TeslaCam-Create-Playlist (for AWS Lambda)

index.js

/*
    Function: TeslaCam-Create-Playlist
    Runtime:  Node.js 10.x
    Environment: AWS Lambda
    
    Description:
     This function is meant to be triggered by a periodic CloudWatch Event.
     Upon execution, it will scan an S3 bucket (containing TeslaCam files),
      build an M3U playlist of processed / merged TeslaCam videos, determine
      how many *new* videos were added, and push a message to AWS SNS (for alerting).
      
    Environment Variables:
     - S3_BUCKET = the.name.of.your.bucket
     - SNS_ARN = your:arn:for:aws:sns:etc-etc
    
    Assumptions:
     1. Your S3 bucket is only used for TeslaCam work
     2. You're using the other two Lambdas:
         - TeslaCam-Identify-Sets-and-Kickoff
         - TeslaCam-Merge-Videos
     3. This Lambda function has a permissions Role enabling it to:
         a. Read from and Write to S3
         b. Publish to SNS
         c. (Recommended) Write to CloudWatch Logs
*/

let AWS = require('aws-sdk');
let s3 = new AWS.S3();
let readline = require('readline');

exports.handler = async (event) => {
    
    var myProxyResponseObj = {
        statusCode: 500,
        body: JSON.stringify('It worked!'),
    };
    
    let playlistParams = { Bucket: process.env.S3_BUCKET, Key: 'playlist.m3u' };
    
    // Check if a playlist exists and populate previousVideos array
    var previousVideos = [];
    try { 
        await s3.headObject(playlistParams).promise();
            // Download the current playlist
        let s3ReadStream = s3.getObject(playlistParams).createReadStream(); 
        let rl = readline.createInterface({ input: s3ReadStream, terminal: false });
        let myPromise = new Promise((resolve, reject) => {
            rl.on('line', (line) => {
                if (line.indexOf("https") >= 0) {
                    previousVideos.push(line.match(/[^\/]+\/[^\/]+$/g)[0]);
                }
            });
            rl.on('error', () => { console.log('error'); });
            rl.on('close', () => { resolve(); });
            })
        try { await myPromise; }
        catch(err) {
            myProxyResponseObj.body = JSON.stringify({ "message": err.message });
            return myProxyResponseObj;
        }
    }
    catch (err) { 
        console.log('There was no previous playlist file (no big deal)');
    }
    
    // Retrieve the keys of previously-processed videos
    var data;
    try { data = await s3.listObjectsV2({ Bucket: process.env.S3_BUCKET, Prefix: 'fullscreen' }).promise(); }
    catch (err) {
        myProxyResponseObj.statusCode = err.statusCode;
        myProxyResponseObj.body = JSON.stringify({ "message": err.message });
        return myProxyResponseObj;
    }
    
    // Build playlist file
    var currentVideos = [];
    var playlist = "#EXTM3U\n";
    for (const obj of data.Contents) {
        currentVideos.push(obj.Key);
        playlist = playlist.concat("#EXTINF:60, "+ obj.Key.split("/")[1] +"\n");
        playlist = playlist.concat("https://s3.amazonaws.com/"+ process.env.S3_BUCKET +"/"+ obj.Key +"\n");
    }
    
    var params = {
        ACL: "public-read",
        Bucket: process.env.S3_BUCKET,
        Key: 'playlist.m3u',
        ContentType: 'text/plain',
        Body: playlist.trim()
    };
    
    // Upload the file to S3
    try { await s3.putObject(params).promise(); } 
    catch(err) { 
        myProxyResponseObj.body = JSON.stringify({ "message": err.message });
        return myProxyResponseObj;
    }
    
    // ==> Determine if there were any new videos in the updated playlist
    let newVideos = currentVideos.filter(
        function(e) { return this.indexOf(e) < 0; }, previousVideos
    );
    
    // If there were new videos, publish to SNS
    if (newVideos.length > 0) {
        let correctWording = newVideos.length == 1 ? " video is " : " videos are ";
        let sns = new AWS.SNS();
        params = {
            Message: newVideos.length +" new"+ correctWording +"available! \n\nhttps://s3.amazonaws.com/shevenell.teslacam/playlist.m3u", 
            Subject: "New Videos",
            TopicArn: process.env.SNS_ARN
        };
        try { await sns.publish(params).promise(); }
        catch(err) {
            console.log(err);
        }
    }

    myProxyResponseObj.statusCode = 200;
    return myProxyResponseObj;
};