[FEATURE] Set up the WhatsApp Echo Bot

[Vinici0]

const https = require("https");

exports.handler = async (event) => {
const VERIFY_TOKEN = "Set_your_verify_token_value_here";
const WHATSAPP_TOKEN = "Paste_whatsapp_access_token_here";

let response;
if (event?.requestContext?.http?.method === "GET") {
// https://developers.facebook.com/docs/graph-api/webhooks/getting-started#verification-requests
// to learn more about GET request for webhook verification
let queryParams = event?.queryStringParameters;
if (queryParams != null) {
const mode = queryParams["hub.mode"];
if (mode == "subscribe") {
const verifyToken = queryParams["hub.verify_token"];
if (verifyToken == VERIFY_TOKEN) {
let challenge = queryParams["hub.challenge"];
response = {
"statusCode": 200,
"body": parseInt(challenge),
"isBase64Encoded": false
};
} else {
const responseBody = "Error, wrong validation token";
response = {
"statusCode": 403,
"body": JSON.stringify(responseBody),
"isBase64Encoded": false
};
}
} else {
const responseBody = "Error, wrong mode";
response = {
"statusCode": 403,
"body": JSON.stringify(responseBody),
"isBase64Encoded": false
};
}
}
else {
const responseBody = "Error, no query parameters";
response = {
"statusCode": 403,
"body": JSON.stringify(responseBody),
"isBase64Encoded": false
};
}
} else if (event?.requestContext?.http?.method === "POST") {
// process POST request (WhatsApp chat messages)
// https://developers.facebook.com/docs/whatsapp/cloud-api/webhooks/payload-examples#text-messages
// to learn about WhatsApp text message payload structure
let body = JSON.parse(event.body)
let entries = body.entry;
for (let entry of entries) {
for (let change of entry.changes) {
let value = change.value;
if(value != null) {
let phone_number_id = value.metadata.phone_number_id;
if (value.messages != null) {
for (let message of value.messages) {
if (message.type === 'text') {
let from = message.from;
let message_body = message.text.body;
let reply_message = "Ack from AWS lambda: " + message_body;
sendReply(phone_number_id, WHATSAPP_TOKEN, from, reply_message);
const responseBody = "Done";
response = {
"statusCode": 200,
"body": JSON.stringify(responseBody),
"isBase64Encoded": false
};
}
}
}
}
}
}
} else {
const responseBody = "Unsupported method";
response = {
"statusCode": 403,
"body": JSON.stringify(responseBody),
"isBase64Encoded": false
};
}

return response;
}

const sendReply = (phone_number_id, whatsapp_token, to, reply_message) => {
let json = {
messaging_product: "whatsapp",
to: to,
text: { body: reply_message },
};
let data = JSON.stringify(json);
let path = "/v12.0/"+phone_number_id+"/messages?access_token="+whatsapp_token;
let options = {
host: "graph.facebook.com",
path: path,
method: "POST",
headers: { "Content-Type": "application/json" }
};
let callback = (response) => {
let str = "";
response.on("data", (chunk) => {
str += chunk;
});
response.on("end", () => {
});
};
let req = https.request(options, callback);
req.on("error", (e) => {});
req.write(data);
req.end();
}