Add translation and TTS caching

tests/test_translation.py

@@ -8,6 +8,7 @@ import httpx
 import pytest
 
 from src.core_utils import TranslationError
+from src import translation
 from src.translation import LMStudioTranslator, TranslationConfig
 
 
@@ -56,7 +57,8 @@ def test_build_contextual_batch_payload_includes_neighboring_segments():
 
     assert payload["model"] == "gemma-3-4b-it"
     assert payload["messages"][0]["role"] == "system"
-    assert "expert audiovisual translator for dubbed video content" in payload["messages"][0]["content"]
+    assert "expert audiovisual translator and dubbing script adapter" in payload["messages"][0]["content"]
+    assert "Preserve segment ids and output order exactly" in payload["messages"][0]["content"]
     assert payload["temperature"] == 0.0
     assert payload["top_p"] == 1.0
     assert user_payload == {
@@ -116,6 +118,29 @@ def test_translate_segments_batches_context_and_preserves_exact_mapping():
     assert [item["id"] for item in requests[1]["segments"]] == ["4", "5", "6"]
 
 
+def test_translate_segments_uses_persistent_cache(tmp_path, monkeypatch):
+    requests = {"count": 0}
+    monkeypatch.setattr(translation, "TRANSLATION_CACHE_DIR", tmp_path)
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        requests["count"] += 1
+        payload = _read_request_json(request)
+        batch_request = json.loads(payload["messages"][1]["content"])
+        translations = [
+            {"id": item["id"], "translated_text": f"cached::{item['text']}"}
+            for item in batch_request["segments"]
+        ]
+        return _mock_batch_response(translations)
+
+    config = TranslationConfig(model="cache-model")
+    first_translator = LMStudioTranslator(config, client=_mock_client(handler))
+    second_translator = LMStudioTranslator(config, client=_mock_client(handler))
+
+    assert first_translator.translate_segments(["hello", "world"], "fr", "en") == ["cached::hello", "cached::world"]
+    assert second_translator.translate_segments(["hello", "world"], "fr", "en") == ["cached::hello", "cached::world"]
+    assert requests["count"] == 1
+
+
 def test_retry_on_transient_http_error_then_succeeds():
     attempts = {"count": 0}