zi: add Gemini audio attribution helper

2 files changed, 69 insertions, 2 deletions

diff --git a/internal/audio/attribution.go b/internal/audio/attribution.go
index 80f2bc3..7c3cda2 100644
--- a/internal/audio/attribution.go
+++ b/internal/audio/attribution.go
@@ -7,7 +7,7 @@ import (
 	"time"
 )
 
-// AttributionParams describes metadata included in OpenAI TTS attribution files.
+// AttributionParams describes metadata included in generated audio attribution files.
 type AttributionParams struct {
 	Word          string
 	Model         string
@@ -25,8 +25,18 @@ func AttributionPath(audioFile string) string {
 
 // BuildOpenAIAttribution builds the attribution content for OpenAI-generated audio.
 func BuildOpenAIAttribution(params AttributionParams) string {
+	return buildAttribution("Audio generated by OpenAI TTS", params)
+}
+
+// BuildGeminiAttribution builds the attribution content for Gemini-generated audio.
+func BuildGeminiAttribution(params AttributionParams) string {
+	return buildAttribution("Audio generated by Google Gemini TTS", params)
+}
+
+func buildAttribution(header string, params AttributionParams) string {
 	var b strings.Builder
-	b.WriteString("Audio generated by OpenAI TTS\n\n")
+	b.WriteString(header)
+	b.WriteString("\n\n")
 	fmt.Fprintf(&b, "Bulgarian word: %s\n", params.Word)
 	fmt.Fprintf(&b, "Model: %s\n", params.Model)
 	fmt.Fprintf(&b, "Voice: %s\n", params.Voice)
diff --git a/internal/audio/attribution_test.go b/internal/audio/attribution_test.go
new file mode 100644
index 0000000..2e310b4
--- /dev/null
+++ b/internal/audio/attribution_test.go
@@ -0,0 +1,57 @@
+package audio
+
+import (
+	"testing"
+	"time"
+)
+
+func TestBuildAttribution(t *testing.T) {
+	params := AttributionParams{
+		Word:          "ябълка",
+		Model:         "gpt-4o-mini-tts",
+		Voice:         "alloy",
+		Instruction:   "Speak clearly.",
+		ProcessedText: "ябълка...",
+		Speed:         1.25,
+		GeneratedAt:   time.Date(2026, time.April, 1, 15, 4, 5, 0, time.UTC),
+	}
+
+	tests := []struct {
+		name string
+		got  string
+		want string
+	}{
+		{
+			name: "openai",
+			got:  BuildOpenAIAttribution(params),
+			want: "Audio generated by OpenAI TTS\n\n" +
+				"Bulgarian word: ябълка\n" +
+				"Model: gpt-4o-mini-tts\n" +
+				"Voice: alloy\n" +
+				"Speed: 1.25\n\n" +
+				"Voice instructions:\nSpeak clearly.\n\n" +
+				"Processed text sent to TTS: ябълка...\n\n" +
+				"Generated at: 2026-04-01 15:04:05\n",
+		},
+		{
+			name: "gemini",
+			got:  BuildGeminiAttribution(params),
+			want: "Audio generated by Google Gemini TTS\n\n" +
+				"Bulgarian word: ябълка\n" +
+				"Model: gpt-4o-mini-tts\n" +
+				"Voice: alloy\n" +
+				"Speed: 1.25\n\n" +
+				"Voice instructions:\nSpeak clearly.\n\n" +
+				"Processed text sent to TTS: ябълка...\n\n" +
+				"Generated at: 2026-04-01 15:04:05\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.got != tt.want {
+				t.Fatalf("unexpected attribution output\nwant:\n%q\n\ngot:\n%q", tt.want, tt.got)
+			}
+		})
+	}
+}