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 {
            AppTheme.background.ignoresSafeArea()

            VStack(spacing: 0) {
                Spacer(minLength: 0)

                // ─── Ring hero ───────────────────────────────────────
                ringHero
                    .padding(.bottom, 28)

                // ─── Completion summary (only on .completed) ─────────
                if case .completed = engine.job.status {
                    completionStrip
                        .padding(.bottom, 28)
                        .transition(.opacity.combined(with: .scale(scale: 0.97)))
                }

                Spacer(minLength: 0)

                // ─── NAS status ───────────────────────────────────────
                nasStatusRow
                    .padding(.horizontal, AppTheme.hPad)
                    .padding(.bottom, 16)

                // ─── Photos access nudge ──────────────────────────────
                if vm.photosAuthStatus != .authorized && vm.photosAuthStatus != .limited {
                    photosAccessRow
                        .padding(.horizontal, AppTheme.hPad)
                        .padding(.bottom, 16)
                        .transition(.opacity.combined(with: .move(edge: .bottom)))
                }

                // ─── Action ───────────────────────────────────────────
                actionButton
                    .padding(.horizontal, AppTheme.hPad)
                    .padding(.bottom, 32)
            }
        }
        .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 { vm.loadPhotoCount(filter: store.backupFilter) }
    }

    // MARK: — Ring hero

    private var ringHero: some View {
        ZStack {
            ProgressRing(
                progress: engine.job.progress,
                lineWidth: 7,
                size: 220,
                color: ringColor,
                backgroundColor: AppTheme.inkQuaternary.opacity(0.4)
            )
            .accessibilityLabel("Backup progress")
            .accessibilityValue("\(Int(engine.job.progress * 100)) percent")

            VStack(spacing: 4) {
                Text(percentText)
                    .font(.system(size: 44, weight: .semibold, design: .rounded))
                    .foregroundStyle(AppTheme.ink)
                    .contentTransition(.numericText())
                    .monospacedDigit()

                ringSubtitle
                    .transition(.opacity)
            }
        }
        .animation(.spring(response: 0.4, dampingFraction: 0.8), value: engine.job.progress)
    }

    @ViewBuilder
    private var ringSubtitle: some View {
        switch engine.job.status {
        case .running:
            VStack(spacing: 2) {
                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)
                }
                Text(engine.job.currentFileName)
                    .font(.system(size: 11, weight: .regular))
                    .foregroundStyle(AppTheme.inkTertiary)
                    .lineLimit(1)
                    .truncationMode(.middle)
                    .frame(maxWidth: 160)
            }
        case .preparing:
            Text("Preparing…")
                .font(AppTheme.caption())
                .foregroundStyle(AppTheme.inkTertiary)
        case .completed:
            Text("Done")
                .font(.system(size: 13, weight: .medium))
                .foregroundStyle(AppTheme.positive)
        case .failed:
            Text("Failed")
                .font(.system(size: 13, weight: .medium))
                .foregroundStyle(AppTheme.destructive)
        case .cancelled:
            Text("Cancelled")
                .font(AppTheme.caption())
                .foregroundStyle(AppTheme.inkTertiary)
        default:
            Text(vm.totalPhotoCount > 0 ? "\(vm.totalPhotoCount) photos ready" : "Ready")
                .font(AppTheme.caption())
                .foregroundStyle(AppTheme.inkTertiary)
        }
    }

    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))%" }

    // MARK: — Completion strip

    private var completionStrip: some View {
        HStack(spacing: 0) {
            statCell("\(engine.job.uploadedFiles)", label: "uploaded")
            thinDivider
            statCell("\(engine.job.skippedFiles)", label: "skipped")
            thinDivider
            statCell(
                "\(engine.job.failedFiles)",
                label: "errors",
                valueColor: engine.job.failedFiles > 0 ? AppTheme.destructive : AppTheme.ink
            )
        }
        .padding(.horizontal, AppTheme.hPad)
        .background(AppTheme.surfaceSunken)
        .clipShape(RoundedRectangle(cornerRadius: AppTheme.radius, style: .continuous))
        .padding(.horizontal, AppTheme.hPad)
    }

    private func statCell(_ value: String, label: String, valueColor: Color = AppTheme.ink) -> some View {
        VStack(spacing: 3) {
            Text(value)
                .font(.system(size: 17, weight: .semibold))
                .foregroundStyle(valueColor)
                .monospacedDigit()
            Text(label)
                .font(AppTheme.micro())
                .foregroundStyle(AppTheme.inkTertiary)
        }
        .frame(maxWidth: .infinity)
        .padding(.vertical, 14)
    }

    private var thinDivider: some View {
        Rectangle()
            .fill(AppTheme.separator)
            .frame(width: 0.5)
            .padding(.vertical, 10)
    }

    // 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 {
                VStack(alignment: .leading, spacing: 1) {
                    Text(conn.host)
                        .font(AppTheme.headline())
                        .foregroundStyle(AppTheme.ink)
                    Text(conn.nasProtocol.rawValue)
                        .font(AppTheme.micro(10))
                        .foregroundStyle(AppTheme.inkTertiary)
                }
            } else {
                Text("No NAS configured")
                    .font(AppTheme.body())
                    .foregroundStyle(AppTheme.inkTertiary)
            }

            Spacer()

            HStack(spacing: 5) {
                Circle()
                    .fill(engine.job.status.isActive ? AppTheme.positive : AppTheme.inkQuaternary)
                    .frame(width: 6, height: 6)
                Text(engine.job.status.isActive ? "Active" : "Ready")
                    .font(AppTheme.micro())
                    .foregroundStyle(engine.job.status.isActive ? AppTheme.positive : AppTheme.inkTertiary)
            }
        }
        .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 == .completed ? "Back up again" : "Start backup")
                }
                .buttonStyle(PrimaryButtonStyle(
                    color: engine.job.status == .completed ? 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"
    }
}