import SwiftUI

struct CustomLightSequenceAnimation: View {
    // 核心循环序列：按"123321123321"规律定义基础单元
    private let baseSequence: [Int] = [1, 2, 3, 3, 2, 1, 1, 2, 3, 3, 2, 1]
    @State private var currentLight: Int = 1  // 当前显示的图片序号
    @State private var sequenceIndex: Int = 0  // 当前在序列中的索引
    
    // 淡入淡出透明度控制（确保切换丝滑）
    @State private var currentOpacity: CGFloat = 1.0
    @State private var nextOpacity: CGFloat = 0.0
    
    // 尺寸参数（适配正方形卡片）
    private let screenWidth = UIScreen.main.bounds.width
    private let squareSize: CGFloat
    private let imageSize: CGFloat
    
    init() {
        self.squareSize = screenWidth * 1.8  // 正方形背景尺寸
        self.imageSize = squareSize / 3      // 光束卡片尺寸（1/3背景大小）
    }
    
    // 卡片中心位置（固定，确保摆正居中）
    private var centerPosition: CGPoint {
        CGPoint(x: screenWidth / 2, y: squareSize * 0.325)
    }
    
    var body: some View {
        ZStack {
            // 底部背景（正方形）
            SVGImage(svgName: "BlindBg")
                .frame(width: squareSize, height: squareSize)
                .position(centerPosition)
            
            // 当前显示的光束卡片（摆正状态）
            SVGImage(svgName: "Light\(currentLight)")
                .frame(width: imageSize, height: imageSize)
                .position(centerPosition)
                .opacity(currentOpacity)
            
            // 下一张待显示的光束卡片（提前加载，摆正状态）
            SVGImage(svgName: "Light\(nextLight)")
                .frame(width: imageSize, height: imageSize)
                .position(centerPosition)
                .opacity(nextOpacity)
        }
        .onAppear {
            startLoopAnimation()
        }
    }
    
    // 计算下一张卡片序号（基于当前索引循环）
    private var nextLight: Int {
        let nextIdx = (sequenceIndex + 1) % baseSequence.count
        return baseSequence[nextIdx]
    }
    
    // 启动循环切换动画
    private func startLoopAnimation() {
        // 每1.2秒切换一次（可调整速度）
        Timer.scheduledTimer(withTimeInterval: 1.2, repeats: true) { _ in
            // 0.5秒淡入淡出过渡（丝滑无卡顿）
            withAnimation(Animation.easeInOut(duration: 0.5)) {
                currentOpacity = 0.0
                nextOpacity = 1.0
            }
            
            // 动画完成后更新状态（确保顺序无偏差）
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                currentLight = nextLight
                sequenceIndex = (sequenceIndex + 1) % baseSequence.count
                currentOpacity = 1.0
                nextOpacity = 0.0
            }
        }
    }
}

// 预览
struct CustomLightSequenceAnimation_Previews: PreviewProvider {
    static var previews: some View {
        CustomLightSequenceAnimation()
    }
}