import * as m from '$lib/paraglide/messages.js';

/**
 * Mirror of the backend ErrorCode enum.
 * Keep in sync with backend/src/main/java/org/raddatz/familienarchiv/exception/ErrorCode.java
 */
export type ErrorCode =
    | 'DOCUMENT_NOT_FOUND'
    | 'DOCUMENT_NO_FILE'
    | 'FILE_NOT_FOUND'
    | 'FILE_UPLOAD_FAILED'
    | 'USER_NOT_FOUND'
    | 'IMPORT_ALREADY_RUNNING'
    | 'UNAUTHORIZED'
    | 'FORBIDDEN'
    | 'VALIDATION_ERROR'
    | 'INTERNAL_ERROR';

export interface BackendError {
    code: ErrorCode;
    message: string; // English developer message — not shown to users
}

/**
 * Attempts to parse a backend ErrorResponse from a failed fetch response.
 * Returns null if the body is not valid JSON or does not contain a code field.
 */
export async function parseBackendError(res: Response): Promise<BackendError | null> {
    try {
        const body = await res.json();
        if (body && typeof body.code === 'string') {
            return body as BackendError;
        }
    } catch {
        // Body was not JSON
    }
    return null;
}

/** Returns a localised message for the given error code via Paraglide. Falls back to INTERNAL_ERROR. */
export function getErrorMessage(code: ErrorCode | string | undefined): string {
    switch (code) {
        case 'DOCUMENT_NOT_FOUND':    return m.error_document_not_found();
        case 'DOCUMENT_NO_FILE':      return m.error_document_no_file();
        case 'FILE_NOT_FOUND':        return m.error_file_not_found();
        case 'FILE_UPLOAD_FAILED':    return m.error_file_upload_failed();
        case 'USER_NOT_FOUND':        return m.error_user_not_found();
        case 'IMPORT_ALREADY_RUNNING':return m.error_import_already_running();
        case 'UNAUTHORIZED':          return m.error_unauthorized();
        case 'FORBIDDEN':             return m.error_forbidden();
        case 'VALIDATION_ERROR':      return m.error_validation_error();
        default:                      return m.error_internal_error();
    }
}