import AVFAudio
import CoreMedia
import Defaults
import Foundation
import Logging
import Repeat
import SwiftUI

final class MPVBackend: PlayerBackend {
    static var controlsUpdateInterval = 0.5
    static var networkStateUpdateInterval = 0.1

    private var logger = Logger(label: "mpv-backend")

    var model: PlayerModel!
    var controls: PlayerControlsModel!
    var playerTime: PlayerTimeModel!
    var networkState: NetworkStateModel!

    var stream: Stream?
    var video: Video?
    var captions: Captions? { didSet {
        guard let captions = captions else {
            client.removeSubs()
            return
        }
        addSubTrack(captions.url)
    }}
    var currentTime: CMTime?

    var loadedVideo = false
    var isLoadingVideo = true { didSet {
        DispatchQueue.main.async { [weak self] in
            guard let self = self else {
                return
            }

            self.controls?.isLoadingVideo = self.isLoadingVideo
            self.setNeedsNetworkStateUpdates(true)
            self.model?.objectWillChange.send()
        }
    }}

    var isPlaying = true { didSet {
        networkStateTimer.start()

        if isPlaying {
            startClientUpdates()
        } else {
            stopControlsUpdates()
        }

        updateControlsIsPlaying()

        #if !os(macOS)
            DispatchQueue.main.async {
                UIApplication.shared.isIdleTimerDisabled = self.model.presentingPlayer && self.isPlaying
            }
        #endif
    }}
    var isSeeking = false {
        didSet {
            DispatchQueue.main.async { [weak self] in
                guard let self = self else { return }
                self.model.isSeeking = self.isSeeking
            }
        }
    }

    var playerItemDuration: CMTime?

    #if !os(macOS)
        var controller: MPVViewController!
    #endif
    var client: MPVClient! { didSet { client.backend = self } }

    private var clientTimer: Repeater!
    private var networkStateTimer: Repeater!

    private var onFileLoaded: (() -> Void)?

    private var controlsUpdates = false
    private var timeObserverThrottle = Throttle(interval: 2)

    var tracks: Int {
        client?.tracksCount ?? -1
    }

    var frameDropCount: Int {
        client?.frameDropCount ?? 0
    }

    var outputFps: Double {
        client?.outputFps ?? 0
    }

    var hwDecoder: String {
        client?.hwDecoder ?? "unknown"
    }

    var bufferingState: Double {
        client?.bufferingState ?? 0
    }

    var cacheDuration: Double {
        client?.cacheDuration ?? 0
    }

    init(
        model: PlayerModel,
        controls: PlayerControlsModel? = nil,
        playerTime: PlayerTimeModel? = nil,
        networkState: NetworkStateModel? = nil
    ) {
        self.model = model
        self.controls = controls
        self.playerTime = playerTime
        self.networkState = networkState

        clientTimer = .init(interval: .seconds(Self.controlsUpdateInterval), mode: .infinite) { [weak self] _ in
            self?.getClientUpdates()
        }

        networkStateTimer = .init(interval: .seconds(Self.networkStateUpdateInterval), mode: .infinite) { [weak self] _ in
            self?.updateNetworkState()
        }
    }

    typealias AreInIncreasingOrder = (Stream, Stream) -> Bool

    func bestPlayable(_ streams: [Stream], maxResolution: ResolutionSetting) -> Stream? {
        streams
            .filter { $0.kind != .hls && $0.resolution <= maxResolution.value }
            .max { lhs, rhs in
                let predicates: [AreInIncreasingOrder] = [
                    { $0.resolution < $1.resolution },
                    { $0.format > $1.format }
                ]

                for predicate in predicates {
                    if !predicate(lhs, rhs), !predicate(rhs, lhs) {
                        continue
                    }

                    return predicate(lhs, rhs)
                }

                return false
            } ??
            streams.first { $0.kind == .hls } ??
            streams.first
    }

    func canPlay(_ stream: Stream) -> Bool {
        stream.resolution != .unknown && stream.format != .av1
    }

    func playStream(_ stream: Stream, of video: Video, preservingTime: Bool, upgrading _: Bool) {
        #if !os(macOS)
            if model.presentingPlayer {
                UIApplication.shared.isIdleTimerDisabled = true
            }
        #endif

        var captions: Captions?
        if let captionsLanguageCode = Defaults[.captionsLanguageCode] {
            captions = video.captions.first { $0.code == captionsLanguageCode } ??
                video.captions.first { $0.code.contains(captionsLanguageCode) }
        }

        let updateCurrentStream = {
            DispatchQueue.main.async { [weak self] in
                self?.stream = stream
                self?.video = video
                self?.model.stream = stream
                self?.captions = captions
            }
        }

        let startPlaying = {
            #if !os(macOS)
                try? AVAudioSession.sharedInstance().setActive(true)
            #endif

            DispatchQueue.main.async { [weak self] in
                guard let self = self else {
                    return
                }

                self.startClientUpdates()

                if !preservingTime,
                   let segment = self.model.sponsorBlock.segments.first,
                   self.model.lastSkipped.isNil
                {
                    self.seek(to: segment.endTime) { finished in
                        guard finished else {
                            return
                        }

                        self.model.lastSkipped = segment
                        self.play()
                    }
                } else {
                    self.play()
                }
            }
        }

        let replaceItem: (CMTime?) -> Void = { [weak self] time in
            guard let self = self else {
                return
            }

            self.stop()

            DispatchQueue.main.async { [weak self] in
                guard let self = self else {
                    return
                }

                if let url = stream.singleAssetURL {
                    self.onFileLoaded = {
                        updateCurrentStream()
                        startPlaying()
                    }

                    self.client.loadFile(url, sub: captions?.url, time: time) { [weak self] _ in
                        self?.isLoadingVideo = true
                    }
                } else {
                    self.onFileLoaded = {
                        updateCurrentStream()
                        startPlaying()
                    }

                    let fileToLoad = self.model.musicMode ? stream.audioAsset.url : stream.videoAsset.url
                    let audioTrack = self.model.musicMode ? nil : stream.audioAsset.url

                    self.client?.loadFile(fileToLoad, audio: audioTrack, sub: captions?.url, time: time) { [weak self] _ in
                        self?.isLoadingVideo = true
                        self?.pause()
                    }
                }
            }
        }

        if preservingTime {
            if model.preservedTime.isNil {
                model.saveTime {
                    replaceItem(self.model.preservedTime)
                }
            } else {
                replaceItem(self.model.preservedTime)
            }
        } else {
            replaceItem(nil)
        }

        startClientUpdates()
    }

    func play() {
        isPlaying = true
        startClientUpdates()

        if controls?.presentingControls ?? false {
            startControlsUpdates()
        }

        setRate(model.currentRate)

        client?.play()
    }

    func pause() {
        isPlaying = false
        stopClientUpdates()

        client?.pause()
    }

    func togglePlay() {
        isPlaying ? pause() : play()
    }

    func stop() {
        client?.stop()
    }

    func seek(to time: CMTime, completionHandler: ((Bool) -> Void)?) {
        client?.seek(to: time) { [weak self] _ in
            self?.getClientUpdates()
            self?.updateControls()
            completionHandler?(true)
        }
    }

    func seek(relative time: CMTime, completionHandler: ((Bool) -> Void)? = nil) {
        client?.seek(relative: time) { [weak self] _ in
            self?.getClientUpdates()
            self?.updateControls()
            completionHandler?(true)
        }
    }

    func setRate(_ rate: Float) {
        client?.setDoubleAsync("speed", Double(rate))
    }

    func closeItem() {
        client?.pause()
        client?.stop()
    }

    func enterFullScreen() {
        model.toggleFullscreen(model?.playingFullScreen ?? false)
    }

    func exitFullScreen() {}

    func closePiP(wasPlaying _: Bool) {}

    func updateControls() {
        guard model.presentingPlayer else {
            return
        }
        DispatchQueue.main.async { [weak self] in
            guard let self = self else {
                return
            }

            self.playerTime.currentTime = self.currentTime ?? .zero
            self.playerTime.duration = self.playerItemDuration ?? .zero
        }
    }

    func startControlsUpdates() {
        self.logger.info("starting controls updates")
        controlsUpdates = true
    }

    func stopControlsUpdates() {
        self.logger.info("stopping controls updates")
        controlsUpdates = false
    }

    func startClientUpdates() {
        clientTimer.start()
    }

    private var handleSegmentsThrottle = Throttle(interval: 1)

    private func getClientUpdates() {
        currentTime = client?.currentTime
        playerItemDuration = client?.duration

        if controlsUpdates {
            updateControls()
        }

        model.updateNowPlayingInfo()

        handleSegmentsThrottle.execute {
            if let currentTime = currentTime {
                model.handleSegments(at: currentTime)
            }
        }

        timeObserverThrottle.execute {
            self.model.updateWatch()
        }
    }

    private func stopClientUpdates() {
        clientTimer.pause()
    }

    private func updateControlsIsPlaying() {
        DispatchQueue.main.async { [weak self] in
            self?.controls?.isPlaying = self?.isPlaying ?? false
        }
    }

    func handle(_ event: UnsafePointer<mpv_event>!) {
        logger.info(.init(stringLiteral: "RECEIVED  event: \(String(cString: mpv_event_name(event.pointee.event_id)))"))

        switch event.pointee.event_id {
        case MPV_EVENT_SHUTDOWN:
            mpv_destroy(client.mpv)
            client.mpv = nil

        case MPV_EVENT_LOG_MESSAGE:
            let logmsg = UnsafeMutablePointer<mpv_event_log_message>(OpaquePointer(event.pointee.data))
            logger.info(.init(stringLiteral: "\(String(cString: (logmsg!.pointee.prefix)!)), "
                    + "\(String(cString: (logmsg!.pointee.level)!)), "
                    + "\(String(cString: (logmsg!.pointee.text)!))"))

        case MPV_EVENT_FILE_LOADED:
            onFileLoaded?()
            startClientUpdates()
            onFileLoaded = nil

        case MPV_EVENT_PLAYBACK_RESTART:
            isLoadingVideo = false
            isSeeking = false

            onFileLoaded?()
            startClientUpdates()
            onFileLoaded = nil

        case MPV_EVENT_PAUSE:
            DispatchQueue.main.async { [weak self] in self?.handleEndOfFile() }
            isPlaying = false
            networkStateTimer.start()

        case MPV_EVENT_UNPAUSE:
            isPlaying = true
            isLoadingVideo = false
            isSeeking = false
            networkStateTimer.start()

        case MPV_EVENT_SEEK:
            isSeeking = true

        case MPV_EVENT_END_FILE:
            DispatchQueue.main.async { [weak self] in self?.handleEndOfFile() }

        default:
            logger.info(.init(stringLiteral: "UNHANDLED event: \(String(cString: mpv_event_name(event.pointee.event_id)))"))
        }
    }

    func handleEndOfFile() {
        guard client.eofReached else {
            return
        }

        getClientUpdates()

        if Defaults[.closeLastItemOnPlaybackEnd] {
            model.prepareCurrentItemForHistory(finished: true)
        }

        if model.queue.isEmpty {
            #if !os(macOS)
                try? AVAudioSession.sharedInstance().setActive(false)
            #endif

            if Defaults[.closeLastItemOnPlaybackEnd] {
                model.resetQueue()
                model.hide()
            }
        } else {
            model.advanceToNextItem()
        }
    }

    func setNeedsDrawing(_ needsDrawing: Bool) {
        client?.setNeedsDrawing(needsDrawing)
    }

    func setSize(_ width: Double, _ height: Double) {
        client?.setSize(width, height)
    }

    func addVideoTrack(_ url: URL) {
        client?.addVideoTrack(url)
    }

    func addSubTrack(_ url: URL) {
        client?.removeSubs()
        client?.addSubTrack(url)
    }

    func setVideoToAuto() {
        client?.setVideoToAuto()
    }

    func setVideoToNo() {
        client?.setVideoToNo()
    }

    func updateNetworkState() {
        guard let client = client, let networkState = networkState else {
            return
        }

        DispatchQueue.main.async {
            networkState.pausedForCache = client.pausedForCache
            networkState.cacheDuration = client.cacheDuration
            networkState.bufferingState = client.bufferingState
        }

        if !networkState.needsUpdates {
            networkStateTimer.pause()
        }
    }

    func setNeedsNetworkStateUpdates(_ needsUpdates: Bool) {
        if needsUpdates {
            networkStateTimer.start()
        } else {
            networkStateTimer.pause()
        }
    }
}