import SwiftUI
import Photos

struct BackupView: View {
    @EnvironmentObject var engine: BackupEngine
    @EnvironmentObject var store: ConnectionStore
    @EnvironmentObject var lanMonitor: LANMonitor
    @EnvironmentObject var statusService: BackupStatusService
    @StateObject private var vm = BackupViewModel()
    @Environment(\.scenePhase) private var scenePhase

    @State private var showMenu = false
    @State private var showDestinationPicker = false
    @State private var pickerPath: String = "/"
    @State private var ringPage = 0
    @State private var ctaFlashGreen = false

    private let ringPageCount = 4

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

            // ─── Menu — aligned with kisani. wordmark ──────────────────
            Button { showMenu = true } label: {
                Image(systemName: "line.3.horizontal")
                    .font(.system(size: 14, weight: .regular))
                    .foregroundStyle(AppTheme.inkSecondary)
                    .frame(width: 44, height: 44)
                    .contentShape(Rectangle())
            }
            .accessibilityLabel("Activity menu")
            .padding(.top, 4)
            .padding(.trailing, AppTheme.hPad - 4)

            VStack(spacing: 0) {

                // ─── Brand ───────────────────────────────────────────
                VStack(spacing: 10) {
                    Text("kisani.")
                        .font(.system(size: 11, weight: .medium, design: .monospaced))
                        .foregroundStyle(AppTheme.ink)
                        .kerning(2)
                    KisaniLogoMark(size: 66)
                }
                .frame(maxWidth: .infinity)
                .padding(.top, 16)

                // flex zone — brand ↔ ring (absorbs screen-size variance)
                Spacer(minLength: 24).frame(maxHeight: 48)

                // ─── Ring ─────────────────────────────────────────────
                ringHero
                    .padding(.bottom, 44)

                // ─── Stats ────────────────────────────────────────────
                statsStrip
                    .padding(.horizontal, AppTheme.hPad)
                    .transition(.opacity.combined(with: .scale(scale: 0.97)))

                // flex zone — stats ↔ cards
                Spacer(minLength: 20).frame(maxHeight: 48)

                // ─── Storage card ─────────────────────────────────────
                nasStatusRow
                    .padding(.horizontal, AppTheme.hPad)
                    .padding(.bottom, 12)

                // ─── Source card ──────────────────────────────────────
                destinationRow
                    .padding(.horizontal, AppTheme.hPad)

                // flex zone — cards ↔ CTA
                Spacer(minLength: 20).frame(maxHeight: 32)

                // ─── Photos access nudge ──────────────────────────────
                if vm.photosAuthStatus != .authorized && vm.photosAuthStatus != .limited {
                    photosAccessRow
                        .padding(.horizontal, AppTheme.hPad)
                        .padding(.bottom, 8)
                        .transition(.opacity.combined(with: .move(edge: .bottom)))
                }

                // ─── CTA ──────────────────────────────────────────────
                actionButton
                    .padding(.horizontal, AppTheme.hPad)
                    .padding(.bottom, 24)

                // bottom absorber — soaks up remaining height to anchor cards+CTA
                Spacer(minLength: 0)
            }
        }
        .navigationTitle("")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar(.hidden, for: .navigationBar)
        .sheet(isPresented: $showMenu) {
            AppMenuView()
                .environmentObject(store)
                .environmentObject(lanMonitor)
                .environmentObject(engine)
        }
        .sheet(isPresented: $showDestinationPicker, onDismiss: {
            guard pickerPath != "/", var conn = store.savedConnection else { return }
            conn.remotePath = pickerPath
            store.savedConnection = conn
        }) {
            if let conn = store.savedConnection {
                BrowseView(connection: conn, selectedPath: $pickerPath, isPickerMode: true, initialPath: pickerPath)
            }
        }
        .animation(.spring(response: 0.35, dampingFraction: 0.82), value: engine.job.status == .completed)
        .animation(.spring(response: 0.35, dampingFraction: 0.82), value: vm.photosAuthStatus == .authorized)
        .task {
            statusService.refresh(force: true)
        }
        .onChange(of: scenePhase) { phase in
            if phase == .active { statusService.refresh(force: true) }
        }
        .onChange(of: lanMonitor.nasReachable) { reachable in
            if reachable == true { statusService.refresh(force: true) }
        }
        .onChange(of: store.savedConnection?.remotePath) { _ in
            statusService.refresh(force: true)
        }
        .onChange(of: engine.job.status) { status in
            if status == .completed {
                // Flash green then revert to black
                withAnimation(.spring(response: 0.3, dampingFraction: 0.8)) { ctaFlashGreen = true }
                Task {
                    try? await Task.sleep(nanoseconds: 2_500_000_000)
                    withAnimation(.spring(response: 0.5, dampingFraction: 0.8)) { ctaFlashGreen = false }
                    // Full reconcile after flash to get accurate counts
                    try? await Task.sleep(nanoseconds: 500_000_000)
                    statusService.refresh(force: true)
                }
            }
        }
    }

    // MARK: — Logo mark (drawn in code — no asset dependency)


    // MARK: — Ring hero

    private var ringHero: some View {
        ZStack {
            ProgressRing(
                progress: engine.job.progress,
                lineWidth: 8,
                size: 206,
                color: ringColor,
                backgroundColor: AppTheme.inkQuaternary.opacity(0.6)
            )
            .shadow(
                color: ringColor.opacity(engine.job.status.isActive ? 0.16 : 0),
                radius: 22, x: 0, y: 0
            )
            .animation(.easeInOut(duration: 0.5), value: engine.job.status.isActive)
            .accessibilityLabel("Backup progress")
            .accessibilityValue("\(Int(engine.job.progress * 100)) percent")

            VStack(spacing: 4) {
                ringCenterContent
                    .transition(.opacity.combined(with: .scale(scale: 0.95)))
                    .id(ringContentID)
            }
            .animation(.spring(response: 0.3, dampingFraction: 0.85), value: ringContentID)
        }
        .gesture(
            DragGesture(minimumDistance: 20)
                .onEnded { value in
                    if value.translation.width < 0 {
                        ringPage = (ringPage + 1) % ringPageCount
                    } else {
                        ringPage = (ringPage - 1 + ringPageCount) % ringPageCount
                    }
                }
        )
        .animation(.spring(response: 0.4, dampingFraction: 0.8), value: engine.job.progress)
    }

    // ID that changes on both page swipe and status transition — drives the ring animation
    private var ringContentID: String {
        switch engine.job.status {
        case .idle, .cancelled: return "\(ringPage)_idle"
        case .preparing:        return "\(ringPage)_preparing"
        case .running:          return "\(ringPage)_running"
        case .paused:           return "\(ringPage)_paused"
        case .completed:        return "\(ringPage)_done"
        case .failed:           return "\(ringPage)_failed"
        }
    }

    @ViewBuilder
    private var ringCenterContent: some View {
        switch ringPage {
        case 0:
            ringMainView

        case 1: // Need backup
            VStack(spacing: 4) {
                Text("\(notBackedUpDisplayCount)")
                    .font(.system(size: 44, weight: .semibold, design: .rounded))
                    .foregroundStyle(AppTheme.ink)
                    .contentTransition(.numericText())
                    .monospacedDigit()
                Text("need backup")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkTertiary)
            }

        case 2: // Failed
            VStack(spacing: 4) {
                Text("\(engine.job.failedFiles)")
                    .font(.system(size: 44, weight: .semibold, design: .rounded))
                    .foregroundStyle(engine.job.failedFiles > 0 ? AppTheme.destructive : AppTheme.ink)
                    .contentTransition(.numericText())
                    .monospacedDigit()
                Text("failed")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkTertiary)
            }

        default: // Backed up
            VStack(spacing: 4) {
                Text("\(engine.job.uploadedFiles)")
                    .font(.system(size: 44, weight: .semibold, design: .rounded))
                    .foregroundStyle(AppTheme.positive)
                    .contentTransition(.numericText())
                    .monospacedDigit()
                Text("backed up")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkTertiary)
            }
        }
    }

    // Page 0 content — changes based on backup state
    @ViewBuilder
    private var ringMainView: some View {
        switch engine.job.status {
        case .idle, .cancelled:
            if statusService.snapshot.phoneTotal > 0 && statusService.snapshot.needBackup == 0 {
                VStack(spacing: 8) {
                    Image(systemName: "checkmark")
                        .font(.system(size: 30, weight: .medium))
                        .foregroundStyle(AppTheme.positive)
                    Text("All photos safe")
                        .font(AppTheme.caption())
                        .foregroundStyle(AppTheme.inkTertiary)
                }
            } else {
                VStack(spacing: 6) {
                    Text("\(statusService.snapshot.needBackup)")
                        .font(.system(size: 44, weight: .semibold, design: .rounded))
                        .foregroundStyle(AppTheme.ink)
                        .contentTransition(.numericText())
                        .monospacedDigit()
                    Text(statusService.snapshot.phoneTotal == 0 ? "No photos found" : "need backup")
                        .font(AppTheme.caption())
                        .foregroundStyle(AppTheme.inkTertiary)
                }
            }

        case .preparing:
            VStack(spacing: 10) {
                ProgressView()
                    .scaleEffect(0.85)
                    .tint(AppTheme.inkTertiary)
                Text("Scanning library…")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkTertiary)
            }

        case .running, .paused:
            VStack(spacing: 5) {
                Text(percentText)
                    .font(.system(size: 44, weight: .semibold, design: .rounded))
                    .foregroundStyle(AppTheme.ink)
                    .contentTransition(.numericText())
                    .monospacedDigit()
                Text("\(engine.job.uploadedFiles) of \(engine.job.totalFiles) backed up")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkSecondary)
                if let eta = engine.job.eta {
                    Text("~\(etaString(eta)) remaining")
                        .font(.system(size: 11, weight: .regular))
                        .foregroundStyle(AppTheme.inkTertiary)
                        .padding(.top, 1)
                }
            }

        case .completed:
            VStack(spacing: 8) {
                Image(systemName: "checkmark")
                    .font(.system(size: 30, weight: .medium))
                    .foregroundStyle(AppTheme.positive)
                Text("\(engine.job.uploadedFiles) photos backed up")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkTertiary)
            }

        case .failed:
            VStack(spacing: 8) {
                Image(systemName: "exclamationmark.circle")
                    .font(.system(size: 30, weight: .light))
                    .foregroundStyle(AppTheme.destructive)
                Text("Backup failed")
                    .font(.system(size: 13, weight: .medium))
                    .foregroundStyle(AppTheme.destructive.opacity(0.8))
            }
        }
    }

    // MARK: — Page indicator

    private var pageIndicator: some View {
        HStack(spacing: 5) {
            ForEach(0..<ringPageCount, id: \.self) { i in
                Capsule(style: .continuous)
                    .fill(i == ringPage ? AppTheme.interactive : AppTheme.inkQuaternary)
                    .frame(width: i == ringPage ? 18 : 5, height: 5)
                    .animation(.spring(response: 0.3, dampingFraction: 0.75), value: ringPage)
            }
        }
    }

    private var ringColor: Color {
        // Active: always orange
        if engine.job.status.isActive { return Color(red: 1.0, green: 0.58, blue: 0.0) }
        // Failed: red
        if case .failed = engine.job.status { return AppTheme.destructive }
        // Green only when ALL phone photos are accounted for (needBackup == 0)
        if statusService.snapshot.phoneTotal > 0 && statusService.snapshot.needBackup == 0 {
            return AppTheme.positive
        }
        // Default: neutral
        return AppTheme.inkQuaternary.opacity(0.55)
    }

    private var percentText: String { "\(Int(engine.job.progress * 100))%" }

    // MARK: — Compact stats strip

    // Invariant: alreadySafe + needBackup == phoneTotal always.
    // During active backup show optimistic count (only newly uploaded, not skipped —
    // skipped files are already counted inside snapshot.alreadySafe from the last reconcile).
    private var alreadySafeDisplayCount: Int {
        let total = statusService.snapshot.phoneTotal
        guard total > 0 else { return 0 }
        let base = statusService.snapshot.alreadySafe
        if engine.job.status.isActive {
            return min(base + engine.job.uploadedFiles, total)
        }
        return min(base, total)  // enforce invariant at all times
    }

    private var notBackedUpDisplayCount: Int {
        let total = statusService.snapshot.phoneTotal
        guard total > 0 else { return 0 }
        if engine.job.status.isActive {
            return max(0, total - alreadySafeDisplayCount)
        }
        return statusService.snapshot.needBackup
    }

    private var statsStrip: some View {
        VStack(spacing: 7) {
            HStack(spacing: 0) {
                compactStat(
                    "\(statusService.snapshot.nasArchiveTotal)",
                    label: "NAS Archive",
                    color: AppTheme.interactive
                )
                thinDivider
                compactStat(
                    "\(statusService.snapshot.phoneTotal)",
                    label: "On iPhone",
                    color: AppTheme.inkSecondary
                )
                thinDivider
                compactStat(
                    "\(notBackedUpDisplayCount)",
                    label: "Need Backup",
                    color: AppTheme.inkSecondary
                )
                thinDivider
                compactStat(
                    "\(alreadySafeDisplayCount)",
                    label: "Already Safe",
                    color: AppTheme.positive
                )
            }
            .frame(height: 48)
            .background(AppTheme.surfaceSunken.opacity(0.85))
            .clipShape(RoundedRectangle(cornerRadius: 14, style: .continuous))

            pageIndicator

            // Subtle refresh status
            HStack(spacing: 5) {
                if statusService.isRefreshing {
                    ProgressView()
                        .scaleEffect(0.5)
                        .tint(AppTheme.inkQuaternary)
                    Text("Checking…")
                        .font(.system(size: 10, weight: .regular))
                        .foregroundStyle(AppTheme.inkQuaternary)
                } else if let checked = statusService.snapshot.lastCheckedAt {
                    Image(systemName: statusService.snapshot.connectionState == .offline
                          ? "wifi.slash" : "checkmark.circle")
                        .font(.system(size: 9, weight: .regular))
                        .foregroundStyle(statusService.snapshot.connectionState == .offline
                                         ? .orange : AppTheme.inkQuaternary)
                    Text(checked, style: .relative)
                        .font(.system(size: 10, weight: .regular))
                        .foregroundColor(AppTheme.inkQuaternary)
                    + Text(" ago")
                        .font(.system(size: 10, weight: .regular))
                        .foregroundColor(AppTheme.inkQuaternary)
                }
                Spacer()
                Button {
                    statusService.refresh(force: true)
                } label: {
                    Image(systemName: "arrow.clockwise")
                        .font(.system(size: 11, weight: .regular))
                        .foregroundStyle(AppTheme.inkQuaternary)
                }
            }
            .frame(height: 16)
        }
    }

    private func compactStat(_ value: String, label: String, color: Color) -> some View {
        VStack(spacing: 2) {
            Text(value)
                .font(.system(size: 15, weight: .semibold))
                .foregroundStyle(color)
                .monospacedDigit()
            Text(label)
                .font(.system(size: 9, weight: .regular))
                .foregroundStyle(AppTheme.inkQuaternary)
                .tracking(0.2)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 6)
    }

    private var thinDivider: some View {
        Rectangle()
            .fill(AppTheme.separator.opacity(0.5))
            .frame(width: 0.5, height: 18)
    }

    // MARK: — Destination row

    private var destinationRow: some View {
        Button(action: {
            pickerPath = store.savedConnection?.remotePath ?? "/"
            showDestinationPicker = true
        }) {
            HStack(spacing: 10) {
                ZStack {
                    Circle()
                        .fill(AppTheme.surfaceSunken)
                        .frame(width: 34, height: 34)
                    Image(systemName: "folder.fill")
                        .font(.system(size: 13, weight: .medium))
                        .foregroundStyle(AppTheme.inkSecondary)
                }

                let path = store.savedConnection?.remotePath ?? "/"
                let folderName = path == "/" ? "Not set" : (path as NSString).lastPathComponent

                VStack(alignment: .leading, spacing: 1) {
                    Text(folderName)
                        .font(AppTheme.headline())
                        .foregroundStyle(path == "/" ? AppTheme.inkTertiary : AppTheme.ink)
                    Text("Backup folder")
                        .font(AppTheme.micro(10))
                        .foregroundStyle(AppTheme.inkTertiary)
                }

                Spacer()

                Image(systemName: "chevron.right")
                    .font(.system(size: 11, weight: .medium))
                    .foregroundStyle(AppTheme.inkQuaternary)
            }
            .padding(.horizontal, 14)
            .padding(.vertical, 12)
            .background(AppTheme.surfaceSunken)
            .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
        }
        .buttonStyle(ScaleButtonStyle())
        .disabled(store.savedConnection == nil)
    }

    private var nasStatusDotColor: Color {
        switch engine.job.status {
        case .running, .preparing, .paused:
            return Color(red: 1.0, green: 0.58, blue: 0.0)
        default:
            switch lanMonitor.nasReachable {
            case true:  return AppTheme.positive
            case false: return AppTheme.destructive
            case nil:   return AppTheme.inkQuaternary
            }
        }
    }

    private var nasStatusLabel: String {
        switch engine.job.status {
        case .running:   return "Backing up"
        case .preparing: return "Preparing"
        case .paused:    return "Paused"
        default:
            return lanMonitor.nasReachable == false ? "Offline" : "Ready"
        }
    }

    // MARK: — NAS status row

    private var nasStatusRow: some View {
        HStack(spacing: 10) {
            ZStack {
                Circle()
                    .fill(AppTheme.surfaceSunken)
                    .frame(width: 34, height: 34)
                Image(systemName: "externaldrive")
                    .font(.system(size: 13, weight: .medium))
                    .foregroundStyle(AppTheme.inkSecondary)
            }

            if let conn = store.savedConnection {
                let friendlyName = conn.displayName == conn.host ? "Home Server" : conn.displayName
                VStack(alignment: .leading, spacing: 1) {
                    Text(friendlyName)
                        .font(AppTheme.headline())
                        .foregroundStyle(AppTheme.ink)
                    Text("\(conn.nasProtocol.rawValue) · \(conn.host)")
                        .font(AppTheme.micro(10))
                        .foregroundStyle(AppTheme.inkTertiary)
                }
            } else {
                Text("No storage connected")
                    .font(AppTheme.body())
                    .foregroundStyle(AppTheme.inkTertiary)
            }

            Spacer()

            VStack(alignment: .trailing, spacing: 2) {
                HStack(spacing: 4) {
                    Circle()
                        .fill(nasStatusDotColor)
                        .frame(width: 6, height: 6)
                        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: nasStatusDotColor == AppTheme.positive)
                    Text(nasStatusLabel)
                        .font(AppTheme.micro())
                        .foregroundStyle(nasStatusDotColor)
                        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: nasStatusLabel)
                }
                if lanMonitor.nasReachable == false {
                    Text("Unreachable")
                        .font(.system(size: 9, weight: .regular))
                        .foregroundStyle(AppTheme.destructive.opacity(0.7))
                } else if lanMonitor.nasReachable == true && !engine.job.status.isActive {
                    Text("Connected")
                        .font(.system(size: 9, weight: .regular))
                        .foregroundStyle(AppTheme.positive.opacity(0.7))
                }
            }
        }
        .padding(.horizontal, 14)
        .padding(.vertical, 12)
        .background(AppTheme.surfaceSunken)
        .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
    }

    // MARK: — Photos access nudge

    private var photosAccessRow: some View {
        Button(action: { Task { await vm.requestPhotosAccess() } }) {
            HStack(spacing: 10) {
                Image(systemName: "photo.on.rectangle")
                    .font(.system(size: 13, weight: .medium))
                    .foregroundStyle(AppTheme.destructive)
                    .frame(width: 20)
                Text("Grant photo library access to enable backup")
                    .font(AppTheme.caption())
                    .foregroundStyle(AppTheme.inkSecondary)
                Spacer()
                Image(systemName: "chevron.right")
                    .font(.system(size: 11, weight: .medium))
                    .foregroundStyle(AppTheme.inkQuaternary)
            }
            .padding(.horizontal, 14)
            .padding(.vertical, 11)
            .background(AppTheme.destructive.opacity(0.06))
            .clipShape(RoundedRectangle(cornerRadius: 10, style: .continuous))
        }
        .buttonStyle(ScaleButtonStyle())
    }

    // MARK: — Action button

    private var actionButton: some View {
        Group {
            switch engine.job.status {
            case .idle, .completed, .failed, .cancelled:
                Button(action: startBackup) {
                    Text(engine.job.status == .idle ? "Start backup" : "Back up again")
                }
                .buttonStyle(PrimaryButtonStyle(
                    color: ctaFlashGreen ? AppTheme.positive : AppTheme.ink
                ))
                .accessibilityHint("Starts backing up your photos to the NAS")

            case .running:
                Button { engine.pause() } label: { Text("Pause") }
                    .buttonStyle(GhostButtonStyle())
                    .accessibilityLabel("Pause backup")

            case .paused:
                HStack(spacing: 10) {
                    Button { engine.resume() } label: { Text("Resume") }
                        .buttonStyle(PrimaryButtonStyle())
                        .accessibilityLabel("Resume backup")
                    Button { engine.cancel() } label: { Text("Cancel") }
                        .buttonStyle(GhostButtonStyle())
                        .frame(width: 90)
                        .accessibilityLabel("Cancel backup")
                }

            case .preparing:
                HStack(spacing: 8) {
                    ProgressView().scaleEffect(0.8).tint(AppTheme.inkSecondary)
                    Text("Preparing…")
                        .font(AppTheme.body())
                        .foregroundStyle(AppTheme.inkSecondary)
                }
                .frame(height: 50)
            }
        }
        .animation(.spring(response: 0.3, dampingFraction: 0.82), value: engine.job.status == .running)
    }

    private func startBackup() {
        guard let conn = store.savedConnection else { return }
        Task { _ = try? await engine.run(connection: conn, filter: store.backupFilter) }
    }

    private func etaString(_ seconds: TimeInterval) -> String {
        Int(seconds) / 60 > 0 ? "\(Int(seconds) / 60)m" : "\(Int(seconds))s"
    }
}