import SwiftUI
import Photos

struct BackupView: View {
    @EnvironmentObject var engine: BackupEngine
    @EnvironmentObject var store: ConnectionStore
    @StateObject private var vm = BackupViewModel()

    var body: some View {
        ZStack {
            Color.white.ignoresSafeArea()

            ScrollView {
                VStack(spacing: AppTheme.sectionGap) {
                    ringSection
                    nasRow
                    optionsCard
                    actionButton
                }
                .padding(.horizontal, AppTheme.hPad)
                .padding(.top, 24)
                .padding(.bottom, 48)
            }
        }
        .task { vm.loadPhotoCount(filter: store.backupFilter) }
    }

    // MARK: — Ring

    private var ringSection: some View {
        VStack(spacing: 20) {
            ZStack {
                ProgressRing(
                    progress: engine.job.progress,
                    lineWidth: 8,
                    size: 180,
                    color: ringColor,
                    backgroundColor: Color(hex: "#EBEBEB")
                )

                VStack(spacing: 3) {
                    Text(percentText)
                        .font(.system(size: 40, weight: .semibold, design: .rounded))
                        .foregroundStyle(AppTheme.ink)
                        .contentTransition(.numericText())

                    if case .running = engine.job.status {
                        Text("\(engine.job.uploadedFiles + engine.job.skippedFiles) of \(engine.job.totalFiles)")
                            .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)
                        }
                    } else {
                        Text("\(vm.totalPhotoCount) photos")
                            .font(AppTheme.caption())
                            .foregroundStyle(AppTheme.inkSecondary)
                    }
                }
            }

            // Completion summary
            if case .completed = engine.job.status {
                HStack(spacing: 0) {
                    statCell("\(engine.job.uploadedFiles)", label: "uploaded")
                    dividerLine
                    statCell("\(engine.job.skippedFiles)", label: "skipped")
                    dividerLine
                    statCell("\(engine.job.failedFiles)", label: "errors",
                             color: engine.job.failedFiles > 0 ? AppTheme.destructive : AppTheme.inkTertiary)
                }
                .background(AppTheme.surfaceSunken)
                .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
                .transition(.opacity.combined(with: .scale(scale: 0.95)))
            }

            // Progress detail
            if case .running = engine.job.status {
                VStack(spacing: 8) {
                    GeometryReader { geo in
                        ZStack(alignment: .leading) {
                            RoundedRectangle(cornerRadius: 2, style: .continuous)
                                .fill(Color(hex: "#EBEBEB"))
                                .frame(height: 3)
                            RoundedRectangle(cornerRadius: 2, style: .continuous)
                                .fill(AppTheme.ink)
                                .frame(width: geo.size.width * engine.job.progress, height: 3)
                                .animation(.spring(response: 0.4, dampingFraction: 0.8), value: engine.job.progress)
                        }
                    }
                    .frame(height: 3)

                    HStack {
                        Text(engine.job.currentFileName)
                            .font(.system(size: 12, weight: .regular))
                            .foregroundStyle(AppTheme.inkSecondary)
                            .lineLimit(1)
                            .truncationMode(.middle)
                        Spacer()
                        Text(formatSpeed(engine.job.speedBytesPerSecond))
                            .font(.system(size: 12, weight: .regular))
                            .foregroundStyle(AppTheme.inkTertiary)
                    }
                }
                .transition(.opacity)
            }
        }
        .animation(.spring(response: 0.4, dampingFraction: 0.8), value: engine.job.status == .completed)
    }

    private var ringColor: Color {
        switch engine.job.status {
        case .completed: return AppTheme.positive
        case .failed:    return AppTheme.destructive
        default:         return AppTheme.ink
        }
    }

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

    private func statCell(_ value: String, label: String, color: Color = AppTheme.ink) -> some View {
        VStack(spacing: 2) {
            Text(value)
                .font(.system(size: 18, weight: .semibold))
                .foregroundStyle(color)
            Text(label)
                .font(AppTheme.micro())
                .foregroundStyle(AppTheme.inkTertiary)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 14)
    }

    private var dividerLine: some View {
        Rectangle()
            .fill(AppTheme.separator)
            .frame(width: 0.5)
            .padding(.vertical, 12)
    }

    // MARK: — NAS row

    private var nasRow: some View {
        HStack(spacing: 10) {
            ZStack {
                Circle()
                    .fill(AppTheme.surfaceSunken)
                    .frame(width: 32, height: 32)
                Image(systemName: "externaldrive")
                    .font(.system(size: 13, weight: .medium))
                    .foregroundStyle(AppTheme.inkSecondary)
            }

            if let conn = store.savedConnection {
                VStack(alignment: .leading, spacing: 1) {
                    Text(conn.host)
                        .font(AppTheme.headline())
                        .foregroundStyle(AppTheme.ink)
                    Text(conn.username)
                        .font(AppTheme.caption())
                        .foregroundStyle(AppTheme.inkSecondary)
                }
            }

            Spacer()

            HStack(spacing: 5) {
                Circle()
                    .fill(AppTheme.positive)
                    .frame(width: 6, height: 6)
                Text("Live")
                    .font(AppTheme.micro())
                    .foregroundStyle(AppTheme.positive)
            }
        }
        .padding(14)
        .background(AppTheme.surfaceSunken)
        .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
    }

    // MARK: — Options

    private var optionsCard: some View {
        VStack(spacing: 0) {
            optionRow(icon: "camera", label: "What to back up") {}
            hairline
            optionRow(icon: "doc.badge.clock", label: "New files only") {}
            hairline
            Button(action: { Task { await vm.requestPhotosAccess() } }) {
                HStack {
                    Image(systemName: "photo.on.rectangle")
                        .font(.system(size: 14, weight: .regular))
                        .foregroundStyle(vm.photosAuthStatus == .authorized
                                         ? AppTheme.inkSecondary : AppTheme.destructive)
                        .frame(width: 20)
                    Text("Photos access")
                        .font(AppTheme.body())
                        .foregroundStyle(AppTheme.ink)
                    Spacer()
                    Text(photosLabel)
                        .font(AppTheme.caption())
                        .foregroundStyle(vm.photosAuthStatus == .authorized
                                         ? AppTheme.positive : AppTheme.destructive)
                    Image(systemName: "chevron.right")
                        .font(.system(size: 12, weight: .medium))
                        .foregroundStyle(AppTheme.inkQuaternary)
                }
                .padding(.horizontal, 16)
                .padding(.vertical, 14)
            }
            .buttonStyle(ScaleButtonStyle())
        }
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
        .shadow(color: AppTheme.cardShadow, radius: 12, x: 0, y: 2)
    }

    private var photosLabel: String {
        switch vm.photosAuthStatus {
        case .authorized: return "Full access"
        case .limited:    return "Limited"
        case .denied:     return "Denied"
        default:          return "Not set"
        }
    }

    private var hairline: some View {
        Rectangle()
            .fill(AppTheme.separator)
            .frame(height: 0.5)
            .padding(.leading, 36)
    }

    private func optionRow(icon: String, label: String, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            HStack {
                Image(systemName: icon)
                    .font(.system(size: 14, weight: .regular))
                    .foregroundStyle(AppTheme.inkSecondary)
                    .frame(width: 20)
                Text(label)
                    .font(AppTheme.body())
                    .foregroundStyle(AppTheme.ink)
                Spacer()
                Image(systemName: "chevron.right")
                    .font(.system(size: 12, weight: .medium))
                    .foregroundStyle(AppTheme.inkQuaternary)
            }
            .padding(.horizontal, 16)
            .padding(.vertical, 14)
        }
        .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 == .completed ? "Back up again" : "Start backup")
                }
                .buttonStyle(PrimaryButtonStyle(
                    color: engine.job.status == .completed ? AppTheme.positive : AppTheme.ink
                ))

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

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

            case .preparing:
                HStack(spacing: 8) {
                    ProgressView()
                        .scaleEffect(0.8)
                    Text("Preparing…")
                        .font(AppTheme.body())
                        .foregroundStyle(AppTheme.inkSecondary)
                }
                .frame(height: 50)
            }
        }
        .animation(.spring(response: 0.3, dampingFraction: 0.8), 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 formatSpeed(_ bps: Double) -> String {
        bps >= 1_000_000
            ? String(format: "%.1f MB/s", bps / 1_000_000)
            : String(format: "%.0f KB/s", bps / 1_000)
    }

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