File name should have changed during query->selector rename.

pkg/labels/selector.go

@@ -0,0 +1,123 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package labels
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Represents a selector.
+type Selector interface {
+	// Returns true if this selector matches the given set of labels.
+	Matches(Labels) bool
+
+	// Prints a human readable version of this selector.
+	String() string
+}
+
+// Everything returns a selector that matches all labels.
+func Everything() Selector {
+	return andTerm{}
+}
+
+type hasTerm struct {
+	label, value string
+}
+
+func (t *hasTerm) Matches(ls Labels) bool {
+	return ls.Get(t.label) == t.value
+}
+
+func (t *hasTerm) String() string {
+	return fmt.Sprintf("%v=%v", t.label, t.value)
+}
+
+type notHasTerm struct {
+	label, value string
+}
+
+func (t *notHasTerm) Matches(ls Labels) bool {
+	return ls.Get(t.label) != t.value
+}
+
+func (t *notHasTerm) String() string {
+	return fmt.Sprintf("%v!=%v", t.label, t.value)
+}
+
+type andTerm []Selector
+
+func (t andTerm) Matches(ls Labels) bool {
+	for _, q := range t {
+		if !q.Matches(ls) {
+			return false
+		}
+	}
+	return true
+}
+
+func (t andTerm) String() string {
+	var terms []string
+	for _, q := range t {
+		terms = append(terms, q.String())
+	}
+	return strings.Join(terms, ",")
+}
+
+func try(selectorPiece, op string) (lhs, rhs string, ok bool) {
+	pieces := strings.Split(selectorPiece, op)
+	if len(pieces) == 2 {
+		return pieces[0], pieces[1], true
+	}
+	return "", "", false
+}
+
+// Given a Set, return a Selector which will match exactly that Set.
+func SelectorFromSet(ls Set) Selector {
+	var items []Selector
+	for label, value := range ls {
+		items = append(items, &hasTerm{label: label, value: value})
+	}
+	if len(items) == 1 {
+		return items[0]
+	}
+	return andTerm(items)
+}
+
+// Takes a string repsenting a selector and returns an object suitable for matching, or an error.
+func ParseSelector(selector string) (Selector, error) {
+	parts := strings.Split(selector, ",")
+	var items []Selector
+	for _, part := range parts {
+		if part == "" {
+			continue
+		}
+		if lhs, rhs, ok := try(part, "!="); ok {
+			items = append(items, &notHasTerm{label: lhs, value: rhs})
+		} else if lhs, rhs, ok := try(part, "=="); ok {
+			items = append(items, &hasTerm{label: lhs, value: rhs})
+		} else if lhs, rhs, ok := try(part, "="); ok {
+			items = append(items, &hasTerm{label: lhs, value: rhs})
+		} else {
+			return nil, fmt.Errorf("invalid selector: '%s'; can't understand '%s'", selector, part)
+		}
+	}
+	if len(items) == 1 {
+		return items[0], nil
+	}
+	return andTerm(items), nil
+}