awsiot_handler.js

/**
 * Lambda function that sends an Email on click of a button. 
 * It creates a SNS topic, subscribes an endpoint (EMAIL) to the topic and publishes to the topic.
 */

// email address.
const  = '*@*.*';

const AWS = require('aws-sdk');
const SNS = new AWS.SNS({ apiVersion: '2010-03-31' });

function findExistingSubscription(topicArn, nextToken, cb) {
    const params = {
        TopicArn: topicArn,
        NextToken: nextToken || null,
    };
    SNS.listSubscriptionsByTopic(params, (err, data) => {
        if (err) {
            console.log('Error listing subscriptions.', err);
            cb(err);
            return;
        }
        const subscription = data.Subscriptions.filter((sub) => sub.Protocol === 'email' && sub.Endpoint === EMAIL)[0];
        if (!subscription) {
            if (!data.NextToken) {
                cb(null, null); // indicate that no subscription was found
            } else {
                findExistingSubscription(topicArn, data.NextToken, cb); // iterate over next token
            }
        } else {
            cb(null, subscription); // a subscription was found
        }
    });
}

/**
 * Subscribe the specified EMAIL to a topic.
 */
function createSubscription(topicArn, cb) {
    // check to see if a subscription already exists
    findExistingSubscription(topicArn, null, (err, res) => {
        if (err) {
            console.log('Error finding existing subscription.', err);
            cb(err);
            return;
        }
        if (!res) {
            // no subscription, create one
            const params = {
                Protocol: 'email',
                TopicArn: topicArn,
                Endpoint: EMAIL,
            };
            SNS.subscribe(params, (err, data) => {
                if (err) {
                    console.log('Error setting up email subscription.', err);
                    cb(err);
                    return;
                }
                // subscription complete
                console.log(`Subscribed ${EMAIL} to ${topicArn}.`);
                cb(null, topicArn);
            });
        } else {
            // subscription already exists, continue
            cb(null, topicArn);
        }
    });
}

/**
 * Create a topic.
 */
function createTopic(topicName, cb) {
    SNS.createTopic({ Name: topicName }, (err, data) => {
        if (err) {
            console.log('Creating topic failed.', err);
            cb(err);
            return;
        }
        const topicArn = data.TopicArn;
        console.log(`Created topic: ${topicArn}`);
        console.log('Creating subscriptions.');
        createSubscription(topicArn, (err, data) => {
            if (err) {
                cb(err);
                return;
            }
            // everything is good
            console.log('Topic setup complete.');
            cb(null, topicArn);
        });
    });
}

exports.handler = (event, context, callback) => {
    console.log('Received event:', event.clickType);

    // create/get topic
    createTopic('aws-iot-button-sns-topic', (err, topicArn) => {
        if (err) {
            callback(err);
            return;
        }
        console.log(`Publishing to topic ${topicArn}`);
        // publish message
        const params = {
            Message: `${event.serialNumber} -- processed by Lambda\nBattery voltage: ${event.batteryVoltage}`,
            Subject: `Hello from your IoT Button ${event.serialNumber}: ${event.clickType}`,
            TopicArn: topicArn
        };
        // result will go to function callback
        SNS.publish(params, callback);
    });
};