Enable model & API key update in SlideDeckAI

src/slidedeckai/core.py

@@ -114,6 +114,7 @@ class SlideDeckAI:
         self.template_idx: int = template_idx if 0 <= template_idx < num_templates else 0
         self.chat_history = ChatMessageHistory()
         self.last_response = None
+        logger.info('Using model: %s', model)
 
     def _initialize_llm(self):
         """
@@ -264,6 +265,27 @@ class SlideDeckAI:
 
         return path
 
+    def set_model(self, model_name: str, api_key: str = None):
+        """
+        Set the LLM model (and API key) to use.
+
+        Args:
+            model_name: The name of the model to use.
+            api_key: The API key for the LLM provider.
+
+        Raises:
+            ValueError: If the model name is not in VALID_MODELS.
+        """
+        if model_name not in GlobalConfig.VALID_MODELS:
+            raise ValueError(
+                f'Invalid model name: {model_name}.'
+                f' Must be one of: {", ".join(VALID_MODEL_NAMES)}.'
+            )
+        self.model = model_name
+        if api_key:
+            self.api_key = api_key
+        logger.debug('Model set to: %s', model_name)
+
     def set_template(self, idx):
         """
         Set the PowerPoint template to use.

tests/unit/test_core.py

@@ -93,6 +93,52 @@ def test_slide_deck_ai_init_valid(slide_deck_ai):
     assert slide_deck_ai.template_idx == 0
 
 
+@mock.patch.dict(
+    'slidedeckai.core.GlobalConfig.VALID_MODELS',
+    {
+        '[or]openai/gpt-3.5-turbo': ('openai', 'gpt-3.5-turbo'),
+        'new-valid-model': ('openai', 'gpt-test')
+    }
+)
+def test_set_model_valid_updates_model(slide_deck_ai) -> None:
+    """Test that set_model updates the model name and keeps api_key when
+    no new api_key is provided.
+
+    This test patches GlobalConfig.VALID_MODELS to a small controlled set so
+    model validation is deterministic.
+    """
+    original_api_key = slide_deck_ai.api_key
+
+    slide_deck_ai.set_model('new-valid-model')
+
+    assert slide_deck_ai.model == 'new-valid-model'
+    assert slide_deck_ai.api_key == original_api_key
+
+
+@mock.patch.dict(
+    'slidedeckai.core.GlobalConfig.VALID_MODELS',
+    {
+        '[or]openai/gpt-3.5-turbo': ('openai', 'gpt-3.5-turbo'),
+        'new-valid-model': ('openai', 'gpt-test')
+    }
+)
+def test_set_model_valid_updates_api_key(slide_deck_ai) -> None:
+    """Test that set_model updates both the model name and the api_key when
+    an api_key is provided explicitly.
+    """
+    slide_deck_ai.set_model('new-valid-model', api_key='new-key')
+
+    assert slide_deck_ai.model == 'new-valid-model'
+    assert slide_deck_ai.api_key == 'new-key'
+
+
+def test_set_model_invalid_raises(slide_deck_ai) -> None:
+    """Test that set_model raises ValueError for an invalid model name."""
+    with pytest.raises(ValueError) as exc_info:
+        slide_deck_ai.set_model('clearly-invalid-model-name')
+    assert 'Invalid model name' in str(exc_info.value)
+
+
 @mock.patch('slidedeckai.core.llm_helper.get_provider_model')
 @mock.patch('slidedeckai.core.llm_helper.get_litellm_llm')
 def test_generate_slide_deck(mock_get_llm, mock_get_provider, mock_temp_file, slide_deck_ai):
@@ -108,7 +154,7 @@ def test_generate_slide_deck(mock_get_llm, mock_get_provider, mock_temp_file, sl
 
 @mock.patch('slidedeckai.core.llm_helper.get_provider_model')
 @mock.patch('slidedeckai.core.llm_helper.get_litellm_llm')
-def test_revise_slide_deck(mock_get_llm, mock_get_provider, mock_temp_file, slide_deck_ai):
+def test_slide_deck(mock_get_llm, mock_get_provider, mock_temp_file, slide_deck_ai):
     """Test revising a slide deck."""
     # Setup mocks
     mock_get_provider.return_value = ('openai', 'gpt-3.5-turbo')