Music_Player3/relax.offline.mp3.music/MP/MPPositive/Models/ViewModels/LoadViewModels/MPPositive_PlayerLoadViewModel.swift

//
//  MPPositive_PlayerLoadViewModel.swift
//  MusicPlayer
//
//  Created by Mr.Zhou on 2024/5/9.
//

import UIKit
///播放器管理ViewModel
class MPPositive_PlayerLoadViewModel: NSObject {
    /// 单曲常规列表
    var songVideos:[MPPositive_SongItemModel]!
    ///随机播放列表
    var randomVideos:[MPPositive_SongItemModel]!
    ///当前播放音乐ViewModel
    var currentVideo:MPPositive_SongViewModel!{
        didSet{
            DispatchQueue.main.async {
                [weak self] in
                guard let self = self else {return}
                if currentVideo != nil {
                    print("当前播放音乐是:\(currentVideo?.song?.title ?? "")")
                    //启动监听器
                    startObservingCurrentVideoItem()
                    //当值变化时通知播放器页面，更新UI
                    NotificationCenter.notificationKey.post(notificationName: .positive_player_reload)
                }
            }
        }
    }
    //监听器
    private var itemObservation: NSKeyValueObservation?
//    private var loadQueue:DispatchQueue!
    ///异步请求组
//    private var group:DispatchGroup!
    ///单曲播放队列ViewModel
    var listViewVideos:[MPPositive_SongViewModel]!
    ///palyer管理model初始化方法
    /// - Parameters:
    ///   - songs: 全部歌曲列表
    ///   - firstVideoId: 需要播放的第一首歌
    init(_ songs:[MPPositive_SongItemModel], currentVideoId: String) {
        super.init()
        self.songVideos = songs
        //根据列表生成一份随机播放列表
        self.randomVideos = self.songVideos.shuffled()
        self.listViewVideos = []
        
    }
    //启动对于当前音乐的监听器
    private func startObservingCurrentVideoItem() {
        itemObservation?.invalidate() // 先移除旧的监听
        //判断当前currentVideo是否已经加载完数据了
        if currentVideo?.resourcePlayerItem != nil {
            //数据已经加载完毕了
            postNoticeAction()
        }else {
            //添加新的监听
            itemObservation = currentVideo?.observe(\.resourcePlayerItem, options: [.new], changeHandler: { [weak self] video, change in
                guard let self = self else {return}
                if change.newValue != nil {
                    // 在这里处理 newItem 的值变化
                    postNoticeAction()
                }else {
                    //获取到值是nil
                    print("无效更新")
                }
            })
        }
    }
    //发起通知告诉播放器已经切换了播放音乐
    private func postNoticeAction() {
        DispatchQueue.main.async {
            [weak self] in
            guard let self = self else {return}
            if currentVideo != nil {
                MP_AnalyticsManager.shared.player_b_pvAction(currentVideo.song.videoId, videoname: currentVideo.title ?? "", artistname: currentVideo.song.shortBylineText ?? "")
                //当值变化时通知播放器页面，更新UI
                NotificationCenter.notificationKey.post(notificationName: .positive_player_reload, object: currentVideo)
            }
        }
    }
    
    ///将选中Video的上1位，下两位项包括本身总计4项Video进行补全转为ViewModel,并播放这首音乐
    func improveData(_ targetVideoId:String, isRandom:Bool = false) {
        //对于选中Video的集合
        var array:[MPPositive_SongItemModel] = []
        if isRandom  {
            //获取targetVideoId的索引
            guard let targetIndex = self.randomVideos.firstIndex(where: {$0.videoId == targetVideoId}) else {
                return
            }
            array.append(self.randomVideos[targetIndex])
//            //获取上一位
//            let previousIndex = targetIndex-1
//            if previousIndex >= 0 {
//                array.append(self.randomVideos[previousIndex])
//            }
            let nextIndex = targetIndex+1
            let lastIndex = targetIndex+2
            if nextIndex < randomVideos.count {
                array.append(self.randomVideos[nextIndex])
            }
            if lastIndex < randomVideos.count  {
                array.append(self.randomVideos[lastIndex])
            }
        }else {
            //获取targetVideoId的索引
            guard let targetIndex = self.songVideos.firstIndex(where: {$0.videoId == targetVideoId}) else {
                return
            }
            array.append(self.songVideos[targetIndex])
//            //获取上一位
//            let previousIndex = targetIndex-1
//            if previousIndex >= 0 {
//                array.append(self.songVideos[previousIndex])
//            }
            let nextIndex = targetIndex+1
            let lastIndex = targetIndex+2
            if nextIndex < songVideos.count {
                array.append(self.songVideos[nextIndex])
            }
            if lastIndex < songVideos.count  {
                array.append(self.songVideos[lastIndex])
            }
        }
        //获取完成，优先检索ViewModel，看看是否已存在补完video
        let videoIDs = Set(listViewVideos.map({$0.song.videoId}))
        //比较videoID,去掉已经补完的内容
        array = array.filter({!videoIDs.contains($0.videoId)})
        //全部转化为MPPositive_SongViewModel
        let viewModels = array.map({(MPPositive_SongViewModel($0))})
        //添加新的ViewModel
        self.listViewVideos.append(contentsOf: viewModels)
//        //只保留最后5首
        self.listViewVideos = self.listViewVideos.suffix(4)
        //更新当前播放音乐
        self.currentVideo = self.listViewVideos.first(where: {$0.song.videoId == targetVideoId})
    }
    ///重新获取指定歌曲资源
    func remakeImproveData(_ completion:@escaping (() -> Void)) {
        currentVideo.configure()
        completion()
    }
    
    ///移除选中的song，并更新listViewVideos，移除相同index的值
    func removeData(_ targetVideoId:String) {
        let targetIndex = songVideos.firstIndex(where: {$0.videoId == targetVideoId}) ?? 0
        //将选中的音乐移除，同时更新listView
        songVideos = songVideos.filter({$0.videoId != targetVideoId})
        randomVideos = randomVideos.filter({$0.videoId != targetVideoId})
        listViewVideos = listViewVideos.filter({$0.song.videoId != targetVideoId})
        if currentVideo != nil {
            //判断是否当前音乐
            if currentVideo.song.videoId == targetVideoId {
                //判断targetIndex是否大于最大音乐值
                if targetIndex < songVideos.count {
                    let videoId = songVideos[targetIndex].videoId ?? ""
                    improveData(videoId)
                }else {
                    //移除的是原来最后一首音乐，播放新的最后一首音乐
                    let videoId = songVideos.last?.videoId ?? ""
                    improveData(videoId)
                }
            }
        }
    }
    
    //销毁时
    deinit {
        itemObservation?.invalidate()
        //释放所有数据
        songVideos = nil
        currentVideo = nil
        randomVideos = nil
        listViewVideos = nil
    }
}