# This file is part of beets.
# 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.

"""Provides the basic, interface-agnostic workflow for importing and
autotagging music files.
"""
from __future__ import with_statement # Python 2.5
import os
import logging
import pickle

from lib.beets import autotag
from lib.beets import library
import lib.beets.autotag.art as beets.autotag.art
from lib.beets import plugins
from lib.beets.util import pipeline
from lib.beets.util import syspath, normpath
from lib.beets.util.enumeration import enum

action = enum(
    'SKIP', 'ASIS', 'TRACKS', 'MANUAL', 'APPLY', 'MANUAL_ID',
    name='action'
)

QUEUE_SIZE = 128
STATE_FILE = os.path.expanduser('~/.beetsstate')

# Global logger.
log = logging.getLogger('beets')

class ImportAbort(Exception):
    """Raised when the user aborts the tagging operation.
    """
    pass


# Utilities.

def tag_log(logfile, status, path):
    """Log a message about a given album to logfile. The status should
    reflect the reason the album couldn't be tagged.
    """
    if logfile:
        print >>logfile, '%s %s' % (status, path)

def log_choice(config, task):
    """Logs the task's current choice if it should be logged.
    """
    path = task.path if task.is_album else task.item.path
    if task.choice_flag is action.ASIS:
        tag_log(config.logfile, 'asis', path)
    elif task.choice_flag is action.SKIP:
        tag_log(config.logfile, 'skip', path)

def _reopen_lib(lib):
    """Because of limitations in SQLite, a given Library is bound to
    the thread in which it was created. This function reopens Library
    objects so that they can be used from separate threads.
    """
    if isinstance(lib, library.Library):
        return library.Library(
            lib.path,
            lib.directory,
            lib.path_formats,
            lib.art_filename,
        )
    else:
        return lib

def _duplicate_check(lib, artist, album, recent=None):
    """Check whether an album already exists in the library. `recent`
    should be a set of (artist, album) pairs that will be built up
    with every call to this function and checked along with the
    library.
    """
    if artist is None:
        # As-is import with no artist. Skip check.
        return False

    # Try the recent albums.
    if recent is not None:
        if (artist, album) in recent:
            return True
        recent.add((artist, album))

    # Look in the library.
    for album_cand in lib.albums(artist=artist):
        if album_cand.album == album:
            return True

    return False

def _item_duplicate_check(lib, artist, title, recent=None):
    """Check whether an item already exists in the library."""
    # Try recent items.
    if recent is not None:
        if (artist, title) in recent:
            return True
        recent.add((artist, title))

    # Check the library.
    item_iter = lib.items(artist=artist, title=title)
    try:
        item_iter.next()
    except StopIteration:
        return False
    finally:
        item_iter.close()

    return True

# Utilities for reading and writing the beets progress file, which
# allows long tagging tasks to be resumed when they pause (or crash).
PROGRESS_KEY = 'tagprogress'
def progress_set(toppath, path):
    """Record that tagging for the given `toppath` was successful up to
    `path`. If path is None, then clear the progress value (indicating
    that the tagging completed).
    """
    try:
        with open(STATE_FILE) as f:
            state = pickle.load(f)
    except IOError:
        state = {PROGRESS_KEY: {}}

    if path is None:
        # Remove progress from file.
        if toppath in state[PROGRESS_KEY]:
            del state[PROGRESS_KEY][toppath]
    else:
        state[PROGRESS_KEY][toppath] = path

    with open(STATE_FILE, 'w') as f:
        pickle.dump(state, f)
def progress_get(toppath):
    """Get the last successfully tagged subpath of toppath. If toppath
    has no progress information, returns None.
    """
    try:
        with open(STATE_FILE) as f:
            state = pickle.load(f)
    except IOError:
        return None
    return state[PROGRESS_KEY].get(toppath)


# The configuration structure.

class ImportConfig(object):
    """Contains all the settings used during an import session. Should
    be used in a "write-once" way -- everything is set up initially and
    then never touched again.
    """
    _fields = ['lib', 'paths', 'resume', 'logfile', 'color', 'quiet',
               'quiet_fallback', 'copy', 'write', 'art', 'delete',
               'choose_match_func', 'should_resume_func', 'threaded',
               'autot', 'singletons', 'timid', 'choose_item_func']
    def __init__(self, **kwargs):
        for slot in self._fields:
            setattr(self, slot, kwargs[slot])

        # Normalize the paths.
        if self.paths:
            self.paths = map(normpath, self.paths)


# The importer task class.

class ImportTask(object):
    """Represents a single set of items to be imported along with its
    intermediate state. May represent an album or a single item.
    """
    def __init__(self, toppath=None, path=None, items=None):
        self.toppath = toppath
        self.path = path
        self.items = items
        self.sentinel = False

    @classmethod
    def done_sentinel(cls, toppath):
        """Create an ImportTask that indicates the end of a top-level
        directory import.
        """
        obj = cls(toppath)
        obj.sentinel = True
        return obj

    @classmethod
    def progress_sentinel(cls, toppath, path):
        """Create a task indicating that a single directory in a larger
        import has finished. This is only required for singleton
        imports; progress is implied for album imports.
        """
        obj = cls(toppath, path)
        obj.sentinel = True
        return obj

    @classmethod
    def item_task(cls, item):
        """Creates an ImportTask for a single item."""
        obj = cls()
        obj.item = item
        obj.is_album = False
        return obj

    def set_match(self, cur_artist, cur_album, candidates, rec):
        """Sets the candidates for this album matched by the
        `autotag.tag_album` method.
        """
        assert not self.sentinel
        self.cur_artist = cur_artist
        self.cur_album = cur_album
        self.candidates = candidates
        self.rec = rec
        self.is_album = True

    def set_null_match(self):
        """Set the candidates to indicate no album match was found.
        """
        self.set_match(None, None, None, None)

    def set_item_match(self, candidates, rec):
        """Set the match for a single-item task."""
        assert not self.is_album
        assert self.item is not None
        self.item_match = (candidates, rec)

    def set_null_item_match(self):
        """For single-item tasks, mark the item as having no matches.
        """
        assert not self.is_album
        assert self.item is not None
        self.item_match = None

    def set_choice(self, choice):
        """Given either an (info, items) tuple or an action constant,
        indicates that an action has been selected by the user (or
        automatically).
        """
        assert not self.sentinel
        # Not part of the task structure:
        assert choice not in (action.MANUAL, action.MANUAL_ID)
        assert choice != action.APPLY # Only used internally.
        if choice in (action.SKIP, action.ASIS, action.TRACKS):
            self.choice_flag = choice
            self.info = None
        else:
            assert not isinstance(choice, action)
            if self.is_album:
                info, items = choice
                self.items = items # Reordered items list.
            else:
                info = choice
            self.info = info
            self.choice_flag = action.APPLY # Implicit choice.

    def save_progress(self):
        """Updates the progress state to indicate that this album has
        finished.
        """
        if self.sentinel and self.path is None:
            # "Done" sentinel.
            progress_set(self.toppath, None)
        elif self.sentinel or self.is_album:
            # "Directory progress" sentinel for singletons or a real
            # album task, which implies the same.
            progress_set(self.toppath, self.path)

    # Logical decisions.
    def should_write_tags(self):
        """Should new info be written to the files' metadata?"""
        if self.choice_flag == action.APPLY:
            return True
        elif self.choice_flag in (action.ASIS, action.TRACKS, action.SKIP):
            return False
        else:
            assert False
    def should_fetch_art(self):
        """Should album art be downloaded for this album?"""
        return self.should_write_tags() and self.is_album
    def should_infer_aa(self):
        """When creating an album structure, should the album artist
        field be inferred from the plurality of track artists?
        """
        assert self.is_album
        if self.choice_flag == action.APPLY:
            # Album artist comes from the info dictionary.
            return False
        elif self.choice_flag == action.ASIS:
            # As-is imports likely don't have an album artist.
            return True
        else:
            assert False
    def should_skip(self):
        """After a choice has been made, returns True if this is a
        sentinel or it has been marked for skipping.
        """
        return self.sentinel or self.choice_flag == action.SKIP


# Full-album pipeline stages.

def read_tasks(config):
    """A generator yielding all the albums (as ImportTask objects) found
    in the user-specified list of paths. In the case of a singleton
    import, yields single-item tasks instead.
    """
    # Look for saved progress.
    progress = config.resume is not False
    if progress:
        resume_dirs = {}
        for path in config.paths:
            resume_dir = progress_get(path)
            if resume_dir:

                # Either accept immediately or prompt for input to decide.
                if config.resume:
                    do_resume = True
                    log.warn('Resuming interrupted import of %s' % path)
                else:
                    do_resume = config.should_resume_func(config, path)

                if do_resume:
                    resume_dirs[path] = resume_dir
                else:
                    # Clear progress; we're starting from the top.
                    progress_set(path, None)
    
    for toppath in config.paths:
        # Check whether the path is to a file.
        if config.singletons and not os.path.isdir(syspath(toppath)):
            item = library.Item.from_path(toppath)
            yield ImportTask.item_task(item)
            continue
        
        # Produce paths under this directory.
        if progress:
            resume_dir = resume_dirs.get(toppath)
        for path, items in autotag.albums_in_dir(toppath):
            if progress and resume_dir:
                # We're fast-forwarding to resume a previous tagging.
                if path == resume_dir:
                    # We've hit the last good path! Turn off the
                    # fast-forwarding.
                    resume_dir = None
                continue

            # Yield all the necessary tasks.
            if config.singletons:
                for item in items:
                    yield ImportTask.item_task(item)
                yield ImportTask.progress_sentinel(toppath, path)
            else:
                yield ImportTask(toppath, path, items)

        # Indicate the directory is finished.
        yield ImportTask.done_sentinel(toppath)

def initial_lookup(config):
    """A coroutine for performing the initial MusicBrainz lookup for an
    album. It accepts lists of Items and yields
    (items, cur_artist, cur_album, candidates, rec) tuples. If no match
    is found, all of the yielded parameters (except items) are None.
    """
    task = None
    while True:
        task = yield task
        if task.sentinel:
            continue

        log.debug('Looking up: %s' % task.path)
        try:
            task.set_match(*autotag.tag_album(task.items, config.timid))
        except autotag.AutotagError:
            task.set_null_match()

def user_query(config):
    """A coroutine for interfacing with the user about the tagging
    process. lib is the Library to import into and logfile may be
    a file-like object for logging the import process. The coroutine
    accepts and yields ImportTask objects.
    """
    lib = _reopen_lib(config.lib)
    recent = set()
    task = None
    while True:
        task = yield task
        if task.sentinel:
            continue
        
        # Ask the user for a choice.
        choice = config.choose_match_func(task, config)
        task.set_choice(choice)
        log_choice(config, task)

        # As-tracks: transition to singleton workflow.
        if choice is action.TRACKS:
            # Set up a little pipeline for dealing with the singletons.
            item_tasks = []
            def emitter():
                for item in task.items:
                    yield ImportTask.item_task(item)
                yield ImportTask.progress_sentinel(task.toppath, task.path)
            def collector():
                while True:
                    item_task = yield
                    item_tasks.append(item_task)
            ipl = pipeline.Pipeline((emitter(), item_lookup(config), 
                                     item_query(config), collector()))
            ipl.run_sequential()
            task = pipeline.multiple(item_tasks)

        # Check for duplicates if we have a match (or ASIS).
        if choice is action.ASIS or isinstance(choice, tuple):
            if choice is action.ASIS:
                artist = task.cur_artist
                album = task.cur_album
            else:
                artist = task.info['artist']
                album = task.info['album']
            if _duplicate_check(lib, artist, album, recent):
                tag_log(config.logfile, 'duplicate', task.path)
                log.warn("This album is already in the library!")
                task.set_choice(action.SKIP)

def show_progress(config):
    """This stage replaces the initial_lookup and user_query stages
    when the importer is run without autotagging. It displays the album
    name and artist as the files are added.
    """
    task = None
    while True:
        task = yield task
        if task.sentinel:
            continue

        log.info(task.path)

        # Behave as if ASIS were selected.
        task.set_null_match()
        task.set_choice(action.ASIS)
        
def apply_choices(config):
    """A coroutine for applying changes to albums during the autotag
    process.
    """
    lib = _reopen_lib(config.lib)
    task = None
    while True:    
        task = yield task
        if task.should_skip():
            continue

        # Change metadata, move, and copy.
        if task.should_write_tags():
            if task.is_album:
                autotag.apply_metadata(task.items, task.info)
            else:
                autotag.apply_item_metadata(task.item, task.info)
        items = task.items if task.is_album else [task.item]
        if config.copy and config.delete:
            task.old_paths = [os.path.realpath(syspath(item.path))
                              for item in items]
        for item in items:
            if config.copy:
                item.move(lib, True, task.is_album)
            if config.write and task.should_write_tags():
                item.write()

        # Add items to library. We consolidate this at the end to avoid
        # locking while we do the copying and tag updates.
        try:
            if task.is_album:
                # Add an album.
                album = lib.add_album(task.items,
                                      infer_aa = task.should_infer_aa())
                task.album_id = album.id
            else:
                # Add tracks.
                for item in items:
                    lib.add(item)
        finally:
            lib.save()

def fetch_art(config):
    """A coroutine that fetches and applies album art for albums where
    appropriate.
    """
    lib = _reopen_lib(config.lib)
    task = None
    while True:
        task = yield task
        if task.should_skip():
            continue

        if task.should_fetch_art():
            artpath = beets.autotag.art.art_for_album(task.info)

            # Save the art if any was found.
            if artpath:
                try:
                    album = lib.get_album(task.album_id)
                    album.set_art(artpath)
                finally:
                    lib.save(False)

def finalize(config):
    """A coroutine that finishes up importer tasks. In particular, the
    coroutine sends plugin events, deletes old files, and saves
    progress. This is a "terminal" coroutine (it yields None).
    """
    lib = _reopen_lib(config.lib)
    while True:
        task = yield
        if task.should_skip():
            if config.resume is not False:
                task.save_progress()
            continue

        items = task.items if task.is_album else [task.item]

        # Announce that we've added an album.
        if task.is_album:
            album = lib.get_album(task.album_id)
            plugins.send('album_imported', lib=lib, album=album)
        else:
            for item in items:
                plugins.send('item_imported', lib=lib, item=item)

        # Finally, delete old files.
        if config.copy and config.delete:
            new_paths = [os.path.realpath(item.path) for item in items]
            for old_path in task.old_paths:
                # Only delete files that were actually moved.
                if old_path not in new_paths:
                    os.remove(syspath(old_path))

        # Update progress.
        if config.resume is not False:
            task.save_progress()


# Singleton pipeline stages.

def item_lookup(config):
    """A coroutine used to perform the initial MusicBrainz lookup for
    an item task.
    """
    task = None
    while True:
        task = yield task
        if task.sentinel:
            continue

        task.set_item_match(*autotag.tag_item(task.item, config.timid))

def item_query(config):
    """A coroutine that queries the user for input on single-item
    lookups.
    """
    lib = _reopen_lib(config.lib)
    task = None
    recent = set()
    while True:
        task = yield task
        if task.sentinel:
            continue

        choice = config.choose_item_func(task, config)
        task.set_choice(choice)
        log_choice(config, task)

        # Duplicate check.
        if task.choice_flag in (action.ASIS, action.APPLY):
            if choice is action.ASIS:
                artist = task.item.artist
                title = task.item.title
            else:
                artist = task.info['artist']
                title = task.info['title']
            if _item_duplicate_check(lib, artist, title, recent):
                tag_log(config.logfile, 'duplicate', task.item.path)
                log.warn("This item is already in the library!")
                task.set_choice(action.SKIP)

def item_progress(config):
    """Skips the lookup and query stages in a non-autotagged singleton
    import. Just shows progress.
    """
    task = None
    log.info('Importing items:')
    while True:
        task = yield task
        if task.sentinel:
            continue

        log.info(task.item.path)
        task.set_null_item_match()
        task.set_choice(action.ASIS)


# Main driver.

def run_import(**kwargs):
    """Run an import. The keyword arguments are the same as those to
    ImportConfig.
    """
    config = ImportConfig(**kwargs)
    
    # Set up the pipeline.
    stages = [read_tasks(config)]
    if config.singletons:
        # Singleton importer.
        if config.autot:
            stages += [item_lookup(config), item_query(config)]
        else:
            stages += [item_progress(config)]
    else:
        # Whole-album importer.
        if config.autot:
            # Only look up and query the user when autotagging.
            stages += [initial_lookup(config), user_query(config)]
        else:
            # When not autotagging, just display progress.
            stages += [show_progress(config)]
    stages += [apply_choices(config)]
    if config.art:
        stages += [fetch_art(config)]
    stages += [finalize(config)]
    pl = pipeline.Pipeline(stages)

    # Run the pipeline.
    try:
        if config.threaded:
            pl.run_parallel(QUEUE_SIZE)
        else:
            pl.run_sequential()
    except ImportAbort:
        # User aborted operation. Silently stop.
        pass