Initial Functionality

The initial functionality works.  There's still a number of TODOs to
clean up, and some edge cases to work around, and some errors that could
be handled better.

pkg/client/helpers.go

@@ -0,0 +1,68 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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 client
+
+import (
+	"fmt"
+	"strings"
+)
+
+// LabelNeq produces a not-equal label selector expression.
+// Label is passed verbatim, and value is double-quote escaped
+// using Go's escaping is used on value (as per the PromQL rules).
+func LabelNeq(label string, value string) string {
+	return fmt.Sprintf("%s!=%q", label, value)
+}
+
+// LabelEq produces a equal label selector expression.
+// Label is passed verbatim, and value is double-quote escaped
+// using Go's escaping is used on value (as per the PromQL rules).
+func LabelEq(label string, value string) string {
+	return fmt.Sprintf("%s=%q", label, value)
+}
+
+// LabelMatches produces a regexp-matching label selector expression.
+// It has similar constraints to LabelNeq.
+func LabelMatches(label string, expr string) string {
+	return fmt.Sprintf("%s=~%q", label, expr)
+}
+
+// LabelNotMatches produces a inverse regexp-matching label selector expression (the opposite of LabelMatches).
+func LabelNotMatches(label string, expr string) string {
+	return fmt.Sprintf("%s!~%q", label, expr)
+}
+
+// NameMatches produces a label selector expression that checks that the series name matches the given expression.
+// It's a convinience wrapper around LabelMatches.
+func NameMatches(expr string) string {
+	return LabelMatches("__name__", expr)
+}
+
+// NameNotMatches produces a label selector expression that checks that the series name doesn't matches the given expression.
+// It's a convinience wrapper around LabelNotMatches.
+func NameNotMatches(expr string) string {
+	return LabelNotMatches("__name__", expr)
+}
+
+// MatchSeries takes a series name, and optionally some label expressions, and returns a series selector.
+// TODO: validate series name and expressions?
+func MatchSeries(name string, labelExpressions ...string) Selector {
+	if len(labelExpressions) == 0 {
+		return Selector(name)
+	}
+
+	return Selector(fmt.Sprintf("%s{%s}", name, strings.Join(labelExpressions, ",")))
+}