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: 24) {
                    // Ring + counts
                    ringSection

                    // NAS status
                    nasStatusRow

                    // Options card
                    optionsCard

                    // Start / pause button
                    actionButton
                }
                .padding(.horizontal, 20)
                .padding(.top, 20)
                .padding(.bottom, 40)
            }
        }
        .task {
            vm.loadPhotoCount(filter: store.backupFilter)
        }
    }

    // MARK: Ring

    private var ringSection: some View {
        VStack(spacing: 16) {
            ZStack {
                ProgressRing(
                    progress: engine.job.progress,
                    lineWidth: 14,
                    size: 200,
                    color: ringColor
                )

                VStack(spacing: 4) {
                    Text(percentText)
                        .font(.system(size: 36, weight: .bold))
                        .foregroundColor(AppTheme.textPrimary)

                    if case .running = engine.job.status {
                        Text("\(engine.job.uploadedFiles + engine.job.skippedFiles) / \(engine.job.totalFiles)")
                            .font(AppTheme.bodyFont)
                            .foregroundColor(AppTheme.textSecondary)
                        if let eta = engine.job.eta {
                            Text("~\(etaString(eta))")
                                .font(AppTheme.captionFont)
                                .foregroundColor(AppTheme.textTertiary)
                        }
                    } else {
                        Text("\(vm.totalPhotoCount) photos")
                            .font(AppTheme.bodyFont)
                            .foregroundColor(AppTheme.textSecondary)
                        Text("0 backed up")
                            .font(AppTheme.captionFont)
                            .foregroundColor(AppTheme.textTertiary)
                    }
                }
            }

            // Completion summary
            if case .completed = engine.job.status {
                completionSummary
            }

            // Progress detail row
            if case .running = engine.job.status {
                progressDetailRow
            }
        }
    }

    private var ringColor: Color {
        switch engine.job.status {
        case .completed: return AppTheme.green
        case .failed:    return AppTheme.red
        default:         return AppTheme.blue
        }
    }

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

    // MARK: Progress detail

    private var progressDetailRow: some View {
        VStack(spacing: 8) {
            ProgressView(value: engine.job.progress)
                .tint(AppTheme.blue)

            HStack {
                Text(engine.job.currentFileName)
                    .font(AppTheme.captionFont)
                    .foregroundColor(AppTheme.textSecondary)
                    .lineLimit(1)
                    .truncationMode(.middle)
                Spacer()
                Text(formatSpeed(engine.job.speedBytesPerSecond))
                    .font(AppTheme.captionFont)
                    .foregroundColor(AppTheme.textTertiary)
            }
        }
    }

    // MARK: Completion

    private var completionSummary: some View {
        HStack(spacing: 24) {
            statPill(count: engine.job.uploadedFiles, label: "uploaded", color: AppTheme.green)
            statPill(count: engine.job.skippedFiles, label: "skipped", color: AppTheme.textSecondary)
            statPill(count: engine.job.failedFiles, label: "errors", color: engine.job.failedFiles > 0 ? AppTheme.red : AppTheme.textTertiary)
        }
    }

    private func statPill(count: Int, label: String, color: Color) -> some View {
        VStack(spacing: 2) {
            Text("\(count)")
                .font(.system(size: 20, weight: .bold))
                .foregroundColor(color)
            Text(label)
                .font(AppTheme.captionFont)
                .foregroundColor(AppTheme.textSecondary)
        }
    }

    // MARK: NAS status row

    private var nasStatusRow: some View {
        HStack {
            Image(systemName: "externaldrive.fill")
                .foregroundColor(AppTheme.blue)
            if let conn = store.savedConnection {
                Text("\(conn.host) — \(conn.username)")
                    .font(AppTheme.bodyFont)
                    .foregroundColor(AppTheme.textPrimary)
            }
            Spacer()
            HStack(spacing: 4) {
                Circle().fill(AppTheme.green).frame(width: 8, height: 8)
                Text("Live")
                    .font(AppTheme.captionFont)
                    .foregroundColor(AppTheme.green)
            }
        }
        .padding(14)
        .background(Color(hex: "#F9FAFB"))
        .clipShape(RoundedRectangle(cornerRadius: 10))
        .overlay(RoundedRectangle(cornerRadius: 10).stroke(AppTheme.cardBorder))
    }

    // MARK: Options card

    private var optionsCard: some View {
        VStack(spacing: 0) {
            optionRow(icon: "camera", title: "What to back up") {}
            Divider().padding(.leading, 44)
            optionRow(icon: "doc.badge.clock", title: "New files only") {}
            Divider().padding(.leading, 44)

            // Photos access row
            Button(action: { Task { await vm.requestPhotosAccess() } }) {
                HStack {
                    Image(systemName: "photo.on.rectangle")
                        .foregroundColor(vm.photosAuthStatus == .authorized ? AppTheme.blue : AppTheme.red)
                        .frame(width: 28)
                    Text("Photos access")
                        .font(AppTheme.bodyFont)
                        .foregroundColor(AppTheme.textPrimary)
                    Spacer()
                    Text(photosAccessLabel)
                        .font(AppTheme.captionFont)
                        .foregroundColor(vm.photosAuthStatus == .authorized ? AppTheme.green : AppTheme.red)
                    Image(systemName: "chevron.right")
                        .font(.system(size: 13))
                        .foregroundColor(AppTheme.textTertiary)
                }
                .padding(.horizontal, 16)
                .padding(.vertical, 14)
            }
        }
        .background(Color.white)
        .clipShape(RoundedRectangle(cornerRadius: AppTheme.cardCornerRadius))
        .overlay(RoundedRectangle(cornerRadius: AppTheme.cardCornerRadius).stroke(AppTheme.cardBorder))
    }

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

    private func optionRow(icon: String, title: String, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            HStack {
                Image(systemName: icon)
                    .foregroundColor(AppTheme.blue)
                    .frame(width: 28)
                Text(title)
                    .font(AppTheme.bodyFont)
                    .foregroundColor(AppTheme.textPrimary)
                Spacer()
                Image(systemName: "chevron.right")
                    .font(.system(size: 13))
                    .foregroundColor(AppTheme.textTertiary)
            }
            .padding(.horizontal, 16)
            .padding(.vertical, 14)
        }
    }

    // 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")
                        .font(.system(size: 17, weight: .semibold))
                        .foregroundColor(.white)
                        .frame(maxWidth: .infinity)
                        .frame(height: 52)
                        .background(engine.job.status == .completed ? AppTheme.green : AppTheme.blue)
                        .clipShape(RoundedRectangle(cornerRadius: 14))
                }
            case .running:
                Button(action: { engine.pause() }) {
                    Text("Pause")
                        .font(.system(size: 17, weight: .semibold))
                        .foregroundColor(.white)
                        .frame(maxWidth: .infinity)
                        .frame(height: 52)
                        .background(Color(hex: "#1E3A5F"))
                        .clipShape(RoundedRectangle(cornerRadius: 14))
                }
            case .paused:
                HStack(spacing: 12) {
                    Button(action: { engine.resume() }) {
                        Text("Resume")
                            .font(.system(size: 17, weight: .semibold))
                            .foregroundColor(.white)
                            .frame(maxWidth: .infinity)
                            .frame(height: 52)
                            .background(AppTheme.blue)
                            .clipShape(RoundedRectangle(cornerRadius: 14))
                    }
                    Button(action: { engine.cancel() }) {
                        Text("Cancel")
                            .font(.system(size: 17, weight: .semibold))
                            .foregroundColor(AppTheme.red)
                            .frame(height: 52)
                            .frame(width: 90)
                            .overlay(RoundedRectangle(cornerRadius: 14).stroke(AppTheme.red))
                    }
                }
            case .preparing:
                HStack {
                    ProgressView()
                    Text("Preparing…")
                        .foregroundColor(AppTheme.textSecondary)
                }
                .frame(height: 52)
            }
        }
    }

    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 {
        let mbps = bps / 1_000_000
        return mbps >= 1 ? String(format: "%.1f MB/s", mbps) : String(format: "%.0f KB/s", bps / 1000)
    }

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