helper/backend: basic path routing (naive)

helper/backend/backend.go

@@ -1,6 +1,9 @@
 package backend
 
 import (
+	"regexp"
+	"sync"
+
 	"github.com/hashicorp/vault/vault"
 )
 
@@ -10,7 +13,13 @@ import (
 //
 // This is recommended over implementing vault.LogicalBackend directly.
 type Backend struct {
+	// Paths are the various routes that the backend responds to.
+	// This cannot be modified after construction (i.e. dynamically changing
+	// paths, including adding or removing, is not allowed once the
+	// backend is in use).
 	Paths []*Path
+
+	once sync.Once
 }
 
 // Path is a single path that the backend responds to.
@@ -42,6 +51,21 @@ type Path struct {
 	Callback func(*vault.Request, *FieldData) (*vault.Response, error)
 }
 
+func (b *Backend) Route(path string) *Path {
+	regexps := make([]*regexp.Regexp, len(b.Paths))
+	for i, p := range b.Paths {
+		regexps[i] = regexp.MustCompile(p.Pattern)
+	}
+
+	for i, re := range regexps {
+		if re.MatchString(path) {
+			return b.Paths[i]
+		}
+	}
+
+	return nil
+}
+
 // FieldSchema is a basic schema to describe the format of a path field.
 type FieldSchema struct {
 	Type    FieldType

helper/backend/backend_test.go

@@ -5,6 +5,51 @@ import (
 	"testing"
 )
 
+func TestBackendRoute(t *testing.T) {
+	cases := map[string]struct {
+		Patterns []string
+		Path     string
+		Match    string
+	}{
+		"no match": {
+			[]string{"foo"},
+			"bar",
+			"",
+		},
+
+		"exact": {
+			[]string{"foo"},
+			"foo",
+			"foo",
+		},
+
+		"regexp": {
+			[]string{"fo+"},
+			"foo",
+			"fo+",
+		},
+	}
+
+	for n, tc := range cases {
+		paths := make([]*Path, len(tc.Patterns))
+		for i, pattern := range tc.Patterns {
+			paths[i] = &Path{Pattern: pattern}
+		}
+
+		b := &Backend{Paths: paths}
+		result := b.Route(tc.Path)
+		match := ""
+		if result != nil {
+			match = result.Pattern
+		}
+
+		if match != tc.Match {
+			t.Fatalf("bad: %s\n\nExpected: %s\nGot: %s",
+				n, tc.Match, match)
+		}
+	}
+}
+
 func TestFieldSchemaDefaultOrZero(t *testing.T) {
 	cases := map[string]struct {
 		Schema *FieldSchema