import SwiftUI

/// 首页(导购)。不设防(未登录可浏览)。进入时先用默认坐标出券,定位回来再刷新成附近的。
struct HomeView: View {
    @State private var vm = HomeViewModel()
    @State private var locationManager = LocationManager()
    @Environment(\.openURL) private var openURL

    var body: some View {
        NavigationStack {
            content
                .navigationTitle("傻瓜比价")
        }
        .task {
            await vm.loadFirstPage()
            // 首屏已出券;定位回来若成功,刷新成附近的(失败则保持默认坐标结果)
            if let coord = await locationManager.requestOnce() {
                await vm.updateLocation(longitude: coord.longitude, latitude: coord.latitude)
            }
        }
    }

    @ViewBuilder
    private var content: some View {
        if vm.isLoading && vm.coupons.isEmpty {
            ProgressView("加载中…")
                .frame(maxWidth: .infinity, maxHeight: .infinity)
        } else if vm.coupons.isEmpty {
            ContentUnavailableView {
                Label("暂时没有优惠", systemImage: "ticket")
            } description: {
                Text(vm.errorMessage ?? "下拉刷新试试")
            }
        } else {
            List {
                ForEach(vm.coupons) { card in
                    CouponCardView(card: card) {
                        Task { await openCard(card) }
                    }
                    .listRowSeparator(.hidden)
                }

                if vm.hasNext {
                    HStack {
                        Spacer()
                        ProgressView()
                        Spacer()
                    }
                    .listRowSeparator(.hidden)
                    .onAppear { Task { await vm.loadNextPage() } }
                }
            }
            .listStyle(.plain)
            .refreshable { await vm.loadFirstPage() }
        }
    }

    /// 点券:换推广链接 → deeplink 优先唤起美团 App,唤不起用 H5 兜底。
    private func openCard(_ card: CouponCard) async {
        let links = await vm.referralLinks(for: card)
        if let deeplink = links.deeplink {
            openURL(deeplink) { accepted in
                if !accepted, let h5 = links.h5 { openURL(h5) }
            }
        } else if let h5 = links.h5 {
            openURL(h5)
        }
    }
}