import SwiftUI

/// 省钱战绩:顶部累计/战绩卡 + 省钱订单明细(实际下单省了多少)。
struct SavingsView: View {
    @State private var vm = SavingsViewModel()

    var body: some View {
        Group {
            if vm.isLoading && vm.summary == nil && vm.records.isEmpty {
                ProgressView().frame(maxWidth: .infinity, maxHeight: .infinity)
            } else {
                List {
                    Section {
                        SavingsHeaderCard(summary: vm.summary, battle: vm.battle)
                    }

                    if vm.loaded && vm.records.isEmpty {
                        Section {
                            Text("还没有省钱订单。比价后下单,省了多少会记在这里。")
                                .font(.subheadline)
                                .foregroundStyle(.secondary)
                        }
                    } else {
                        Section("省钱明细") {
                            ForEach(vm.records) { SavingsRecordRow(record: $0) }
                            if vm.hasMore {
                                HStack { Spacer(); ProgressView(); Spacer() }
                                    .onAppear { Task { await vm.loadMore() } }
                            }
                        }
                    }
                }
                .listStyle(.insetGrouped)
                .refreshable { await vm.loadFirst() }
            }
        }
        .navigationTitle("省钱战绩")
        .navigationBarTitleDisplayMode(.inline)
        .task { if !vm.loaded { await vm.loadFirst() } }
    }
}

private struct SavingsHeaderCard: View {
    let summary: SavingsSummaryDTO?
    let battle: SavingsBattleDTO?

    var body: some View {
        VStack(spacing: 12) {
            Text("累计帮你省了")
                .font(.subheadline)
                .foregroundStyle(.secondary)
            Text((summary?.totalSavedCents ?? 0).centsToYuanText)
                .font(.system(size: 36, weight: .bold))
                .foregroundStyle(AppColors.success)
            Text("共 \(summary?.orderCount ?? 0) 单 · 平均每单省 \((summary?.avgSavedCents ?? 0).centsToYuanText)")
                .font(.caption)
                .foregroundStyle(.secondary)

            Divider()

            HStack {
                stat("本周省", (battle?.weekSavedCents ?? 0).centsToYuanText)
                Divider()
                stat("击败用户", "\(battle?.beatPercent ?? 0)%")
                Divider()
                stat("连续打卡", "\(battle?.streakDays ?? 0)天")
            }
            .frame(height: 44)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 8)
    }

    private func stat(_ title: String, _ value: String) -> some View {
        VStack(spacing: 4) {
            Text(value).font(.headline)
            Text(title).font(.caption2).foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity)
    }
}

private struct SavingsRecordRow: View {
    let record: SavingsRecordDTO

    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            HStack {
                Text(record.platform ?? record.shopName ?? "订单")
                    .font(.subheadline.bold())
                    .lineLimit(1)
                Spacer()
                Text(AppDate.friendly(record.createdAt))
                    .font(.caption2)
                    .foregroundStyle(.secondary)
            }

            if !record.dishes.isEmpty {
                Text(record.dishes.joined(separator: "、"))
                    .font(.caption).foregroundStyle(.secondary).lineLimit(1)
            } else if let title = record.title {
                Text(title).font(.caption).foregroundStyle(.secondary).lineLimit(1)
            }

            HStack(spacing: 8) {
                Text("实付 \(record.orderAmountCents.centsToYuanText)")
                    .font(.subheadline)
                if let orig = record.originalPriceCents, orig > record.orderAmountCents {
                    Text(orig.centsToYuanText)
                        .font(.caption).strikethrough().foregroundStyle(.secondary)
                }
                Spacer()
                if record.savedAmountCents > 0 {
                    Text("省\(record.savedAmountCents.centsToYuanText)")
                        .font(.caption.bold())
                        .padding(.horizontal, 8).padding(.vertical, 3)
                        .background(AppColors.successBg)
                        .foregroundStyle(AppColors.success)
                        .clipShape(Capsule())
                }
            }
        }
        .padding(.vertical, 4)
    }
}