Add support for dropwizard input format (#2846)

internal/templating/matcher.go

@@ -0,0 +1,58 @@
+package templating
+
+import (
+	"strings"
+)
+
+// matcher determines which template should be applied to a given metric
+// based on a filter tree.
+type matcher struct {
+	root            *node
+	defaultTemplate *Template
+}
+
+// newMatcher creates a new matcher.
+func newMatcher(defaultTemplate *Template) *matcher {
+	return &matcher{
+		root:            &node{},
+		defaultTemplate: defaultTemplate,
+	}
+}
+
+func (m *matcher) addSpec(tmplt templateSpec) error {
+	// Parse out the default tags specific to this template
+	tags := map[string]string{}
+	if tmplt.tagstring != "" {
+		for _, kv := range strings.Split(tmplt.tagstring, ",") {
+			parts := strings.Split(kv, "=")
+			tags[parts[0]] = parts[1]
+		}
+	}
+
+	tmpl, err := NewTemplate(tmplt.separator, tmplt.template, tags)
+	if err != nil {
+		return err
+	}
+	m.add(tmplt.filter, tmpl)
+	return nil
+}
+
+// add inserts the template in the filter tree based the given filter
+func (m *matcher) add(filter string, template *Template) {
+	if filter == "" {
+		m.defaultTemplate = template
+		m.root.separator = template.separator
+		return
+	}
+	m.root.insert(filter, template)
+}
+
+// match returns the template that matches the given measurement line.
+// If no template matches, the default template is returned.
+func (m *matcher) match(line string) *Template {
+	tmpl := m.root.search(line)
+	if tmpl != nil {
+		return tmpl
+	}
+	return m.defaultTemplate
+}