task 002: centralize Gemini voice fallbacks

2 files changed, 78 insertions, 0 deletions

diff --git a/internal/audio/fallbacks.go b/internal/audio/fallbacks.go
new file mode 100644
index 0000000..bd0c86e
--- /dev/null
+++ b/internal/audio/fallbacks.go
@@ -0,0 +1,29 @@
+package audio
+
+import (
+	"fmt"
+	"strings"
+)
+
+// RunWithVoiceFallbacks tries the selected Gemini voice first, then the remaining known voices.
+func RunWithVoiceFallbacks(initialVoice string, generate func(voice string) error) (usedVoice string, err error) {
+	attempted := make([]string, 0, len(GeminiVoices))
+	var lastErr error
+
+	for _, voice := range GeminiVoiceFallbacks(initialVoice) {
+		attempted = append(attempted, voice)
+
+		err := generate(voice)
+		if err == nil {
+			return voice, nil
+		}
+		if !IsGeminiNoAudioDataError(err) {
+			return "", err
+		}
+
+		lastErr = err
+		fmt.Printf("Warning: Gemini returned no audio for voice %s\n", voice)
+	}
+
+	return "", fmt.Errorf("Gemini returned no audio for voices %s: %w", strings.Join(attempted, ", "), lastErr)
+}
diff --git a/internal/audio/voices_test.go b/internal/audio/voices_test.go
index ea0f797..5e940d0 100644
--- a/internal/audio/voices_test.go
+++ b/internal/audio/voices_test.go
@@ -1,10 +1,13 @@
 package audio
 
 import (
+	"errors"
 	"reflect"
 	"testing"
 )
 
+var errTestSentinel = errors.New("test sentinel error")
+
 func TestVoiceLists(t *testing.T) {
 	t.Parallel()
 
@@ -57,3 +60,49 @@ func TestGeminiVoiceFallbacks(t *testing.T) {
 		}
 	})
 }
+
+func TestRunWithVoiceFallbacks(t *testing.T) {
+	originalVoices := append([]string(nil), GeminiVoices...)
+	t.Cleanup(func() {
+		GeminiVoices = originalVoices
+	})
+	GeminiVoices = []string{"Charon", "Kore", "Leda"}
+
+	t.Run("retries no-audio errors until success", func(t *testing.T) {
+		var attempted []string
+		usedVoice, err := RunWithVoiceFallbacks("Charon", func(voice string) error {
+			attempted = append(attempted, voice)
+			if voice == "Charon" {
+				return ErrGeminiNoAudioData
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatalf("RunWithVoiceFallbacks() unexpected error: %v", err)
+		}
+		if usedVoice != "Kore" {
+			t.Fatalf("used voice = %q, want %q", usedVoice, "Kore")
+		}
+		if got, want := attempted, []string{"Charon", "Kore"}; !reflect.DeepEqual(got, want) {
+			t.Fatalf("attempted voices = %#v, want %#v", got, want)
+		}
+	})
+
+	t.Run("returns non-retryable errors immediately", func(t *testing.T) {
+		sentinel := errTestSentinel
+		var attempted []string
+		usedVoice, err := RunWithVoiceFallbacks("Charon", func(voice string) error {
+			attempted = append(attempted, voice)
+			return sentinel
+		})
+		if !errors.Is(err, sentinel) {
+			t.Fatalf("error = %v, want %v", err, sentinel)
+		}
+		if usedVoice != "" {
+			t.Fatalf("used voice = %q, want empty", usedVoice)
+		}
+		if got, want := attempted, []string{"Charon"}; !reflect.DeepEqual(got, want) {
+			t.Fatalf("attempted voices = %#v, want %#v", got, want)
+		}
+	})
+}