import CoreImage.CIFilterBuiltins
import ManaCore
import SwiftUI

#if canImport(UIKit)
    import UIKit
#elseif canImport(AppKit)
    import AppKit
#endif

/// Account-Sheet: TOTP-2FA aktivieren. 3-Phasen-Wizard.
///
/// 1. Passwort eingeben (Re-Auth)
/// 2. QR-Code mit Authenticator-App scannen + Test-Code eingeben
/// 3. Backup-Codes anzeigen und vom User bestätigen lassen
public struct ManaTwoFactorEnrollView: View {
    @Environment(\.manaBrand) private var brand
    @State private var model: TwoFactorEnrollmentViewModel
    private let onDone: () -> Void

    public init(auth: AuthClient, onDone: @escaping () -> Void) {
        _model = State(initialValue: TwoFactorEnrollmentViewModel(auth: auth))
        self.onDone = onDone
    }

    public var body: some View {
        ManaAuthScaffold(showsHeader: false) {
            switch model.phase {
            case .password:
                passwordPhase
            case let .verify(uri, _):
                verifyPhase(uri: uri)
            case let .backupCodes(codes):
                backupCodesPhase(codes: codes)
            }
        }
    }

    // MARK: - Phase 1: Password

    @ViewBuilder
    private var passwordPhase: some View {
        VStack(spacing: 16) {
            Image(systemName: "lock.shield")
                .font(.system(size: 56, weight: .light))
                .foregroundStyle(brand.primary)

            Text("Zwei-Faktor aktivieren")
                .font(.title2)
                .fontWeight(.semibold)
                .foregroundStyle(brand.foreground)

            Text("Schütze deinen Account mit einem zusätzlichen Code. Bestätige dazu erst dein Passwort.")
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .multilineTextAlignment(.center)

            ManaSecureField(
                "Passwort",
                text: $model.password,
                textContentType: .password
            )

            ManaPrimaryButton(
                "Weiter",
                isLoading: model.isWorking,
                isEnabled: model.canSubmitPassword
            ) {
                Task { await model.enrollWithPassword() }
            }

            if case let .error(message) = model.status {
                Text(message)
                    .font(.footnote)
                    .foregroundStyle(brand.error)
                    .multilineTextAlignment(.center)
            }

            Button("Abbrechen", action: onDone)
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .padding(.top, 12)
        }
    }

    // MARK: - Phase 2: QR + Verify

    @ViewBuilder
    private func verifyPhase(uri: String) -> some View {
        VStack(spacing: 16) {
            Text("Code scannen")
                .font(.title2)
                .fontWeight(.semibold)
                .foregroundStyle(brand.foreground)

            Text("Öffne deine Authenticator-App (z.B. 1Password, Aegis, Google Authenticator) und scanne diesen QR-Code.")
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .multilineTextAlignment(.center)

            qrCode(for: uri)
                .frame(width: 220, height: 220)
                .padding(8)
                .background(Color.white, in: RoundedRectangle(cornerRadius: 12))

            Text("Gib zur Bestätigung den 6-stelligen Code aus der App ein:")
                .font(.subheadline)
                .foregroundStyle(brand.foreground)
                .multilineTextAlignment(.center)
                .padding(.top, 8)

            ManaTextField("123 456", text: $model.verifyCode)
                .autocorrectionDisabled()
                .font(.system(.title3, design: .monospaced))
            #if os(iOS)
                .keyboardType(.numberPad)
                .textInputAutocapitalization(.never)
            #endif

            ManaPrimaryButton(
                "Weiter zu Backup-Codes",
                isEnabled: model.canSubmitVerify
            ) {
                model.confirmVerify()
            }

            Button("Abbrechen", action: onDone)
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .padding(.top, 12)
        }
    }

    // MARK: - Phase 3: Backup-Codes

    @ViewBuilder
    private func backupCodesPhase(codes: [String]) -> some View {
        VStack(spacing: 16) {
            Image(systemName: "checkmark.shield.fill")
                .font(.system(size: 56, weight: .light))
                .foregroundStyle(brand.success)

            Text("Zwei-Faktor aktiv")
                .font(.title2)
                .fontWeight(.semibold)
                .foregroundStyle(brand.foreground)

            Text("Sichere diese Backup-Codes JETZT. Du brauchst sie wenn du dein Authenticator-Gerät verlierst. Jeder Code lässt sich nur einmal verwenden.")
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .multilineTextAlignment(.center)

            VStack(spacing: 6) {
                ForEach(codes, id: \.self) { code in
                    Text(code)
                        .font(.system(.body, design: .monospaced))
                        .foregroundStyle(brand.foreground)
                        .frame(maxWidth: .infinity)
                        .padding(.vertical, 8)
                        .background(brand.surface, in: RoundedRectangle(cornerRadius: 6))
                }
            }
            .padding(.vertical, 8)

            Button(action: { copyToClipboard(codes.joined(separator: "\n")) }) {
                Label("Alle Codes kopieren", systemImage: "doc.on.doc")
                    .frame(maxWidth: .infinity)
                    .padding(.vertical, 10)
                    .background(brand.surface, in: RoundedRectangle(cornerRadius: 8))
                    .foregroundStyle(brand.primary)
            }
            .buttonStyle(.plain)

            ManaPrimaryButton("Fertig — Codes sind gesichert") {
                onDone()
            }
            .padding(.top, 12)
        }
    }

    // MARK: - QR-Code

    /// Rendert eine `otpauth://`-URI als QR-Code via `CoreImage`. Auf
    /// iOS/macOS sind `CIFilter.qrCodeGenerator()` system-bordmittel.
    @ViewBuilder
    private func qrCode(for content: String) -> some View {
        if let cgImage = makeQRCode(from: content) {
            #if canImport(UIKit)
                Image(uiImage: UIImage(cgImage: cgImage))
                    .interpolation(.none)
                    .resizable()
                    .scaledToFit()
            #elseif canImport(AppKit)
                Image(nsImage: NSImage(cgImage: cgImage, size: NSSize(width: 220, height: 220)))
                    .interpolation(.none)
                    .resizable()
                    .scaledToFit()
            #else
                Text(content)
                    .font(.system(.caption, design: .monospaced))
            #endif
        } else {
            Text("QR-Code konnte nicht generiert werden — bitte URI manuell kopieren:\n\(content)")
                .font(.system(.caption, design: .monospaced))
                .foregroundStyle(brand.mutedForeground)
        }
    }

    private func makeQRCode(from string: String) -> CGImage? {
        let context = CIContext()
        let filter = CIFilter.qrCodeGenerator()
        filter.message = Data(string.utf8)
        filter.correctionLevel = "M"
        guard let output = filter.outputImage else { return nil }
        // Upscale damit der QR-Code scharf bleibt (kein anti-aliasing).
        let transform = CGAffineTransform(scaleX: 10, y: 10)
        let scaled = output.transformed(by: transform)
        return context.createCGImage(scaled, from: scaled.extent)
    }

    private func copyToClipboard(_ text: String) {
        #if canImport(UIKit)
            UIPasteboard.general.string = text
        #elseif canImport(AppKit)
            NSPasteboard.general.clearContents()
            NSPasteboard.general.setString(text, forType: .string)
        #endif
    }
}

/// Account-Sheet: TOTP-2FA wieder deaktivieren. Einfacher Single-Step
/// mit Passwort-Re-Auth.
public struct ManaTwoFactorDisableView: View {
    @Environment(\.manaBrand) private var brand
    @State private var password: String = ""
    @State private var status: DisableStatus = .idle
    private let auth: AuthClient
    private let onDone: () -> Void

    public init(auth: AuthClient, onDone: @escaping () -> Void) {
        self.auth = auth
        self.onDone = onDone
    }

    private enum DisableStatus: Equatable {
        case idle
        case working
        case done
        case error(String)
    }

    public var body: some View {
        ManaAuthScaffold(showsHeader: false) {
            switch status {
            case .done:
                doneView
            default:
                formView
            }
        }
    }

    @ViewBuilder
    private var formView: some View {
        VStack(spacing: 16) {
            Image(systemName: "lock.shield")
                .font(.system(size: 56, weight: .light))
                .foregroundStyle(brand.mutedForeground)

            Text("Zwei-Faktor deaktivieren")
                .font(.title2)
                .fontWeight(.semibold)
                .foregroundStyle(brand.foreground)

            Text("Dein Account wird wieder nur mit Email + Passwort geschützt. Backup-Codes verlieren ihre Gültigkeit.")
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .multilineTextAlignment(.center)

            ManaSecureField("Passwort", text: $password, textContentType: .password)

            ManaPrimaryButton(
                "2FA deaktivieren",
                role: .destructive,
                isLoading: status == .working,
                isEnabled: !password.isEmpty && status != .working
            ) {
                Task { await submit() }
            }

            if case let .error(message) = status {
                Text(message)
                    .font(.footnote)
                    .foregroundStyle(brand.error)
                    .multilineTextAlignment(.center)
            }

            Button("Abbrechen", action: onDone)
                .font(.subheadline)
                .foregroundStyle(brand.mutedForeground)
                .padding(.top, 12)
        }
    }

    @ViewBuilder
    private var doneView: some View {
        VStack(spacing: 16) {
            Image(systemName: "lock.open")
                .font(.system(size: 56, weight: .light))
                .foregroundStyle(brand.mutedForeground)

            Text("Zwei-Faktor deaktiviert")
                .font(.title2)
                .fontWeight(.semibold)
                .foregroundStyle(brand.foreground)

            ManaPrimaryButton("Fertig") { onDone() }
                .padding(.top, 16)
        }
    }

    private func submit() async {
        guard !password.isEmpty else { return }
        status = .working
        do {
            try await auth.disableTotp(password: password)
            password = ""
            status = .done
        } catch let error as AuthError {
            status = .error(error.errorDescription ?? "Deaktivieren fehlgeschlagen")
        } catch {
            status = .error(String(describing: error))
        }
    }
}