import SwiftUI

enum ImagePreviewSource: Identifiable, Equatable {
    case local(UIImage)
    case remote(String)
    var id: String {
        switch self {
        case .local(let img):
            return String(describing: img.hashValue)
        case .remote(let url):
            return url
        }
    }
    static func == (lhs: ImagePreviewSource, rhs: ImagePreviewSource) -> Bool {
        switch (lhs, rhs) {
        case let (.local(l), .local(r)):
            return l.pngData() == r.pngData()
        case let (.remote(l), .remote(r)):
            return l == r
        default:
            return false
        }
    }
}

struct ImagePreviewPager: View {
    let images: [ImagePreviewSource]
    @Binding var currentIndex: Int
    let onClose: () -> Void
    
    // 本地图片构造器
    init(images: [UIImage], currentIndex: Binding<Int>, onClose: @escaping () -> Void) {
        self.images = images.map { .local($0) }
        self._currentIndex = currentIndex
        self.onClose = onClose
    }
    // 远程图片构造器
    init(images: [String], currentIndex: Binding<Int>, onClose: @escaping () -> Void) {
        self.images = images.map { .remote($0) }
        self._currentIndex = currentIndex
        self.onClose = onClose
    }
    
    var body: some View {
        ZStack(alignment: .topTrailing) {
            Color.black.ignoresSafeArea()
            TabView(selection: $currentIndex) {
                ForEach(Array(images.enumerated()), id: \ .element.id) { idx, source in
                    Group {
                        switch source {
                        case .local(let img):
                            Image(uiImage: img)
                                .resizable()
                                .aspectRatio(contentMode: .fit)
                                .frame(maxWidth: .infinity, maxHeight: .infinity)
                                .background(Color.black)
                        case .remote(let urlStr):
                            CachedAsyncImage(url: urlStr) { image in
                                image
                                    .resizable()
                                    .aspectRatio(contentMode: .fit)
                                    .frame(maxWidth: .infinity, maxHeight: .infinity)
                                    .background(Color.black)
                            } placeholder: {
                                Rectangle()
                                    .fill(Color.gray.opacity(0.3))
                                    .overlay(
                                        ProgressView()
                                            .progressViewStyle(CircularProgressViewStyle(tint: .white.opacity(0.6)))
                                            .scaleEffect(0.8)
                                    )
                            }
                        }
                    }
                    .tag(idx)
                }
            }
            .tabViewStyle(PageTabViewStyle(indexDisplayMode: .always))
            Button(action: { onClose() }) {
                Image(systemName: "xmark.circle.fill")
                    .font(.system(size: 32))
                    .foregroundColor(.white)
                    .padding(24)
            }
        }
    }
}