phpjs/functions/xdiff/xdiff_string_patch.js

php.js offers community built php functions in javascript

function xdiff_string_patch(originalStr, patch, flags, error) {
  // From: http://phpjs.org/functions
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // +   improved by: Steven Levithan (stevenlevithan.com)
  // %        note 1: The XDIFF_PATCH_IGNORESPACE flag and the error argument are not currently supported
  // %        note 2: This has not been widely tested
  // *     example 1: xdiff_string_patch('', '@@ -0,0 +1,1 @@\n+Hello world!');
  // *     returns 1: 'Hello world!'

  // First two functions were adapted from Steven Levithan, also under an MIT license
  // Adapted from XRegExp 1.5.0
  // (c) 2007-2010 Steven Levithan
  // MIT License
  // <http://xregexp.com>
  var getNativeFlags = function(regex) {
    return (regex.global ? 'g' : '') + (regex.ignoreCase ? 'i' : '') + (regex.multiline ? 'm' : '') + (regex.extended ? 'x' : '') + // Proposed for ES4; included in AS3
        (regex.sticky ? 'y' : '');
  };
  cbSplit = function(str, s /* separator */ ) {
    // If separator `s` is not a regex, use the native `split`
    if (!(s instanceof RegExp)) { // Had problems to get it to work here using prototype test
      return String.prototype.split.apply(str, arguments);
    }
    str = str + '';
    var output = [],
            lastLastIndex = 0,
            match, lastLength, limit = Infinity;

    // This is required if not `s.global`, and it avoids needing to set `s.lastIndex` to zero
    // and restore it to its original value when we're done using the regex
    var x = s._xregexp;
    s = new RegExp(s.source, getNativeFlags(s) + 'g'); // Brett paring down
    if (x) {
      s._xregexp = {
        source: x.source,
        captureNames: x.captureNames ? x.captureNames.slice(0) : null
      };
    }

    while ((match = s.exec(str))) { // Run the altered `exec` (required for `lastIndex` fix, etc.)
      if (s.lastIndex > lastLastIndex) {
        output.push(str.slice(lastLastIndex, match.index));

        if (match.length > 1 && match.index < str.length) {
          Array.prototype.push.apply(output, match.slice(1));
        }

        lastLength = match[0].length;
        lastLastIndex = s.lastIndex;

        if (output.length >= limit) break;
      }

      if (s.lastIndex === match.index) {
        s.lastIndex++;
      }
    }

    if (lastLastIndex === str.length) {
      if (!s.test('') || lastLength) {
        output.push('');
      }
    } else {
      output.push(str.slice(lastLastIndex));
    }

    return output.length > limit ? output.slice(0, limit) : output;
  };
  i = 0,
  ll = 0,
  ranges = [],
  lastLinePos = 0,
  firstChar = '',
  rangeExp = /^@@\s+-(\d+),(\d+)\s+\+(\d+),(\d+)\s+@@$/,
  lineBreaks = /\r?\n/,
  lines = cbSplit(patch.replace(/(\r?\n)+$/, ''), lineBreaks),
  origLines = cbSplit(originalStr, lineBreaks),
  newStrArr = [],
  linePos = 0,
  errors = '',
  // Both string & integer (constant) input is allowed
  optTemp = 0,
  OPTS = { // Unsure of actual PHP values, so better to rely on string
    'XDIFF_PATCH_NORMAL': 1,
    'XDIFF_PATCH_REVERSE': 2,
    'XDIFF_PATCH_IGNORESPACE': 4
  };

  // Input defaulting & sanitation
  if (typeof originalStr !== 'string' || !patch) {
    return false;
  }
  if (!flags) {
    flags = 'XDIFF_PATCH_NORMAL';
  }

  if (typeof flags !== 'number') { // Allow for a single string or an array of string flags
    flags = [].concat(flags);
    for (i = 0; i < flags.length; i++) {
      // Resolve string input to bitwise e.g. 'XDIFF_PATCH_NORMAL' becomes 1
      if (OPTS[flags[i]]) {
        optTemp = optTemp | OPTS[flags[i]];
      }
    }
    flags = optTemp;
  }

  if (flags & OPTS.XDIFF_PATCH_NORMAL) {
    for (i = 0, ll = lines.length; i < ll; i++) {
      ranges = lines[i].match(rangeExp);
      if (ranges) {
        lastLinePos = linePos;
        linePos = ranges[1] - 1;
        while (lastLinePos < linePos) {
          newStrArr[newStrArr.length] = origLines[lastLinePos++];
        }
        while (lines[++i] && (rangeExp.exec(lines[i])) == null) {
          firstChar = lines[i].charAt(0);
          switch (firstChar) {
            case '-':
              ++linePos; // Skip including that line
              break;
            case '+':
              newStrArr[newStrArr.length] = lines[i].slice(1);
              break;
            case ' ':
              newStrArr[newStrArr.length] = origLines[linePos++];
              break;
            default:
              throw 'Unrecognized initial character in unidiff line'; // Reconcile with returning errrors arg?
          }
        }
        if (lines[i]) {
          i--;
        }
      }
    }
	while (linePos > 0 && linePos < origLines.length) {
	  newStrArr[newStrArr.length] = origLines[linePos++];
	}
  } else if (flags & OPTS.XDIFF_PATCH_REVERSE) { // Only differs from above by a few lines
    for (i = 0, ll = lines.length; i < ll; i++) {
      ranges = lines[i].match(rangeExp);
      if (ranges) {
        lastLinePos = linePos;
        linePos = ranges[3] - 1;
        while (lastLinePos < linePos) {
          newStrArr[newStrArr.length] = origLines[lastLinePos++];
        }
        while (lines[++i] && (rangeExp.exec(lines[i])) == null) {
          firstChar = lines[i].charAt(0);
          switch (firstChar) {
            case '-':
              newStrArr[newStrArr.length] = lines[i].slice(1);
              break;
            case '+':
              ++linePos; // Skip including that line
              break;
            case ' ':
              newStrArr[newStrArr.length] = origLines[linePos++];
              break;
            default:
              throw 'Unrecognized initial character in unidiff line'; // Reconcile with returning errrors arg?
          }
        }
        if (lines[i]) {
          i--;
        }
      }
    }
	while (linePos > 0 && linePos < origLines.length) {
	  newStrArr[newStrArr.length] = origLines[linePos++];
	}
  }
  if (typeof error === 'string') {
    this.window[error] = errors;
  }
  return newStrArr.join('\n');
}