import os
import subprocess
from tempfile import TemporaryFile, NamedTemporaryFile
from StringIO import StringIO
import wave
import audioop

from .utils import _fd_or_path_or_tempfile, db_to_float
from .exceptions import TooManyMissingFrames
from .exceptions import InvalidDuration


AUDIO_FILE_EXT_ALIASES = {
    "m4a": "mp4"
}


class AudioSegment(object):
    """
    Note: AudioSegment objects are immutable

    slicable using milliseconds. for example: Get the first second of an mp3...

    a = AudioSegment.from_mp3(mp3file)
    first_second = a[:1000]
    """

    def __init__(self, data=None, *args, **kwargs):
        if kwargs.get('metadata', False):
            # internal use only
            self._data = data
            for attr, val in kwargs.pop('metadata').items():
                setattr(self, attr, val)
        else:
            # normal construction
            data = data if isinstance(data, basestring) else data.read()

            raw = wave.open(StringIO(data), 'rb')

            raw.rewind()
            self.channels = raw.getnchannels()
            self.sample_width = raw.getsampwidth()
            self.frame_rate = raw.getframerate()
            self.frame_width = self.channels * self.sample_width

            raw.rewind()
            self._data = raw.readframes(float('inf'))

        super(AudioSegment, self).__init__(*args, **kwargs)

    def __len__(self):
        """
        returns the length of this audio segment in milliseconds
        """
        return round(1000 * (self.frame_count() / self.frame_rate))

    def __iter__(self):
        return (self[i] for i in xrange(len(self)))

    def __getitem__(self, millisecond):
        if isinstance(millisecond, slice):
            start = millisecond.start if millisecond.start is not None else 0
            end = millisecond.stop if millisecond.stop is not None \
                else len(self)

            start = min(start, len(self))
            end = min(end, len(self))
        else:
            start = millisecond
            end = millisecond + 1

        start = self._parse_position(start) * self.frame_width
        end = self._parse_position(end) * self.frame_width
        data = self._data[start:end]

        # ensure the output is as long as the requester is expecting
        expected_length = end - start
        missing_frames = (expected_length - len(data)) / self.frame_width
        if missing_frames:
            if missing_frames > self.frame_count(ms=2):
                raise TooManyMissingFrames("You should never be filling in "\
                "   more than 2 ms with silence here, missing frames: %s" % \
                missing_frames)
            silence = audioop.mul(data[:self.frame_width],
                self.sample_width, 0)
            data += (silence * missing_frames)

        return self._spawn(data)

    def __add__(self, arg):
        if isinstance(arg, AudioSegment):
            return self.append(arg, crossfade=0)
        else:
            return self.apply_gain(arg)

    def __sub__(self, arg):
        if isinstance(arg, AudioSegment):
            raise TypeError("AudioSegment objects can't be subtracted from "\
                "each other")
        else:
            return self.apply_gain(-arg)

    def __mul__(self, arg):
        """
        If the argument is an AudioSegment, overlay the multiplied audio
        segment.


        If it's a number, just use the string multiply operation to repeat the
        audio so the following would return an AudioSegment that contains the
        audio of audio_seg eight times

        audio_seg * 8
        """
        if isinstance(arg, AudioSegment):
            return self.overlay(arg, position=0, loop=True)
        else:
            return self._spawn(data=self._data * arg)

    def _spawn(self, data, overrides={}):
        """
        Creates a new audio segment using the meta data from the current one
        and the data passed in. Should be used whenever an AudioSegment is
        being returned by an operation that alters the current one, since
        AudioSegment objects are immutable.
        """
        # accept lists of data chunks
        if isinstance(data, list):
            data = ''.join(data)

        # accept file-like objects
        if hasattr(data, 'read'):
            if hasattr(data, 'seek'):
                data.seek(0)
            data = data.read()

        metadata = {
                    'sample_width': self.sample_width,
                    'frame_rate': self.frame_rate,
                    'frame_width': self.frame_width,
                    'channels': self.channels
                    }
        metadata.update(overrides)
        return AudioSegment(data=data, metadata=metadata)

    @classmethod
    def _sync(cls, seg1, seg2):
        s1_len, s2_len = len(seg1), len(seg2)

        channels = max(seg1.channels, seg2.channels)
        seg1 = seg1.set_channels(channels)
        seg2 = seg2.set_channels(channels)

        frame_rate = max(seg1.frame_rate, seg2.frame_rate)
        seg1 = seg1.set_frame_rate(frame_rate)
        seg2 = seg2.set_frame_rate(frame_rate)

        assert(len(seg1) == s1_len)
        assert(len(seg2) == s2_len)

        return seg1, seg2

    def _parse_position(self, val):
        if val < 0:
            val = len(self) - abs(val)
        val = self.frame_count(ms=len(self)) if val == float("inf") else \
            self.frame_count(ms=val)
        return int(val)

    @classmethod
    def from_file(cls, file, format=None):
        file = _fd_or_path_or_tempfile(file, 'rb', tempfile=False)

        if not format:
            format = os.path.splitext(file.name)[1]
        format = AUDIO_FILE_EXT_ALIASES.get(format, format)

        if format == 'wav':
            return cls.from_wav(file)

        input = NamedTemporaryFile(mode='wb')
        input.write(file.read())
        input.flush()

        output = NamedTemporaryFile(mode="rb")

        ffmpeg_call = ['ffmpeg',
                       '-y',  # always overwrite existing files
                       ]
        if format:
            ffmpeg_call += ["-f", format]
        ffmpeg_call += [
                        "-i", input.name,  # input options (filename last)
                        "-vn",  # Drop any video streams if there are any

                        "-f", "wav",  # output options (filename last)
                        output.name
                        ]

        subprocess.call(ffmpeg_call,
                        stderr=open(os.devnull)
                        )
        input.close()
        return cls.from_wav(output)

    @classmethod
    def from_mp3(cls, file):
        return cls.from_file(file, 'mp3')

    @classmethod
    def from_flv(cls, file):
        return cls.from_file(file, 'flv')

    @classmethod
    def from_ogg(cls, file):
        return cls.from_file(file, 'ogg')

    @classmethod
    def from_wav(cls, file):
        file = _fd_or_path_or_tempfile(file, 'rb', tempfile=False)
        file.seek(0)
        return cls(data=file)

    def export(self, out_f=None, format='mp3'):
        out_f = _fd_or_path_or_tempfile(out_f, 'wb+')
        out_f.seek(0)
        # for wav output we can just write the data directly to out_f
        if format == "wav":
            data = out_f
        else:
            data = NamedTemporaryFile(mode="wb", delete=False)

        wave_data = wave.open(data, 'wb')
        wave_data.setnchannels(self.channels)
        wave_data.setsampwidth(self.sample_width)
        wave_data.setframerate(self.frame_rate)
        wave_data.setnframes(self.frame_count())
        wave_data.writeframesraw(self._data)
        wave_data.close()

        # for wav files, we're done (wav data is written directly to out_f)
        if format == 'wav':
            return out_f

        output = NamedTemporaryFile(mode="w+")

        # read stdin / write stdout
        subprocess.call(['ffmpeg',
            '-y',  # always overwrite existing files
            "-f", "wav", "-i", data.name,  # input options (filename last)
            "-f", format, output.name,  # output options (filename last)
        ],

                        # make ffmpeg shut up
                        stderr=open(os.devnull))

        output.seek(0)
        out_f.write(output.read())

        data.unlink(data.name)
        out_f.seek(0)
        return out_f

    def get_frame(self, index):
        frame_start = index * self.frame_width
        frame_end = frame_start + self.frame_width
        return self._data[frame_start:frame_end]

    def frame_count(self, ms=None):
        """
        returns the number of frames for the given number of milliseconds, or
            if not specified, the number of frames in the whole AudioSegment
        """
        if ms is not None:
            return ms * (self.frame_rate / 1000.0)
        else:
            return float(len(self._data) / self.frame_width)

    def set_frame_rate(self, frame_rate):
        if frame_rate == self.frame_rate:
            return self

        converted, _ = audioop.ratecv(self._data, self.sample_width,
            self.channels, self.frame_rate, frame_rate, None)
        return self._spawn(data=converted,
            overrides={'frame_rate': frame_rate})

    def set_channels(self, channels):
        if channels == self.channels:
            return self

        if channels == 2 and self.channels == 1:
            fn = 'tostereo'
            frame_width = self.frame_width * 2
        elif channels == 1 and self.channels == 2:
            fn = 'tomono'
            frame_width = self.frame_width / 2

        fn = getattr(audioop, fn)
        converted = fn(self._data, self.sample_width, 1, 1)

        return self._spawn(data=converted, overrides={'channels': channels,
            'frame_width': frame_width})

    @property
    def rms(self):
        return audioop.rms(self._data, self.frame_width)

    def apply_gain(self, volume_change):
        return self._spawn(data=audioop.mul(self._data, self.frame_width,
            db_to_float(float(volume_change))))

    def overlay(self, seg, position=0, loop=False):
        output = TemporaryFile()

        seg1, seg2 = AudioSegment._sync(self, seg)
        frame_width = seg1.frame_width
        spawn = seg1._spawn

        output.write(seg1[:position]._data)

        # drop down to the raw data
        seg1 = seg1[position:]._data
        seg2 = seg2._data
        pos = 0
        seg1_len = len(seg1)
        seg2_len = len(seg2)
        while True:
            remaining = max(0, seg1_len - pos)
            if seg2_len >= remaining:
                seg2 = seg2[:remaining]
                seg2_len = remaining
                loop = False

            output.write(audioop.add(seg1[pos:pos + seg2_len], seg2,
                frame_width))
            pos += seg2_len

            if not loop:
                break

        output.write(seg1[pos:])

        return spawn(data=output)

    def append(self, seg, crossfade=100):
        output = TemporaryFile()

        seg1, seg2 = AudioSegment._sync(self, seg)

        if not crossfade:
            return seg1._spawn(seg1._data + seg2._data)

        xf = seg1[-crossfade:].fade(to_gain=-120, start=0, end=float('inf'))
        xf *= seg1[:crossfade].fade(from_gain=-120, start=0, end=float('inf'))

        output.write(seg1[:-crossfade]._data)
        output.write(xf._data)
        output.write(seg2[crossfade:]._data)

        output.seek(0)
        return seg1._spawn(data=output)

    def fade(self, to_gain=0, from_gain=0, start=None, end=None,
            duration=None):
        """
        Fade the volume of this audio segment.

        to_gain (float):
            resulting volume_change in db

        start (int):
            default = beginning of the segment
            when in this segment to start fading in milliseconds

        end (int):
            default = end of the segment
            when in this segment to start fading in milliseconds

        duration (int):
            default = until the end of the audio segment
            the duration of the fade
        """
        if None not in [duration, end, start]:
            raise TypeError('Only two of the three arguments, "start", '\
                '"end", and "duration" may be specified')

        # no fade == the same audio
        if to_gain == 0 and from_gain == 0:
            return self

        frames = self.frame_count()

        start = min(len(self), start)
        end = min(len(self), end)

        if start is not None and start < 0:
            start += len(self)
        if end is not None and end < 0:
            end += len(self)

        if duration is not None and duration < 0:
            raise InvalidDuration("duration must be a positive integer")

        if duration:
            if start is not None:
                end = start + duration
            elif end is not None:
                start = end - duration
        else:
            duration = end - start

        from_power = db_to_float(from_gain)

        output = []

        # original data - up until the crossfade portion, as is
        before_fade = self[:start]._data
        if from_gain != 0:
            before_fade = audioop.mul(before_fade, self.sample_width,
                from_power)
        output.append(before_fade)

        gain_delta = db_to_float(to_gain) - from_power
        scale_step = gain_delta / duration

        for i in range(duration):
            volume_change = from_power + (scale_step * i)
            chunk = self[start + i]
            chunk = audioop.mul(chunk._data, self.sample_width, volume_change)

            output.append(chunk)

        # original data after the crossfade portion, at the new volume
        after_fade = self[end:]._data
        if to_gain != 0:
            after_fade = audioop.mul(after_fade, self.sample_width,
                db_to_float(to_gain))
        output.append(after_fade)

        return self._spawn(data=output)

    def fade_out(self, duration):
        return self.fade(to_gain=-120, duration=duration, end=float('inf'))

    def fade_in(self, duration):
        return self.fade(from_gain=-120, duration=duration, start=0)
