import SwiftUI
import UniformTypeIdentifiers

struct PlaylistView: View {
    @EnvironmentObject var engine: PlayerEngine
    @State private var showFileImporter = false
    
    var body: some View {
        VStack(spacing: 0) {
            // 顶部工具栏
            HStack {
                Text("播放列表")
                    .font(.headline)
                
                Spacer()
                
                Text("\(engine.queue.count)")
                    .font(.caption)
                    .foregroundStyle(.secondary)
                    .padding(.horizontal, 8)
                    .padding(.vertical, 2)
                    .background(.quaternary, in: Capsule())
                
                Button {
                    showFileImporter = true
                } label: {
                    Image(systemName: "plus.circle.fill")
                        .font(.title3)
                }
                .buttonStyle(.plain)
                
                if !engine.queue.isEmpty {
                    Button {
                        engine.queue.removeAll()
                        engine.currentIndex = -1
                        engine.pause()
                        engine.player.replaceCurrentItem(with: nil)
                    } label: {
                        Image(systemName: "trash")
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                    .buttonStyle(.plain)
                }
            }
            .padding(.horizontal, 16)
            .padding(.vertical, 12)
            
            Divider()
            
            // 列表
            if engine.queue.isEmpty {
                Spacer()
                VStack(spacing: 8) {
                    Image(systemName: "music.note.list")
                        .font(.largeTitle)
                        .foregroundStyle(.tertiary)
                    Text("列表为空")
                        .font(.subheadline)
                        .foregroundStyle(.tertiary)
                    Button("添加文件") {
                        showFileImporter = true
                    }
                    .font(.caption)
                }
                Spacer()
            } else {
                List {
                    ForEach(Array(engine.queue.enumerated()), id: \.element.id) { idx, item in
                        playlistRow(item: item, index: idx)
                            .contentShape(Rectangle())
                            .onTapGesture {
                                engine.play(index: idx)
                            }
                    }
                    .onDelete { offsets in
                        engine.remove(at: offsets)
                    }
                    .onMove { source, destination in
                        engine.move(from: source, to: destination)
                    }
                }
                .listStyle(.plain)
            }
        }
        .fileImporter(
            isPresented: $showFileImporter,
            allowedContentTypes: supportedTypes,
            allowsMultipleSelection: true
        ) { result in
            if case .success(let urls) = result {
                engine.addToQueue(urls: urls)
            }
        }
    }
    
    // MARK: - 列表行
    
    @ViewBuilder
    private func playlistRow(item: MediaItem, index: Int) -> some View {
        let isCurrent = index == engine.currentIndex
        
        HStack(spacing: 10) {
            // 序号/播放指示
            ZStack {
                if isCurrent {
                    Image(systemName: engine.isPlaying ? "waveform" : "pause.fill")
                        .font(.caption)
                        .foregroundStyle(.blue)
                        .symbolEffect(.variableColor.iterative, isActive: engine.isPlaying && isCurrent)
                } else {
                    Text("\(index + 1)")
                        .font(.caption.monospacedDigit())
                        .foregroundStyle(.tertiary)
                }
            }
            .frame(width: 20)
            
            // 类型图标
            Image(systemName: iconName(for: item.type))
                .font(.caption)
                .foregroundStyle(isCurrent ? .blue : .secondary)
            
            // 文件名
            Text(item.name)
                .font(.system(size: 13))
                .lineLimit(1)
                .foregroundStyle(isCurrent ? .primary : .secondary)
            
            Spacer()
        }
        .padding(.vertical, 4)
        .listRowBackground(isCurrent ? Color.accentColor.opacity(0.1) : Color.clear)
    }
    
    private func iconName(for type: MediaType) -> String {
        switch type {
        case .video: return "film"
        case .audio: return "music.note"
        case .stream: return "dot.radiowaves.left.and.right"
        }
    }
    
    // 支持的文件类型
    private var supportedTypes: [UTType] {
        var types: [UTType] = [
            .movie, .video, .audio, .mpeg4Movie, .quickTimeMovie, .mp3,
            .mpeg4Audio, .avi, .url
        ]
        // 扩展常见格式
        for ext in ["mkv", "flac", "wav", "ogg", "m3u8", "m3u", "ts", "mov", "webm"] {
            if let uttype = UTType(filenameExtension: ext) {
                types.append(uttype)
            }
        }
        return types
    }
}