import ManaCore
import Observation
import SwiftUI

/// Account-Sheet: Passwort ändern. Erfordert aktuelles Passwort (Re-Auth).
///
/// **Server-Limitation (v0.1.0):** funktioniert erst nach Phase-3-
/// Server-PR (`mana-auth` braucht Bearer-Plugin).
public struct ManaChangePasswordView: View {
    @Environment(\.manaBrand) private var brand
    @State private var model: ChangePasswordViewModel
    private let onDone: () -> Void

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

    public var body: some View {
        switch model.status {
        case .done:
            doneView
        default:
            formView
        }
    }

    @ViewBuilder
    private var formView: some View {
        ManaAuthScaffold(showsHeader: false) {
            VStack(spacing: 16) {
                Text("Passwort ändern")
                    .font(.title2)
                    .fontWeight(.semibold)
                    .foregroundStyle(brand.foreground)
                    .frame(maxWidth: .infinity, alignment: .leading)

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

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

                ManaSecureField(
                    "Neues Passwort bestätigen",
                    text: $model.confirmPassword,
                    textContentType: .newPassword
                )

                if let hint = model.validationHint {
                    Text(hint)
                        .font(.footnote)
                        .foregroundStyle(brand.mutedForeground)
                        .frame(maxWidth: .infinity, alignment: .leading)
                }

                ManaPrimaryButton(
                    "Passwort ändern",
                    isLoading: model.isSubmitting,
                    isEnabled: model.canSubmit
                ) {
                    Task { await model.submit() }
                }

                if case let .error(message) = model.status {
                    Text(message)
                        .font(.footnote)
                        .foregroundStyle(brand.error)
                        .multilineTextAlignment(.center)
                        .padding(.top, 4)
                }
            }
            .padding(.top, 16)

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

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

                Text("Passwort geändert")
                    .font(.title2)
                    .fontWeight(.semibold)
                    .foregroundStyle(brand.foreground)

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

@MainActor
@Observable
final class ChangePasswordViewModel {
    enum Status: Equatable {
        case idle
        case submitting
        case done
        case error(String)
    }

    var currentPassword: String = ""
    var newPassword: String = ""
    var confirmPassword: String = ""
    private(set) var status: Status = .idle

    private let auth: AuthClient

    init(auth: AuthClient) {
        self.auth = auth
    }

    var canSubmit: Bool {
        guard !currentPassword.isEmpty, !newPassword.isEmpty, !confirmPassword.isEmpty else { return false }
        guard newPassword == confirmPassword else { return false }
        guard newPassword.count >= 8 else { return false }
        if case .submitting = status { return false }
        return true
    }

    var isSubmitting: Bool {
        if case .submitting = status { return true }
        return false
    }

    var validationHint: String? {
        if !newPassword.isEmpty, newPassword.count < 8 {
            return "Neues Passwort muss mindestens 8 Zeichen lang sein."
        }
        if !confirmPassword.isEmpty, newPassword != confirmPassword {
            return "Die neuen Passwörter stimmen nicht überein."
        }
        return nil
    }

    func submit() async {
        guard canSubmit else { return }

        status = .submitting
        do {
            try await auth.changePassword(currentPassword: currentPassword, newPassword: newPassword)
            currentPassword = ""
            newPassword = ""
            confirmPassword = ""
            status = .done
        } catch let error as AuthError {
            status = .error(error.errorDescription ?? "Änderung fehlgeschlagen")
        } catch {
            status = .error(String(describing: error))
        }
    }
}