vscode-extension-samples/chat-sample/src/simple.ts

import { renderPrompt } from '@vscode/prompt-tsx';
import * as vscode from 'vscode';
import { PlayPrompt } from './play';

const CAT_NAMES_COMMAND_ID = 'cat.namesInEditor';
const CAT_PARTICIPANT_ID = 'chat-sample.cat';

interface ICatChatResult extends vscode.ChatResult {
	metadata: {
		command: string;
	}
}

export function registerSimpleParticipant(context: vscode.ExtensionContext) {

	// Define a Cat chat handler.
	const handler: vscode.ChatRequestHandler = async (request: vscode.ChatRequest, context: vscode.ChatContext, stream: vscode.ChatResponseStream, token: vscode.CancellationToken): Promise<ICatChatResult> => {
		// To talk to an LLM in your subcommand handler implementation, your
		// extension can use VS Code's `requestChatAccess` API to access the Copilot API.
		// The GitHub Copilot Chat extension implements this provider.
		if (request.command === 'randomTeach') {
			stream.progress('Picking the right topic to teach...');
			const topic = getTopic(context.history);
			try {
				const messages = [
					vscode.LanguageModelChatMessage.User('You are a cat! Your job is to explain computer science concepts in the funny manner of a cat. Always start your response by stating what concept you are explaining. Always include code samples.'),
					vscode.LanguageModelChatMessage.User(topic)
				];

				const chatResponse = await request.model.sendRequest(messages, {}, token);
				for await (const fragment of chatResponse.text) {
					stream.markdown(fragment);
				}

			} catch (err) {
				handleError(logger, err, stream);
			}

			stream.button({
				command: CAT_NAMES_COMMAND_ID,
				title: vscode.l10n.t('Use Cat Names in Editor')
			});

			logger.logUsage('request', { kind: 'randomTeach' });
			return { metadata: { command: 'randomTeach' } };
		} else if (request.command === 'play') {
			stream.progress('Throwing away the computer science books and preparing to play with some Python code...');
			try {
				// Here's an example of how to use the prompt-tsx library to build a prompt
				const { messages } = await renderPrompt(
					PlayPrompt,
					{ userQuery: request.prompt },
					{ modelMaxPromptTokens: request.model.maxInputTokens },
					request.model);

				const chatResponse = await request.model.sendRequest(messages, {}, token);
				for await (const fragment of chatResponse.text) {
					stream.markdown(fragment);
				}

			} catch (err) {
				handleError(logger, err, stream);
			}

			logger.logUsage('request', { kind: 'play' });
			return { metadata: { command: 'play' } };
		} else {
			try {
				const messages = [
					vscode.LanguageModelChatMessage.User(`You are a cat! Think carefully and step by step like a cat would.
                        Your job is to explain computer science concepts in the funny manner of a cat, using cat metaphors. Always start your response by stating what concept you are explaining. Always include code samples.`),
					vscode.LanguageModelChatMessage.User(request.prompt)
				];

				const chatResponse = await request.model.sendRequest(messages, {}, token);
				for await (const fragment of chatResponse.text) {
					// Process the output from the language model
					// Replace all python function definitions with cat sounds to make the user stop looking at the code and start playing with the cat
					const catFragment = fragment.replaceAll('def', 'meow');
					stream.markdown(catFragment);
				}
			} catch (err) {
				handleError(logger, err, stream);
			}

			logger.logUsage('request', { kind: '' });
			return { metadata: { command: '' } };
		}
	};

	// Chat participants appear as top-level options in the chat input
	// when you type `@`, and can contribute sub-commands in the chat input
	// that appear when you type `/`.
	const cat = vscode.chat.createChatParticipant(CAT_PARTICIPANT_ID, handler);
	cat.iconPath = vscode.Uri.joinPath(context.extensionUri, 'cat.jpeg');
	cat.followupProvider = {
		provideFollowups(_result: ICatChatResult, _context: vscode.ChatContext, _token: vscode.CancellationToken) {
			return [{
				prompt: 'let us play',
				label: vscode.l10n.t('Play with the cat'),
				command: 'play'
			} satisfies vscode.ChatFollowup];
		}
	};

	const logger = vscode.env.createTelemetryLogger({
		sendEventData(eventName, data) {
			// Capture event telemetry
			console.log(`Event: ${eventName}`);
			console.log(`Data: ${JSON.stringify(data)}`);
		},
		sendErrorData(error, data) {
			// Capture error telemetry
			console.error(`Error: ${error}`);
			console.error(`Data: ${JSON.stringify(data)}`);
		}
	});

	context.subscriptions.push(cat.onDidReceiveFeedback((feedback: vscode.ChatResultFeedback) => {
		// Log chat result feedback to be able to compute the success matric of the participant
		// unhelpful / totalRequests is a good success metric
		logger.logUsage('chatResultFeedback', {
			kind: feedback.kind
		});
	}));

	context.subscriptions.push(
		cat,
		// Register the command handler for the /meow followup
		vscode.commands.registerTextEditorCommand(CAT_NAMES_COMMAND_ID, async (textEditor: vscode.TextEditor) => {
			// Replace all variables in active editor with cat names and words
			const text = textEditor.document.getText();

			let chatResponse: vscode.LanguageModelChatResponse | undefined;
			try {
				// Use gpt-4o since it is fast and high quality.
				const [model] = await vscode.lm.selectChatModels({ vendor: 'copilot', family: 'gpt-4o' });
				if (!model) {
					console.log('Model not found. Please make sure the GitHub Copilot Chat extension is installed and enabled.');
					return;
				}

				const messages = [
					vscode.LanguageModelChatMessage.User(`You are a cat! Think carefully and step by step like a cat would.
                    Your job is to replace all variable names in the following code with funny cat variable names. Be creative. IMPORTANT respond just with code. Do not use markdown!`),
					vscode.LanguageModelChatMessage.User(text)
				];
				chatResponse = await model.sendRequest(messages, {}, new vscode.CancellationTokenSource().token);

			} catch (err) {
				if (err instanceof vscode.LanguageModelError) {
					console.log(err.message, err.code, err.cause);
				} else {
					throw err;
				}
				return;
			}

			// Clear the editor content before inserting new content
			await textEditor.edit(edit => {
				const start = new vscode.Position(0, 0);
				const end = new vscode.Position(textEditor.document.lineCount - 1, textEditor.document.lineAt(textEditor.document.lineCount - 1).text.length);
				edit.delete(new vscode.Range(start, end));
			});

			// Stream the code into the editor as it is coming in from the Language Model
			try {
				for await (const fragment of chatResponse.text) {
					await textEditor.edit(edit => {
						const lastLine = textEditor.document.lineAt(textEditor.document.lineCount - 1);
						const position = new vscode.Position(lastLine.lineNumber, lastLine.text.length);
						edit.insert(position, fragment);
					});
				}
			} catch (err) {
				// async response stream may fail, e.g network interruption or server side error
				await textEditor.edit(edit => {
					const lastLine = textEditor.document.lineAt(textEditor.document.lineCount - 1);
					const position = new vscode.Position(lastLine.lineNumber, lastLine.text.length);
					edit.insert(position, (err as Error).message);
				});
			}
		}),
	);
}

// eslint-disable-next-line @typescript-eslint/no-explicit-any
function handleError(logger: vscode.TelemetryLogger, err: any, stream: vscode.ChatResponseStream): void {
	// making the chat request might fail because
	// - model does not exist
	// - user consent not given
	// - quote limits exceeded
	logger.logError(err);

	if (err instanceof vscode.LanguageModelError) {
		console.log(err.message, err.code, err.cause);
		if (err.cause instanceof Error && err.cause.message.includes('off_topic')) {
			stream.markdown(vscode.l10n.t('I\'m sorry, I can only explain computer science concepts.'));
		}
	} else {
		// re-throw other errors so they show up in the UI
		throw err;
	}
}

// Get a random topic that the cat has not taught in the chat history yet
function getTopic(history: ReadonlyArray<vscode.ChatRequestTurn | vscode.ChatResponseTurn>): string {
	const topics = ['linked list', 'recursion', 'stack', 'queue', 'pointers'];
	// Filter the chat history to get only the responses from the cat
	const previousCatResponses = history.filter(h => {
		return h instanceof vscode.ChatResponseTurn && h.participant === CAT_PARTICIPANT_ID;
	}) as vscode.ChatResponseTurn[];
	// Filter the topics to get only the topics that have not been taught by the cat yet
	const topicsNoRepetition = topics.filter(topic => {
		return !previousCatResponses.some(catResponse => {
			return catResponse.response.some(r => {
				return r instanceof vscode.ChatResponseMarkdownPart && r.value.value.includes(topic);
			});
		});
	});

	return topicsNoRepetition[Math.floor(Math.random() * topicsNoRepetition.length)] || 'I have taught you everything I know. Meow!';
}