convert-transcribe-vtt.js

const moment = require('moment');
const momentDurationFormatSetup = require('moment-duration-format');

function processItems(structure) {
	const maxSentenceLength = 32;
	const maxParagraphLength = 64; //we want to keep this to 64 or less (per line)

	let srtTranscription = "WEBVTT\n\n";
	let numberOfChars = 0; 
	let sentence = "";
	let startTime = null;
	let endTime = null;
	let newLine = false;

	for(let i = 0; i < structure.results.items.length; i++) {
		let item = structure.results.items[i];
		let content = item.alternatives[0].content;
		
		const newSentenceLength = (sentence + " " + content).length;

		if (startTime === null) {
			startTime = moment.duration(parseFloat(item.start_time), "seconds").format("hh:mm:ss.SSS", {trim: false});
		}

		switch (item.type) {
			case "pronunciation": {
				if (newSentenceLength >= maxParagraphLength) {
					i--;
					break;
				}

				if (newSentenceLength >= maxSentenceLength && newLine === false) {
					sentence += "\n";
					newLine = true;
				}

				sentence += " " + content;
				endTime = moment.duration(parseFloat(item.end_time), "seconds").format("hh:mm:ss.SSS", {trim: false});

				break;
			}

			case "punctuation": {
				sentence += content;

				break;
			}
		}

		if (newSentenceLength >= maxParagraphLength || (item.type === "punctuation" && content === '.')) {
			
			//We are done. Start new block;
			srtTranscription += (startTime + " --> " + endTime + "\n");
			srtTranscription += (sentence + "\n" + "\n");
			numberOfChars += sentence.length;

			startTime = endTime = null;
			sentence = "";
			newLine = false;
		}
	}

	return {
		transcription: srtTranscription,
		numberOfChars: numberOfChars
	};
}

exports.handler = (structure) => {
	console.log('Processing AWS Transcription JSON');

	const transcription = processItems(structure);

	return transcription;
}