vscode-extension-samples/chat-sample/src/extension.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;
    }
}

// Use gpt-4o since it is fast and high quality. gpt-3.5-turbo and gpt-4 are also available.
const MODEL_SELECTOR: vscode.LanguageModelChatSelector = { vendor: 'copilot', family: 'gpt-4o' };

export function activate(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 === 'teach') {
            stream.progress('Picking the right topic to teach...');
            const topic = getTopic(context.history);
            try {
                // To get a list of all available models, do not pass any selector to the selectChatModels.
                const [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
                if (model) {
                    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 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: 'teach'});
            return { metadata: { command: 'teach' } };
        } else if (request.command === 'play') {
            stream.progress('Throwing away the computer science books and preparing to play with some Python code...');
            try {
                const [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
                if (model) {
                    // 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: model.maxInputTokens },
                        model);
                    
                    const chatResponse = await 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 [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
                if (model) {
                    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 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 {
                const [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
                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, (<Error>err).message);
                });
            }
        }),
    );
}

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!';
}

export function deactivate() { }