Invercargill-Sql/src/connection-factory.vala

namespace InvercargillSql {

    /**
     * Static factory for creating database connections from connection strings.
     * 
     * This factory maintains a registry of connection providers indexed by scheme.
     * The SQLite provider is automatically registered on first use.
     * 
     * Example usage:
     * ```vala
     * // Simple connection
     * var conn = ConnectionFactory.create_and_open("sqlite:///mydb.sqlite");
     * 
     * // With options
     * var conn = ConnectionFactory.create_and_open("sqlite:///readonly.db?mode=ro");
     * 
     * // Register custom provider
     * ConnectionFactory.register_provider("postgresql", new PostgresProvider());
     * var conn = ConnectionFactory.create_and_open("postgresql://user:pass@host/db");
     * ```
     */
    public class ConnectionFactory : Object {

        private static bool _sqlite_registered = false;
        private static ConnectionProvider? _sqlite_provider = null;
        private static bool _postgres_registered = false;
        private static ConnectionProvider? _postgres_provider = null;

        /**
         * Creates a new database connection from a connection string.
         * 
         * The connection is created but not opened. Call open() on the
         * returned connection to establish the database connection, or
         * use create_and_open() to create and open in one step.
         * 
         * @param connection_string The connection string to parse
         * @return A new Connection instance (not opened)
         * @throws SqlError.INVALID_CONNECTION_STRING if the format is invalid
         * @throws SqlError.CONNECTION_FAILED if provider creation fails
         */
        public static Connection create(string connection_string) throws SqlError {
            ConnectionString cs = ConnectionString.parse(connection_string);
            ConnectionProvider provider = get_provider(cs.scheme);
            return provider.create_connection(cs);
        }

        /**
         * Creates and opens a database connection from a connection string.
         * 
         * This is a convenience method that combines create() and open().
         * 
         * @param connection_string The connection string to parse
         * @return A new Connection instance (opened)
         * @throws SqlError.INVALID_CONNECTION_STRING if the format is invalid
         * @throws SqlError.CONNECTION_FAILED if connection fails
         */
        public static Connection create_and_open(string connection_string) throws SqlError {
            Connection conn = create(connection_string);
            conn.open();
            return conn;
        }

        /**
         * Creates and opens a database connection asynchronously.
         * 
         * @param connection_string The connection string to parse
         * @return A new Connection instance (opened)
         * @throws SqlError.INVALID_CONNECTION_STRING if the format is invalid
         * @throws SqlError.CONNECTION_FAILED if connection fails
         */
        public async static Connection create_and_open_async(string connection_string) throws SqlError {
            ConnectionString cs = ConnectionString.parse(connection_string);
            ConnectionProvider provider = get_provider(cs.scheme);
            Connection conn = yield provider.create_connection_async(cs);
            conn.open();
            return conn;
        }

        /**
         * Registers a connection provider for a scheme.
         * 
         * If a provider is already registered for the scheme, it will be
         * replaced.
         * 
         * @param scheme The scheme (e.g., "sqlite", "postgresql")
         * @param provider The provider instance
         */
        public static void register_provider(string scheme, ConnectionProvider provider) {
            string scheme_lower = scheme.down();

            if (scheme_lower == "sqlite") {
                _sqlite_provider = provider;
                _sqlite_registered = true;
            } else if (scheme_lower == "postgres" || scheme_lower == "postgresql") {
                _postgres_provider = provider;
                _postgres_registered = true;
            }
            // Other providers can be registered once a dictionary of
            // schemes is introduced; sqlite and postgres are the natives.
        }

        /**
         * Gets the provider for a scheme.
         * 
         * Auto-registers SQLite provider on first access.
         * 
         * @param scheme The scheme to look up
         * @return The ConnectionProvider for the scheme
         * @throws SqlError.INVALID_CONNECTION_STRING if no provider is registered
         */
        private static ConnectionProvider get_provider(string scheme) throws SqlError {
            string scheme_lower = scheme.down();

            if (scheme_lower == "sqlite") {
                if (!_sqlite_registered) {
                    _sqlite_provider = new SqliteProvider();
                    _sqlite_registered = true;
                }
                return _sqlite_provider;
            }

            if (scheme_lower == "postgres" || scheme_lower == "postgresql") {
                if (!_postgres_registered) {
                    _postgres_provider = new PostgresProvider();
                    _postgres_registered = true;
                }
                return _postgres_provider;
            }

            throw new SqlError.INVALID_CONNECTION_STRING(
                "No connection provider registered for scheme: %s".printf(scheme)
            );
        }

        /**
         * Clears all registered providers.
         * 
         * Useful for testing or when reconfiguring the factory.
         */
        public static void clear_providers() {
            _sqlite_provider = null;
            _sqlite_registered = false;
            _postgres_provider = null;
            _postgres_registered = false;
        }

        /**
         * Checks if a provider is registered for a scheme.
         * 
         * @param scheme The scheme to check
         * @return true if a provider is registered
         */
        public static bool has_provider(string scheme) {
            string scheme_lower = scheme.down();

            if (scheme_lower == "sqlite") {
                return _sqlite_registered;
            }

            if (scheme_lower == "postgres" || scheme_lower == "postgresql") {
                return _postgres_registered;
            }

            return false;
        }
    }
}