Implement a server-side config service interface.

luci_config/server/cfgclient/backend/get_all.go

+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package backend
+
+import (
+        "bytes"
+
+        "github.com/luci/luci-go/common/errors"
+)
+
+// GetAllTarget is the type of configuration to retrieve with GetAll.
+//
+// GetAllTarget marshals/unmarshals to/from a compact JSON representation. This is
+// used by the caching layer.
+type GetAllTarget string
+
+const (
+        // GetAllProject indicates that project configus should be retrieved.
+        GetAllProject = GetAllTarget("Project")
+        // GetAllRef indicates that ref configs should be retrieved.
+        GetAllRef = GetAllTarget("Ref")
+)
+
+var (
+        projectJSON = []byte(`"P"`)
+        refJSON     = []byte(`"R"`)
+)
+
+// MarshalJSON implements json.Marshaler.
+func (gat GetAllTarget) MarshalJSON() ([]byte, error) {
+        switch gat {
+        case GetAllProject:
+                return projectJSON, nil
+        case GetAllRef:
+                return refJSON, nil
+        default:
+                return nil, errors.Reason("unknown GetAllTarget: %(value)v").D("value", gat).Err()
+        }
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (gat *GetAllTarget) UnmarshalJSON(d []byte) error {
+        switch {
+        case bytes.Equal(d, projectJSON):
+                *gat = GetAllProject
+        case bytes.Equal(d, refJSON):
+                *gat = GetAllRef
+        default:
+                return errors.Reason("unknown GetAllTarget: %(value)q").D("value", d).Err()
+        }
+        return nil
+}