feat(doc-stores): Add support for InMemoryDocStore (#127)

packages/langchain/lib/src/documents/documents.dart

@@ -2,5 +2,6 @@ export 'embeddings/embeddings.dart';
 export 'loaders/loaders.dart';
 export 'models/models.dart';
 export 'retrievers/retrievers.dart';
+export 'stores/stores.dart';
 export 'transformers/transformers.dart';
 export 'vector_stores/vector_stores.dart';

packages/langchain/lib/src/documents/stores/base.dart

@@ -0,0 +1,18 @@
+import '../models/models.dart';
+
+/// {@template doc_store}
+/// Interface to access to place that stores documents.
+/// {@endtemplate}
+abstract interface class DocStore {
+  /// {@macro doc_store}
+  const DocStore();
+
+  /// Search for document.
+  Future<Document> search(final String query);
+
+  /// Adds documents.
+  Future<void> add(final Map<String, Document> documents);
+
+  /// Deletes documents by id.
+  Future<void> delete(final List<String> ids);
+}

packages/langchain/lib/src/documents/stores/in_memory.dart

@@ -0,0 +1,34 @@
+import '../../utils/exception.dart';
+import '../models/models.dart';
+import 'base.dart';
+
+/// {@template in_memory_doc_store}
+/// Simple in memory [DocStore] in the form of a map.
+/// {@endtemplate}
+class InMemoryDocStore implements DocStore {
+  /// {@macro in_memory_doc_store}
+  InMemoryDocStore(
+    final Map<String, Document>? initialDocuments,
+  ) : _documents = {...?initialDocuments};
+
+  final Map<String, Document> _documents;
+
+  @override
+  Future<Document> search(final String query) async {
+    final doc = _documents[query];
+    if (doc == null) {
+      throw LangChainException(message: 'Document  with id=$query not found');
+    }
+    return doc;
+  }
+
+  @override
+  Future<void> add(final Map<String, Document> documents) async {
+    _documents.addAll(documents);
+  }
+
+  @override
+  Future<void> delete(final List<String> ids) async {
+    ids.forEach(_documents.remove);
+  }
+}

packages/langchain/lib/src/documents/stores/stores.dart

@@ -0,0 +1,2 @@
+export 'base.dart';
+export 'in_memory.dart';

packages/langchain/test/documents/stores/in_memory.dart

@@ -0,0 +1,55 @@
+import 'package:langchain/langchain.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('InMemoryDocStore tests', () {
+    late InMemoryDocStore store;
+
+    final Map<String, Document> initialDocs = {
+      'doc1': const Document(
+        id: 'doc1',
+        pageContent: 'content',
+        metadata: {'author': 'Author1'},
+      ),
+      'doc2': const Document(
+        id: 'doc2',
+        pageContent: 'content',
+        metadata: {'author': 'Author2'},
+      ),
+    };
+
+    setUp(() {
+      store = InMemoryDocStore(initialDocs);
+    });
+
+    test('search returns the correct document for an existing id', () async {
+      final doc = await store.search('doc1');
+      expect(doc, equals(initialDocs['doc1']));
+    });
+
+    test('search throws an exception for a non-existent id', () async {
+      expect(
+        () => store.search('non-existent'),
+        throwsA(isA<LangChainException>()),
+      );
+    });
+
+    test('add inserts new documents into the document store', () async {
+      final newDocs = {
+        'doc3': const Document(id: 'doc3', pageContent: 'content3'),
+        'doc4': const Document(id: 'doc4', pageContent: 'content4'),
+      };
+
+      await store.add(newDocs);
+
+      expect(await store.search('doc3'), equals(newDocs['doc3']));
+      expect(await store.search('doc4'), equals(newDocs['doc4']));
+    });
+
+    test('delete removes documents from the document store', () async {
+      await store.delete(['doc1']);
+
+      expect(() => store.search('doc1'), throwsA(isA<LangChainException>()));
+    });
+  });
+}