import SwiftUI
import SwiftData

/// 설정 화면: 화면 모드 선택 + 기간 지난 데이터 정리.
struct SettingsView: View {
    @Environment(\.dismiss) private var dismiss
    @Environment(\.modelContext) private var context
    @Query private var allRecords: [ProductRecord]

    @AppStorage(appearanceStorageKey) private var appearanceRaw = AppearanceMode.dark.rawValue

    @State private var confirmDeleteExpired = false
    @State private var toastText: String?
    @State private var toastTask: Task<Void, Never>?

    /// 유통기한이 이미 지난 기록(매장 무관 전체).
    private var expiredRecords: [ProductRecord] {
        allRecords.filter { KoreanCalendar.daysFromToday(to: $0.expiryDate) < 0 }
    }

    var body: some View {
        NavigationStack {
            ZStack {
                Theme.bg.ignoresSafeArea()
                ScrollView {
                    VStack(alignment: .leading, spacing: 26) {
                        appearanceSection
                        dataSection
                    }
                    .padding(20)
                }

                if let toastText {
                    VStack {
                        Spacer()
                        toast(toastText)
                            .padding(.bottom, 30)
                    }
                    .transition(.move(edge: .bottom).combined(with: .opacity))
                }
            }
            .navigationTitle("설정")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .confirmationAction) {
                    Button("완료") { dismiss() }
                        .font(.body.weight(.semibold))
                }
            }
            .animation(.snappy, value: toastText)
        }
        .confirmationDialog(
            deleteDialogTitle,
            isPresented: $confirmDeleteExpired,
            titleVisibility: .visible
        ) {
            Button("삭제", role: .destructive) { deleteExpired() }
            Button("취소", role: .cancel) {}
        } message: {
            Text("매장과 상관없이 유통기한이 지난 기록이 모두 삭제됩니다. 되돌릴 수 없어요.")
        }
        .onDisappear { toastTask?.cancel() }
    }

    // MARK: - 화면 모드

    private var appearanceSection: some View {
        section(title: "화면 모드", subtitle: "앱 전체의 밝기 테마를 선택하세요.") {
            HStack(spacing: 10) {
                ForEach(AppearanceMode.allCases) { mode in
                    appearanceChip(mode)
                }
            }
        }
    }

    private func appearanceChip(_ mode: AppearanceMode) -> some View {
        let isSelected = appearanceRaw == mode.rawValue
        return Button {
            guard !isSelected else { return }
            appearanceRaw = mode.rawValue
            Haptics.tap()
        } label: {
            VStack(spacing: 8) {
                Image(systemName: mode.icon)
                    .font(.title3)
                    .foregroundStyle(isSelected ? Theme.onAccent : Theme.textSecondary)
                Text(mode.title)
                    .font(.system(.subheadline, design: .rounded).weight(.semibold))
                    .foregroundStyle(isSelected ? Theme.onAccent : Theme.textPrimary)
            }
            .frame(maxWidth: .infinity)
            .frame(height: 74)
            .background(
                RoundedRectangle(cornerRadius: 16, style: .continuous)
                    .fill(isSelected ? AnyShapeStyle(Theme.accentGradient) : AnyShapeStyle(Theme.surfaceHi))
            )
            .overlay(
                RoundedRectangle(cornerRadius: 16, style: .continuous)
                    .strokeBorder(isSelected ? .clear : Theme.stroke, lineWidth: 1)
            )
        }
        .buttonStyle(.plain)
    }

    // MARK: - 데이터 관리

    private var dataSection: some View {
        let count = expiredRecords.count
        return section(title: "데이터 관리", subtitle: "유통기한이 지난 기록을 한 번에 정리합니다.") {
            Button {
                confirmDeleteExpired = true
            } label: {
                HStack(spacing: 12) {
                    Image(systemName: "trash")
                        .font(.body.weight(.semibold))
                    VStack(alignment: .leading, spacing: 2) {
                        Text("기간 지난 데이터 삭제")
                            .font(.system(.body, design: .rounded).weight(.semibold))
                        Text(count > 0 ? "지난 기록 \(count)개" : "지난 기록이 없어요")
                            .font(.caption)
                            .foregroundStyle(count > 0 ? Theme.danger.opacity(0.8) : Theme.textSecondary)
                    }
                    Spacer()
                    if count > 0 {
                        Image(systemName: "chevron.right")
                            .font(.footnote.weight(.semibold))
                            .foregroundStyle(Theme.textSecondary)
                    }
                }
                .foregroundStyle(count > 0 ? Theme.danger : Theme.textSecondary)
                .padding(16)
                .frame(maxWidth: .infinity, alignment: .leading)
                .cardStyle()
            }
            .buttonStyle(.plain)
            .disabled(count == 0)
        }
    }

    private var deleteDialogTitle: String {
        "지난 기록 \(expiredRecords.count)개를 삭제할까요?"
    }

    private func deleteExpired() {
        let targets = expiredRecords
        guard !targets.isEmpty else { return }
        for record in targets {
            context.delete(record)
        }
        try? context.save()
        Haptics.warning()
        showToast("지난 기록 \(targets.count)개를 삭제했어요")
    }

    // MARK: - 공용

    private func section<Content: View>(
        title: String,
        subtitle: String,
        @ViewBuilder content: () -> Content
    ) -> some View {
        VStack(alignment: .leading, spacing: 12) {
            VStack(alignment: .leading, spacing: 3) {
                Text(title)
                    .font(.system(.headline, design: .rounded))
                    .foregroundStyle(Theme.textPrimary)
                Text(subtitle)
                    .font(.caption)
                    .foregroundStyle(Theme.textSecondary)
            }
            content()
        }
    }

    private func showToast(_ text: String) {
        toastTask?.cancel()
        toastText = text
        toastTask = Task {
            try? await Task.sleep(for: .seconds(1.8))
            guard !Task.isCancelled else { return }
            toastText = nil
        }
    }

    private func toast(_ text: String) -> some View {
        Label(text, systemImage: "checkmark.circle.fill")
            .font(.system(.subheadline, design: .rounded).weight(.semibold))
            .foregroundStyle(Theme.onAccent)
            .padding(.horizontal, 16)
            .padding(.vertical, 10)
            .background(Capsule().fill(Theme.accentGradient))
    }
}