all: add ApplicationOption's and a way to get cast dns by name

Added ApplicationOption's which can be used to configure the
application.

Changed to use a variable for 'connectionRetries' instead of the
hardcoded 5. Can also be configured with the ApplicationOption.

New method in 'dns' to quickly and easily get a cast dns entry by name.

Author: vishen

application/application.go

@@ -90,25 +90,56 @@ type Application struct {
 	playedItems   map[string]PlayedItem
 	cacheDisabled bool
 	cache         *storage.Storage
+
+	// Number of connection retries to try before returning
+	// and error.
+	connectionRetries int
+}
+
+type ApplicationOption func(*Application)
+
+func WithIface(iface *net.Interface) ApplicationOption {
+	return func(a *Application) {
+		a.iface = iface
+	}
 }
 
-func NewApplication(iface *net.Interface, debug, cacheDisabled bool) *Application {
-	// TODO(vishen): make cast.Connection an interface, most likely will just need
-	// the Send method
-	// Channel to receive messages from the cast connecttion. 5 is a randomly
-	// chosen number.
+func WithDebug(debug bool) ApplicationOption {
+	return func(a *Application) {
+		a.debug = debug
+		a.conn.SetDebug(debug)
+	}
+}
+
+func WithCacheDisabled(cacheDisabled bool) ApplicationOption {
+	return func(a *Application) {
+		a.cacheDisabled = cacheDisabled
+	}
+}
+
+func WithConnectionRetries(connectionRetries int) ApplicationOption {
+	return func(a *Application) {
+		a.connectionRetries = connectionRetries
+	}
+}
+
+func NewApplication(opts ...ApplicationOption) *Application {
 	recvMsgChan := make(chan *pb.CastMessage, 5)
 	a := &Application{
-		recvMsgChan:   recvMsgChan,
-		resultChanMap: map[int]chan *pb.CastMessage{},
-		messageChan:   make(chan *pb.CastMessage),
-		conn:          cast.NewConnection(recvMsgChan, debug),
-		debug:         debug,
-		cacheDisabled: cacheDisabled,
-		playedItems:   map[string]PlayedItem{},
-		cache:         storage.NewStorage(),
-		iface:         iface,
+		recvMsgChan:       recvMsgChan,
+		resultChanMap:     map[int]chan *pb.CastMessage{},
+		messageChan:       make(chan *pb.CastMessage),
+		conn:              cast.NewConnection(recvMsgChan),
+		playedItems:       map[string]PlayedItem{},
+		cache:             storage.NewStorage(),
+		connectionRetries: 5,
+	}
+
+	// Apply options
+	for _, o := range opts {
+		o(a)
 	}
+
 	// Kick off the listener for asynchronous messages received from the
 	// cast connection.
 	go a.recvMessages()
@@ -119,6 +150,7 @@ func NewApplication(iface *net.Interface, debug, cacheDisabled bool) *Applicatio
 
 func (a *Application) Application() *cast.Application { return a.application }
 func (a *Application) Media() *cast.Media             { return a.media }
+func (a *Application) Volume() *cast.Volume           { return a.volumeReceiver }
 
 func (a *Application) AddMessageFunc(f CastMessageFunc) {
 	a.messageMu.Lock()
@@ -236,7 +268,10 @@ func (a *Application) Update() error {
 	var err error
 	// Simple retry. We need this for when the device isn't currently
 	// available, but it is likely that it will come up soon.
-	for i := 0; i < 5; i++ {
+	// TODO: This seems to happen when changing media on the cast device,
+	// not sure how to fix but there might be some way of knowing from the
+	// payload?
+	for i := 0; i < a.connectionRetries; i++ {
 		recvStatus, err = a.getReceiverStatus()
 		if err == nil {
 			break

cast/connection.go

@@ -32,10 +32,9 @@ type Connection struct {
 	connected bool
 }
 
-func NewConnection(recvMsgChan chan *pb.CastMessage, debug bool) *Connection {
+func NewConnection(recvMsgChan chan *pb.CastMessage) *Connection {
 	c := &Connection{
 		recvMsgChan: recvMsgChan,
-		debug:       debug,
 		connected:   false,
 	}
 	return c

cmd/utils.go

@@ -65,6 +65,11 @@ func castApplication(cmd *cobra.Command, args []string) (*application.Applicatio
 	dnsTimeoutSeconds, _ := cmd.Flags().GetInt("dns-timeout")
 	useFirstDevice, _ := cmd.Flags().GetBool("first")
 
+	applicationOptions := []application.ApplicationOption{
+		application.WithDebug(debug),
+		application.WithCacheDisabled(disableCache),
+	}
+
 	// If we need to look on a specific network interface for mdns or
 	// for finding a network ip to host from, ensure that the network
 	// interface exists.
@@ -74,6 +79,7 @@ func castApplication(cmd *cobra.Command, args []string) (*application.Applicatio
 		if iface, err = net.InterfaceByName(ifaceName); err != nil {
 			return nil, errors.Wrap(err, fmt.Sprintf("unable to find interface %q", ifaceName))
 		}
+		applicationOptions = append(applicationOptions, application.WithIface(iface))
 	}
 
 	var entry castdns.CastDNSEntry
@@ -116,7 +122,7 @@ func castApplication(cmd *cobra.Command, args []string) (*application.Applicatio
 			Port: p,
 		}
 	}
-	app := application.NewApplication(iface, debug, disableCache)
+	app := application.NewApplication(applicationOptions...)
 	if err := app.Start(entry); err != nil {
 		// NOTE: currently we delete the dns cache every time we get
 		// an error, this is to make sure that if the device gets a new

dns/dns.go

@@ -54,6 +54,22 @@ func (e CastEntry) GetPort() int {
 	return e.Port
 }
 
+// DiscoverCastDNSEntryByName returns the first cast dns device
+// found that matches the name.
+func DiscoverCastDNSEntryByName(ctx context.Context, iface *net.Interface, name string) (CastEntry, error) {
+	castEntryChan, err := DiscoverCastDNSEntries(ctx, iface)
+	if err != nil {
+		return CastEntry{}, err
+	}
+
+	for d := range castEntryChan {
+		if d.DeviceName == name {
+			return d, nil
+		}
+	}
+	return CastEntry{}, fmt.Errorf("No cast device found with name %q", name)
+}
+
 // DiscoverCastDNSEntries will return a channel with any cast dns entries
 // found.
 func DiscoverCastDNSEntries(ctx context.Context, iface *net.Interface) (<-chan CastEntry, error) {