Update reranker.py (#99)

sage/reranker.py

@@ -20,30 +20,45 @@ class RerankerProvider(Enum):
     VOYAGE = "voyage"
 
 
-def build_reranker(provider: str, model: Optional[str] = None, top_k: Optional[int] = 5) -> BaseDocumentCompressor:
+def build_reranker(provider: str, model: Optional[str] = None, top_k: int = 5) -> Optional[BaseDocumentCompressor]:
     if provider == RerankerProvider.NONE.value:
         return None
+
+    api_key_env_vars = {
+        RerankerProvider.COHERE.value: "COHERE_API_KEY",
+        RerankerProvider.NVIDIA.value: "NVIDIA_API_KEY",
+        RerankerProvider.JINA.value: "JINA_API_KEY",
+        RerankerProvider.VOYAGE.value: "VOYAGE_API_KEY"
+    }
+
+    provider_defaults = {
+        RerankerProvider.HUGGINGFACE.value: "cross-encoder/ms-marco-MiniLM-L-6-v2",
+        RerankerProvider.COHERE.value: "rerank-english-v3.0",
+        RerankerProvider.NVIDIA.value: "nvidia/nv-rerankqa-mistral-4b-v3",
+        RerankerProvider.VOYAGE.value: "rerank-1"
+    }
+
+    model = model or provider_defaults.get(provider)
+
     if provider == RerankerProvider.HUGGINGFACE.value:
-        model = model or "cross-encoder/ms-marco-MiniLM-L-6-v2"
         encoder_model = HuggingFaceCrossEncoder(model_name=model)
         return CrossEncoderReranker(model=encoder_model, top_n=top_k)
-    if provider == RerankerProvider.COHERE.value:
-        if not os.environ.get("COHERE_API_KEY"):
-            raise ValueError("Please set the COHERE_API_KEY environment variable")
-        model = model or "rerank-english-v3.0"
-        return CohereRerank(model=model, cohere_api_key=os.environ.get("COHERE_API_KEY"), top_n=top_k)
-    if provider == RerankerProvider.NVIDIA.value:
-        if not os.environ.get("NVIDIA_API_KEY"):
-            raise ValueError("Please set the NVIDIA_API_KEY environment variable")
-        model = model or "nvidia/nv-rerankqa-mistral-4b-v3"
-        return NVIDIARerank(model=model, api_key=os.environ.get("NVIDIA_API_KEY"), top_n=top_k, truncate="END")
-    if provider == RerankerProvider.JINA.value:
-        if not os.environ.get("JINA_API_KEY"):
-            raise ValueError("Please set the JINA_API_KEY environment variable")
-        return JinaRerank(top_n=top_k)
-    if provider == RerankerProvider.VOYAGE.value:
-        if not os.environ.get("VOYAGE_API_KEY"):
-            raise ValueError("Please set the VOYAGE_API_KEY environment variable")
-        model = model or "rerank-1"
-        return VoyageAIRerank(model=model, api_key=os.environ.get("VOYAGE_API_KEY"), top_k=top_k)
+
+    if provider in api_key_env_vars:
+        api_key = os.getenv(api_key_env_vars[provider])
+        if not api_key:
+            raise ValueError(f"Please set the {api_key_env_vars[provider]} environment variable")
+
+        if provider == RerankerProvider.COHERE.value:
+            return CohereRerank(model=model, cohere_api_key=api_key, top_n=top_k)
+
+        if provider == RerankerProvider.NVIDIA.value:
+            return NVIDIARerank(model=model, api_key=api_key, top_n=top_k, truncate="END")
+
+        if provider == RerankerProvider.JINA.value:
+            return JinaRerank(top_n=top_k)
+
+        if provider == RerankerProvider.VOYAGE.value:
+            return VoyageAIRerank(model=model, api_key=api_key, top_k=top_k)
+
     raise ValueError(f"Invalid reranker provider: {provider}")