Align apartment core validation errors (#43)

frontend/src/app/services/http-error-message.ts

@@ -1,3 +1,13 @@
+export interface FieldValidationError {
+	field: string;
+	code: string;
+}
+
+export interface SaveFailure {
+	message: string;
+	fieldErrors: FieldValidationError[];
+}
+
 export function httpErrorMessage(error: unknown, fallback: string): string {
 	return typeof error === 'object' &&
 		error !== null &&
@@ -9,3 +19,49 @@ export function httpErrorMessage(error: unknown, fallback: string): string {
 		? error.error.message
 		: fallback;
 }
+
+export function saveFailure(error: unknown, fallback: string): SaveFailure {
+	const validationErrors = validationErrorsFrom(error);
+	if (validationErrors) {
+		return {
+			message: 'Veuillez corriger les champs signalés.',
+			fieldErrors: validationErrors,
+		};
+	}
+
+	return {
+		message: isConflict(error) ? httpErrorMessage(error, fallback) : fallback,
+		fieldErrors: [],
+	};
+}
+
+function validationErrorsFrom(error: unknown): FieldValidationError[] | null {
+	if (
+		typeof error !== 'object' ||
+		error === null ||
+		!('error' in error) ||
+		typeof error.error !== 'object' ||
+		error.error === null ||
+		!('code' in error.error) ||
+		error.error.code !== 'validation_failed' ||
+		!('errors' in error.error) ||
+		!Array.isArray(error.error.errors)
+	) {
+		return null;
+	}
+
+	const fieldErrors = error.error.errors.filter(
+		(fieldError): fieldError is FieldValidationError =>
+			typeof fieldError === 'object' &&
+			fieldError !== null &&
+			'field' in fieldError &&
+			typeof fieldError.field === 'string' &&
+			'code' in fieldError &&
+			typeof fieldError.code === 'string',
+	);
+	return fieldErrors.length === error.error.errors.length ? fieldErrors : null;
+}
+
+function isConflict(error: unknown): error is { status: number } {
+	return typeof error === 'object' && error !== null && 'status' in error && error.status === 409;
+}