func parseExp()

in lib/auditlogsapi/filters.go [56:123]
56 lines of code
23 McCabe index (conditional complexity)

func parseExp(s string) (*exp, error) {
	s = strings.TrimSpace(s)
	matches := expRE.FindAllStringSubmatch(s, -1)
	if len(matches) == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "unknown expression format")
	}
	ss := matches[0][1:]

	var field expField
	for _, f := range allowFields {
		if ss[0] == string(f) {
			field = f
		}
	}
	if len(field) == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "unknown expression field: %s", ss[0])
	}

	switch field {
	case fieldTime:
		// time allows >= and <=
		if ss[1] != string(gte) && ss[1] != string(lte) {
			return nil, status.Errorf(codes.InvalidArgument, "not allowed op for time field: %s", ss[1])
		}
	case fieldType:
		// type allows =
		if ss[1] != string(equals) {
			return nil, status.Errorf(codes.InvalidArgument, "not allowed op for type field: %s", ss[1])
		}
	case fieldText:
		// text allows : and =
		if ss[1] != string(equals) && ss[1] != string(contains) {
			return nil, status.Errorf(codes.InvalidArgument, "not allowed op for text field: %s", ss[1])
		}
	case fieldDecision:
		// decision allows =
		if ss[1] != string(equals) {
			return nil, status.Errorf(codes.InvalidArgument, "not allowed op for decision field: %s", ss[1])
		}
	default:
		return nil, status.Errorf(codes.Internal, "unknown expression field in op checker: %s", field)
	}

	op := expOp(ss[1])

	value := strings.Trim(ss[2], `"`)

	if field == fieldTime {
		if _, err := time.Parse(time.RFC3339, value); err != nil {
			return nil, status.Errorf(codes.InvalidArgument, "time value not in RFC3339 format: %s", value)
		}
	}

	if field == fieldType {
		if value != apb.LogType_REQUEST.String() && value != apb.LogType_POLICY.String() {
			return nil, status.Errorf(codes.InvalidArgument, "type value not allowed: %s", value)
		}
	}

	if field == fieldDecision {
		value = strings.ToUpper(value)
		if value != apb.Decision_PASS.String() && value != apb.Decision_FAIL.String() {
			return nil, status.Errorf(codes.InvalidArgument, "decision value not allowed: %s", value)
		}
	}

	return &exp{field: field, op: op, value: value}, nil
}