/*
 This file is part of Airsonic.

 Airsonic is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 Airsonic is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with Airsonic.  If not, see <http://www.gnu.org/licenses/>.

 Copyright 2016 (C) Airsonic Authors
 Based upon Subsonic, Copyright 2009 (C) Sindre Mehus
 */
package org.airsonic.player.service;

import org.airsonic.player.dao.AlbumDao;
import org.airsonic.player.dao.ArtistDao;
import org.airsonic.player.dao.MediaFileDao;
import org.airsonic.player.domain.*;
import org.airsonic.player.service.search.IndexManager;
import org.apache.commons.lang.ObjectUtils;
import org.apache.commons.lang3.time.DateUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;

import java.io.File;
import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;
import java.util.*;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

/**
 * Provides services for scanning the music library.
 *
 * @author Sindre Mehus
 */
@Service
public class MediaScannerService {

    private static final Logger LOG = LoggerFactory.getLogger(MediaScannerService.class);

    private boolean scanning;

    private ScheduledExecutorService scheduler;

    @Autowired
    private SettingsService settingsService;
    @Autowired
    private IndexManager indexManager;
    @Autowired
    private PlaylistService playlistService;
    @Autowired
    private MediaFileService mediaFileService;
    @Autowired
    private MediaFileDao mediaFileDao;
    @Autowired
    private ArtistDao artistDao;
    @Autowired
    private AlbumDao albumDao;
    private int scanCount;

    @PostConstruct
    public void init() {
        indexManager.initializeIndexDirectory();
        schedule();
    }

    public void initNoSchedule() {
        indexManager.deleteOldIndexFiles();
    }

    /**
     * Schedule background execution of media library scanning.
     */
    public synchronized void schedule() {
        if (scheduler != null) {
            scheduler.shutdown();
        }

        long daysBetween = settingsService.getIndexCreationInterval();
        int hour = settingsService.getIndexCreationHour();

        if (daysBetween == -1) {
            LOG.info("Automatic media scanning disabled.");
            return;
        }

        scheduler = Executors.newSingleThreadScheduledExecutor();

        LocalDateTime now = LocalDateTime.now();
        LocalDateTime nextRun = now.withHour(hour).withMinute(0).withSecond(0);
        if (now.compareTo(nextRun) > 0)
            nextRun = nextRun.plusDays(1);

        long initialDelay = ChronoUnit.MILLIS.between(now, nextRun);

        scheduler.scheduleAtFixedRate(() -> scanLibrary(), initialDelay, TimeUnit.DAYS.toMillis(daysBetween), TimeUnit.MILLISECONDS);

        LOG.info("Automatic media library scanning scheduled to run every {} day(s), starting at {}", daysBetween, nextRun);

        // In addition, create index immediately if it doesn't exist on disk.
        if (neverScanned()) {
            LOG.info("Media library never scanned. Doing it now.");
            scanLibrary();
        }
    }

    boolean neverScanned() {
        return indexManager.getStatistics() == null;
    }

    /**
     * Returns whether the media library is currently being scanned.
     */
    public synchronized boolean isScanning() {
        return scanning;
    }

    /**
     * Returns the number of files scanned so far.
     */
    public int getScanCount() {
        return scanCount;
    }

    /**
     * Scans the media library.
     * The scanning is done asynchronously, i.e., this method returns immediately.
     */
    public synchronized void scanLibrary() {
        if (isScanning()) {
            return;
        }
        scanning = true;

        Thread thread = new Thread("MediaLibraryScanner") {
            @Override
            public void run() {
                doScanLibrary();
                playlistService.importPlaylists();
                mediaFileDao.checkpoint();
            }
        };

        thread.setPriority(Thread.MIN_PRIORITY);
        thread.start();
    }

    private void doScanLibrary() {
        LOG.info("Starting to scan media library.");
        MediaLibraryStatistics statistics = new MediaLibraryStatistics(
                DateUtils.truncate(new Date(), Calendar.SECOND));
        LOG.debug("New last scan date is " + statistics.getScanDate());

        try {

            // Maps from artist name to album count.
            Map<String, Integer> albumCount = new HashMap<String, Integer>();
            Genres genres = new Genres();

            scanCount = 0;

            mediaFileService.setMemoryCacheEnabled(false);
            indexManager.startIndexing();

            mediaFileService.clearMemoryCache();

            // Recurse through all files on disk.
            for (MusicFolder musicFolder : settingsService.getAllMusicFolders()) {
                MediaFile root = mediaFileService.getMediaFile(musicFolder.getPath(), false);
                scanFile(root, musicFolder, statistics, albumCount, genres, false);
            }

            // Scan podcast folder.
            File podcastFolder = new File(settingsService.getPodcastFolder());
            if (podcastFolder.exists()) {
                scanFile(mediaFileService.getMediaFile(podcastFolder), new MusicFolder(podcastFolder, null, true, null),
                         statistics, albumCount, genres, true);
            }

            LOG.info("Scanned media library with " + scanCount + " entries.");

            LOG.info("Marking non-present files.");
            mediaFileDao.markNonPresent(statistics.getScanDate());
            LOG.info("Marking non-present artists.");
            artistDao.markNonPresent(statistics.getScanDate());
            LOG.info("Marking non-present albums.");
            albumDao.markNonPresent(statistics.getScanDate());

            // Update statistics
            statistics.incrementArtists(albumCount.size());
            for (Integer albums : albumCount.values()) {
                statistics.incrementAlbums(albums);
            }

            // Update genres
            mediaFileDao.updateGenres(genres.getGenres());

            LOG.info("Completed media library scan.");

        } catch (Throwable x) {
            LOG.error("Failed to scan media library.", x);
        } finally {
            mediaFileService.setMemoryCacheEnabled(true);
            indexManager.stopIndexing(statistics);
            scanning = false;
        }
    }

    private void scanFile(MediaFile file, MusicFolder musicFolder, MediaLibraryStatistics statistics,
                          Map<String, Integer> albumCount, Genres genres, boolean isPodcast) {
        scanCount++;
        if (scanCount % 250 == 0) {
            LOG.info("Scanned media library with " + scanCount + " entries.");
        }

        LOG.trace("Scanning file {}", file.getPath());

        // Update the root folder if it has changed.
        if (!musicFolder.getPath().getPath().equals(file.getFolder())) {
            file.setFolder(musicFolder.getPath().getPath());
            mediaFileDao.createOrUpdateMediaFile(file);
        }

        indexManager.index(file);

        if (file.isDirectory()) {
            for (MediaFile child : mediaFileService.getChildrenOf(file, true, false, false, false)) {
                scanFile(child, musicFolder, statistics, albumCount, genres, isPodcast);
            }
            for (MediaFile child : mediaFileService.getChildrenOf(file, false, true, false, false)) {
                scanFile(child, musicFolder, statistics, albumCount, genres, isPodcast);
            }
        } else {
            if (!isPodcast) {
                updateAlbum(file, musicFolder, statistics.getScanDate(), albumCount);
                updateArtist(file, musicFolder, statistics.getScanDate(), albumCount);
            }
            statistics.incrementSongs(1);
        }

        updateGenres(file, genres);
        mediaFileDao.markPresent(file.getPath(), statistics.getScanDate());
        artistDao.markPresent(file.getAlbumArtist(), statistics.getScanDate());

        if (file.getDurationSeconds() != null) {
            statistics.incrementTotalDurationInSeconds(file.getDurationSeconds());
        }
        if (file.getFileSize() != null) {
            statistics.incrementTotalLengthInBytes(file.getFileSize());
        }
    }

    private void updateGenres(MediaFile file, Genres genres) {
        String genre = file.getGenre();
        if (genre == null) {
            return;
        }
        if (file.isAlbum()) {
            genres.incrementAlbumCount(genre);
        } else if (file.isAudio()) {
            genres.incrementSongCount(genre);
        }
    }

    private void updateAlbum(MediaFile file, MusicFolder musicFolder, Date lastScanned, Map<String, Integer> albumCount) {
        String artist = file.getAlbumArtist() != null ? file.getAlbumArtist() : file.getArtist();
        if (file.getAlbumName() == null || artist == null || file.getParentPath() == null || !file.isAudio()) {
            return;
        }

        Album album = albumDao.getAlbumForFile(file);
        if (album == null) {
            album = new Album();
            album.setPath(file.getParentPath());
            album.setName(file.getAlbumName());
            album.setArtist(artist);
            album.setCreated(file.getChanged());
        }
        if (file.getMusicBrainzReleaseId() != null) {
            album.setMusicBrainzReleaseId(file.getMusicBrainzReleaseId());
        }
        if (file.getYear() != null) {
            album.setYear(file.getYear());
        }
        if (file.getGenre() != null) {
            album.setGenre(file.getGenre());
        }
        MediaFile parent = mediaFileService.getParentOf(file);
        if (parent != null && parent.getCoverArtPath() != null) {
            album.setCoverArtPath(parent.getCoverArtPath());
        }

        boolean firstEncounter = !lastScanned.equals(album.getLastScanned());
        if (firstEncounter) {
            album.setFolderId(musicFolder.getId());
            album.setDurationSeconds(0);
            album.setSongCount(0);
            Integer n = albumCount.get(artist);
            albumCount.put(artist, n == null ? 1 : n + 1);
        }
        if (file.getDurationSeconds() != null) {
            album.setDurationSeconds(album.getDurationSeconds() + file.getDurationSeconds());
        }
        if (file.isAudio()) {
            album.setSongCount(album.getSongCount() + 1);
        }
        album.setLastScanned(lastScanned);
        album.setPresent(true);
        albumDao.createOrUpdateAlbum(album);
        if (firstEncounter) {
            indexManager.index(album);
        }

        // Update the file's album artist, if necessary.
        if (!ObjectUtils.equals(album.getArtist(), file.getAlbumArtist())) {
            file.setAlbumArtist(album.getArtist());
            mediaFileDao.createOrUpdateMediaFile(file);
        }
    }

    private void updateArtist(MediaFile file, MusicFolder musicFolder, Date lastScanned, Map<String, Integer> albumCount) {
        if (file.getAlbumArtist() == null || !file.isAudio()) {
            return;
        }

        Artist artist = artistDao.getArtist(file.getAlbumArtist());
        if (artist == null) {
            artist = new Artist();
            artist.setName(file.getAlbumArtist());
        }
        if (artist.getCoverArtPath() == null) {
            MediaFile parent = mediaFileService.getParentOf(file);
            if (parent != null) {
                artist.setCoverArtPath(parent.getCoverArtPath());
            }
        }
        boolean firstEncounter = !lastScanned.equals(artist.getLastScanned());

        if (firstEncounter) {
            artist.setFolderId(musicFolder.getId());
        }
        Integer n = albumCount.get(artist.getName());
        artist.setAlbumCount(n == null ? 0 : n);

        artist.setLastScanned(lastScanned);
        artist.setPresent(true);
        artistDao.createOrUpdateArtist(artist);

        if (firstEncounter) {
            indexManager.index(artist, musicFolder);
        }
    }

    public void setSettingsService(SettingsService settingsService) {
        this.settingsService = settingsService;
    }

    public void setMediaFileService(MediaFileService mediaFileService) {
        this.mediaFileService = mediaFileService;
    }

    public void setMediaFileDao(MediaFileDao mediaFileDao) {
        this.mediaFileDao = mediaFileDao;
    }

    public void setArtistDao(ArtistDao artistDao) {
        this.artistDao = artistDao;
    }

    public void setAlbumDao(AlbumDao albumDao) {
        this.albumDao = albumDao;
    }

    public void setPlaylistService(PlaylistService playlistService) {
        this.playlistService = playlistService;
    }
}