import SwiftUI

/// 省钱战绩 = 累计汇总(summary)+ 战绩(battle)+ 省钱订单明细(records 分页)。
@MainActor
@Observable
final class SavingsViewModel {
    private(set) var summary: SavingsSummaryDTO?
    private(set) var battle: SavingsBattleDTO?
    private(set) var records: [SavingsRecordDTO] = []
    private(set) var isLoading = false
    private(set) var isLoadingMore = false
    private(set) var hasMore = false
    private(set) var loaded = false

    private var cursor: Int?
    private let service = SavingsService()

    func loadFirst() async {
        guard !isLoading else { return }
        isLoading = true
        defer { isLoading = false; loaded = true }
        // 三个接口并发拉,各自容错(某个失败不影响其它)
        async let summaryTask = service.summary()
        async let battleTask = service.battle()
        async let recordsTask = service.records(cursor: nil)

        summary = try? await summaryTask
        battle = try? await battleTask
        if let page = try? await recordsTask {
            records = page.items
            cursor = page.nextCursor
            hasMore = page.nextCursor != nil
        } else {
            hasMore = false
        }
    }

    func loadMore() async {
        guard hasMore, !isLoading, !isLoadingMore, let cursor else { return }
        isLoadingMore = true
        defer { isLoadingMore = false }
        if let page = try? await service.records(cursor: cursor) {
            records += page.items
            self.cursor = page.nextCursor
            hasMore = page.nextCursor != nil
        }
    }
}