# -*- coding: utf-8 -*-
# This file is part of beets.
# Copyright 2016, Verrus, <github.com/Verrus/beets-plugin-featInTitle>
#
# 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.

"""Moves "featured" artists to the title from the artist field.
"""
from __future__ import division, absolute_import, print_function

import re

from beets import plugins
from beets import ui
from beets.util import displayable_path


def split_on_feat(artist):
    """Given an artist string, split the "main" artist from any artist
    on the right-hand side of a string like "feat". Return the main
    artist, which is always a string, and the featuring artist, which
    may be a string or None if none is present.
    """
    # split on the first "feat".
    regex = re.compile(plugins.feat_tokens(), re.IGNORECASE)
    parts = [s.strip() for s in regex.split(artist, 1)]
    if len(parts) == 1:
        return parts[0], None
    else:
        return tuple(parts)


def contains_feat(title):
    """Determine whether the title contains a "featured" marker.
    """
    return bool(re.search(plugins.feat_tokens(), title, flags=re.IGNORECASE))


def find_feat_part(artist, albumartist):
    """Attempt to find featured artists in the item's artist fields and
    return the results. Returns None if no featured artist found.
    """
    # Look for the album artist in the artist field. If it's not
    # present, give up.
    albumartist_split = artist.split(albumartist, 1)
    if len(albumartist_split) <= 1:
        return None

    # If the last element of the split (the right-hand side of the
    # album artist) is nonempty, then it probably contains the
    # featured artist.
    elif albumartist_split[1] != '':
        # Extract the featured artist from the right-hand side.
        _, feat_part = split_on_feat(albumartist_split[1])
        return feat_part

    # Otherwise, if there's nothing on the right-hand side, look for a
    # featuring artist on the left-hand side.
    else:
        lhs, rhs = split_on_feat(albumartist_split[0])
        if lhs:
            return lhs

    return None


class FtInTitlePlugin(plugins.BeetsPlugin):
    def __init__(self):
        super(FtInTitlePlugin, self).__init__()

        self.config.add({
            'auto': True,
            'drop': False,
            'format': u'feat. {0}',
        })

        self._command = ui.Subcommand(
            'ftintitle',
            help=u'move featured artists to the title field')

        self._command.parser.add_option(
            u'-d', u'--drop', dest='drop',
            action='store_true', default=None,
            help=u'drop featuring from artists and ignore title update')

        if self.config['auto']:
            self.import_stages = [self.imported]

    def commands(self):

        def func(lib, opts, args):
            self.config.set_args(opts)
            drop_feat = self.config['drop'].get(bool)
            write = ui.should_write()

            for item in lib.items(ui.decargs(args)):
                self.ft_in_title(item, drop_feat)
                item.store()
                if write:
                    item.try_write()

        self._command.func = func
        return [self._command]

    def imported(self, session, task):
        """Import hook for moving featuring artist automatically.
        """
        drop_feat = self.config['drop'].get(bool)

        for item in task.imported_items():
            self.ft_in_title(item, drop_feat)
            item.store()

    def update_metadata(self, item, feat_part, drop_feat):
        """Choose how to add new artists to the title and set the new
        metadata. Also, print out messages about any changes that are made.
        If `drop_feat` is set, then do not add the artist to the title; just
        remove it from the artist field.
        """
        # In all cases, update the artist fields.
        self._log.info(u'artist: {0} -> {1}', item.artist, item.albumartist)
        item.artist = item.albumartist
        if item.artist_sort:
            # Just strip the featured artist from the sort name.
            item.artist_sort, _ = split_on_feat(item.artist_sort)

        # Only update the title if it does not already contain a featured
        # artist and if we do not drop featuring information.
        if not drop_feat and not contains_feat(item.title):
            feat_format = self.config['format'].as_str()
            new_format = feat_format.format(feat_part)
            new_title = u"{0} {1}".format(item.title, new_format)
            self._log.info(u'title: {0} -> {1}', item.title, new_title)
            item.title = new_title

    def ft_in_title(self, item, drop_feat):
        """Look for featured artists in the item's artist fields and move
        them to the title.
        """
        artist = item.artist.strip()
        albumartist = item.albumartist.strip()

        # Check whether there is a featured artist on this track and the
        # artist field does not exactly match the album artist field. In
        # that case, we attempt to move the featured artist to the title.
        _, featured = split_on_feat(artist)
        if featured and albumartist != artist and albumartist:
            self._log.info('{}', displayable_path(item.path))

            feat_part = None

            # Attempt to find the featured artist.
            feat_part = find_feat_part(artist, albumartist)

            # If we have a featuring artist, move it to the title.
            if feat_part:
                self.update_metadata(item, feat_part, drop_feat)
            else:
                self._log.info(u'no featuring artists found')