Module 3. Build a serverless backend

// Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

const AWS = require('aws-sdk');
const appstream = new AWS.AppStream;
const ses = new AWS.SES();
const crypto = require('crypto');

exports.handler = (event, context, callback) => {
    var eventdata = JSON.parse(event.body);

    var length = 16; //Adjust this value to shorten or lengthen the AS2 username - 32 chars is max length an AS2 username can be
    var username = crypto.randomBytes(Math.ceil(length / 2)).toString('hex').slice(0, length); //generates a random string
    
    /* 
    Username could also be the name or email parameter from the event body

    var username = eventdata.name
    var username = eventdata.email

    */
    
    console.log("username: " + username);

    var params = { 
        FleetName: '<Fleet-Name>', /* required */
        StackName: '<Stack-Name>', /* required */
        UserId: username,
        Validity: 5 //TTL of URL

    };

    createas2streamingurl(params, eventdata, context.awsRequestId, callback);

};

function errorResponse(errorMessage, awsRequestId, callback) { //Function for handling error messaging back to client
    callback(null, {
        statusCode: 500,
        body: JSON.stringify({
            Error: errorMessage,
            Reference: awsRequestId,
        }),
        headers: {
            'Access-Control-Allow-Origin': '<origin-domain>', //This should be the domain of the website that originated the request, example: amazonaws.com
        },
    });
}

function createas2streamingurl(params, sesdata, awsRequestId, callback) {
    var request = appstream.createStreamingURL(params);
    request.
        on('success', function (response) { //Successful Response
            console.log("Success! AS2 Streaming URL created.");
            var output = response.data;
            var url = output.StreamingURL;
            sendEmail(sesdata); //With a successful AS2 URL generated, trigger the SES SendEmail function
            callback(null, {
                statusCode: 201,
                body: JSON.stringify({
                    Message: url,
                    Reference: awsRequestId,
                }),
                headers: {
                    'Access-Control-Allow-Origin': '<origin-domain>', //This should be the domain of the website that originated the request, example: amazonaws.com
                },
            });
        }).
        on('error', function (response) { //an error occoured 
            console.log("error: "  + JSON.stringify(response.message));
            errorResponse('Error creating AS2 streaming URL.', awsRequestId, callback);

        }).
        send();
}

function sendEmail(data) {
    var sender = "<sender@example.com>"; //Sender needs to be a verified address in SES
    var receiver = data.email.trim(); /*Trim the string of any preceding and trailing whitespaces*/
    var name = data.name.trim();
    var params = {
        Destination: {
            ToAddresses: [receiver]
        },
        Message: {
            Body: {
                Text: {
                    Data: 'Hello ' + name + ',' + '\n\nThank you for trying Example Corp\'s Application Suite.',
                    Charset: 'UTF-8'
                }
            },
            Subject: {
                Data: 'Thank you for trying Example Corp ' + name,
                Charset: 'UTF-8'
            }
        },
        Source: sender
    };
    console.log("Sending Email.");
    ses.sendEmail(params, function (err, data) {
        if (err) console.log(err, err.stack); // an error occurred
        else console.log(data);           // successful response
    });
}