import SwiftUI
import SwiftData

/// 특정 날짜에 기록된 제품 사진 목록.
struct DayDetailView: View {
    let store: Store
    let year: Int
    let month: Int
    let day: Int

    @Environment(\.modelContext) private var context
    @Query private var allRecords: [ProductRecord]
    @State private var viewer: ViewerLaunch?
    @State private var isSelecting = false
    @State private var selectedIDs = Set<PersistentIdentifier>()
    @State private var confirmBulkDelete = false
    @State private var editTarget: ProductRecord?

    private struct ViewerLaunch: Identifiable {
        let index: Int
        var id: Int { index }
    }

    private var records: [ProductRecord] {
        allRecords
            .filter {
                guard $0.store === store else { return false }
                let c = KoreanCalendar.calendar.dateComponents([.year, .month, .day], from: $0.expiryDate)
                return c.year == year && c.month == month && c.day == day
            }
            .sorted { $0.createdAt < $1.createdAt }
    }

    var body: some View {
        ZStack {
            Theme.bg.ignoresSafeArea()
            VStack(alignment: .leading, spacing: 18) {
                header
                if records.isEmpty {
                    emptyState
                } else {
                    photoGrid
                }
                Spacer(minLength: 0)
            }
            .padding(20)
        }
        .presentationDetents([.medium, .large])
        .presentationDragIndicator(.visible)
        .presentationBackground(Theme.bg)
        .fullScreenCover(item: $viewer) { launch in
            PhotoViewerView(store: store, year: year, month: month, day: day, startIndex: launch.index)
        }
        .overlay(alignment: .bottom) {
            if isSelecting { selectionBar }
        }
        .onChange(of: records.count) {
            if records.isEmpty { exitSelection() }
        }
        .confirmationDialog(
            "사진 \(selectedIDs.count)장을 삭제할까요?",
            isPresented: $confirmBulkDelete,
            titleVisibility: .visible
        ) {
            Button("삭제", role: .destructive) { deleteSelected() }
            Button("취소", role: .cancel) {}
        }
        .sheet(item: $editTarget) { record in
            RecordEditView(record: record)
        }
    }

    // MARK: - 헤더

    private var header: some View {
        HStack(alignment: .center, spacing: 10) {
            VStack(alignment: .leading, spacing: 3) {
                Text(dateTitle)
                    .font(.system(.title3, design: .rounded).weight(.bold))
                    .foregroundStyle(Theme.textPrimary)
                if !records.isEmpty {
                    Text("제품 \(records.count)개")
                        .font(.caption)
                        .foregroundStyle(Theme.textSecondary)
                }
            }
            Spacer()
            ddayChip
            if !records.isEmpty {
                selectToggleButton
            }
        }
        .padding(.top, 14)
    }

    private var selectToggleButton: some View {
        Button {
            if isSelecting {
                exitSelection()
            } else {
                isSelecting = true
            }
            Haptics.tap()
        } label: {
            Text(isSelecting ? "취소" : "선택")
                .font(.caption.weight(.bold))
                .foregroundStyle(isSelecting ? Theme.textPrimary : Theme.accent)
                .padding(.horizontal, 12)
                .padding(.vertical, 6)
                .background(Capsule().fill(isSelecting ? Theme.surfaceHi : Theme.accentSoft))
        }
    }

    private func exitSelection() {
        isSelecting = false
        selectedIDs = []
    }

    private var date: Date {
        KoreanCalendar.date(year: year, month: month, day: day) ?? .now
    }

    private var dateTitle: String {
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "ko_KR")
        formatter.dateFormat = "M월 d일 EEEE"
        return formatter.string(from: date)
    }

    private func timeText(_ date: Date) -> String {
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "ko_KR")
        formatter.dateFormat = "a h:mm"
        return formatter.string(from: date)
    }

    private var ddayChip: some View {
        let diff = KoreanCalendar.daysFromToday(to: date)
        let (text, color): (String, Color) =
            diff > 0 ? ("D-\(diff)", Theme.accent)
            : diff == 0 ? ("오늘까지", Theme.warn)
            : ("\(-diff)일 지남", Theme.danger)
        return Text(text)
            .font(.caption.weight(.bold))
            .foregroundStyle(color)
            .padding(.horizontal, 10)
            .padding(.vertical, 5)
            .background(Capsule().fill(color.opacity(0.15)))
    }

    // MARK: - 사진 그리드

    private var photoGrid: some View {
        let columns = Array(repeating: GridItem(.flexible(), spacing: 8), count: 3)
        return ScrollView {
            LazyVGrid(columns: columns, spacing: 8) {
                ForEach(Array(records.enumerated()), id: \.element.persistentModelID) { index, record in
                    photoCell(record: record, index: index)
                }
            }
            .padding(.bottom, isSelecting ? 70 : 0)
        }
        .scrollIndicators(.hidden)
    }

    private func photoCell(record: ProductRecord, index: Int) -> some View {
        let isSelected = selectedIDs.contains(record.persistentModelID)
        return Button {
            if isSelecting {
                toggleSelection(record)
            } else {
                viewer = ViewerLaunch(index: index)
            }
        } label: {
            Color.clear
                .aspectRatio(1, contentMode: .fit)
                .overlay {
                    if let image = UIImage(data: record.thumbnailData) {
                        Image(uiImage: image)
                            .resizable()
                            .scaledToFill()
                    } else {
                        Theme.surfaceHi
                    }
                }
                .clipShape(RoundedRectangle(cornerRadius: 14, style: .continuous))
                .overlay {
                    if isSelecting && isSelected {
                        RoundedRectangle(cornerRadius: 14, style: .continuous)
                            .fill(Theme.accent.opacity(0.22))
                    }
                }
                .overlay(alignment: .topTrailing) {
                    if isSelecting {
                        Image(systemName: isSelected ? "checkmark.circle.fill" : "circle")
                            .font(.title3)
                            .symbolRenderingMode(isSelected ? .palette : .monochrome)
                            .foregroundStyle(isSelected ? Theme.onAccent : .white.opacity(0.85), Theme.accent)
                            .shadow(color: .black.opacity(0.5), radius: 3)
                            .padding(6)
                    }
                }
                .overlay(alignment: .bottomLeading) {
                    if record.hasTime {
                        Label(timeText(record.expiryDate), systemImage: "clock.fill")
                            .font(.system(size: 10, weight: .bold, design: .rounded))
                            .foregroundStyle(.white)
                            .padding(.horizontal, 6)
                            .padding(.vertical, 3)
                            .background(Capsule().fill(.black.opacity(0.55)))
                            .padding(5)
                    }
                }
                .overlay(
                    RoundedRectangle(cornerRadius: 14, style: .continuous)
                        .strokeBorder(
                            isSelecting && isSelected ? Theme.accent : Theme.stroke,
                            lineWidth: isSelecting && isSelected ? 2 : 1
                        )
                )
        }
        .buttonStyle(.plain)
        .contextMenu {
            if !isSelecting {
                Button {
                    editTarget = record
                } label: {
                    Label("날짜·시간 수정", systemImage: "calendar.badge.clock")
                }
                Button(role: .destructive) {
                    delete(record)
                } label: {
                    Label("삭제", systemImage: "trash")
                }
            }
        }
    }

    private func toggleSelection(_ record: ProductRecord) {
        let id = record.persistentModelID
        if selectedIDs.contains(id) {
            selectedIDs.remove(id)
        } else {
            selectedIDs.insert(id)
        }
        Haptics.tap()
    }

    // MARK: - 선택 삭제 바

    private var selectionBar: some View {
        let allSelected = selectedIDs.count == records.count && !records.isEmpty
        return HStack(spacing: 12) {
            Button {
                selectedIDs = allSelected ? [] : Set(records.map(\.persistentModelID))
                Haptics.tap()
            } label: {
                Text(allSelected ? "전체 해제" : "전체 선택")
                    .font(.system(.subheadline, design: .rounded).weight(.semibold))
                    .foregroundStyle(Theme.textPrimary)
                    .padding(.horizontal, 18)
                    .frame(height: 46)
                    .background(Capsule().fill(Theme.surfaceHi))
            }
            Button {
                confirmBulkDelete = true
            } label: {
                Label("\(selectedIDs.count)장 삭제", systemImage: "trash.fill")
                    .font(.system(.subheadline, design: .rounded).weight(.bold))
                    .foregroundStyle(.white)
                    .frame(maxWidth: .infinity)
                    .frame(height: 46)
                    .background(Capsule().fill(selectedIDs.isEmpty ? Theme.danger.opacity(0.3) : Theme.danger))
            }
            .disabled(selectedIDs.isEmpty)
        }
        .padding(.horizontal, 20)
        .padding(.bottom, 12)
    }

    private func deleteSelected() {
        let targets = records.filter { selectedIDs.contains($0.persistentModelID) }
        for record in targets {
            context.delete(record)
        }
        try? context.save()
        exitSelection()
        Haptics.warning()
    }

    private func delete(_ record: ProductRecord) {
        context.delete(record)
        try? context.save()
        Haptics.warning()
    }

    // MARK: - 빈 상태

    private var emptyState: some View {
        VStack(spacing: 12) {
            Image(systemName: "photo.on.rectangle.angled")
                .font(.system(size: 38))
                .foregroundStyle(Theme.textSecondary.opacity(0.6))
            Text("이 날짜에 기록이 없어요")
                .font(.subheadline)
                .foregroundStyle(Theme.textSecondary)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 60)
    }
}

/// 전체 화면 사진 뷰어 (좌우 스와이프 + 삭제)
struct PhotoViewerView: View {
    let store: Store
    let year: Int
    let month: Int
    let day: Int
    let startIndex: Int

    @Environment(\.modelContext) private var context
    @Environment(\.dismiss) private var dismiss
    @Query private var allRecords: [ProductRecord]
    @State private var index: Int
    @State private var confirmDelete = false
    @State private var editTarget: ProductRecord?

    init(store: Store, year: Int, month: Int, day: Int, startIndex: Int) {
        self.store = store
        self.year = year
        self.month = month
        self.day = day
        self.startIndex = startIndex
        _index = State(initialValue: startIndex)
    }

    private var records: [ProductRecord] {
        allRecords
            .filter {
                guard $0.store === store else { return false }
                let c = KoreanCalendar.calendar.dateComponents([.year, .month, .day], from: $0.expiryDate)
                return c.year == year && c.month == month && c.day == day
            }
            .sorted { $0.createdAt < $1.createdAt }
    }

    var body: some View {
        ZStack {
            Color.black.ignoresSafeArea()
            if records.isEmpty {
                Color.clear.onAppear { dismiss() }
            } else {
                pager
            }
        }
        .overlay(alignment: .top) { topBar }
        .onChange(of: records.count) {
            if records.isEmpty {
                dismiss()
            } else if index > records.count - 1 {
                index = records.count - 1
            }
        }
        .confirmationDialog("이 사진을 삭제할까요?", isPresented: $confirmDelete, titleVisibility: .visible) {
            Button("삭제", role: .destructive) { deleteCurrent() }
            Button("취소", role: .cancel) {}
        }
        .sheet(item: $editTarget) { record in
            RecordEditView(record: record)
        }
    }

    private var currentRecord: ProductRecord? {
        let current = records
        guard !current.isEmpty else { return nil }
        return current[min(index, current.count - 1)]
    }

    private var pager: some View {
        TabView(selection: $index) {
            ForEach(Array(records.enumerated()), id: \.element.persistentModelID) { i, record in
                Group {
                    if let image = UIImage(data: record.imageData) {
                        Image(uiImage: image)
                            .resizable()
                            .scaledToFit()
                    } else {
                        Text("사진을 불러올 수 없어요")
                            .foregroundStyle(Theme.textSecondary)
                    }
                }
                .tag(i)
            }
        }
        .tabViewStyle(.page(indexDisplayMode: .never))
    }

    private var topBar: some View {
        HStack {
            circleButton(systemName: "xmark") { dismiss() }
            Spacer()
            if !records.isEmpty {
                Text(verbatim: "\(min(index, records.count - 1) + 1) / \(records.count)")
                    .font(.system(.subheadline, design: .rounded).weight(.semibold))
                    .foregroundStyle(.white.opacity(0.9))
            }
            Spacer()
            HStack(spacing: 10) {
                circleButton(systemName: "calendar.badge.clock") {
                    editTarget = currentRecord
                    Haptics.tap()
                }
                circleButton(systemName: "trash", tint: Theme.danger) { confirmDelete = true }
            }
        }
        .padding(.horizontal, 20)
        .padding(.top, 8)
    }

    private func circleButton(systemName: String, tint: Color = .white, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            Image(systemName: systemName)
                .font(.body.weight(.semibold))
                .foregroundStyle(tint)
                .frame(width: 40, height: 40)
                .background(Circle().fill(.white.opacity(0.12)))
        }
    }

    private func deleteCurrent() {
        guard let target = currentRecord else { return }
        context.delete(target)
        try? context.save()
        Haptics.warning()
    }
}