community: Add PolygonAPIWrapper and get_last_quote endpoint (#15971)

- **Description:** Added a `PolygonAPIWrapper` and an initial
`get_last_quote` endpoint, which allows us to get the last price quote
for a given `ticker`. Once merged, I can add a Polygon tool in `tools/`
for agents to use.
- **Twitter handle:** [@virattt](https://twitter.com/virattt)

The Polygon.io Stocks API provides REST endpoints that let you query the
latest market data from all US stock exchanges.

libs/community/langchain_community/utilities/polygon.py

@@ -0,0 +1,46 @@
+"""
+Util that calls several of Polygon's stock market REST APIs.
+Docs: https://polygon.io/docs/stocks/getting-started
+"""
+import json
+from typing import Dict, Optional
+
+import requests
+from langchain_core.pydantic_v1 import BaseModel, root_validator
+from langchain_core.utils import get_from_dict_or_env
+
+POLYGON_BASE_URL = "https://api.polygon.io/"
+
+
+class PolygonAPIWrapper(BaseModel):
+    """Wrapper for Polygon API."""
+
+    polygon_api_key: Optional[str] = None
+
+    @root_validator()
+    def validate_environment(cls, values: Dict) -> Dict:
+        """Validate that api key in environment."""
+        polygon_api_key = get_from_dict_or_env(
+            values, "polygon_api_key", "POLYGON_API_KEY"
+        )
+        values["polygon_api_key"] = polygon_api_key
+
+        return values
+
+    def get_last_quote(self, ticker: str) -> Optional[dict]:
+        """Get the most recent National Best Bid and Offer (Quote) for a ticker."""
+        url = f"{POLYGON_BASE_URL}v2/last/nbbo/{ticker}?apiKey={self.polygon_api_key}"
+        response = requests.get(url)
+        data = response.json()
+
+        status = data.get("status", None)
+        if status != "OK":
+            raise ValueError(f"API Error: {data}")
+
+        return data.get("results", None)
+
+    def run(self, mode: str, ticker: str) -> str:
+        if mode == "get_last_quote":
+            return json.dumps(self.get_last_quote(ticker))
+        else:
+            raise ValueError(f"Invalid mode {mode} for Polygon API.")