import SwiftUI

/// 首页(导购)逻辑,对齐安卓 HomeViewModel:feed 分页 + 定位更新 + 换推广链接。
@MainActor
@Observable
final class HomeViewModel {
    private(set) var coupons: [CouponCard] = []
    private(set) var isLoading = false
    private(set) var isLoadingMore = false
    private(set) var hasNext = true
    private(set) var errorMessage: String?

    // 默认天安门,定位失败兜底(对齐安卓)
    private var longitude = 116.404
    private var latitude = 39.928
    private var page = 1
    private let service = MeituanService()

    func loadFirstPage() async {
        guard !isLoading else { return }
        isLoading = true
        errorMessage = nil
        defer { isLoading = false }
        do {
            let resp = try await service.feed(longitude: longitude, latitude: latitude, page: 1)
            coupons = resp.items
            page = resp.page
            hasNext = resp.hasNext
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? "加载失败,请下拉重试"
        }
    }

    func loadNextPage() async {
        guard hasNext, !isLoading, !isLoadingMore else { return }
        isLoadingMore = true
        defer { isLoadingMore = false }
        do {
            let resp = try await service.feed(longitude: longitude, latitude: latitude, page: page + 1)
            coupons += resp.items
            page = resp.page
            hasNext = resp.hasNext
        } catch {
            // 加载更多失败静默,不打断已有列表
        }
    }

    /// 拿到真实定位后刷新成附近的券。
    func updateLocation(longitude: Double, latitude: Double) async {
        self.longitude = longitude
        self.latitude = latitude
        await loadFirstPage()
    }

    /// 点券 → 换推广链接 → 返回(deeplink 优先唤起美团 App,H5 兜底)。
    func referralLinks(for card: CouponCard) async -> (deeplink: URL?, h5: URL?) {
        do {
            let resp = try await service.referralLink(
                productViewSign: card.productViewSign,
                platform: card.platform,
                bizLine: card.bizLine
            )
            let deeplink = resp.linkMap["3"].flatMap { URL(string: $0) }
            let h5raw = resp.linkMap["1"] ?? resp.link
            return (deeplink, URL(string: h5raw))
        } catch {
            return (nil, nil)
        }
    }
}