Split text into equal length strings keeping words intact

Question

I have this code that break longer lines into array of equal length strings keeping words it also take into account the formatting like [[u;#fff;]some text], it split text so each string can be converted into html independently:

var format_re = /\[\[([!gbiuso]*;[^;\]]*;[^;\]]*(?:;|[^\]()]*);?[^\]]*)\]([^\]]*\\\][^\]]*|[^\]]*|[^\[]*\[[^\]]*)\]?/gi;
var format_begin_re = /(\[\[[!gbiuso]*;[^;]*;[^\]]*\])/i;
var format_last_re = /\[\[[!gbiuso]*;[^;]*;[^\]]*\]?$/i;
$.terminal.split_equal = function(str, length, words) {
  var formatting = false;
  var in_text = false;
  var prev_format = '';
  var result = [];
  // add format text as 5th paramter to formatting it's used for
  // data attribute in format function
  var array = str.replace(format_re, function(_, format, text) {
    var semicolons = format.match(/;/g).length;
    // missing semicolons
    if (semicolons == 2) {
      semicolons = ';;';
    } else if (semicolons == 3) {
      semicolons = ';';
    } else {
      semicolons = '';
    }
    // return '[[' + format + ']' + text + ']';
    // closing braket will break formatting so we need to escape
    // those using html entity equvalent
    return '[[' + format + semicolons +
      text.replace(/\\\]/g, ']').replace(/\n/g, '\\n') + ']' +
      text + ']';
  }).split(/\n/g);
  for (var i = 0, len = array.length; i < len; ++i) {
    if (array[i] === '') {
      result.push('');
      continue;
    }
    var line = array[i];
    var first_index = 0;
    var count = 0;
    var space = -1;
    for (var j=0, jlen=line.length; j<jlen; ++j) {
      if (line[j] === '[' && line[j+1] === '[') {
        formatting = true;
      } else if (formatting && line[j] === ']') {
        if (in_text) {
          formatting = false;
          in_text = false;
        } else {
          in_text = true;
        }
      } else if ((formatting && in_text) || !formatting) {
        if (line[j] === '&') { // treat entity as one character
          var m = line.substring(j).match(/^(&[^;]+;)/);
          if (!m) {
            // should never happen if used by terminal,
            // because it always calls $.terminal.encode
            // before this function
            throw new Error("Unclosed html entity in line " +
                            (i+1) + ' at char ' + (j+1));
          }
          j+=m[1].length-2; // because continue adds 1 to j
          // if entity is at the end there is no next loop
          // issue #77
          if (j === jlen-1) {
            result.push(output + m[1]);
          }
          continue;
        } else if (line[j] === ']' && line[j-1] === '\\') {
          // escape \] counts as one character
          --count;
        } else {
          ++count;
        }
      }
      function is_space() {
        return line.substring(j-6, j) == '&nbsp;' ||
          line.substring(j-1, j) == ' ';
      }
      if (is_space() && ((formatting && in_text) || !formatting)) {
        space = j;
      }
      if ((count === length || j === jlen-1) &&
          ((formatting && in_text) || !formatting)) {
        var output;
        var after = line.substring(space, j+length+1);
        var text = $('<span>' + after + '</span>').text();
        var can_break = text.match(/\s/);
        if (words && space != -1 && j !== jlen-1 && can_break) {
          // get text to last space
          output = line.substring(first_index, space);
          j = space-1;
          space = -1;
        } else {
          output = line.substring(first_index, j+1);
        }
        if (words) {
          output = output.replace(/^(&nbsp;|\s)+|(&nbsp;|\s)+$/g, '');
        }
        first_index = j+1;
        count = 0;
        if (prev_format) {
          output = prev_format + output;
          if (output.match(']')) {
            prev_format = '';
          }
        }
        // Fix output if formatting not closed
        var matched = output.match(format_re);
        if (matched) {
          var last = matched[matched.length-1];
          if (last[last.length-1] !== ']') {
            prev_format = last.match(format_begin_re)[1];
            output += ']';
          } else if (output.match(format_last_re)) {
            var line_len = output.length;
            // why this line ???
            //var f_len = line_len-last[last.length-1].length;
            output = output.replace(format_last_re, '');
            prev_format = last.match(format_begin_re)[1];
          }
        }
        result.push(output);
      }
    }
  }
  return result;
};

It work almost right but some lines are shorter then it should like:

is cracker.The term

in this FIDDLE, it work right when you strip formatting, checking checkbox. I work on this for couple of hours and have no clue why that line is shorter, any help will be very appreciated.

Answer 1

Here's how to fix the original code:

Add the following after line 40:

in_text = false;

The in_text flag is used by the code to determine if the current position is in regular text. However, it was not clearing the flag when it entered a region of formatting markup. This was the cause care of the main issue described in the question with the ultra-short line.

Change the if statement at line 76/77 to:

if (is_space() && ((formatting && in_text) || !formatting || (line[j] === '[' && line[j+1] === '['))) {

This takes care of a lesser problem where line breaks were not happening on spaces between regular text and formatted text.

Working fiddle here: https://jsfiddle.net/2w10xp3m/1/