community: Factorize AstraDB components constructors (#16779)

* Adds `AstraDBEnvironment` class and use it in `AstraDBLoader`,
`AstraDBCache`, `AstraDBSemanticCache`, `AstraDBBaseStore` and
`AstraDBChatMessageHistory`
* Create an `AsyncAstraDB` if we only have an `AstraDB` and vice-versa
so:
  * we always have an instance of `AstraDB`
* we always have an instance of `AsyncAstraDB` for recent versions of
astrapy
* Create collection if not exists in `AstraDBBaseStore`
* Some typing improvements

Note: `AstraDB` `VectorStore` not using `AstraDBEnvironment` at the
moment. This will be done after the `langchain-astradb` package is out.

libs/community/langchain_community/utilities/astradb.py

@@ -0,0 +1,84 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Optional
+
+if TYPE_CHECKING:
+    from astrapy.db import (
+        AstraDB,
+        AsyncAstraDB,
+    )
+
+
+class AstraDBEnvironment:
+    def __init__(
+        self,
+        token: Optional[str] = None,
+        api_endpoint: Optional[str] = None,
+        astra_db_client: Optional[AstraDB] = None,
+        async_astra_db_client: Optional[AsyncAstraDB] = None,
+        namespace: Optional[str] = None,
+    ) -> None:
+        self.token = token
+        self.api_endpoint = api_endpoint
+        astra_db = astra_db_client
+        self.async_astra_db = async_astra_db_client
+        self.namespace = namespace
+
+        from astrapy import db
+
+        try:
+            from astrapy.db import AstraDB
+        except (ImportError, ModuleNotFoundError):
+            raise ImportError(
+                "Could not import a recent astrapy python package. "
+                "Please install it with `pip install --upgrade astrapy`."
+            )
+
+        supports_async = hasattr(db, "AsyncAstraDB")
+
+        # Conflicting-arg checks:
+        if astra_db_client is not None or async_astra_db_client is not None:
+            if token is not None or api_endpoint is not None:
+                raise ValueError(
+                    "You cannot pass 'astra_db_client' or 'async_astra_db_client' to "
+                    "AstraDBEnvironment if passing 'token' and 'api_endpoint'."
+                )
+
+        if token and api_endpoint:
+            astra_db = AstraDB(
+                token=self.token,
+                api_endpoint=self.api_endpoint,
+                namespace=self.namespace,
+            )
+            if supports_async:
+                self.async_astra_db = db.AsyncAstraDB(
+                    token=self.token,
+                    api_endpoint=self.api_endpoint,
+                    namespace=self.namespace,
+                )
+
+        if astra_db:
+            self.astra_db = astra_db
+        else:
+            if self.async_astra_db:
+                self.astra_db = AstraDB(
+                    token=self.async_astra_db.token,
+                    api_endpoint=self.async_astra_db.base_url,
+                    api_path=self.async_astra_db.api_path,
+                    api_version=self.async_astra_db.api_version,
+                    namespace=self.async_astra_db.namespace,
+                )
+            else:
+                raise ValueError(
+                    "Must provide 'astra_db_client' or 'async_astra_db_client' or "
+                    "'token' and 'api_endpoint'"
+                )
+
+        if not self.async_astra_db and self.astra_db and supports_async:
+            self.async_astra_db = db.AsyncAstraDB(
+                token=self.astra_db.token,
+                api_endpoint=self.astra_db.base_url,
+                api_path=self.astra_db.api_path,
+                api_version=self.astra_db.api_version,
+                namespace=self.astra_db.namespace,
+            )