feat: add model modules

backend/src/models/__init__.py

@@ -0,0 +1,3 @@
+from .factory import create_chat_model
+
+__all__ = ["create_chat_model"]

backend/src/models/factory.py

@@ -0,0 +1,43 @@
+from langchain.chat_models import BaseChatModel
+
+from src.config import get_app_config
+from src.reflection import resolve_class
+
+
+def create_chat_model(
+    name: str | None = None, thinking_enabled: bool = False, **kwargs
+) -> BaseChatModel:
+    """Create a chat model instance from the config.
+
+    Args:
+        name: The name of the model to create. If None, the first model in the config will be used.
+
+    Returns:
+        A chat model instance.
+    """
+    config = get_app_config()
+    if name is None:
+        name = config.models[0].name
+    model_config = config.get_model_config(name)
+    if model_config is None:
+        raise ValueError(f"Model {name} not found in config") from None
+    model_class = resolve_class(model_config.use, BaseChatModel)
+    model_settings_from_config = model_config.model_dump(
+        exclude_none=True,
+        exclude={
+            "use",
+            "name",
+            "display_name",
+            "description",
+            "supports_thinking",
+            "when_thinking_enabled",
+        },
+    )
+    if thinking_enabled and model_config.when_thinking_enabled is not None:
+        if not model_config.supports_thinking:
+            raise ValueError(
+                f"Model {name} does not support thinking. Set `supports_thinking` to true in the `config.yaml` to enable thinking."
+            ) from None
+        model_settings_from_config.update(model_config.when_thinking_enabled)
+    model_instance = model_class(**kwargs, **model_settings_from_config)
+    return model_instance