1 files changed, 97 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/pkg/prometheus/selector/parse.go b/src/go/collectors/go.d.plugin/pkg/prometheus/selector/parse.go
new file mode 100644
index 000000000..29c1d4fbf
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/pkg/prometheus/selector/parse.go
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package selector
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/netdata/netdata/go/go.d.plugin/pkg/matcher"
+)
+
+var (
+	reLV = regexp.MustCompile(`^(?P<label_name>[a-zA-Z0-9_]+)(?P<op>=~|!~|=\*|!\*|=|!=)"(?P<pattern>.+)"$`)
+)
+
+func Parse(expr string) (Selector, error) {
+	var srs []Selector
+	lvs := strings.Split(unsugarExpr(expr), ",")
+
+	for _, lv := range lvs {
+		sr, err := parseSelector(lv)
+		if err != nil {
+			return nil, err
+		}
+		srs = append(srs, sr)
+	}
+
+	switch len(srs) {
+	case 0:
+		return nil, nil
+	case 1:
+		return srs[0], nil
+	default:
+		return And(srs[0], srs[1], srs[2:]...), nil
+	}
+}
+
+func parseSelector(line string) (Selector, error) {
+	sub := reLV.FindStringSubmatch(strings.TrimSpace(line))
+	if sub == nil {
+		return nil, fmt.Errorf("invalid selector syntax: '%s'", line)
+	}
+
+	name, op, pattern := sub[1], sub[2], strings.Trim(sub[3], "\"")
+
+	var m matcher.Matcher
+	var err error
+
+	switch op {
+	case OpEqual, OpNegEqual:
+		m, err = matcher.NewStringMatcher(pattern, true, true)
+	case OpRegexp, OpNegRegexp:
+		m, err = matcher.NewRegExpMatcher(pattern)
+	case OpSimplePatterns, OpNegSimplePatterns:
+		m, err = matcher.NewSimplePatternsMatcher(pattern)
+	default:
+		err = fmt.Errorf("unknown matching operator: %s", op)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	sr := labelSelector{
+		name: name,
+		m:    m,
+	}
+
+	if neg := strings.HasPrefix(op, "!"); neg {
+		return Not(sr), nil
+	}
+	return sr, nil
+}
+
+func unsugarExpr(expr string) string {
+	// name                => __name__=*"name"
+	// name{label="value"} => __name__=*"name",label="value"
+	// {label="value"}     => label="value"
+	expr = strings.TrimSpace(expr)
+
+	switch idx := strings.IndexByte(expr, '{'); true {
+	case idx == -1:
+		expr = fmt.Sprintf(`__name__%s"%s"`,
+			OpSimplePatterns,
+			strings.TrimSpace(expr),
+		)
+	case idx == 0:
+		expr = strings.Trim(expr, "{}")
+	default:
+		expr = fmt.Sprintf(`__name__%s"%s",%s`,
+			OpSimplePatterns,
+			strings.TrimSpace(expr[:idx]),
+			strings.Trim(expr[idx:], "{}"),
+		)
+	}
+	return expr
+}