state: add annotations to StateWatcher

state/api/params/params.go

 package params
 
 import (
         "bytes"
         "encoding/json"
         "fmt"
         "launchpad.net/juju-core/constraints"
 )
 
 // DestroyRelation holds the parameters for making the DestroyRelation call.
@@ skipping 136 matching lines @@
         EntityId string
         Pairs    map[string]string
 }
 
 // SetServiceConstraints stores parameters for making the SetServiceConstraints call.
 type SetServiceConstraints struct {
         ServiceName string
         Constraints constraints.Value
 }
 
+// CharmInfo stores parameters for a CharmInfo call.
+type CharmInfo struct {
+        CharmURL string
+}
+
 // Delta holds details of a change to the environment.
 type Delta struct {
         // If Removed is true, the entity has been removed;
         // otherwise it has been created or changed.
         Removed bool
         // Entity holds data about the entity that has changed.
         Entity EntityInfo
 }
 
 // MarshalJSON implements json.Marshaler.
@@ skipping 39 matching lines @@
         }
         switch entityKind {
         case "machine":
                 d.Entity = new(MachineInfo)
         case "service":
                 d.Entity = new(ServiceInfo)
         case "unit":
                 d.Entity = new(UnitInfo)
         case "relation":
                 d.Entity = new(RelationInfo)
+        case "annotation":
+                d.Entity = new(AnnotationInfo)
         default:
                 return fmt.Errorf("Unexpected entity name %q", entityKind)
         }
         if err := json.Unmarshal(elements[2], &d.Entity); err != nil {
                 return err
         }
         return nil
 }
 
 // EntityInfo is implemented by all entity Info types.
@@ skipping 38 matching lines @@
 func (i *UnitInfo) EntityId() interface{} { return i.Name }
 func (i *UnitInfo) EntityKind() string    { return "unit" }
 
 type RelationInfo struct {
         Key string `bson:"_id"`
 }
 
 func (i *RelationInfo) EntityId() interface{} { return i.Key }
 func (i *RelationInfo) EntityKind() string    { return "relation" }
 
-// CharmInfo stores parameters for a CharmInfo call.
-type CharmInfo struct {
-        CharmURL string
+type AnnotationInfo struct {
+        // TODO(rog) GlobalKey should not be necessary here, but is
+        // until there's a level of indirection between mgo documents
+        // and StateWatcher results. We ensure that it's not serialised
+        // for the API by specifying the json tag.
+        GlobalKey   string `bson:"_id" json:"-"`
+        EntityName  string
+        Annotations map[string]string
 }
+
+func (i *AnnotationInfo) EntityId() interface{} { return i.GlobalKey }
+func (i *AnnotationInfo) EntityKind() string    { return "annotation" }