vidforward: simplify manager file save/load

When saving and loading manager state to and from file, we don't
need to worry about the slate exit signals. Now that we have
broadcast status i.e. "play" or "slate", we can derive whether we
need an exit signal based only on that.

Approved-by: Trek Hopton

cmd/vidforward/file.go

@@ -51,8 +51,7 @@ type BroadcastBasic struct {
 // ManagerBasic is a crude version of the BroadcastManager struct use to simplify
 // marshal/unmarshal overriding.
 type ManagerBasic struct {
-	Broadcasts       map[MAC]*Broadcast
-	SlateExitSignals []MAC
+	Broadcasts map[MAC]*Broadcast
 }
 
 // MarshalJSON calls the default marshalling behaviour for the BroadcastBasic
@@ -94,14 +93,7 @@ func (b *Broadcast) UnmarshalJSON(data []byte) error {
 // MarshalJSON calls the default marshaller for a ManagerBasic value using data
 // from a broadcastManager value.
 func (m *broadcastManager) MarshalJSON() ([]byte, error) {
-	var signals []MAC
-	for k := range m.slateExitSignals {
-		signals = append(signals, k)
-	}
-	return json.Marshal(ManagerBasic{
-		Broadcasts:       m.broadcasts,
-		SlateExitSignals: signals,
-	})
+	return json.Marshal(ManagerBasic{Broadcasts: m.broadcasts})
 }
 
 // UnmarshalJSON populates a ManagerBasic value from the provided data and then
@@ -123,20 +115,23 @@ func (m *broadcastManager) UnmarshalJSON(data []byte) error {
 	}
 	m.dogNotifier = notifier
 
-	for _, mac := range mb.SlateExitSignals {
-		sigCh := make(chan struct{})
-		m.slateExitSignals[mac] = sigCh
-		rv := m.getPipeline(mac)
-		if rv == nil {
-			panic("no pipeline for MAC")
-		}
-		if !inTest {
-			err := writeSlateAndCheckErrors(rv, sigCh, m.log)
-			if err != nil {
-				return fmt.Errorf("couldn't write slate for MAC %v: %w", mac, err)
+	for mac, b := range m.broadcasts {
+		if b.status == statusSlate {
+			sigCh := make(chan struct{})
+			m.slateExitSignals[mac] = sigCh
+			rv := m.getPipeline(mac)
+			if rv == nil {
+				panic("no pipeline for MAC")
+			}
+			if !inTest {
+				err := writeSlateAndCheckErrors(rv, sigCh, m.log)
+				if err != nil {
+					return fmt.Errorf("couldn't write slate for MAC %v: %w", mac, err)
+				}
 			}
 		}
 	}
+
 	return nil
 }