import SwiftUI
import SDWebImageSwiftUI

private extension String {
    var trimmedNonEmpty: String? {
        let t = trimmingCharacters(in: .whitespacesAndNewlines)
        return t.isEmpty ? nil : t
    }
}

// MARK: - ViewModel
@MainActor
final class StopsViewModel: ObservableObject {
    @Published var stops: [StopDetail] = []
    @Published var isLoading: Bool = false
    @Published var selectedStopId: Int?

    func fetchStops(for routeId: Int) {
        guard let url = URL(string: "https://white-nights.krbl.ru/services/content/route/\(routeId)/station") else { return }
        isLoading = true

        Task {
            do {
                let (data, _) = try await URLSession.shared.data(from: url)
                let decoder = JSONDecoder()
                decoder.keyDecodingStrategy = .convertFromSnakeCase
                let stops = try decoder.decode([StopDetail].self, from: data)
                self.stops = stops
            } catch {
                print("Ошибка загрузки остановок:", error)
                self.stops = []
            }
            self.isLoading = false
        }
    }

    func toggleStop(id: Int) {
        withAnimation(.easeInOut(duration: 0.25)) {
            if selectedStopId == id {
                selectedStopId = nil
            } else {
                selectedStopId = id
            }
        }
    }
}

// MARK: - BottomMenu
struct BottomMenu: View {
    @Binding var isPresented: Bool
    @State private var dragOffset: CGFloat = 0
    @State private var selectedTab: Tab = .sights
    @EnvironmentObject var appState: AppState
    @StateObject private var stopsVM = StopsViewModel()

    enum Tab { case sights, stops }

    private let columns: [GridItem] = Array(
        repeating: GridItem(.flexible(), spacing: 16, alignment: .top),
        count: 3
    )

    var body: some View {
        GeometryReader { geo in
            ZStack {
                if isPresented {
                    Color.black.opacity(0.4)
                        .ignoresSafeArea()
                        .onTapGesture { isPresented = false }
                        .transition(.opacity)
                }

                VStack {
                    Spacer()

                    VStack(spacing: 20) {
                        Capsule()
                            .fill(Color.white.opacity(0.8))
                            .frame(width: 120, height: 3)
                            .padding(.top, 8)

                        VStack(spacing: 12) {
                            menuButton(title: "Достопримечательности", tab: .sights)
                            menuButton(title: "Остановки", tab: .stops)

                            if selectedTab == .sights {
                                // --- Достопримечательности ---
                                ScrollView {
                                    LazyVGrid(columns: columns, spacing: 20) {
                                        ForEach(appState.sights) { sight in
                                            VStack(spacing: 8) {
                                                SightThumbnail(
                                                    url: URL(string: "https://white-nights.krbl.ru/services/content/media/\(sight.thumbnail)/download"),
                                                    size: 80
                                                )
                                                .onTapGesture {
                                                    appState.sightId = sight.id
                                                    isPresented = false
                                                }

                                                Text(sight.name)
                                                    .font(.footnote)
                                                    .multilineTextAlignment(.center)
                                                    .foregroundColor(.white)
                                                    .lineLimit(2)
                                                    .frame(maxHeight: .infinity, alignment: .top)
                                            }
                                        }
                                    }
                                    .padding(.horizontal, 20)
                                    .padding(.vertical, 10)
                                }
                            } else {
                                // --- Остановки + пересадки ---
                                ScrollView {
                                    LazyVStack(spacing: 0) {
                                        if stopsVM.isLoading {
                                            ProgressView("Загрузка остановок...")
                                                .padding()
                                        } else {
                                            ForEach(stopsVM.stops) { stop in
                                                VStack(alignment: .leading, spacing: 0) {
                                                    Button {
                                                        stopsVM.toggleStop(id: stop.id)
                                                    } label: {
                                                        Text(stop.name)
                                                            .font(.subheadline) // меньше размер
                                                            .frame(maxWidth: .infinity, alignment: .leading) // левое выравнивание
                                                            .padding(.vertical, 10)
                                                            .padding(.horizontal, 20)
                                                            .foregroundColor(.white)
                                                            .transaction { $0.animation = nil }
                                                    }
                                                    .overlay(
                                                        Rectangle()
                                                            .frame(height: 1)
                                                            .foregroundColor(.white.opacity(0.3)),
                                                        alignment: .bottom
                                                    )

                                                    if stopsVM.selectedStopId == stop.id {
                                                        transfersView(for: stop)
                                                            .transition(.opacity.combined(with: .move(edge: .top)))
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                                .onAppear {
                                    if stopsVM.stops.isEmpty,
                                       let routeId = appState.selectedRoute?.id {
                                        stopsVM.fetchStops(for: routeId)
                                    }
                                }
                            }
                        }
                        .padding(.horizontal, 20)
                        .padding(.top, 2)

                        HStack(spacing: 16) {
                            Image("GAT_Icon")
                                .resizable()
                                .scaledToFit()
                                .frame(height: 30)

                            Spacer()

                            HStack(spacing: 2) {
                                Image("ru_lang_icon").resizable().scaledToFit().frame(width: 24, height: 24)
                                Image("zh_lang_icon").resizable().scaledToFit().frame(width: 24, height: 24)
                                Image("en_lang_icon").resizable().scaledToFit().frame(width: 24, height: 24)
                            }
                        }
                        .padding(.horizontal, 26)
                        .padding(.top, 16)
                        .padding(.bottom, 32)
                    }
                    .frame(height: geo.size.height * 0.8)
                    .frame(maxWidth: .infinity)
                    .background(
                        Color(hex: 0x806C59)
                            .cornerRadius(24, corners: [.topLeft, .topRight])
                            .shadow(radius: 10)
                    )
                    .offset(y: isPresented ? dragOffset : geo.size.height)
                    .animation(.spring(response: 0.35, dampingFraction: 0.9), value: isPresented)
                    .animation(.spring(response: 0.35, dampingFraction: 0.9), value: dragOffset)
                    .gesture(
                        DragGesture()
                            .onChanged { value in
                                if value.translation.height > 0 {
                                    dragOffset = value.translation.height
                                }
                            }
                            .onEnded { value in
                                if value.translation.height > 100 { isPresented = false }
                                dragOffset = 0
                            }
                    )
                }
                .ignoresSafeArea(edges: .bottom)
            }
        }
    }

    // MARK: - Menu Button
    @ViewBuilder
    private func menuButton(title: String, tab: Tab) -> some View {
        Button { selectedTab = tab } label: {
            Text(title)
                .frame(maxWidth: .infinity)
                .frame(height: 47)
                .foregroundColor(.white)
                .background(
                    RoundedRectangle(cornerRadius: 16)
                        .fill(selectedTab == tab ? Color(hex: 0x6D5743) : Color(hex: 0xB3A598))
                )
        }
        .buttonStyle(.plain)
    }

    // MARK: - Transfers View
    @ViewBuilder
    private func transfersView(for stop: StopDetail) -> some View {
        let t = stop.transfers
        let items: [(String, String)] = [
            ("tram_icon",          t.tram?.trimmedNonEmpty),
            ("trolley_icon",       t.trolleybus?.trimmedNonEmpty),
            ("bus_icon",           t.bus?.trimmedNonEmpty),
            ("train_icon",         t.train?.trimmedNonEmpty),
            ("metro_red_icon",     t.metroRed?.trimmedNonEmpty),
            ("metro_green_icon",   t.metroGreen?.trimmedNonEmpty),
            ("metro_blue_icon",    t.metroBlue?.trimmedNonEmpty),
            ("metro_purple_icon",  t.metroPurple?.trimmedNonEmpty),
            ("metro_orange_icon",  t.metroOrange?.trimmedNonEmpty),
        ].compactMap { icon, text in
            guard let text = text else { return nil }
            return (icon, text)
        }

        if items.isEmpty {
            Text("Нет пересадок")
                .font(.caption) // меньше размер
                .foregroundColor(.white.opacity(0.7))
                .padding(.leading, 20)
                .padding(.vertical, 8)
        } else {
            VStack(alignment: .leading, spacing: 6) { // меньше расстояние
                ForEach(items, id: \.0) { icon, text in
                    HStack(spacing: 8) {
                        Image(icon)
                            .resizable()
                            .scaledToFit()
                            .frame(width: 18, height: 18)
                        Text(text)
                            .font(.caption) // меньше размер
                            .foregroundColor(.white)
                            .fixedSize(horizontal: false, vertical: true)
                            .frame(maxWidth: .infinity, alignment: .leading) // левое выравнивание
                    }
                    .padding(.leading, 20)
                    .padding(.vertical, 4)
                }
            }
            .padding(.bottom, 8)
            .padding(.top, 6)
        }
    }
}

// MARK: - Sight Thumbnail
struct SightThumbnail: View {
    let url: URL?
    let size: CGFloat

    var body: some View {
        ZStack {
            Circle()
                .fill(Color.white)
                .frame(width: size, height: size)

            WebImage(url: url)
                .resizable()
                .scaledToFit()
                .frame(width: size, height: size)
                .clipShape(Circle())
                .overlay(
                    Group {
                        if url == nil {
                            ProgressView().frame(width: size, height: size)
                        }
                    }
                )
        }
    }
}