index.js

/*
 * Javascript Diff Algorithm
 *  By John Resig (http://ejohn.org/)
 *  Modified by Chu Alan "sprite"
 *
 * Released under the MIT license.
 *
 * More Info:
 *  http://ejohn.org/projects/javascript-diff-algorithm/
 */

/*
 * Modified for Society Builder (http://github.com/lez/societybuilder):
 * - remove support for empty strings
 * - html markup, html escaping removed
 * - no extra newline at end of text
 * - raw json output
 * - merge chunks for fewer items in diff
 *
 *   by Laszlo Megyer (lez)
 */

var JsDiff = {

  // Takes two strings, an old and a new one
  // Returns an array of sections where sections are either unchanged text or
  //   changed text, where removed and added parts are both included. Example:
  // diffString('What a time to be alive!', 'Bad time to be sick.')
  // returns:
  // [
  //   {add: 'Bad ', remove: 'What a '},
  //   {text: 'time to be '},
  //   {add: 'sick.', remove: 'alive!'}
  // ]
  diffString: function (o, n) {

    var out = this.diff(o.split(/\s+/), n.split(/\s+/));
    var str = "";
    var diff = [];
    var optr = 0;
    var nptr = 0;
    var entry;

    var oSpace = o.match(/\s+/g);
    if (oSpace == null) {
      oSpace = [""];
    } else {
      oSpace.push("");
    }

    var nSpace = n.match(/\s+/g);
    if (nSpace == null) {
      nSpace = [""];
    } else {
      nSpace.push("");
    }

    while (optr < out.o.length || nptr < out.n.length) {
      entry = {remove: '', add: ''}
      while (optr < out.o.length && out.o[optr].text == null) {
        entry.remove += out.o[optr] + oSpace[optr]
        optr++;
      }
      while (nptr < out.n.length && out.n[nptr].text == null) {
        entry.add += out.n[nptr] + nSpace[nptr]
        nptr++;
      }

      if (entry.add || entry.remove){
        diff.push(entry)
      }

      entry = {text: ''}
      while (optr < out.o.length && nptr < out.n.length && out.o[optr].text != null && out.n[nptr].text != null) {
        entry.text += out.o[optr].text + oSpace[optr]
        optr++;
        nptr++;
      }
      if (entry.text) {
        diff.push(entry);
      }
    }

    return diff
  },

  diff: function(o, n) {

    var ns = new Object();
    var os = new Object();

    for ( var i = 0; i < n.length; i++ ) {
      if ( ns[ n[i] ] == null )
        ns[ n[i] ] = { rows: new Array(), o: null };
      ns[ n[i] ].rows.push( i );
    }

    for ( var i = 0; i < o.length; i++ ) {
      if ( os[ o[i] ] == null )
        os[ o[i] ] = { rows: new Array(), n: null };
      os[ o[i] ].rows.push( i );
    }

    for ( var i in ns ) {
      if ( ns[i].rows.length == 1 && typeof(os[i]) != "undefined" && os[i].rows.length == 1 ) {
        n[ ns[i].rows[0] ] = { text: n[ ns[i].rows[0] ], row: os[i].rows[0] };
        o[ os[i].rows[0] ] = { text: o[ os[i].rows[0] ], row: ns[i].rows[0] };
      }
    }

    for ( var i = 0; i < n.length - 1; i++ ) {
      if ( n[i].text != null && n[i+1].text == null && n[i].row + 1 < o.length && o[ n[i].row + 1 ].text == null &&
           n[i+1] == o[ n[i].row + 1 ] ) {
        n[i+1] = { text: n[i+1], row: n[i].row + 1 };
        o[n[i].row+1] = { text: o[n[i].row+1], row: i + 1 };
      }
    }

    for ( var i = n.length - 1; i > 0; i-- ) {
      if ( n[i].text != null && n[i-1].text == null && n[i].row > 0 && o[ n[i].row - 1 ].text == null &&
           n[i-1] == o[ n[i].row - 1 ] ) {
        n[i-1] = { text: n[i-1], row: n[i].row - 1 };
        o[n[i].row-1] = { text: o[n[i].row-1], row: i - 1 };
      }
    }

    return { o: o, n: n };
  }

}

module.exports = JsDiff