Using OpenAI's Function Calling with a JavaScript Fetch API.

openai-function-calling.js

//
// Import Modules
//
const pubnub = require('pubnub');
const xhr = require('xhr');
const vault = require('vault');

//
// Request Event Handler (Main)
//
export default (request, response) => {
    // Natural language request input for AI model
    let naturalCommand = request.body; 

    // Ask AI to make decisions and provide progress updates
    return getOpenaiApiKey().then(apikey => {
        return openAI(naturalCommand).then(aiResponse => {
            console.log("OPENAI TASK RESULT:", aiResponse);
            return response.send(aiResponse);
        });
    });
};

//
// Get API Key for OpenAI
// Key is populated via Vault Secret Manager
//
let OPENAI_API_KEY = null; 
function getOpenaiApiKey() {
    // Use cached key
    if (OPENAI_API_KEY) {
        return new Promise(resolve => resolve(OPENAI_API_KEY));
    }
    // Fetch key from vault
    return vault.get("OPENAI_API_KEY").then(apikey => {
        OPENAI_API_KEY = apikey;
        return new Promise(resolve => resolve(OPENAI_API_KEY));
    });
}

//
// Publish a Message to a Channel
//
function publishMessage(channel, message) {
    return pubnub.publish({
        channel: channel,
        message: message,
    });
}
publishMessage.instructions = {
    "name": "publishMessage",
    "description": "Send a message to a channel",
    "parameters": {
        "type": "object",
        "properties": {
            "channel": {
                "type": "string",
                "description": "The name of the channel to send a message to",
            },
            "message": {"type": "object", "properties": {
                "text" : { "type": "string", "description": "The message text that will be sent to the channel"}
            }},
        },
        "required": ["channel", "message"],
    }
};

//
// Get the Last Message from a Channel
//
function lastMessage(channel) {
    return pubnub.history({
        channel: channel,
        count: 1,
    });
}
lastMessage.instructions = {
    "name": "lastMessage",
    "description": "Get the most recent message that was sent to a channel",
    "parameters": {
        "type": "object",
        "properties": {
            "channel": {
                "type": "string",
                "description": "The name of the channel to send a message to",
            },
        },
        "required": ["channel"],
    }
};

//
// API Call to OpenAI asking the AI to run functions if it thinks it needs to
//
function openAI(naturalCommand, messages) {
    // Generate Function Instructions for the AI
    const functions = [publishMessage, lastMessage].map(fn => fn.instructions);
    const url = 'https://api.openai.com/v1/chat/completions';
    let msgs = messages || [{"role": "user", "content": naturalCommand}];
    const http_options = {
        'method': 'POST',
        'headers': { 
            "Content-Type": "application/json",
            "Authorization": `Bearer ${OPENAI_API_KEY}`,
         },
        'body': JSON.stringify({
            "model": "gpt-3.5-turbo-0613",
            "messages": msgs,
            "functions": functions,
            "function_call": "auto",
        }),
    };

    return xhr.fetch(url, http_options)
        .then((resp) => {
            const body = JSON.parse(resp.body);
            const function_call = body.choices[0].finish_reason === "function_call";
            const message = body.choices[0].message;

            // Call function and resend to OpenAI the result
            if (function_call) {
                return handelFunctionCalls(message).then(result => {
                    msgs.push(message);
                    msgs.push({
                        "role": "function",
                        "name": message.function_call.name,
                        "content": JSON.stringify(result),
                    });

                    return openAI(naturalCommand, msgs);
                });
            }

            // Send status update about completed task
            const content = message.content;
            return new Promise(resolve => resolve(content));
        })
        .catch((err) => {
            return new Promise((_, reject) => reject(err));
        });  
}

//
// Handel Function Calls from OpenAI Requests
//
function handelFunctionCalls(message) {
    let args = JSON.parse(message.function_call.arguments);
    switch (message.function_call.name) {
        case "publishMessage":
            return publishMessage(args.channel, args.message);
            break;

        case "lastMessage":
            return lastMessage(args.channel);
            break;
    }
}

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