// 
// Copyright 2021 New Vector Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

import Foundation
import DSWaveformImage

enum VoiceMessagePlaybackControllerState {
    case stopped
    case playing
    case paused
    case error
}

class VoiceMessagePlaybackController: VoiceMessageAudioPlayerDelegate, VoiceMessagePlaybackViewDelegate {
    
    private enum Constants {
        static let elapsedTimeFormat = "m:ss"
    }
    
    private static let timeFormatter: DateFormatter = {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = Constants.elapsedTimeFormat
        return dateFormatter
    }()
    
    private let cacheManager: VoiceMessageAttachmentCacheManager
    
    private let audioPlayer: VoiceMessageAudioPlayer
    private var displayLink: CADisplayLink!
    private var samples: [Float] = []
    
    private var state: VoiceMessagePlaybackControllerState = .stopped {
        didSet {
            updateUI()
            displayLink.isPaused = (state != .playing)
        }
    }
    
    let playbackView: VoiceMessagePlaybackView
    
    init(mediaServiceProvider: VoiceMessageMediaServiceProvider,
         cacheManager: VoiceMessageAttachmentCacheManager) {
        self.cacheManager = cacheManager
        
        playbackView = VoiceMessagePlaybackView.loadFromNib()
        audioPlayer = mediaServiceProvider.audioPlayer()
        
        audioPlayer.registerDelegate(self)
        playbackView.delegate = self
        
        displayLink = CADisplayLink(target: WeakDisplayLinkTarget(self, selector: #selector(handleDisplayLinkTick)), selector: WeakDisplayLinkTarget.triggerSelector)
        displayLink.isPaused = true
        displayLink.add(to: .current, forMode: .common)
        
        NotificationCenter.default.addObserver(self, selector: #selector(updateTheme), name: .themeServiceDidChangeTheme, object: nil)
        updateTheme()
        updateUI()
    }
    
    var attachment: MXKAttachment? {
        didSet {
            loadAttachmentData()
        }
    }
    
    // MARK: - VoiceMessagePlaybackViewDelegate
    
    func voiceMessagePlaybackViewDidRequestPlaybackToggle() {
        if audioPlayer.isPlaying {
            audioPlayer.pause()
        } else {
            audioPlayer.play()
        }
    }
    
    // MARK: - VoiceMessageAudioPlayerDelegate
    
    func audioPlayerDidFinishLoading(_ audioPlayer: VoiceMessageAudioPlayer) {
        updateUI()
    }
    
    func audioPlayerDidStartPlaying(_ audioPlayer: VoiceMessageAudioPlayer) {
        state = .playing
    }
    
    func audioPlayerDidPausePlaying(_ audioPlayer: VoiceMessageAudioPlayer) {
        state = .paused
    }
    
    func audioPlayerDidStopPlaying(_ audioPlayer: VoiceMessageAudioPlayer) {
        state = .stopped
    }
    
    func audioPlayer(_ audioPlayer: VoiceMessageAudioPlayer, didFailWithError error: Error) {
        state = .error
        MXLog.error("Failed playing voice message with error: \(error)")
    }
    
    func audioPlayerDidFinishPlaying(_ audioPlayer: VoiceMessageAudioPlayer) {
        audioPlayer.seekToTime(0.0)
        state = .stopped
    }
    
    // MARK: - Private
    
    @objc private func handleDisplayLinkTick() {
        updateUI()
    }
    
    private func updateUI() {
        var details = VoiceMessagePlaybackViewDetails()
        
        details.playbackEnabled = (state != .error)
        details.playing = (state == .playing)
        details.samples = samples
        
        switch state {
        case .stopped:
            details.currentTime = VoiceMessagePlaybackController.timeFormatter.string(from: Date(timeIntervalSinceReferenceDate: audioPlayer.duration))
            details.progress = 0.0
        default:
            details.currentTime = VoiceMessagePlaybackController.timeFormatter.string(from: Date(timeIntervalSinceReferenceDate: audioPlayer.currentTime))
            details.progress = (audioPlayer.duration > 0.0 ? audioPlayer.currentTime / audioPlayer.duration : 0.0)
        }
        
        playbackView.configureWithDetails(details)
    }
        
    private func loadAttachmentData() {
        guard let attachment = attachment else {
            return
        }
        
        let requiredNumberOfSamples = playbackView.getRequiredNumberOfSamples()
        
        cacheManager.loadAttachment(attachment, numberOfSamples: requiredNumberOfSamples) { result in
            switch result {
            case .success(let result):
                self.audioPlayer.loadContentFromURL(result.0)
                self.samples = result.1
                self.updateUI()
            case .failure:
                self.state = .error
            }
        }
    }
    
    @objc private func updateTheme() {
        playbackView.update(theme: ThemeService.shared().theme)
    }
}