import SwiftUI
import UIKit

/// 带缓存、并发控制、图片解密、双指选择效果和分享功能的异步图片视图
struct AsyncImageView: View {
    let url: String
    let nums: [Int]
    let index: Int
    @State private var image: UIImage?
    @State private var isLoading = false
    @State private var error: Error?
    
    @State private var isSelecting = false  // 是否处于选择状态
    @State private var pressStartTime: Date?
    @State private var longPressActive = false
    @State private var showShareSheet = false  // 控制分享面板显示
    
    private static var currentlyLoadingIndices: Set<Int> = []
    private static let maxConcurrentLoads = 4
    private static let longPressThreshold: TimeInterval = 0.1  // 长按阈值（秒）

    var body: some View {
        Group {
            if let image = image {
                ZStack(alignment: .center) {
                    // 原始图片
                    Image(uiImage: image)
                        .resizable()
                        .aspectRatio(contentMode: .fit)
                    
                    // 选择状态的视觉效果
                    if isSelecting {
                        Image(uiImage: image)
                            .resizable()
                            .aspectRatio(contentMode: .fit)
                            .colorMultiply(.white)
                            .opacity(0.7)
                            .overlay(
                                RoundedRectangle(cornerRadius: 4)
                                    .stroke(Color.blue, lineWidth: 3)  // 改为蓝色边框更醒目
                            )
                            .blendMode(.lighten)
                        
                        // 分享按钮（仅在选择状态显示）
                        VStack {
                            Spacer()
                            Button(action: {
                                showShareSheet = true
                            }) {
                                Image(systemName: "square.and.arrow.up")
                                    .foregroundColor(.white)
                                    .padding()
                                    .background(Color.blue)
                                    .clipShape(Circle())
                                    .shadow(radius: 4)
                            }
                            .padding()
                        }
                    }
                }
                // 双指手势识别
                .gesture(
                    MagnificationGesture(minimumScaleDelta: 0)
                        .onChanged { _ in
                            handleTwoFingerGesture()
                        }
                        .onEnded { _ in
                            // 只有长按超过阈值才保持选择状态
                            let shouldKeepSelection = pressStartTime.map {
                                Date().timeIntervalSince($0) >= Self.longPressThreshold
                            } ?? false
                            
                            withAnimation(.easeOut) {
                                isSelecting = shouldKeepSelection
                            }
                            
                            if !shouldKeepSelection {
                                pressStartTime = nil
                                longPressActive = false
                            }
                        }
                )
                // 分享视图
                .sheet(isPresented: $showShareSheet) {
                    ShareSheet(activityItems: [image]) { completed in
                        if completed {
                            withAnimation(.easeOut) {
                                isSelecting = false
                            }
                            pressStartTime = nil
                            longPressActive = false
                        }
                    }
                }
            } else if isLoading {
                ProgressView()
                    .frame(height: 200)
            } else if error != nil {
                VStack(spacing: 8) {
                    Image(systemName: "exclamationmark.triangle")
                        .foregroundColor(.red)
                    Text(error?.localizedDescription ?? "未知错误")
                        .font(.caption)
                        .foregroundColor(.gray)
                }
                .frame(height: 200)
            } else {
                Color.gray.opacity(0.3)
                    .frame(height: 200)
            }
        }
        .onAppear {
            loadImage()
        }
        .onDisappear {
            Self.currentlyLoadingIndices.remove(index)
        }
    }
    
    // 处理双指手势
    private func handleTwoFingerGesture() {
        if pressStartTime == nil {
            pressStartTime = Date()
        } else {
            // 检查是否超过长按阈值
            let pressDuration = Date().timeIntervalSince(pressStartTime!)
            if pressDuration >= Self.longPressThreshold && !longPressActive {
                longPressActive = true
                // 显示选择效果
                withAnimation(.easeIn) {
                    isSelecting = true
                }
            }
        }
    }
    
    // 图片加载核心逻辑
    private func loadImage() {
        let cacheKey = extractCacheKey(from: url)
        
        // 1. 先检查缓存，如果有直接使用
        if let cachedImage = ImageCacheManager.shared.getImage(for: cacheKey) {
            image = cachedImage
            print("从缓存加载 - 键: \(cacheKey)")
            return
        }
        
        // 2. 检查并发加载限制
        guard !Self.currentlyLoadingIndices.contains(index),
              Self.currentlyLoadingIndices.count < Self.maxConcurrentLoads else {
            return
        }
        
        // 3. 开始加载流程
        Self.currentlyLoadingIndices.insert(index)
        isLoading = true
        error = nil
        
        // 4. 验证解密参数
        guard let decodeNum = nums[safe: index] else {
            error = NSError(domain: "数据错误", code: 1, userInfo: [NSLocalizedDescriptionKey: "图片参数不匹配"])
            isLoading = false
            Self.currentlyLoadingIndices.remove(index)
            return
        }
        
        print("调试信息：加载图片 - URL: \(url), 缓存键: \(cacheKey), 解密参数: \(decodeNum), 索引: \(index)")
        
        // 5. 验证URL有效性
        guard let imageUrl = URL(string: url) else {
            error = NSError(domain: "URL错误", code: 2, userInfo: [NSLocalizedDescriptionKey: "无效的图片URL"])
            isLoading = false
            Self.currentlyLoadingIndices.remove(index)
            return
        }
        
        // 6. 网络请求加载图片
        URLSession.shared.dataTask(with: imageUrl) { data, response, error in
            DispatchQueue.main.async {
                // 清理加载状态
                Self.currentlyLoadingIndices.remove(index)
                self.isLoading = false
                
                // 处理网络错误
                if let error = error {
                    self.error = error
                    print("图片加载失败（网络错误）: \(error.localizedDescription)")
                    return
                }
                
                // 验证响应和数据
                guard let httpResponse = response as? HTTPURLResponse,
                      (200...299).contains(httpResponse.statusCode),
                      let data = data, !data.isEmpty else {
                    self.error = NSError(domain: "响应错误", code: 3, userInfo: [NSLocalizedDescriptionKey: "无效的服务器响应"])
                    print("图片加载失败（无效响应）")
                    return
                }
                
                // 解码图片并应用解密
                guard let loadedImage = UIImage(data: data) else {
                    self.error = NSError(domain: "解码错误", code: 4, userInfo: [NSLocalizedDescriptionKey: "无法解析图片数据"])
                    print("图片加载失败（数据无效）")
                    return
                }
                
                // 解密并缓存图片（使用简化键）
                let decodedImage = loadedImage.decodeImage(num: decodeNum)
                self.image = decodedImage
                ImageCacheManager.shared.saveImage(decodedImage, for: cacheKey)
                print("图片加载成功（已缓存） - 键: \(cacheKey)")
            }
        }.resume()
    }
    
    /// 从URL中提取简化的缓存键
    private func extractCacheKey(from urlString: String) -> String {
        guard let url = URL(string: urlString) else {
            return urlString.hashValue.description
        }
        
        let pathComponents = url.pathComponents
        
        if let photosIndex = pathComponents.firstIndex(of: "photos"),
           photosIndex + 1 < pathComponents.count,
           photosIndex + 2 < pathComponents.count {
            let idComponent = pathComponents[photosIndex + 1]
            var fileComponent = pathComponents[photosIndex + 2]
            
            if let dotIndex = fileComponent.lastIndex(of: ".") {
                fileComponent = String(fileComponent[..<dotIndex])
            }
            
            return "\(idComponent)/\(fileComponent)"
        }
        
        return url.path.hashValue.description
    }
}

// 分享视图包装器
struct ShareSheet: UIViewControllerRepresentable {
    let activityItems: [Any]
    let completion: (Bool) -> Void
    
    func makeUIViewController(context: Context) -> UIActivityViewController {
        let controller = UIActivityViewController(activityItems: activityItems, applicationActivities: nil)
        controller.completionWithItemsHandler = { (activityType, completed, returnedItems, error) in
            completion(completed)
        }
        return controller
    }
    
    func updateUIViewController(_ uiViewController: UIActivityViewController, context: Context) {}
}

// 数组安全访问扩展
extension Array {
    subscript(safe index: Int) -> Element? {
        return indices.contains(index) ? self[index] : nil
    }
}