Add contextual compression base classes (langchain-ai#917)

* add

* create entrypoints

Author: dev2049

langchain/scripts/create-entrypoints.js

@@ -101,6 +101,8 @@ const entrypoints = {
   "retrievers/supabase": "retrievers/supabase",
   "retrievers/metal": "retrievers/metal",
   "retrievers/databerry": "retrievers/databerry",
+  "retrievers/contextual_compression": "retrievers/contextual_compression",
+  "retrievers/document_compressors": "retrievers/document_compressors/index",
   // cache
   cache: "cache/index",
   "cache/redis": "cache/redis",

langchain/src/retrievers/contextual_compression.ts

@@ -0,0 +1,33 @@
+import { BaseDocumentCompressor } from "./document_compressors/index.js";
+import { Document } from "../document.js";
+import { BaseRetriever } from "../schema/index.js";
+
+export interface ContextualCompressionRetrieverArgs {
+  baseCompressor: BaseDocumentCompressor;
+  baseRetriever: BaseRetriever;
+}
+
+export class ContextualCompressionRetriever extends BaseRetriever {
+  baseCompressor: BaseDocumentCompressor;
+
+  baseRetriever: BaseRetriever;
+
+  constructor({
+    baseCompressor,
+    baseRetriever,
+  }: ContextualCompressionRetrieverArgs) {
+    super();
+
+    this.baseCompressor = baseCompressor;
+    this.baseRetriever = baseRetriever;
+  }
+
+  async getRelevantDocuments(query: string): Promise<Document[]> {
+    const docs = await this.baseRetriever.getRelevantDocuments(query);
+    const compressedDocs = await this.baseCompressor.compressDocuments(
+      docs,
+      query
+    );
+    return compressedDocs;
+  }
+}

langchain/src/retrievers/document_compressors/index.ts

@@ -0,0 +1,11 @@
+import { Document } from "../../document.js";
+
+/**
+ * Base Document Compression class. All compressors should extend this class.
+ */
+export abstract class BaseDocumentCompressor {
+  abstract compressDocuments(
+    documents: Document[],
+    query: string
+  ): Promise<Document[]>;
+}