Text To Audio Lambda Function using Polly - For Serverless Web API Article

index.js

const AWS = require('aws-sdk');
const Stream = require('stream')
const Fs = require('fs');

const convertTextToVoice = function(data, callback){
    const polly = new AWS.Polly();
    
    var params = {
        OutputFormat: "mp3", 
        SampleRate: "8000", 
        Text: data.text, 
        TextType: "text", 
        VoiceId: data.voice
    };
     
    polly.synthesizeSpeech(params, callback);
}

const saveToS3 = function(postId, filePath, callback){
    const S3 = new AWS.S3();
    const readStream = Fs.createReadStream(filePath);
    var params = {
        Bucket : process.env.BUCKET_NAME,
        Key : postId + ".mp3",
        Body : readStream,
        ACL: "public-read"
    };
    
    S3.upload(params, callback);
}

const deleteSQSMessage = function(receiptHandle){
    const sqs = new AWS.SQS();
    sqs.deleteMessage({
        QueueUrl: process.env.SQS_URL,
        ReceiptHandle: receiptHandle
    });
}

const updateRecord = function(postId, status, url, callback){
    const docClient = new AWS.DynamoDB.DocumentClient();
 
    const params = {
        TableName: process.env.DB_TABLE_NAME,
        Key: {
            "id": postId
        },
        UpdateExpression: "set #statusAtt = :s, #urlAtt=:u",
        ExpressionAttributeNames: {
            "#statusAtt": "status",
            "#urlAtt": "url"
        },
        ExpressionAttributeValues:{
            ":s": status,
            ":u": url
        }
    };
    
    docClient.update(params, callback);
}
exports.handler = (event, context, callback) => {
    var postId = event["Records"][0].body;
    var receiptHandle= event["Records"][0].receiptHandle;
    
    deleteSQSMessage(receiptHandle);
    
    console.log('Converting Post', postId);
    
    const docClient = new AWS.DynamoDB.DocumentClient();
    
    const params = {
        TableName: process.env.DB_TABLE_NAME,
        Key: {
            "id": postId
        }
    };
    
    docClient.get(params, (err, data) => {
        if(err){
            context.succeed({success: false, error: err});
        }else{
            console.log('Converting Text', data.Item.text, 'to voice', data.Item.voice);
            
            convertTextToVoice(data.Item, (err, data) => {
                if(err){
                    context.succeed({success: false, error: err});
                }else{
                    if (data.AudioStream instanceof Buffer) {
                        const filePath = "/tmp/" + postId + ".mp3";
                        
                        Fs.writeFile(filePath, data.AudioStream, function(err) {
                            if (err) {
                                context.succeed({success: false, error: err});
                            }else{
                                console.log('File ready to upload', filePath);
                                
                                saveToS3(postId, filePath, (err, data) => {
                                    if(err){
                                        context.succeed({success: false, error: err});
                                    }else{
                                        updateRecord(postId, 'READY', data.Location, (err, data) => {
                                            if (err) {
                                                context.succeed({success: false, error: err});
                                            }else{
                                                context.succeed({success: true, data: data});
                                            }
                                        })
                                    }
                                }); 
                            }
                        })
                    }
                }
            });
        }
    });
};