enum AuthenticationMode { demo, azure }

class AuthService {
  AuthService._();

  static const String _configuredMode = String.fromEnvironment(
    "AUTH_MODE",
    defaultValue: "demo",
  );
  static const String azureTenantId = String.fromEnvironment("AZURE_TENANT_ID");
  static const String azureSpaClientId = String.fromEnvironment(
    "AZURE_SPA_CLIENT_ID",
  );
  static const String azureApiScope = String.fromEnvironment("AZURE_API_SCOPE");

  static const String demoStudentEmail = "lucas.martin@ensitech.eu";
  static const String demoResponsableEmail = "karim.benali@ensup.eu";

  static String? _demoEmail;

  static AuthenticationMode get mode {
    return switch (_configuredMode) {
      "demo" => AuthenticationMode.demo,
      "azure" => AuthenticationMode.azure,
      _ => throw StateError("AUTH_MODE doit valoir demo ou azure."),
    };
  }

  static void selectDemoStudent() {
    _ensureDemoMode();
    _demoEmail = demoStudentEmail;
  }

  static void selectDemoResponsable() {
    _ensureDemoMode();
    _demoEmail = demoResponsableEmail;
  }

  static void clearSession() {
    _demoEmail = null;
  }

  static Map<String, String> requestHeaders() {
    if (mode == AuthenticationMode.azure) {
      throw StateError("La session Microsoft n'est pas encore initialisee.");
    }

    final email = _demoEmail;
    if (email == null) {
      throw StateError("Aucun utilisateur de demonstration selectionne.");
    }

    return {"x-user-email": email};
  }

  static void _ensureDemoMode() {
    if (mode != AuthenticationMode.demo) {
      throw StateError(
        "Une identite de demonstration est interdite en mode Azure.",
      );
    }
  }
}