFRelease.argtypes = [ctypes.c_void_p]

# Create a file:// URL.
_corefoundation.CFURLCreateFromFileSystemRepresentation.restype = \
    ctypes.c_void_p
_corefoundation.CFURLCreateFromFileSystemRepresentation.argtypes = \
    [ctypes.c_int, ctypes.c_char_p, ctypes.c_int, ctypes.c_bool]

# Get a string representation of a URL.
_corefoundation.CFURLGetString.restype = ctypes.c_void_p
_corefoundation.CFURLGetString.argtypes = [ctypes.c_void_p]

# Open an audio file for reading.
_coreaudio.ExtAudioFileOpenURL.restype = ctypes.c_int
_coreaudio.ExtAudioFileOpenURL.argtypes = [ctypes.c_void_p, ctypes.c_void_p]

# Set audio file property.
_coreaudio.ExtAudioFileSetProperty.restype = ctypes.c_int
_coreaudio.ExtAudioFileSetProperty.argtypes = \
    [ctypes.c_void_p, ctypes.c_uint, ctypes.c_uint, ctypes.c_void_p]

# Get audio file property.
_coreaudio.ExtAudioFileGetProperty.restype = ctypes.c_int
_coreaudio.ExtAudioFileGetProperty.argtypes = \
    [ctypes.c_void_p, ctypes.c_uint, ctypes.c_void_p, ctypes.c_void_p]

# Read from an audio file.
_coreaudio.ExtAudioFileRead.restype = ctypes.c_int
_coreaudio.ExtAudioFileRead.argtypes = \
    [ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p]

# Close/free an audio file.
_coreaudio.ExtAudioFileDispose.restype = ctypes.c_int
_coreaudio.ExtAudioFileDispose.argtypes = [ctypes.c_void_p]


# Constants used in CoreAudio.

def multi_char_literal(chars):
    """Emulates character integer literals in C. Given a string "abc",
    returns the value of the C single-quoted literal 'abc'.
    """
    num = 0
    for index, char in enumerate(chars):
        shift = (len(chars) - index - 1) * 8
        num |= ord(char) << shift
    return num


PROP_FILE_DATA_FORMAT = multi_char_literal('ffmt')
PROP_CLIENT_DATA_FORMAT = multi_char_literal('cfmt')
PROP_LENGTH = multi_char_literal('#frm')
AUDIO_ID_PCM = multi_char_literal('lpcm')
PCM_IS_FLOAT = 1 << 0
PCM_IS_BIG_ENDIAN = 1 << 1
PCM_IS_SIGNED_INT = 1 << 2
PCM_IS_PACKED = 1 << 3
ERROR_TYPE = multi_char_literal('typ?')
ERROR_FORMAT = multi_char_literal('fmt?')
ERROR_NOT_FOUND = -43


# Check for errors in functions that return error codes.

class MacError(DecodeError):
    def __init__(self, code):
        if code == ERROR_TYPE:
            msg = 'unsupported audio type'
        elif code == ERROR_FORMAT:
            msg = 'unsupported format'
        else:
            msg = 'error %i' % code
        super().__init__(msg)


def check(err):
    """If err is nonzero, raise a MacError exception."""
    if err == ERROR_NOT_FOUND:
        raise OSError('file not found')
    elif err != 0:
        raise MacError(err)


# CoreFoundation objects.

class CFObject:
    def __init__(self, obj):
        if obj == 0:
            raise ValueError('object is zero')
        self._obj = obj

    def __del__(self):
        if _corefoundation:
            _corefoundation.CFRelease(self._obj)


class CFURL(CFObject):
    def __init__(self, filename):
        filename = os.path.abspath(os.path.expanduser(filename))
        if not isinstance(filename, bytes):
            filename = filename.encode(sys.getfilesystemencoding())
        url = _corefoundation.CFURLCreateFromFileSystemRepresentation(
            0, filename, len(filename), False
        )
        super().__init__(url)

    def __str__(self):
        cfstr = _corefoundation.CFURLGetString(self._obj)
        out = _corefoundation.CFStringGetCStringPtr(cfstr, 0)
        # Resulting CFString does not need to be released according to docs.
        return out


# Structs used in CoreAudio.

class AudioStreamBasicDescription(ctypes.Structure):
    _fields_ = [
        ("mSampleRate",       ctypes.c_double),
        ("mFormatID",         ctypes.c_uint),
        ("mFormatFlags",      ctypes.c_uint),
        ("mBytesPerPacket",   ctypes.c_uint),
        ("mFramesPerPacket",  ctypes.c_uint),
        ("mBytesPerFrame",    ctypes.c_uint),
        ("mChannelsPerFrame", ctypes.c_uint),
        ("mBitsPerChannel",   ctypes.c_uint),
        ("mReserved",         ctypes.c_uint),
    ]


class AudioBuffer(ctypes.Structure):
    _fields_ = [
        ("mNumberChannels", ctypes.c_uint),
        ("mDataByteSize",   ctypes.c_uint),
        ("mData",           ctypes.c_void_p),
    ]


class AudioBufferList(ctypes.Structure):
    _fields_ = [
        ("mNumberBuffers",  ctypes.c_uint),
        ("mBuffers", AudioBuffer * 1),
    ]


# Main functionality.

class ExtAudioFile(AudioFile):
    """A CoreAudio "extended audio file". Reads information and raw PCM
    audio data from any file that CoreAudio knows how to decode.

        >>> with ExtAudioFile('something.m4a') as f:
        >>>     print f.samplerate
        >>>     print f.channels
        >>>     print f.duration
        >>>     for block in f:
        >>>         do_something(block)

    """
    def __init__(self, filename):
        url = CFURL(filename)
        try:
            self._obj = self._open_url(url)
        except:
            self.closed = True
            raise
        del url

        self.closed = False
        self._file_fmt = None
        self._client_fmt = None

        self.setup()

    @classmethod
    def _open_url(cls, url):
        """Given a CFURL Python object, return an opened ExtAudioFileRef.
        """
        file_obj = ctypes.c_void_p()
        check(_coreaudio.ExtAudioFileOpenURL(
            url._obj, ctypes.byref(file_obj)
        ))
        return file_obj

    def set_client_format(self, desc):
        """Get the client format description. This describes the
        encoding of the data that the program will read from this
        object.
        """
        assert desc.mFormatID == AUDIO_ID_PCM
        check(_coreaudio.ExtAudioFileSetProperty(
            self._obj, PROP_CLIENT_DATA_FORMAT, ctypes.sizeof(desc),
            ctypes.byref(desc)
        ))
        self._client_fmt = desc

    def get_file_format(self):
        """Get the file format description. This describes the type of
        data stored on disk.
        """
        # Have cached file format?
        if self._file_fmt is not None:
            return self._file_fmt

        # Make the call to retrieve it.
        desc = AudioStreamBasicDescription()
        size = ctypes.c_int(ctypes.sizeof(desc))
        check(_coreaudio.ExtAudioFileGetProperty(
            self._obj, PROP_FILE_DATA_FORMAT, ctypes.byref(size),
            ctypes.byref(desc)
        ))

        # Cache result.
        self._file_fmt = desc
        return desc

    @property
    def channels(self):
        """The number of channels in the audio source."""
        return int(self.get_file_format().mChannelsPerFrame)

    @property
    def samplerate(self):
        """Gets the sample rate of the audio."""
        return int(self.get_file_format().mSampleRate)

    @property
    def duration(self):
        """Gets the length of the file in seconds (a float)."""
        return float(self.nframes) / self.samplerate

    @property
    def nframes(self):
        """Gets the number of frames in the source file."""
        length = ctypes.c_long()
        size = ctypes.c_int(ctypes.sizeof(length))
        check(_coreaudio.ExtAudioFileGetProperty(
            self._obj, PROP_LENGTH, ctypes.byref(size), ctypes.byref(length)
        ))
        return length.value

    def setup(self, bitdepth=16):
        """Set the client format parameters, specifying the desired PCM
        audio data format to be read from the file. Must be called
        before reading from the file.
        """
        fmt = self.get_file_format()
        newfmt = copy.copy(fmt)

        newfmt.mFormatID = AUDIO_ID_PCM
        newfmt.mFormatFlags = \
            PCM_IS_SIGNED_INT | PCM_IS_PACKED
        newfmt.mBitsPerChannel = bitdepth
        newfmt.mBytesPerPacket = \
            (fmt.mChannelsPerFrame * newfmt.mBitsPerChannel // 8)
        newfmt.mFramesPerPacket = 1
        newfmt.mBytesPerFrame = newfmt.mBytesPerPacket
        self.set_client_format(newfmt)

    def read_data(self, blocksize=4096):
        """Generates byte strings reflecting the audio data in the file.
        """
        frames = ctypes.c_uint(blocksize // self._client_fmt.mBytesPerFrame)
        buf = ctypes.create_string_buffer(blocksize)

        buflist = AudioBufferList()
        buflist.mNumberBuffers = 1
        buflist.mBuffers[0].mNumberChannels = \
            self._client_fmt.mChannelsPerFrame
        buflist.mBuffers[0].mDataByteSize = blocksize
        buflist.mBuffers[0].mData = ctypes.cast(buf, ctypes.c_void_p)

        while True:
            check(_coreaudio.ExtAudioFileRead(
                self._obj, ctypes.byref(frames), ctypes.byref(buflist)
            ))

            assert buflist.mNumberBuffers == 1
            size = buflist.mBuffers[0].mDataByteSize
            if not size:
                break

            data = ctypes.cast(buflist.mBuffers[0].mData,
                               ctypes.POINTER(ctypes.c_char))
            blob = data[:size]
            yield blob

    def close(self):
        """Close the audio file and free associated memory."""
        if not self.closed:
            check(_coreaudio.ExtAudioFileDispose(self._obj))
            self.closed = True

    def __del__(self):
        if _coreaudio:
            self.close()

    # Context manager methods.
    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()
        return False

    # Iteration.
    def __iter__(self):
        return self.read_data()
