1 files changed, 154 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/agent/discovery/sd/pipeline/selector.go b/src/go/collectors/go.d.plugin/agent/discovery/sd/pipeline/selector.go
new file mode 100644
index 000000000..8bb5fb061
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/agent/discovery/sd/pipeline/selector.go
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package pipeline
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/netdata/netdata/go/go.d.plugin/agent/discovery/sd/model"
+)
+
+type selector interface {
+	matches(model.Tags) bool
+}
+
+type (
+	exactSelector string
+	trueSelector  struct{}
+	negSelector   struct{ selector }
+	orSelector    struct{ lhs, rhs selector }
+	andSelector   struct{ lhs, rhs selector }
+)
+
+func (s exactSelector) matches(tags model.Tags) bool { _, ok := tags[string(s)]; return ok }
+func (s trueSelector) matches(model.Tags) bool       { return true }
+func (s negSelector) matches(tags model.Tags) bool   { return !s.selector.matches(tags) }
+func (s orSelector) matches(tags model.Tags) bool    { return s.lhs.matches(tags) || s.rhs.matches(tags) }
+func (s andSelector) matches(tags model.Tags) bool   { return s.lhs.matches(tags) && s.rhs.matches(tags) }
+
+func (s exactSelector) String() string { return "{" + string(s) + "}" }
+func (s negSelector) String() string   { return "{!" + stringify(s.selector) + "}" }
+func (s trueSelector) String() string  { return "{*}" }
+func (s orSelector) String() string    { return "{" + stringify(s.lhs) + "|" + stringify(s.rhs) + "}" }
+func (s andSelector) String() string   { return "{" + stringify(s.lhs) + ", " + stringify(s.rhs) + "}" }
+func stringify(sr selector) string     { return strings.Trim(fmt.Sprintf("%s", sr), "{}") }
+
+func parseSelector(line string) (sr selector, err error) {
+	words := strings.Fields(line)
+	if len(words) == 0 {
+		return trueSelector{}, nil
+	}
+
+	var srs []selector
+	for _, word := range words {
+		if idx := strings.IndexByte(word, '|'); idx > 0 {
+			sr, err = parseOrSelectorWord(word)
+		} else {
+			sr, err = parseSingleSelectorWord(word)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("selector '%s' contains selector '%s' with forbidden symbol", line, word)
+		}
+		srs = append(srs, sr)
+	}
+
+	switch len(srs) {
+	case 0:
+		return trueSelector{}, nil
+	case 1:
+		return srs[0], nil
+	default:
+		return newAndSelector(srs[0], srs[1], srs[2:]...), nil
+	}
+}
+
+func parseOrSelectorWord(orWord string) (sr selector, err error) {
+	var srs []selector
+	for _, word := range strings.Split(orWord, "|") {
+		if sr, err = parseSingleSelectorWord(word); err != nil {
+			return nil, err
+		}
+		srs = append(srs, sr)
+	}
+	switch len(srs) {
+	case 0:
+		return trueSelector{}, nil
+	case 1:
+		return srs[0], nil
+	default:
+		return newOrSelector(srs[0], srs[1], srs[2:]...), nil
+	}
+}
+
+func parseSingleSelectorWord(word string) (selector, error) {
+	if len(word) == 0 {
+		return nil, errors.New("empty word")
+	}
+	neg := word[0] == '!'
+	if neg {
+		word = word[1:]
+	}
+	if len(word) == 0 {
+		return nil, errors.New("empty word")
+	}
+	if word != "*" && !isSelectorWordValid(word) {
+		return nil, errors.New("forbidden symbol")
+	}
+
+	var sr selector
+	switch word {
+	case "*":
+		sr = trueSelector{}
+	default:
+		sr = exactSelector(word)
+	}
+	if neg {
+		return negSelector{sr}, nil
+	}
+	return sr, nil
+}
+
+func newAndSelector(lhs, rhs selector, others ...selector) selector {
+	m := andSelector{lhs: lhs, rhs: rhs}
+	switch len(others) {
+	case 0:
+		return m
+	default:
+		return newAndSelector(m, others[0], others[1:]...)
+	}
+}
+
+func newOrSelector(lhs, rhs selector, others ...selector) selector {
+	m := orSelector{lhs: lhs, rhs: rhs}
+	switch len(others) {
+	case 0:
+		return m
+	default:
+		return newOrSelector(m, others[0], others[1:]...)
+	}
+}
+
+func isSelectorWordValid(word string) bool {
+	// valid:
+	// *
+	// ^[a-zA-Z][a-zA-Z0-9=_.]*$
+	if len(word) == 0 {
+		return false
+	}
+	if word == "*" {
+		return true
+	}
+	for i, b := range word {
+		switch {
+		case b >= 'a' && b <= 'z':
+		case b >= 'A' && b <= 'Z':
+		case b >= '0' && b <= '9' && i > 0:
+		case (b == '=' || b == '_' || b == '.') && i > 0:
+		default:
+			return false
+		}
+	}
+	return true
+}