fix: discover Chromecast devices via mDNS

go.mod

@@ -33,6 +33,7 @@ require (
 	github.com/atotto/clipboard v0.1.4 // indirect
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/buger/jsonparser v1.2.0 // indirect
+	github.com/cenkalti/backoff v2.2.1+incompatible // indirect
 	github.com/charmbracelet/colorprofile v0.4.3 // indirect
 	github.com/charmbracelet/x/ansi v0.11.7 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.15 // indirect
@@ -53,13 +54,15 @@ require (
 	github.com/gobwas/pool v0.2.1 // indirect
 	github.com/gobwas/ws v1.4.0 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/grandcat/zeroconf v1.0.0 // indirect
 	github.com/h2non/filetype v1.1.3 // indirect
 	github.com/knadh/koanf/maps v0.1.2 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.4.0 // indirect
 	github.com/mattn/go-isatty v0.0.23 // indirect
 	github.com/mattn/go-localereader v0.0.1 // indirect
 	github.com/mattn/go-runewidth v0.0.24 // indirect
+	github.com/miekg/dns v1.1.62 // indirect
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
@@ -75,7 +78,10 @@ require (
 	golang.org/x/crypto v0.54.0 // indirect
 	golang.org/x/exp v0.0.0-20260718201538-764159d718ef // indirect
 	golang.org/x/image v0.44.0 // indirect
+	golang.org/x/mod v0.38.0 // indirect
+	golang.org/x/net v0.57.0 // indirect
 	golang.org/x/sys v0.47.0 // indirect
 	golang.org/x/text v0.40.0 // indirect
+	golang.org/x/tools v0.48.0 // indirect
 	gopkg.in/ini.v1 v1.67.3 // indirect
 )

internal/device/device.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/huin/goupnp"
+	castdns "github.com/vishen/go-chromecast/dns"
 )
 
 type Type string
@@ -68,17 +69,43 @@ func FindInfo(ctx context.Context, timeout time.Duration, dtype Type, name strin
 	return Info{}, fmt.Errorf("device %q (type %s) not found", name, dtype)
 }
 
-// Discover scans the local network for DLNA renderers. (Chromecast discovery
-// requires mDNS which the current dependency set doesn't ship; callers
-// connect to known Chromecast addresses directly.)
+// Discover scans the local network for DLNA and Chromecast renderers.
 func Discover(ctx context.Context, timeout time.Duration) ([]Info, error) {
 	ctx, cancel := context.WithTimeout(ctx, timeout)
 	defer cancel()
 
+	type result struct {
+		kind    Type
+		devices []Info
+		err     error
+	}
+	results := make(chan result, 2)
+
+	go func() {
+		devices, err := discoverDLNA(ctx)
+		results <- result{kind: TypeDLNA, devices: devices, err: err}
+	}()
+	go func() {
+		devices, err := discoverChromecasts(ctx)
+		results <- result{kind: TypeChromecast, devices: devices, err: err}
+	}()
+
+	var devices []Info
+	for range 2 {
+		result := <-results
+		if result.err != nil {
+			slog.WarnContext(ctx, "device discovery error", "type", result.kind, "error", result.err)
+			continue
+		}
+		devices = append(devices, result.devices...)
+	}
+	return devices, nil
+}
+
+func discoverDLNA(ctx context.Context) ([]Info, error) {
 	results, err := goupnp.DiscoverDevicesCtx(ctx, "urn:schemas-upnp-org:device:MediaRenderer:1")
 	if err != nil {
-		slog.WarnContext(ctx, "DLNA discovery error", "error", err)
-		return nil, nil
+		return nil, err
 	}
 
 	devices := make([]Info, 0, len(results))
@@ -94,3 +121,31 @@ func Discover(ctx context.Context, timeout time.Duration) ([]Info, error) {
 	}
 	return devices, nil
 }
+
+func discoverChromecasts(ctx context.Context) ([]Info, error) {
+	entries, err := castdns.DiscoverCastDNSEntries(ctx, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	var devices []Info
+	for entry := range entries {
+		info, ok := chromecastInfo(entry)
+		if !ok {
+			continue
+		}
+		devices = append(devices, info)
+	}
+	return devices, nil
+}
+
+func chromecastInfo(entry castdns.CastEntry) (Info, bool) {
+	if entry.DeviceName == "" || entry.AddrV4 == nil {
+		return Info{}, false
+	}
+	return Info{
+		Name:    entry.DeviceName,
+		Type:    TypeChromecast,
+		Address: entry.AddrV4.String(),
+	}, true
+}

internal/device/device_test.go

@@ -0,0 +1,30 @@
+package device
+
+import (
+	"net"
+	"testing"
+
+	castdns "github.com/vishen/go-chromecast/dns"
+)
+
+func TestChromecastInfo(t *testing.T) {
+	entry := castdns.CastEntry{
+		DeviceName: "Office Display",
+		AddrV4:     net.ParseIP("192.0.2.10"),
+	}
+
+	got, ok := chromecastInfo(entry)
+	if !ok {
+		t.Fatal("chromecastInfo() rejected a complete entry")
+	}
+	want := Info{Name: "Office Display", Type: TypeChromecast, Address: "192.0.2.10"}
+	if got != want {
+		t.Errorf("chromecastInfo() = %+v, want %+v", got, want)
+	}
+}
+
+func TestChromecastInfoRejectsIncompleteEntry(t *testing.T) {
+	if _, ok := chromecastInfo(castdns.CastEntry{DeviceName: "Office Display"}); ok {
+		t.Error("chromecastInfo() accepted an entry without an IPv4 address")
+	}
+}