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

import * as vscode from 'vscode';

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

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

const MODEL_SELECTOR: vscode.LanguageModelChatSelector = { vendor: 'copilot', family: 'gpt-3.5-turbo' };

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);
            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 [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
            const chatResponse = await model.sendRequest(messages, {}, token);
            for await (const fragment of chatResponse.text) {
                stream.markdown(fragment);
            }

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

            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...');
            const messages = [
                vscode.LanguageModelChatMessage.User('You are a cat! Reply in the voice of a cat, using cat analogies when appropriate. Be concise to prepare for cat play time.'),
                vscode.LanguageModelChatMessage.User('Give a small random python code samples (that have cat names for variables). ' + request.prompt)
            ];
            const [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
            const chatResponse = await model.sendRequest(messages, {}, token);
            for await (const fragment of chatResponse.text) {
                stream.markdown(fragment);
            }
            return { metadata: { command: 'play' } };
        } else {
            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 [model] = await vscode.lm.selectChatModels(MODEL_SELECTOR);
            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);
            }

            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];
        }
    };

    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();
            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)
            ];

            let chatResponse: vscode.LanguageModelChatResponse | undefined;
            try {
                const [model] = await vscode.lm.selectChatModels({ vendor: 'copilot', family: 'gpt-3.5-turbo' });
                chatResponse = await model.sendRequest(messages, {}, new vscode.CancellationTokenSource().token);

            } catch (err) {
                // making the chat request might fail because
                // - model does not exist
                // - user consent not given
                // - quote limits exceeded
                if (err instanceof vscode.LanguageModelError) {
                    console.log(err.message, err.code, err.cause)
                }
                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);
                });
            }
        }),
    );
}

// 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() { }