feat: SQL agent improvements (#8709)

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Oleg Ivaniv <me@olegivaniv.com>

packages/@n8n/nodes-langchain/utils/descriptions.ts

@@ -0,0 +1,34 @@
+import type { INodeProperties } from 'n8n-workflow';
+
+export const promptTypeOptions: INodeProperties = {
+	displayName: 'Prompt',
+	name: 'promptType',
+	type: 'options',
+	options: [
+		{
+			// eslint-disable-next-line n8n-nodes-base/node-param-display-name-miscased
+			name: 'Take from previous node automatically',
+			value: 'auto',
+			description: 'Looks for an input field called chatInput',
+		},
+		{
+			// eslint-disable-next-line n8n-nodes-base/node-param-display-name-miscased
+			name: 'Define below',
+			value: 'define',
+			description: 'Use an expression to reference data in previous nodes or enter static text',
+		},
+	],
+	default: 'auto',
+};
+
+export const textInput: INodeProperties = {
+	displayName: 'Text',
+	name: 'text',
+	type: 'string',
+	required: true,
+	default: '',
+	placeholder: 'e.g. Hello, how can you help me?',
+	typeOptions: {
+		rows: 2,
+	},
+};

packages/@n8n/nodes-langchain/utils/helpers.ts

@@ -3,6 +3,7 @@ import type { EventNamesAiNodesType, IDataObject, IExecuteFunctions } from 'n8n-
 import { BaseChatModel } from 'langchain/chat_models/base';
 import { BaseChatModel as BaseChatModelCore } from '@langchain/core/language_models/chat_models';
 import type { BaseOutputParser } from '@langchain/core/output_parsers';
+import { BaseMessage } from 'langchain/schema';
 
 export function getMetadataFiltersValues(
 	ctx: IExecuteFunctions,
@@ -77,3 +78,17 @@ export async function logAiEvent(
 		executeFunctions.logger.debug(`Error logging AI event: ${event}`);
 	}
 }
+
+export function serializeChatHistory (chatHistory: Array<BaseMessage>): string {
+	return chatHistory
+		.map((chatMessage) => {
+			if (chatMessage._getType() === 'human') {
+				return `Human: ${chatMessage.content}`;
+			} else if (chatMessage._getType() === 'ai') {
+				return `Assistant: ${chatMessage.content}`;
+			} else {
+				return `${chatMessage.content}`;
+			}
+		})
+		.join('\n');
+}