Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tools/search/sort.go

@@ -0,0 +1,67 @@
+package search
+
+import (
+	"fmt"
+	"strings"
+)
+
+const (
+	randomSortKey string = "@random"
+	rowidSortKey  string = "@rowid"
+)
+
+// sort field directions
+const (
+	SortAsc  string = "ASC"
+	SortDesc string = "DESC"
+)
+
+// SortField defines a single search sort field.
+type SortField struct {
+	Name      string `json:"name"`
+	Direction string `json:"direction"`
+}
+
+// BuildExpr resolves the sort field into a valid db sort expression.
+func (s *SortField) BuildExpr(fieldResolver FieldResolver) (string, error) {
+	// special case for random sort
+	if s.Name == randomSortKey {
+		return "RANDOM()", nil
+	}
+
+	// special case for the builtin SQLite rowid column
+	if s.Name == rowidSortKey {
+		return fmt.Sprintf("[[_rowid_]] %s", s.Direction), nil
+	}
+
+	result, err := fieldResolver.Resolve(s.Name)
+
+	// invalidate empty fields and non-column identifiers
+	if err != nil || len(result.Params) > 0 || result.Identifier == "" || strings.ToLower(result.Identifier) == "null" {
+		return "", fmt.Errorf("invalid sort field %q", s.Name)
+	}
+
+	return fmt.Sprintf("%s %s", result.Identifier, s.Direction), nil
+}
+
+// ParseSortFromString parses the provided string expression
+// into a slice of SortFields.
+//
+// Example:
+//
+//	fields := search.ParseSortFromString("-name,+created")
+func ParseSortFromString(str string) (fields []SortField) {
+	data := strings.Split(str, ",")
+
+	for _, field := range data {
+		// trim whitespaces
+		field = strings.TrimSpace(field)
+		if strings.HasPrefix(field, "-") {
+			fields = append(fields, SortField{strings.TrimPrefix(field, "-"), SortDesc})
+		} else {
+			fields = append(fields, SortField{strings.TrimPrefix(field, "+"), SortAsc})
+		}
+	}
+
+	return
+}