import SwiftUI

/// BricksView — SwiftBricks的主入口视图
/// 从JSON schema渲染完整的UI页面
/// 
/// 用法:
/// ```swift
/// BricksView(json: jsonString, engine: engine)
/// BricksView(url: "/api/page.dspy", engine: engine)
/// ```
public struct BricksView: View {
    @ObservedObject var engine: BricksEngine
    @State private var isLoaded: Bool = false
    @State private var loadError: String?
    
    private var jsonString: String?
    private var loadURL: String?
    
    /// 从JSON字符串创建
    public init(json: String, engine: BricksEngine) {
        self.jsonString = json
        self.loadURL = nil
        self._engine = ObservedObject(wrappedValue: engine)
    }
    
    /// 从URL加载
    public init(url: String, engine: BricksEngine) {
        self.jsonString = nil
        self.loadURL = url
        self._engine = ObservedObject(wrappedValue: engine)
    }
    
    /// 从已加载的schema创建
    public init(schema: ControlSchema, engine: BricksEngine) {
        self.jsonString = nil
        self.loadURL = nil
        self._engine = ObservedObject(wrappedValue: engine)
        // 立即加载
        engine.loadSchema(schema)
    }
    
    public var body: some View {
        ZStack {
            if let schema = engine.rootSchema {
                // 主内容
                ControlRenderer(schema: schema, engine: engine)
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
                
                // 弹窗层
                if let popup = engine.activePopup {
                    popupOverlay(popup)
                }
                
                // 加载指示器
                if engine.isLoading {
                    Color.black.opacity(0.01)
                        .overlay(ProgressView())
                }
            } else if let error = loadError {
                errorView(error)
            } else {
                ProgressView("加载中...")
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
            }
        }
        .task {
            await performLoad()
        }
        .alert("错误", isPresented: .init(
            get: { engine.errorMessage != nil },
            set: { if !$0 { engine.errorMessage = nil } }
        )) {
            Button("确定") { engine.errorMessage = nil }
        } message: {
            Text(engine.errorMessage ?? "")
        }
    }
    
    // MARK: - 加载
    
    private func performLoad() async {
        if let json = jsonString {
            do {
                try engine.loadJSON(json)
                isLoaded = true
            } catch {
                loadError = "JSON解析失败: \(error.localizedDescription)"
            }
        } else if let url = loadURL {
            do {
                try await engine.loadFromURL(url)
                isLoaded = true
            } catch {
                loadError = error.localizedDescription
            }
        }
    }
    
    // MARK: - 弹窗层
    
    private func popupOverlay(_ popup: PopupInfo) -> some View {
        ZStack {
            // 遮罩
            Color.black.opacity(0.3)
                .ignoresSafeArea()
                .onTapGesture {
                    engine.activePopup = nil
                }
            
            // 弹窗内容
            PopupWindowControl(schema: popup.schema, engine: engine)
                .frame(
                    maxWidth: popupWidth(popup.options),
                    maxHeight: popupHeight(popup.options)
                )
                .padding(20)
        }
    }
    
    private func popupWidth(_ opts: PopupOptions) -> CGFloat? {
        if let cw = opts.cwidth { return CGFloat(cw * 8) }
        if let w = opts.width, let px = Double(w.replacingOccurrences(of: "px", with: "")) {
            return CGFloat(px)
        }
        return 400
    }
    
    private func popupHeight(_ opts: PopupOptions) -> CGFloat? {
        if let ch = opts.cheight { return CGFloat(ch * 16) }
        if let h = opts.height {
            if h.hasSuffix("%") { return nil } // 百分比用maxHeight
            if let px = Double(h.replacingOccurrences(of: "px", with: "")) {
                return CGFloat(px)
            }
        }
        return nil
    }
    
    // MARK: - 错误视图
    
    private func errorView(_ error: String) -> some View {
        VStack(spacing: 12) {
            Image(systemName: "exclamationmark.triangle.fill")
                .font(.largeTitle)
                .foregroundColor(.orange)
            Text("加载失败")
                .font(.headline)
            Text(error)
                .font(.caption)
                .foregroundColor(.secondary)
                .multilineTextAlignment(.center)
            Button("重试") {
                Task { await performLoad() }
            }
        }
        .padding(40)
    }
}