Chalkboard feature added.

hall/hall.go

@@ -108,6 +108,12 @@ type Hall struct {
 	history     []ChatHistoryEntry
 	timestamp   time.Time
 	data        map[string]interface{}
+	chalkboard  ChalkboardState
+}
+
+type ChalkboardState struct {
+	Text     string `json:"text"`
+	Revision uint64 `json:"revision"`
 }
 
 func (g *Hall) Name() string {
@@ -165,6 +171,20 @@ func (g *Hall) UpdateData(d map[string]interface{}) {
 	}
 }
 
+func (g *Hall) Chalkboard() ChalkboardState {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	return g.chalkboard
+}
+
+func (g *Hall) UpdateChalkboard(text string) ChalkboardState {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.chalkboard.Text = text
+	g.chalkboard.Revision++
+	return g.chalkboard
+}
+
 func (g *Hall) Description() *Description {
 	g.mu.Lock()
 	defer g.mu.Unlock()