import SwiftUI

struct ConnectView: View {
    @StateObject private var vm = ConnectViewModel()
    @State private var navigateToDashboard = false
    @State private var showPassword = false
    @State private var folderPickerPath = "/"
    @FocusState private var focused: ConnectField?

    private var isAuthenticated: Bool { vm.connectionState.isAuthenticated }
    private var isFailed: Bool { vm.connectionState.errorMessage != nil }

    var body: some View {
        NavigationStack {
            ZStack {
                AppTheme.background.ignoresSafeArea()

                ScrollView {
                    VStack(spacing: 0) {
                        headerSection
                        protocolPicker
                        hostField
                        credentialsCard
                        connectedBanner
                        destinationRow
                        statusLine
                    }
                }
                .scrollDismissesKeyboard(.interactively)
                .safeAreaInset(edge: .bottom) { ctaBar }
            }
            .navigationBarHidden(true)
            .navigationDestination(isPresented: $navigateToDashboard) { MainTabView() }
            .sheet(isPresented: $vm.showFolderBrowser) { folderSheet }
        }
    }

    // MARK: – Header

    private var headerSection: some View {
        VStack(spacing: 10) {
            Text("kisani.")
                .font(.system(size: 11, weight: .medium, design: .monospaced))
                .foregroundStyle(AppTheme.ink)
                .kerning(2)
                .padding(.top, 52)
            KisaniLogoMark(size: 66)
            UGreenCompatibilityBadge(selectedProtocol: vm.selectedProtocol)
                .padding(.top, 4)
        }
        .frame(maxWidth: .infinity)
        .padding(.bottom, 28)
    }

    // MARK: – Protocol picker

    private var protocolPicker: some View {
        HStack(spacing: 0) {
            ForEach(NASProtocol.allCases, id: \.self) { proto in
                Button {
                    withAnimation(.spring(response: 0.25, dampingFraction: 0.8)) {
                        vm.selectedProtocol = proto
                        vm.resetAuth()
                    }
                } label: {
                    Text(proto.rawValue)
                        .font(.system(size: 12, weight: .medium))
                        .foregroundStyle(vm.selectedProtocol == proto ? AppTheme.ink : AppTheme.inkTertiary)
                        .frame(maxWidth: .infinity)
                        .padding(.vertical, 7)
                        .background(
                            RoundedRectangle(cornerRadius: 7, style: .continuous)
                                .fill(vm.selectedProtocol == proto ? AppTheme.surfaceRaised : .clear)
                                .shadow(color: vm.selectedProtocol == proto ? .black.opacity(0.06) : .clear,
                                        radius: 3, x: 0, y: 1)
                        )
                }
                .buttonStyle(PlainButtonStyle())
            }
        }
        .padding(3)
        .background(AppTheme.surfaceSunken)
        .clipShape(RoundedRectangle(cornerRadius: 10, style: .continuous))
        .padding(.horizontal, AppTheme.hPad)
        .padding(.bottom, 20)
    }

    // MARK: – Host field

    private var hostField: some View {
        VStack(alignment: .leading, spacing: 8) {
            HStack(spacing: 12) {
                Image(systemName: "network")
                    .font(.system(size: 14))
                    .foregroundStyle(AppTheme.inkSecondary)
                    .frame(width: 20)
                TextField("IP address or hostname", text: $vm.host)
                    .font(AppTheme.body())
                    .foregroundStyle(AppTheme.ink)
                    .keyboardType(.URL)
                    .autocorrectionDisabled()
                    .textInputAutocapitalization(.never)
                    .focused($focused, equals: .host)
                    .submitLabel(.next)
                    .onSubmit { focused = .username }
                    .onChange(of: vm.host) { _ in vm.resetAuth() }
                if !vm.host.isEmpty {
                    Button { vm.host = ""; vm.resetAuth() } label: {
                        Image(systemName: "xmark.circle.fill").foregroundStyle(AppTheme.inkQuaternary)
                    }
                }
            }
            .padding(.horizontal, 16).padding(.vertical, 14)
            .background(AppTheme.surfaceRaised)
            .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
            .shadow(color: AppTheme.cardShadow, radius: 12, x: 0, y: 2)

            Text("e.g. 192.168.1.10  or  MY_NAS")
                .font(AppTheme.micro(11))
                .foregroundStyle(AppTheme.inkTertiary)
                .padding(.leading, 4)
        }
        .padding(.horizontal, AppTheme.hPad)
        .padding(.bottom, 12)
    }

    // MARK: – Credentials card

    private var credentialsCard: some View {
        VStack(spacing: 0) {
            HStack(spacing: 12) {
                Image(systemName: "person")
                    .font(.system(size: 14))
                    .foregroundStyle(AppTheme.inkSecondary)
                    .frame(width: 20)
                TextField("Username", text: $vm.username)
                    .font(AppTheme.body())
                    .foregroundStyle(AppTheme.ink)
                    .autocorrectionDisabled()
                    .textInputAutocapitalization(.never)
                    .focused($focused, equals: .username)
                    .submitLabel(.next)
                    .onSubmit { focused = .password }
                    .onChange(of: vm.username) { _ in vm.resetAuth() }
                if !vm.username.isEmpty {
                    Button { vm.username = ""; vm.resetAuth() } label: {
                        Image(systemName: "xmark.circle.fill").foregroundStyle(AppTheme.inkQuaternary)
                    }
                }
            }
            .padding(.horizontal, 16).padding(.vertical, 14)

            Rectangle().fill(AppTheme.separator).frame(height: 0.5).padding(.leading, 44)

            HStack(spacing: 12) {
                Image(systemName: "lock")
                    .font(.system(size: 14))
                    .foregroundStyle(AppTheme.inkSecondary)
                    .frame(width: 20)
                Group {
                    if showPassword {
                        TextField("Password", text: $vm.password)
                    } else {
                        SecureField("Password", text: $vm.password)
                    }
                }
                .font(AppTheme.body())
                .foregroundStyle(AppTheme.ink)
                .focused($focused, equals: .password)
                .submitLabel(.go)
                .onSubmit { focused = nil; Task { await vm.authenticate() } }
                .onChange(of: vm.password) { _ in vm.resetAuth() }
                Button { showPassword.toggle() } label: {
                    Image(systemName: showPassword ? "eye.slash" : "eye")
                        .font(.system(size: 14))
                        .foregroundStyle(AppTheme.inkTertiary)
                }
            }
            .padding(.horizontal, 16).padding(.vertical, 14)
        }
        .background(AppTheme.surfaceRaised)
        .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
        .overlay(
            RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous)
                .stroke(cardBorderColor, lineWidth: 1)
        )
        .shadow(color: AppTheme.cardShadow, radius: 12, x: 0, y: 2)
        .padding(.horizontal, AppTheme.hPad)
        .padding(.bottom, 12)
        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: isAuthenticated)
        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: isFailed)
    }

    private var cardBorderColor: Color {
        if isAuthenticated { return AppTheme.positive.opacity(0.5) }
        if isFailed        { return AppTheme.destructive.opacity(0.4) }
        return .clear
    }

    // MARK: – Connected banner (appears after auth)

    @ViewBuilder
    private var connectedBanner: some View {
        if isAuthenticated {
            HStack(spacing: 8) {
                Circle()
                    .fill(AppTheme.positive)
                    .frame(width: 7, height: 7)
                Text("Connected to \(vm.host)")
                    .font(AppTheme.micro())
                    .foregroundStyle(AppTheme.inkSecondary)
                Spacer()
                Button {
                    withAnimation(.spring(response: 0.3, dampingFraction: 0.8)) { vm.resetAuth() }
                } label: {
                    Text("Disconnect")
                        .font(AppTheme.micro())
                        .foregroundStyle(AppTheme.inkTertiary)
                }
            }
            .padding(.horizontal, 16)
            .padding(.vertical, 10)
            .background(AppTheme.surfaceSunken)
            .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
            .padding(.horizontal, AppTheme.hPad)
            .padding(.bottom, 12)
            .transition(.opacity.combined(with: .move(edge: .top)))
        }
    }

    // MARK: – Destination row

    private var destinationRow: some View {
        Button(action: { if isAuthenticated { vm.showFolderBrowser = true } }) {
            HStack(spacing: 12) {
                Image(systemName: vm.selectedDestination.isEmpty ? "folder" : "folder.fill")
                    .font(.system(size: 14))
                    .foregroundStyle(destinationIconColor)
                    .frame(width: 20)
                VStack(alignment: .leading, spacing: 2) {
                    Text(vm.selectedDestination.isEmpty
                         ? (isAuthenticated ? "Select destination folder" : "Connect to your NAS first")
                         : vm.selectedDestination)
                        .font(AppTheme.body())
                        .foregroundStyle(destinationTextColor)
                        .lineLimit(2)
                        .multilineTextAlignment(.leading)
                    if vm.connectionState == .destinationSelected {
                        Text("Backup destination ready")
                            .font(AppTheme.micro(11))
                            .foregroundStyle(AppTheme.positive)
                    }
                }
                .frame(maxWidth: .infinity, alignment: .leading)
                Image(systemName: isAuthenticated ? "chevron.right" : "lock")
                    .font(.system(size: isAuthenticated ? 12 : 11, weight: .medium))
                    .foregroundStyle(AppTheme.inkQuaternary)
            }
            .padding(.horizontal, 16).padding(.vertical, 14)
            .background(AppTheme.surfaceRaised)
            .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
            .overlay(
                RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous)
                    .stroke(vm.connectionState == .destinationSelected
                            ? AppTheme.positive.opacity(0.5) : Color.clear, lineWidth: 1)
            )
            .shadow(color: AppTheme.cardShadow, radius: 12, x: 0, y: 2)
            .opacity(isAuthenticated ? 1 : 0.4)
        }
        .buttonStyle(ScaleButtonStyle())
        .padding(.horizontal, AppTheme.hPad)
        .padding(.bottom, 20)
        .allowsHitTesting(isAuthenticated)
        .animation(.spring(response: 0.35, dampingFraction: 0.8), value: isAuthenticated)
        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: vm.connectionState)
    }

    private var destinationIconColor: Color {
        if !isAuthenticated { return AppTheme.inkQuaternary }
        return vm.selectedDestination.isEmpty ? AppTheme.inkSecondary : AppTheme.positive
    }

    private var destinationTextColor: Color {
        if !isAuthenticated { return AppTheme.inkQuaternary }
        return vm.selectedDestination.isEmpty ? AppTheme.inkTertiary : AppTheme.ink
    }

    // MARK: – Status line

    private var statusLine: some View {
        HStack(spacing: 6) {
            Image(systemName: statusIcon)
                .font(.system(size: 12))
            Text(vm.statusMessage)
                .font(AppTheme.caption())
        }
        .foregroundStyle(statusColor)
        .frame(maxWidth: .infinity, alignment: .center)
        .padding(.horizontal, AppTheme.hPad)
        .padding(.bottom, 24)
        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: vm.connectionState)
    }

    private var statusIcon: String {
        switch vm.connectionState {
        case .idle:                 return "circle.dotted"
        case .authenticating:       return "arrow.trianglehead.2.clockwise"
        case .authenticated:        return "checkmark.circle"
        case .destinationSelected:  return "checkmark.circle.fill"
        case .failed:               return "exclamationmark.circle"
        }
    }

    private var statusColor: Color {
        switch vm.connectionState {
        case .idle, .authenticating:    return AppTheme.inkTertiary
        case .authenticated:            return AppTheme.positive
        case .destinationSelected:      return AppTheme.positive
        case .failed:                   return AppTheme.destructive
        }
    }

    // MARK: – CTA bar

    private var ctaBar: some View {
        VStack(spacing: 0) {
            Button(action: handleCTA) {
                Group {
                    if vm.connectionState == .authenticating {
                        ProgressView().tint(.white)
                    } else {
                        Text(ctaLabel)
                    }
                }
                .frame(maxWidth: .infinity)
            }
            .buttonStyle(PrimaryButtonStyle(color: ctaColor))
            .padding(.horizontal, AppTheme.hPad)
            .padding(.top, 12)
            .padding(.bottom, 32)
            .disabled(!ctaEnabled)
            .animation(.spring(response: 0.3, dampingFraction: 0.8), value: vm.connectionState)
        }
        .background(AppTheme.background)
    }

    private var ctaLabel: String {
        switch vm.connectionState {
        case .idle, .failed:            return "Connect"
        case .authenticating:           return "Connecting…"
        case .authenticated:            return "Choose Destination"
        case .destinationSelected:      return "Get Started"
        }
    }

    private var ctaColor: Color {
        vm.connectionState == .destinationSelected ? AppTheme.positive : AppTheme.ink
    }

    private var ctaEnabled: Bool {
        switch vm.connectionState {
        case .idle, .failed:            return vm.canConnect
        case .authenticating:           return false
        case .authenticated:            return true
        case .destinationSelected:      return true
        }
    }

    private func handleCTA() {
        focused = nil
        switch vm.connectionState {
        case .idle, .failed:
            Task { await vm.authenticate() }
        case .authenticating:
            break
        case .authenticated:
            vm.showFolderBrowser = true
        case .destinationSelected:
            navigateToDashboard = true
        }
    }

    // MARK: – Folder sheet

    private var folderSheet: some View {
        Group {
            if let conn = ConnectionStore.shared.savedConnection {
                BrowseView(connection: conn, selectedPath: $folderPickerPath, isPickerMode: true)
                    .onDisappear {
                        if folderPickerPath != "/" {
                            withAnimation(.spring(response: 0.35, dampingFraction: 0.8)) {
                                vm.confirmDestination(folderPickerPath)
                            }
                        }
                    }
            }
        }
    }
}