originally from https://github.com/pietrop/srtParserComposer and modified from PopcornJs srt parser. https://github.com/mozilla/popcorn-js/blob/master/parsers/parserSRT/popcorn.parserSRT.js - given a setence with start and end timecode it can compute and estimate start and end timings for each word.

interpolateWordsTimesFromSentence.js

/*
* originally from https://github.com/pietrop/srtParserComposer/blob/master/srtJsonToWordLinesJson.js()
* refactored 
* Module to convert srtJson to nested array of line word objects.
Line to word timecode accuracty.
Original code modified from Popcorn srt parser.
https://github.com/mozilla/popcorn-js/blob/master/parsers/parserSRT/popcorn.parserSRT.js

input example
```js
 {
    "startTime": 4.89,
    "endTime": 3.30,
    "text": "There’s this door on the 10th floor I just\nhate so much.\n"
  }
  ```

output looks something like this 
```
[
  [
    {
      "start": 4.89,
      "end": 1.88,
      "text": "There’s"
    },
    {
      "start": 4.46,
      "end": 2.74,
      "text": "this"
    },
    {
      "start": 4.029999999999999,
      "end": 2.3099999999999996,
      "text": "door"
    },
    ....
  ]
  ...
]
```
*/

/**
* takes in a srtJson and converts it into an array of lines containing word objects with
* word level timing.
*/
// function convertTowordsLines(srtJson){
//     // console.log(srtJson)
//   var resultLines = [];
//     for(var i=0; i<srtJson.length ; i++){
//       var line = [];
//       var srtJsonLine = srtJson[i];
  
//       // console.log("-----")
//       // console.log(srtJsonLine)
//       var arOfWords= convertOneSrtLine(srtJsonLine)//cb
//       // line = ;
//       resultLines.push(arOfWords);
//     }
//     return resultLines;
//   }
  
  /*
  * Converts one srtJson line into array of words with accourate time attributes.
  */

  /**
   * 
   * @param {string} lineText - text of the line sentence
   * @param {float} lineStartTime - start time for the sentence
   * @param {float} lineEndTime - end time for the sentence
   */
  function interpolateWordsTimesFromSentence(lineText, lineStartTime, lineEndTime){//cb
    var resultWords = [];

    var words = lineText.split(" ");
    var wordCount = words.length;
    var numberOfLettersInALine = 0;
    //to calculate numberOfLettersInALine iterate over array of words and add up lenght of each.
    for (var j=0; j< words.length; j++){
      var oneWord = words[j];
      var numberOfLettersInOneWord =oneWord.length;
      numberOfLettersInALine +=numberOfLettersInOneWord;
    }

    //line duration in seconds
    var lineDuration =  lineEndTime  - lineStartTime ;
    // Define Word level granularity
    var averageWordDuration = lineDuration / wordCount;
    //word counter resets for every new line
    var wordCounter = 0;
    for(var k = 0; k< words.length; k++){
      var word = words[k];
      var wordDuration = word.length * averageWordDuration;
      var wordStartTime = lineStartTime + wordCounter * averageWordDuration;
      var wordEndTime = wordStartTime + wordDuration;
      var correspondingWord = words[wordCounter];
      var wordO = createWord(wordStartTime, wordEndTime, correspondingWord)
      // console.log(wordO)
      resultWords.push(wordO)
      wordCounter+=1;
    }
    return resultWords
    // console.log(result)
  }
  
  
  /**
  * Helper function
  */
  function createWord(start, end, text){
    word = {};
    word.start = start;
    word.end = end;
    word.text = text;
    return word;
  }
  
  
  module.exports =  interpolateWordsTimesFromSentence;