LibreTube/app/src/main/java/com/github/libretube/services/BackgroundMode.kt

package com.github.libretube.services

import android.app.Notification
import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.Service
import android.content.Intent
import android.os.Build
import android.os.Handler
import android.os.IBinder
import android.os.Looper
import android.widget.Toast
import com.fasterxml.jackson.databind.ObjectMapper
import com.github.libretube.R
import com.github.libretube.api.RetrofitInstance
import com.github.libretube.constants.BACKGROUND_CHANNEL_ID
import com.github.libretube.constants.IntentData
import com.github.libretube.constants.PLAYER_NOTIFICATION_ID
import com.github.libretube.constants.PreferenceKeys
import com.github.libretube.extensions.toID
import com.github.libretube.util.AutoPlayHelper
import com.github.libretube.util.NowPlayingNotification
import com.github.libretube.util.PlayerHelper
import com.github.libretube.util.PlayingQueue
import com.github.libretube.util.PreferenceHelper
import com.google.android.exoplayer2.C
import com.google.android.exoplayer2.ExoPlayer
import com.google.android.exoplayer2.MediaItem
import com.google.android.exoplayer2.PlaybackException
import com.google.android.exoplayer2.Player
import com.google.android.exoplayer2.audio.AudioAttributes
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch

/**
 * Loads the selected videos audio in background mode with a notification area.
 */
class BackgroundMode : Service() {
    /**
     * VideoId of the video
     */
    private lateinit var videoId: String

    /**
     *PlaylistId for autoplay
     */
    private var playlistId: String? = null

    /**
     * The response that gets when called the Api.
     */
    private var streams: com.github.libretube.api.obj.Streams? = null

    /**
     * The [ExoPlayer] player. Followed tutorial [here](https://developer.android.com/codelabs/exoplayer-intro)
     */
    private var player: ExoPlayer? = null
    private var playWhenReadyPlayer = true

    /**
     * The [AudioAttributes] handle the audio focus of the [player]
     */
    private lateinit var audioAttributes: AudioAttributes

    /**
     * SponsorBlock Segment data
     */
    private var segmentData: com.github.libretube.api.obj.Segments? = null

    /**
     * [Notification] for the player
     */
    private lateinit var nowPlayingNotification: NowPlayingNotification

    /**
     * The [videoId] of the next stream for autoplay
     */
    private var nextStreamId: String? = null

    /**
     * Helper for finding the next video in the playlist
     */
    private lateinit var autoPlayHelper: AutoPlayHelper

    /**
     * Autoplay Preference
     */
    private val handler = Handler(Looper.getMainLooper())

    /**
     * Setting the required [Notification] for running as a foreground service
     */
    override fun onCreate() {
        super.onCreate()
        if (Build.VERSION.SDK_INT >= 26) {
            val channelId = BACKGROUND_CHANNEL_ID
            val channel = NotificationChannel(
                channelId,
                "Background Service",
                NotificationManager.IMPORTANCE_DEFAULT
            )
            val notificationManager = getSystemService(NOTIFICATION_SERVICE) as NotificationManager
            notificationManager.createNotificationChannel(channel)
            val notification: Notification = Notification.Builder(this, channelId)
                .setContentTitle(getString(R.string.app_name))
                .setContentText(getString(R.string.playingOnBackground)).build()
            startForeground(PLAYER_NOTIFICATION_ID, notification)
        }
    }

    /**
     * Initializes the [player] with the [MediaItem].
     */
    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        try {
            // clear the playing queue
            PlayingQueue.clear()

            // get the intent arguments
            videoId = intent?.getStringExtra(IntentData.videoId)!!
            playlistId = intent.getStringExtra(IntentData.playlistId)
            val position = intent.getLongExtra(IntentData.position, 0L)

            // initialize the playlist autoPlay Helper
            autoPlayHelper = AutoPlayHelper(playlistId)

            // play the audio in the background
            loadAudio(videoId, position)
        } catch (e: Exception) {
            onDestroy()
        }
        return super.onStartCommand(intent, flags, startId)
    }

    /**
     * Gets the video data and prepares the [player].
     */
    private fun loadAudio(
        videoId: String,
        seekToPosition: Long = 0
    ) {
        // append the video to the playing queue
        PlayingQueue.add(videoId)
        CoroutineScope(Dispatchers.IO).launch {
            try {
                streams = RetrofitInstance.api.getStreams(videoId)
            } catch (e: Exception) {
                return@launch
            }

            handler.post {
                playAudio(seekToPosition)
            }
        }
    }

    private fun playAudio(
        seekToPosition: Long
    ) {
        PlayingQueue.updateCurrent(videoId)

        initializePlayer()
        setMediaItem()

        // create the notification
        if (!this@BackgroundMode::nowPlayingNotification.isInitialized) {
            nowPlayingNotification = NowPlayingNotification(this@BackgroundMode, player!!)
        }
        nowPlayingNotification.updatePlayerNotification(streams!!)

        player?.apply {
            playWhenReady = playWhenReadyPlayer
            prepare()
        }

        // seek to the previous position if available
        if (seekToPosition != 0L) player?.seekTo(seekToPosition)

        // set the playback speed
        val playbackSpeed = PreferenceHelper.getString(
            PreferenceKeys.BACKGROUND_PLAYBACK_SPEED,
            "1"
        ).toFloat()
        player?.setPlaybackSpeed(playbackSpeed)

        fetchSponsorBlockSegments()

        if (PlayerHelper.autoPlayEnabled) setNextStream()
    }

    /**
     * create the player
     */
    private fun initializePlayer() {
        if (player != null) return

        audioAttributes = AudioAttributes.Builder()
            .setUsage(C.USAGE_MEDIA)
            .setContentType(C.AUDIO_CONTENT_TYPE_MUSIC)
            .build()
        player = ExoPlayer.Builder(this)
            .setHandleAudioBecomingNoisy(true)
            .setAudioAttributes(audioAttributes, true)
            .build()

        /**
         * Listens for changed playbackStates (e.g. pause, end)
         * Plays the next video when the current one ended
         */
        player?.addListener(object : Player.Listener {
            override fun onPlaybackStateChanged(state: Int) {
                when (state) {
                    Player.STATE_ENDED -> {
                        if (PlayerHelper.autoPlayEnabled) playNextVideo()
                    }
                    Player.STATE_IDLE -> {
                        onDestroy()
                    }
                    Player.STATE_BUFFERING -> {}
                    Player.STATE_READY -> {}
                }
            }

            override fun onPlayerError(error: PlaybackException) {
                // show a toast on errors
                Handler(Looper.getMainLooper()).post {
                    Toast.makeText(
                        this@BackgroundMode.applicationContext,
                        error.localizedMessage,
                        Toast.LENGTH_SHORT
                    ).show()
                }
            }
        })
    }

    /**
     * set the videoId of the next stream for autoplay
     */
    private fun setNextStream() {
        if (streams!!.relatedStreams!!.isNotEmpty()) {
            nextStreamId = streams?.relatedStreams!![0].url!!.toID()
        }

        if (playlistId == null) return
        if (!this::autoPlayHelper.isInitialized) autoPlayHelper = AutoPlayHelper(playlistId!!)
        // search for the next videoId in the playlist
        CoroutineScope(Dispatchers.IO).launch {
            nextStreamId = autoPlayHelper.getNextVideoId(videoId, streams!!.relatedStreams!!)
        }
    }

    /**
     * Plays the first related video to the current (used when the playback of the current video ended)
     */
    private fun playNextVideo() {
        if (nextStreamId == null || nextStreamId == videoId) return
        val nextQueueVideo = PlayingQueue.getNext()
        if (nextQueueVideo != null) nextStreamId = nextQueueVideo

        // play new video on background
        this.videoId = nextStreamId!!
        this.segmentData = null
        loadAudio(videoId)
    }

    /**
     * Sets the [MediaItem] with the [streams] into the [player]
     */
    private fun setMediaItem() {
        streams?.let {
            val uri = if (streams!!.hls != null) {
                streams!!.hls
            } else if (streams!!.audioStreams!!.isNotEmpty()) {
                PlayerHelper.getAudioSource(
                    this,
                    streams!!.audioStreams!!
                )
            } else {
                return
            }
            val mediaItem = MediaItem.Builder()
                .setUri(uri)
                .build()
            player?.setMediaItem(mediaItem)
        }
    }

    /**
     * fetch the segments for SponsorBlock
     */
    private fun fetchSponsorBlockSegments() {
        CoroutineScope(Dispatchers.IO).launch {
            kotlin.runCatching {
                val categories = PlayerHelper.getSponsorBlockCategories()
                if (categories.size > 0) {
                    segmentData =
                        RetrofitInstance.api.getSegments(
                            videoId,
                            ObjectMapper().writeValueAsString(categories)
                        )
                    checkForSegments()
                }
            }
        }
    }

    /**
     * check for SponsorBlock segments
     */
    private fun checkForSegments() {
        Handler(Looper.getMainLooper()).postDelayed(this::checkForSegments, 100)

        if (segmentData == null || segmentData!!.segments.isEmpty()) return

        segmentData!!.segments.forEach { segment: com.github.libretube.api.obj.Segment ->
            val segmentStart = (segment.segment!![0] * 1000f).toLong()
            val segmentEnd = (segment.segment[1] * 1000f).toLong()
            val currentPosition = player?.currentPosition
            if (currentPosition in segmentStart until segmentEnd) {
                if (PlayerHelper.sponsorBlockNotifications) {
                    try {
                        Toast.makeText(this, R.string.segment_skipped, Toast.LENGTH_SHORT)
                            .show()
                    } catch (e: Exception) {
                        // Do nothing.
                    }
                }
                player?.seekTo(segmentEnd)
            }
        }
    }

    /**
     * destroy the [BackgroundMode] foreground service
     */
    override fun onDestroy() {
        // clear the playing queue
        PlayingQueue.clear()

        // called when the user pressed stop in the notification
        // stop the service from being in the foreground and remove the notification
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            stopForeground(STOP_FOREGROUND_REMOVE)
        } else {
            @Suppress("DEPRECATION")
            stopForeground(true)
        }
        // destroy the service
        stopSelf()
        if (this::nowPlayingNotification.isInitialized) nowPlayingNotification.destroy()
        super.onDestroy()
    }

    override fun onBind(p0: Intent?): IBinder? {
        return null
    }
}