# This file is part of beets.
# Copyright 2012, Fabrice Laporte.
#
# 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.

import logging
import subprocess
import os

from beets import ui
from beets.plugins import BeetsPlugin
from beets.util import syspath
from beets.ui import commands

log = logging.getLogger('beets')

DEFAULT_REFERENCE_LOUDNESS = 89

class ReplayGainError(Exception):
    """Raised when an error occurs during mp3gain/aacgain execution.
    """

def call(args):
    """Execute the command indicated by `args` (a list of strings) and
    return the command's output. The stderr stream is ignored. If the
    command exits abnormally, a ReplayGainError is raised.
    """
    try:
        with open(os.devnull, 'w') as devnull:
            return subprocess.check_output(args, stderr=devnull)
    except subprocess.CalledProcessError as e:
        raise ReplayGainError(
            "{0} exited with status {1}".format(args[0], e.returncode)
        )

def parse_tool_output(text):
    """Given the tab-delimited output from an invocation of mp3gain
    or aacgain, parse the text and return a list of dictionaries
    containing information about each analyzed file.
    """
    out = []
    for line in text.split('\n'):
        parts = line.split('\t')
        if len(parts) != 6 or parts[0] == 'File':
            continue
        out.append({
            'file': parts[0],
            'mp3gain': int(parts[1]),
            'gain': float(parts[2]),
            'peak': float(parts[3]),
            'maxgain': int(parts[4]),
            'mingain': int(parts[5]),
        })
    return out

class ReplayGainPlugin(BeetsPlugin):
    """Provides ReplayGain analysis.
    """
    def __init__(self):
        super(ReplayGainPlugin, self).__init__()
        self.import_stages = [self.imported]

    def configure(self, config):
        self.overwrite = ui.config_val(config, 'replaygain',
                                       'overwrite', False, bool)
        self.noclip = ui.config_val(config, 'replaygain',
                                    'noclip', True, bool)
        self.apply_gain = ui.config_val(config, 'replaygain',
                                        'apply_gain', False, bool)
        target_level = float(ui.config_val(config, 'replaygain',
                                           'targetlevel',
                                           DEFAULT_REFERENCE_LOUDNESS))
        self.gain_offset = int(target_level - DEFAULT_REFERENCE_LOUDNESS)
        self.automatic = ui.config_val(config, 'replaygain',
                                       'automatic', True, bool)

        self.command = ui.config_val(config,'replaygain','command', None)
        if self.command:
            # Explicit executable path.
            if not os.path.isfile(self.command):
                raise ui.UserError(
                    'replaygain command does not exist: {0}'.format(
                        self.command
                    )
                )
        else:
            # Check whether the program is in $PATH.
            for cmd in ('mp3gain', 'aacgain'):
                try:
                    call([cmd, '-v'])
                    self.command = cmd
                except OSError:
                    pass
        if not self.command:
            raise ui.UserError(
                'no replaygain command found: install mp3gain or aacgain'
            )

    def imported(self, config, task):
        """Our import stage function."""
        if not self.automatic:
            return

        if task.is_album:
            album = config.lib.get_album(task.album_id)
            items = list(album.items())
        else:
            items = [task.item]

        results = self.compute_rgain(items, task.is_album)
        if results:
            self.store_gain(config.lib, items, results,
                            album if task.is_album else None)

    def commands(self):
        """Provide a ReplayGain command."""
        def func(lib, config, opts, args):
            write = ui.config_val(config, 'beets', 'import_write',
                                  commands.DEFAULT_IMPORT_WRITE, bool)

            if opts.album:
                # Analyze albums.
                for album in lib.albums(ui.decargs(args)):
                    log.info('analyzing {0} - {1}'.format(album.albumartist,
                                                          album.album))
                    items = list(album.items())
                    results = self.compute_rgain(items, True)
                    if results:
                        self.store_gain(lib, items, results, album)

                    if write:
                        for item in items:
                            item.write()

            else:
                # Analyze individual tracks.
                for item in lib.items(ui.decargs(args)):
                    log.info('analyzing {0} - {1}'.format(item.artist,
                                                          item.title))
                    results = self.compute_rgain([item], False)
                    if results:
                        self.store_gain(lib, [item], results, None)

                    if write:
                        item.write()

        cmd = ui.Subcommand('replaygain', help='analyze for ReplayGain')
        cmd.parser.add_option('-a', '--album', action='store_true',
                              help='analyze albums instead of tracks')
        cmd.func = func
        return [cmd]

    def requires_gain(self, item, album=False):
        """Does the gain need to be computed?"""
        return self.overwrite or \
               (not item.rg_track_gain or not item.rg_track_peak) or \
               ((not item.rg_album_gain or not item.rg_album_peak) and \
                album)

    def compute_rgain(self, items, album=False):
        """Compute ReplayGain values and return a list of results
        dictionaries as given by `parse_tool_output`.
        """
        # Skip calculating gain only when *all* files don't need
        # recalculation. This way, if any file among an album's tracks
        # needs recalculation, we still get an accurate album gain
        # value.
        if all([not self.requires_gain(i, album) for i in items]):
            log.debug('replaygain: no gain to compute')
            return

        # Construct shell command. The "-o" option makes the output
        # easily parseable (tab-delimited). "-s s" forces gain
        # recalculation even if tags are already present and disables
        # tag-writing; this turns the mp3gain/aacgain tool into a gain
        # calculator rather than a tag manipulator because we take care
        # of changing tags ourselves.
        cmd = [self.command, '-o', '-s', 's']
        if self.noclip:
            # Adjust to avoid clipping.
            cmd = cmd + ['-k']
        else:
            # Disable clipping warning. 
            cmd = cmd + ['-c']
        if self.apply_gain:
            # Lossless audio adjustment.
            cmd = cmd + ['-a' if album else '-r']
        cmd = cmd + ['-d', str(self.gain_offset)]
        cmd = cmd + [syspath(i.path) for i in items]

        log.debug('replaygain: analyzing {0} files'.format(len(items)))
        output = call(cmd)
        log.debug('replaygain: analysis finished')
        results = parse_tool_output(output)

        return results

    def store_gain(self, lib, items, rgain_infos, album=None): 
        """Store computed ReplayGain values to the Items and the Album
        (if it is provided).
        """
        for item, info in zip(items, rgain_infos):
            item.rg_track_gain = info['gain']
            item.rg_track_peak = info['peak']
            lib.store(item)

            log.debug('replaygain: applied track gain {0}, peak {1}; '
                        'album gain {2}, peak {3}'.format(
                item.rg_track_gain, item.rg_track_peak,
                item.rg_album_gain, item.rg_album_peak
            ))

        if album:
            assert len(rgain_infos) == len(items) + 1
            album_info = rgain_infos[-1]
            album.rg_album_gain = album_info['gain']
            album.rg_album_peak = album_info['peak']