Checks enum values

check_enum_values.sql

CREATE FUNCTION check_enum_value(in_enum text, in_value text, in_name text = NULL) RETURNS void AS $BODY$
DECLARE
  items text[];
BEGIN
  EXECUTE(format('SELECT enum_range(null::%I)::text', in_enum)) INTO items;
  IF (NOT(items @> ARRAY[in_value])) THEN
    RAISE EXCEPTION USING MESSAGE = format(
        $$'%s' must be one of: %s - '%s' was given$$,
        CASE WHEN in_name IS NOT NULL THEN in_name ELSE in_enum END,
        array_to_string(
            (SELECT array_agg(format($$'%s'$$, item)) FROM unnest(items) AS item),
          ', '
        ),
        in_value
    );
  END IF;
END $BODY$ LANGUAGE plpgsql VOLATILE;

CREATE FUNCTION is_enum_value(in_enum text, in_value text) RETURNS boolean AS $$
BEGIN
  PERFORM check_enum_value(in_enum, in_value);
  RETURN TRUE;
  EXCEPTION WHEN OTHERS THEN RETURN FALSE;
END $$ LANGUAGE plpgsql VOLATILE;

CREATE FUNCTION is_enum_value(in_enum json, in_value json) RETURNS boolean AS $$
BEGIN
  PERFORM check_enum_value(in_enum, in_value);
  RETURN TRUE;
  EXCEPTION WHEN OTHERS THEN RETURN FALSE;
END $$ LANGUAGE plpgsql VOLATILE;

CREATE FUNCTION check_enum_value(in_enum json, in_value json) RETURNS void AS $$
DECLARE
  object record;
BEGIN
  IF (in_value::text = '{}'::text) THEN
    RETURN;
  END IF;
  FOR object IN SELECT key, value FROM json_each_text(in_enum)
  LOOP
    IF (in_value::jsonb ? object.key) THEN
      PERFORM check_enum_value(object.value, in_value->>object.key, object.key);
    END IF;
  END LOOP;
END $$ LANGUAGE plpgsql VOLATILE;