feat: Add AI tool building capabilities (#7336)

Github issue / Community forum post (link here to close automatically):
https://community.n8n.io/t/langchain-memory-chat/23733

---------

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Val <68596159+valya@users.noreply.github.com>
Co-authored-by: Alex Grozav <alex@grozav.com>
Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>
Co-authored-by: Deborah <deborah@starfallprojects.co.uk>
Co-authored-by: Jesper Bylund <mail@jesperbylund.com>
Co-authored-by: Jon <jonathan.bennetts@gmail.com>
Co-authored-by: Michael Kret <88898367+michael-radency@users.noreply.github.com>
Co-authored-by: Giulio Andreini <andreini@netseven.it>
Co-authored-by: Mason Geloso <Mason.geloso@gmail.com>
Co-authored-by: Mason Geloso <hone@Masons-Mac-mini.local>
Co-authored-by: Mutasem Aldmour <mutasem@n8n.io>

packages/@n8n/nodes-langchain/nodes/memory/MemoryChatRetriever/MemoryChatRetriever.node.ts

@@ -0,0 +1,104 @@
+/* eslint-disable n8n-nodes-base/node-dirname-against-convention */
+import {
+	NodeConnectionType,
+	type IDataObject,
+	type IExecuteFunctions,
+	type INodeExecutionData,
+	type INodeType,
+	type INodeTypeDescription,
+} from 'n8n-workflow';
+import type { BaseChatMemory } from 'langchain/memory';
+import type { BaseMessage } from 'langchain/schema';
+
+function simplifyMessages(messages: BaseMessage[]) {
+	const chunkedMessages = [];
+	for (let i = 0; i < messages.length; i += 2) {
+		chunkedMessages.push([messages[i], messages[i + 1]]);
+	}
+
+	const transformedMessages = chunkedMessages.map((exchange) => {
+		const simplified = {
+			[exchange[0]._getType()]: exchange[0].content,
+		};
+
+		if (exchange[1]) {
+			simplified[exchange[1]._getType()] = exchange[1].content;
+		}
+
+		return {
+			json: simplified,
+		};
+	});
+	return transformedMessages;
+}
+
+export class MemoryChatRetriever implements INodeType {
+	description: INodeTypeDescription = {
+		displayName: 'Chat Messages Retriever',
+		name: 'memoryChatRetriever',
+		icon: 'fa:database',
+		group: ['transform'],
+		version: 1,
+		description: 'Retrieve chat messages from memory and use them in the workflow',
+		defaults: {
+			name: 'Chat Messages Retriever',
+		},
+		codex: {
+			categories: ['AI'],
+			subcategories: {
+				AI: ['Miscellaneous'],
+			},
+			resources: {
+				primaryDocumentation: [
+					{
+						url: 'https://docs.n8n.io/integrations/builtin/cluster-nodes/sub-nodes/n8n-nodes-langchain.memorychatretriever/',
+					},
+				],
+			},
+		},
+		// eslint-disable-next-line n8n-nodes-base/node-class-description-inputs-wrong-regular-node
+		inputs: [
+			NodeConnectionType.Main,
+			{
+				displayName: 'Memory',
+				maxConnections: 1,
+				type: NodeConnectionType.AiMemory,
+				required: true,
+			},
+		],
+		// eslint-disable-next-line n8n-nodes-base/node-class-description-outputs-wrong
+		outputs: [NodeConnectionType.Main],
+		properties: [
+			{
+				displayName: 'Simplify Output',
+				name: 'simplifyOutput',
+				type: 'boolean',
+				description: 'Whether to simplify the output to only include the sender and the text',
+				default: true,
+			},
+		],
+	};
+
+	async execute(this: IExecuteFunctions): Promise<INodeExecutionData[][]> {
+		this.logger.verbose('Executing Chat Memory Retriever');
+
+		const memory = (await this.getInputConnectionData(NodeConnectionType.AiMemory, 0)) as
+			| BaseChatMemory
+			| undefined;
+		const simplifyOutput = this.getNodeParameter('simplifyOutput', 0) as boolean;
+
+		const messages = await memory?.chatHistory.getMessages();
+
+		if (simplifyOutput && messages) {
+			return this.prepareOutputData(simplifyMessages(messages));
+		}
+
+		const serializedMessages =
+			messages?.map((message) => {
+				const serializedMessage = message.toJSON();
+				return { json: serializedMessage as unknown as IDataObject };
+			}) ?? [];
+
+		return this.prepareOutputData(serializedMessages);
+	}
+}