Merge pull request #1417 from ether/diff-view

Adds an API endpoint for Diff view

src/node/db/API.js

@@ -30,6 +30,7 @@ var async = require("async");
 var exportHtml = require("../utils/ExportHtml");
 var importHtml = require("../utils/ImportHtml");
 var cleanText = require("./Pad").cleanText;
+var PadDiff = require("../utils/padDiff");
 
 /**********************/
 /**GROUP FUNCTIONS*****/
@@ -656,6 +657,86 @@ exports.getChatHead = function(padID, callback)
   });
 }
 
+/**
+createDiffHTML(padID, startRev, endRev) returns an object of diffs from 2 points in a pad
+
+Example returns:
+
+{"code":0,"message":"ok","data":{"html":"<style>\n.authora_HKIv23mEbachFYfH {background-color: #a979d9}\n.authora_n4gEeMLsv1GivNeh {background-color: #a9b5d9}\n.removed {text-decoration: line-through; -ms-filter:'progid:DXImageTransform.Microsoft.Alpha(Opacity=80)'; filter: alpha(opacity=80); opacity: 0.8; }\n</style>Welcome to Etherpad Lite!<br><br>This pad text is synchronized as you type, so that everyone viewing this page sees the same text. This allows you to collaborate seamlessly on documents!<br><br>Get involved with Etherpad at <a href=\"http&#x3a;&#x2F;&#x2F;etherpad&#x2e;org\">http:&#x2F;&#x2F;etherpad.org</a><br><span class=\"authora_HKIv23mEbachFYfH\">aw</span><br><br>","authors":["a.HKIv23mEbachFYfH",""]}}
+{"code":4,"message":"no or wrong API Key","data":null}
+*/
+exports.createDiffHTML = function(padID, startRev, endRev, callback){
+  //check if rev is a number
+  if(startRev !== undefined && typeof startRev != "number")
+  {
+    //try to parse the number
+    if(!isNaN(parseInt(startRev)))
+    {
+      startRev = parseInt(startRev, 10);
+    }
+    else
+    {
+      callback({stop: "startRev is not a number"});
+      return;
+    }
+  }
+ 
+  //check if rev is a number
+  if(endRev !== undefined && typeof endRev != "number")
+  {
+    //try to parse the number
+    if(!isNaN(parseInt(endRev)))
+    {
+      endRev = parseInt(endRev, 10);
+    }
+    else
+    {
+      callback({stop: "endRev is not a number"});
+      return;
+    }
+  }
+ 
+  //get the pad
+  getPadSafe(padID, true, function(err, pad)
+  {
+    if(err){
+      return callback(err);
+    }
+ 
+    try {
+      var padDiff = new PadDiff(pad, startRev, endRev);
+    } catch(e) {
+      return callback({stop:e.message});
+    }
+    var html, authors;
+ 
+    async.series([
+      function(callback){
+        padDiff.getHtml(function(err, _html){
+          if(err){
+            return callback(err);
+          }
+ 
+          html = _html;
+          callback();
+        });
+      },
+      function(callback){
+        padDiff.getAuthors(function(err, _authors){
+          if(err){
+            return callback(err);
+          }
+ 
+          authors = _authors;
+          callback();
+        });
+      }
+    ], function(err){
+      callback(err, {html: html, authors: authors})
+    });
+  });
+}
+
 /******************************/
 /** INTERNAL HELPER FUNCTIONS */
 /******************************/

src/node/db/AuthorManager.js

@@ -24,6 +24,10 @@ var db = require("./DB").db;
 var async = require("async");
 var randomString = require('ep_etherpad-lite/static/js/pad_utils').randomString;
 
+exports.getColorPalette = function(){
+  return ["#ffc7c7", "#fff1c7", "#e3ffc7", "#c7ffd5", "#c7ffff", "#c7d5ff", "#e3c7ff", "#ffc7f1", "#ff8f8f", "#ffe38f", "#c7ff8f", "#8fffab", "#8fffff", "#8fabff", "#c78fff", "#ff8fe3", "#d97979", "#d9c179", "#a9d979", "#79d991", "#79d9d9", "#7991d9", "#a979d9", "#d979c1", "#d9a9a9", "#d9cda9", "#c1d9a9", "#a9d9b5", "#a9d9d9", "#a9b5d9", "#c1a9d9", "#d9a9cd", "#4c9c82", "#12d1ad", "#2d8e80", "#7485c3", "#a091c7", "#3185ab", "#6818b4", "#e6e76d", "#a42c64", "#f386e5", "#4ecc0c", "#c0c236", "#693224", "#b5de6a", "#9b88fd", "#358f9b", "#496d2f", "#e267fe", "#d23056", "#1a1a64", "#5aa335", "#d722bb", "#86dc6c", "#b5a714", "#955b6a", "#9f2985", "#4b81c8", "#3d6a5b", "#434e16", "#d16084", "#af6a0e", "#8c8bd8"];
+};
+
 /**
  * Checks if the author exists
  */

src/node/db/Pad.js

@@ -213,6 +213,48 @@ Pad.prototype.getInternalRevisionAText = function getInternalRevisionAText(targe
   });
 };
 
+Pad.prototype.getRevision = function getRevisionChangeset(revNum, callback) {
+  db.get("pad:"+this.id+":revs:"+revNum, callback);
+};
+
+Pad.prototype.getAllAuthorColors = function getAllAuthorColors(callback){
+  var authors = this.getAllAuthors();
+  var returnTable = {};
+  var colorPalette = authorManager.getColorPalette();
+
+  async.forEach(authors, function(author, callback){
+    authorManager.getAuthorColorId(author, function(err, colorId){
+      if(err){
+        return callback(err);
+      }
+      //colorId might be a hex color or an number out of the palette
+      returnTable[author]=colorPalette[colorId] || colorId;
+
+      callback();
+    });
+  }, function(err){
+    callback(err, returnTable);
+  });
+};
+
+Pad.prototype.getValidRevisionRange = function getValidRevisionRange(startRev, endRev) {
+  startRev = parseInt(startRev, 10);
+  var head = this.getHeadRevisionNumber();
+  endRev = endRev ? parseInt(endRev, 10) : head;
+  if(isNaN(startRev) || startRev < 0 || startRev > head) {
+    startRev = null;
+  }
+  if(isNaN(endRev) || endRev < startRev) {
+    endRev = null;
+  } else if(endRev > head) {
+    endRev = head;
+  }
+  if(startRev !== null && endRev !== null) {
+    return { startRev: startRev , endRev: endRev }
+  }
+  return null;
+};
+
 Pad.prototype.getKeyRevisionNumber = function getKeyRevisionNumber(revNum) {
   return Math.floor(revNum / 100) * 100;
 };

src/node/handler/APIHandler.js

@@ -180,6 +180,7 @@ var version =
   , "deleteGroup"               : ["groupID"]
   , "listPads"                  : ["groupID"]
   , "listAllPads"               : []
+  , "createDiffHTML"	        : ["padID", "startRev", "endRev"]
   , "createPad"                 : ["padID", "text"]
   , "createGroupPad"            : ["groupID", "padName", "text"]
   , "createAuthor"              : ["name"]

src/node/handler/PadMessageHandler.js

@@ -1028,7 +1028,7 @@ function handleClientReady(client, message)
               "globalPadId": message.padId,
               "time": currentTime,
           },
-          "colorPalette": ["#ffc7c7", "#fff1c7", "#e3ffc7", "#c7ffd5", "#c7ffff", "#c7d5ff", "#e3c7ff", "#ffc7f1", "#ff8f8f", "#ffe38f", "#c7ff8f", "#8fffab", "#8fffff", "#8fabff", "#c78fff", "#ff8fe3", "#d97979", "#d9c179", "#a9d979", "#79d991", "#79d9d9", "#7991d9", "#a979d9", "#d979c1", "#d9a9a9", "#d9cda9", "#c1d9a9", "#a9d9b5", "#a9d9d9", "#a9b5d9", "#c1a9d9", "#d9a9cd", "#4c9c82", "#12d1ad", "#2d8e80", "#7485c3", "#a091c7", "#3185ab", "#6818b4", "#e6e76d", "#a42c64", "#f386e5", "#4ecc0c", "#c0c236", "#693224", "#b5de6a", "#9b88fd", "#358f9b", "#496d2f", "#e267fe", "#d23056", "#1a1a64", "#5aa335", "#d722bb", "#86dc6c", "#b5a714", "#955b6a", "#9f2985", "#4b81c8", "#3d6a5b", "#434e16", "#d16084", "#af6a0e", "#8c8bd8"],
+          "colorPalette": authorManager.getColorPalette(),
           "clientIp": "127.0.0.1",
           "userIsGuest": true,
           "userColor": authorColorId,

src/node/utils/ExportHtml.js

@@ -1,12 +1,12 @@
 /**
  * Copyright 2009 Google Inc.
- * 
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS-IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -91,8 +91,9 @@ function getPadHTML(pad, revNum, callback)
 }
 
 exports.getPadHTML = getPadHTML;
+exports.getHTMLFromAtext = getHTMLFromAtext;
 
-function getHTMLFromAtext(pad, atext)
+function getHTMLFromAtext(pad, atext, authorColors)
 {
   var apool = pad.apool();
   var textLines = atext.text.slice(0, -1).split('\n');
@@ -101,6 +102,42 @@ function getHTMLFromAtext(pad, atext)
   var tags = ['h1', 'h2', 'strong', 'em', 'u', 's'];
   var props = ['heading1', 'heading2', 'bold', 'italic', 'underline', 'strikethrough'];
   var anumMap = {};
+  var css = "";
+
+  var stripDotFromAuthorID = function(id){
+    return id.replace(/\./g,'_');
+  };
+
+  if(authorColors){
+    css+="<style>\n";
+    
+    for (var a in apool.numToAttrib) {
+      var attr = apool.numToAttrib[a];
+      
+      //skip non author attributes
+      if(attr[0] === "author" && attr[1] !== ""){
+        //add to props array
+        var propName = "author" + stripDotFromAuthorID(attr[1]);
+        var newLength = props.push(propName);
+        anumMap[a] = newLength -1;
+        
+        css+="." + propName + " {background-color: " + authorColors[attr[1]]+ "}\n";
+      } else if(attr[0] === "removed") {
+        var propName = "removed";
+        
+        var newLength = props.push(propName);
+        anumMap[a] = newLength -1;
+        
+        css+=".removed {text-decoration: line-through; " + 
+             "-ms-filter:'progid:DXImageTransform.Microsoft.Alpha(Opacity=80)'; "+ 
+             "filter: alpha(opacity=80); "+
+             "opacity: 0.8; "+
+             "}\n";
+      }
+    }
+    
+    css+="</style>";
+  }
 
   props.forEach(function (propName, i)
   {
@@ -125,22 +162,53 @@ function getHTMLFromAtext(pad, atext)
     // <b>Just bold <i>Bold and italics</i></b> <i>Just italics</i>
     var taker = Changeset.stringIterator(text);
     var assem = Changeset.stringAssembler();
-
     var openTags = [];
+
+    function getSpanClassFor(i){
+      //return if author colors are disabled
+      if (!authorColors) return false;
+      
+      var property = props[i];
+   
+      if(property.substr(0,6) === "author"){
+        return stripDotFromAuthorID(property);
+      }
+      
+      if(property === "removed"){
+        return "removed";
+      }
+      
+      return false;
+    }
+
     function emitOpenTag(i)
     {
       openTags.unshift(i);
-      assem.append('<');
+      var spanClass = getSpanClassFor(i);
-      assem.append(tags[i]);
+      
-      assem.append('>');
+      if(spanClass){
+        assem.append('<span class="');
+        assem.append(spanClass);
+        assem.append('">');
+      } else {
+        assem.append('<');
+        assem.append(tags[i]);
+        assem.append('>');
+      }
     }
 
     function emitCloseTag(i)
     {
       openTags.shift();
-      assem.append('</');
+      var spanClass = getSpanClassFor(i);
-      assem.append(tags[i]);
+      
-      assem.append('>');
+      if(spanClass){
+        assem.append('</span>');
+      } else {
+        assem.append('</');
+        assem.append(tags[i]);
+        assem.append('>');
+      }
     }
     
     function orderdCloseTags(tags2close)
@@ -303,7 +371,7 @@ function getHTMLFromAtext(pad, atext)
 
     return _processSpaces(assem.toString());
   } // end getLineHTML
-  var pieces = [];
+  var pieces = [css];
 
   // Need to deal with constraints imposed on HTML lists; can
   // only gain one level of nesting at once, can't change type

src/node/utils/padDiff.js

@@ -0,0 +1,554 @@
+var Changeset = require("../../static/js/Changeset");
+var async = require("async");
+var exportHtml = require('./ExportHtml');
+ 
+function PadDiff (pad, fromRev, toRev){      
+  //check parameters
+  if(!pad || !pad.id || !pad.atext || !pad.pool)
+  {
+    throw new Error('Invalid pad');
+  }
+ 
+  var range = pad.getValidRevisionRange(fromRev, toRev);
+  if(!range) { throw new Error('Invalid revision range.' + 
+      ' startRev: ' + fromRev +
+      ' endRev: ' + toRev); }
+  
+  this._pad = pad;
+  this._fromRev = range.startRev;
+  this._toRev = range.endRev;
+  this._html = null;
+  this._authors = [];
+}
+ 
+PadDiff.prototype._isClearAuthorship = function(changeset){
+  //unpack
+  var unpacked = Changeset.unpack(changeset);
+  
+  //check if there is nothing in the charBank
+  if(unpacked.charBank !== "")
+    return false;
+  
+  //check if oldLength == newLength
+  if(unpacked.oldLen !== unpacked.newLen)
+    return false;
+ 
+  //lets iterator over the operators
+  var iterator = Changeset.opIterator(unpacked.ops);
+  
+  //get the first operator, this should be a clear operator
+  var clearOperator = iterator.next();
+  
+  //check if there is only one operator
+  if(iterator.hasNext() === true)
+    return false;
+    
+  //check if this operator doesn't change text
+  if(clearOperator.opcode !== "=")
+    return false;
+    
+  //check that this operator applys to the complete text
+  //if the text ends with a new line, its exactly one character less, else it has the same length
+  if(clearOperator.chars !== unpacked.oldLen-1 && clearOperator.chars !== unpacked.oldLen)
+    return false;
+  
+  var attributes = [];
+  Changeset.eachAttribNumber(changeset, function(attrNum){
+    attributes.push(attrNum);
+  });
+    
+  //check that this changeset uses only one attribute
+  if(attributes.length !== 1)
+    return false;
+    
+  var appliedAttribute = this._pad.pool.getAttrib(attributes[0]);
+  
+  //check if the applied attribute is an anonymous author attribute
+  if(appliedAttribute[0] !== "author" || appliedAttribute[1] !== "")
+    return false;
+    
+  return true;
+}
+ 
+PadDiff.prototype._createClearAuthorship = function(rev, callback){
+  var self = this;
+  this._pad.getInternalRevisionAText(rev, function(err, atext){
+   if(err){
+     return callback(err);
+   }
+   
+   //build clearAuthorship changeset
+   var builder = Changeset.builder(atext.text.length);
+   builder.keepText(atext.text, [['author','']], self._pad.pool);
+   var changeset = builder.toString();
+   
+   callback(null, changeset);
+  });
+}
+ 
+PadDiff.prototype._createClearStartAtext = function(rev, callback){
+  var self = this;
+  
+  //get the atext of this revision
+  this._pad.getInternalRevisionAText(rev, function(err, atext){
+   if(err){
+     return callback(err);
+   }
+   
+   //create the clearAuthorship changeset
+   self._createClearAuthorship(rev, function(err, changeset){
+     if(err){
+       return callback(err);
+     }
+   
+     //apply the clearAuthorship changeset
+     var newAText = Changeset.applyToAText(changeset, atext, self._pad.pool);
+     
+     callback(null, newAText);
+   });
+  });
+}
+ 
+PadDiff.prototype._getChangesetsInBulk = function(startRev, count, callback) {
+  var self = this;
+  
+  //find out which revisions we need
+  var revisions = [];
+  for(var i=startRev;i<(startRev+count) && i<=this._pad.head;i++){
+    revisions.push(i);
+  }
+  
+  var changesets = [], authors = [];
+  
+  //get all needed revisions
+  async.forEach(revisions, function(rev, callback){
+    self._pad.getRevision(rev, function(err, revision){
+      if(err){
+        return callback(err)
+      }
+      
+      var arrayNum = rev-startRev;
+      
+      changesets[arrayNum] = revision.changeset;
+      authors[arrayNum] = revision.meta.author;
+  
+      callback();
+    });
+  }, function(err){
+    callback(err, changesets, authors);
+  });
+}
+ 
+PadDiff.prototype._addAuthors = function(authors) {
+  var self = this;
+  //add to array if not in the array
+  authors.forEach(function(author){
+    if(self._authors.indexOf(author) == -1){
+      self._authors.push(author);
+    }
+  });
+}
+ 
+PadDiff.prototype._createDiffAtext = function(callback) {
+  var self = this;
+  var bulkSize = 100;
+  
+  //get the cleaned startAText
+  self._createClearStartAtext(self._fromRev, function(err, atext){
+    if(err) { return callback(err); }
+    
+    var superChangeset = null;
+    
+    var rev = self._fromRev + 1;
+ 
+    //async while loop
+    async.whilst(
+      //loop condition
+      function () { return rev <= self._toRev; },
+      
+      //loop body
+      function (callback) {
+        //get the bulk
+        self._getChangesetsInBulk(rev,bulkSize,function(err, changesets, authors){
+          var addedAuthors = [];
+          
+          //run trough all changesets
+          for(var i=0;i<changesets.length && (rev+i)<=self._toRev;i++){
+            var changeset = changesets[i];
+            
+            //skip clearAuthorship Changesets
+            if(self._isClearAuthorship(changeset)){
+              continue;
+            }
+            
+            changeset = self._extendChangesetWithAuthor(changeset, authors[i], self._pad.pool);
+            
+            //add this author to the authorarray
+            addedAuthors.push(authors[i]);
+            
+            //compose it with the superChangset            
+            if(superChangeset === null){
+              superChangeset = changeset;
+            } else {           
+              superChangeset = Changeset.composeWithDeletions(superChangeset, changeset, self._pad.pool);
+            }
+          }
+          
+          //add the authors to the PadDiff authorArray
+          self._addAuthors(addedAuthors);
+        
+          //lets continue with the next bulk 
+          rev += bulkSize;
+          callback();
+        });
+      },
+      
+      //after the loop has ended
+      function (err) {
+        //if there are only clearAuthorship changesets, we don't get a superChangeset, so we can skip this step
+        if(superChangeset){
+          var deletionChangeset = self._createDeletionChangeset(superChangeset,atext,self._pad.pool);
+        
+          //apply the superChangeset, which includes all addings
+          atext = Changeset.applyToAText(superChangeset,atext,self._pad.pool);
+          //apply the deletionChangeset, which adds a deletions
+          atext = Changeset.applyToAText(deletionChangeset,atext,self._pad.pool);
+        }      
+ 
+        callback(err, atext);
+      }
+    );
+  });
+}
+ 
+PadDiff.prototype.getHtml = function(callback){
+  //cache the html
+  if(this._html != null){
+    return callback(null, this._html);
+  }
+  
+  var self = this;
+  var atext, html, authorColors;
+  
+  async.series([
+    //get the diff atext
+    function(callback){
+      self._createDiffAtext(function(err, _atext){
+        if(err){
+          return callback(err);
+        }
+        
+        atext = _atext;
+        callback();
+      });
+    },
+    //get the authorColor table
+    function(callback){
+      self._pad.getAllAuthorColors(function(err, _authorColors){
+        if(err){
+          return callback(err);
+        }
+        
+        authorColors = _authorColors;
+        callback();
+      });
+    },
+    //convert the atext to html
+    function(callback){
+      html = exportHtml.getHTMLFromAtext(self._pad, atext, authorColors);
+      self._html = html;
+      callback();
+    }
+  ], function(err){
+    callback(err, html);
+  });
+};
+ 
+PadDiff.prototype.getAuthors = function(callback){
+  var self = this;
+  
+  //check if html was already produced, if not produce it, this generates the author array at the same time
+  if(self._html == null){
+    self.getHtml(function(err){
+      if(err){
+        return callback(err);
+      }
+      
+      callback(null, self._authors);
+    });
+  } else {
+    callback(null, self._authors);
+  }
+}
+ 
+PadDiff.prototype._extendChangesetWithAuthor = function(changeset, author, apool) {  
+  //unpack
+  var unpacked = Changeset.unpack(changeset);  
+  
+  var iterator = Changeset.opIterator(unpacked.ops);
+  var assem = Changeset.opAssembler();
+  
+  //create deleted attribs
+  var authorAttrib = apool.putAttrib(["author", author || ""]);
+  var deletedAttrib = apool.putAttrib(["removed", true]);
+  var attribs = "*" + Changeset.numToString(authorAttrib) + "*" + Changeset.numToString(deletedAttrib);
+  
+  //iteratore over the operators of the changeset
+  while(iterator.hasNext()){
+    var operator = iterator.next();
+    
+    //this is a delete operator, extend it with the author
+    if(operator.opcode === "-"){
+      operator.attribs = attribs;
+    } 
+    //this is operator changes only attributes, let's mark which author did that
+    else if(operator.opcode === "=" && operator.attribs){
+      operator.attribs+="*"+Changeset.numToString(authorAttrib);
+    }
+    
+    //append the new operator to our assembler
+    assem.append(operator);
+  }
+  
+  //return the modified changeset
+  return Changeset.pack(unpacked.oldLen, unpacked.newLen, assem.toString(), unpacked.charBank);
+}
+ 
+//this method is 80% like Changeset.inverse. I just changed so instead of reverting, it adds deletions and attribute changes to to the atext.
+PadDiff.prototype._createDeletionChangeset = function(cs, startAText, apool) {
+  var lines = Changeset.splitTextLines(startAText.text);
+  var alines = Changeset.splitAttributionLines(startAText.attribs, startAText.text);
+  
+  // lines and alines are what the exports is meant to apply to.
+  // They may be arrays or objects with .get(i) and .length methods.
+  // They include final newlines on lines.
+ 
+  function lines_get(idx) {
+    if (lines.get) {
+      return lines.get(idx);
+    } else {
+      return lines[idx];
+    }
+  }
+ 
+  function lines_length() {
+    if ((typeof lines.length) == "number") {
+      return lines.length;
+    } else {
+      return lines.length();
+    }
+  }
+ 
+  function alines_get(idx) {
+    if (alines.get) {
+      return alines.get(idx);
+    } else {
+      return alines[idx];
+    }
+  }
+ 
+  function alines_length() {
+    if ((typeof alines.length) == "number") {
+      return alines.length;
+    } else {
+      return alines.length();
+    }
+  }
+ 
+  var curLine = 0;
+  var curChar = 0;
+  var curLineOpIter = null;
+  var curLineOpIterLine;
+  var curLineNextOp = Changeset.newOp('+');
+ 
+  var unpacked = Changeset.unpack(cs);
+  var csIter = Changeset.opIterator(unpacked.ops);
+  var builder = Changeset.builder(unpacked.newLen);
+ 
+  function consumeAttribRuns(numChars, func /*(len, attribs, endsLine)*/ ) {
+ 
+    if ((!curLineOpIter) || (curLineOpIterLine != curLine)) {
+      // create curLineOpIter and advance it to curChar
+      curLineOpIter = Changeset.opIterator(alines_get(curLine));
+      curLineOpIterLine = curLine;
+      var indexIntoLine = 0;
+      var done = false;
+      while (!done) {
+        curLineOpIter.next(curLineNextOp);
+        if (indexIntoLine + curLineNextOp.chars >= curChar) {
+          curLineNextOp.chars -= (curChar - indexIntoLine);
+          done = true;
+        } else {
+          indexIntoLine += curLineNextOp.chars;
+        }
+      }
+    }
+ 
+    while (numChars > 0) {
+      if ((!curLineNextOp.chars) && (!curLineOpIter.hasNext())) {
+        curLine++;
+        curChar = 0;
+        curLineOpIterLine = curLine;
+        curLineNextOp.chars = 0;
+        curLineOpIter = Changeset.opIterator(alines_get(curLine));
+      }
+      if (!curLineNextOp.chars) {
+        curLineOpIter.next(curLineNextOp);
+      }
+      var charsToUse = Math.min(numChars, curLineNextOp.chars);
+      func(charsToUse, curLineNextOp.attribs, charsToUse == curLineNextOp.chars && curLineNextOp.lines > 0);
+      numChars -= charsToUse;
+      curLineNextOp.chars -= charsToUse;
+      curChar += charsToUse;
+    }
+ 
+    if ((!curLineNextOp.chars) && (!curLineOpIter.hasNext())) {
+      curLine++;
+      curChar = 0;
+    }
+  }
+ 
+  function skip(N, L) {
+    if (L) {
+      curLine += L;
+      curChar = 0;
+    } else {
+      if (curLineOpIter && curLineOpIterLine == curLine) {
+        consumeAttribRuns(N, function () {});
+      } else {
+        curChar += N;
+      }
+    }
+  }
+ 
+  function nextText(numChars) {
+    var len = 0;
+    var assem = Changeset.stringAssembler();
+    var firstString = lines_get(curLine).substring(curChar);
+    len += firstString.length;
+    assem.append(firstString);
+ 
+    var lineNum = curLine + 1;
+    while (len < numChars) {
+      var nextString = lines_get(lineNum);
+      len += nextString.length;
+      assem.append(nextString);
+      lineNum++;
+    }
+ 
+    return assem.toString().substring(0, numChars);
+  }
+ 
+  function cachedStrFunc(func) {
+    var cache = {};
+    return function (s) {
+      if (!cache[s]) {
+        cache[s] = func(s);
+      }
+      return cache[s];
+    };
+  }
+ 
+  var attribKeys = [];
+  var attribValues = [];
+ 
+  //iterate over all operators of this changeset
+  while (csIter.hasNext()) {
+    var csOp = csIter.next();
+ 
+    if (csOp.opcode == '=') {      
+      var textBank = nextText(csOp.chars);
+ 
+      // decide if this equal operator is an attribution change or not. We can see this by checkinf if attribs is set.
+      // If the text this operator applies to is only a star, than this is a false positive and should be ignored
+      if (csOp.attribs && textBank != "*") {
+        var deletedAttrib = apool.putAttrib(["removed", true]);
+        var authorAttrib = apool.putAttrib(["author", ""]);;
+ 
+        attribKeys.length = 0;
+        attribValues.length = 0;
+        Changeset.eachAttribNumber(csOp.attribs, function (n) {
+          attribKeys.push(apool.getAttribKey(n));
+          attribValues.push(apool.getAttribValue(n));
+ 
+          if(apool.getAttribKey(n) === "author"){
+            authorAttrib = n;
+          };
+        });
+ 
+        var undoBackToAttribs = cachedStrFunc(function (attribs) {
+          var backAttribs = [];
+          for (var i = 0; i < attribKeys.length; i++) {
+            var appliedKey = attribKeys[i];
+            var appliedValue = attribValues[i];
+            var oldValue = Changeset.attribsAttributeValue(attribs, appliedKey, apool);
+            if (appliedValue != oldValue) {
+              backAttribs.push([appliedKey, oldValue]);
+            }
+          }
+          return Changeset.makeAttribsString('=', backAttribs, apool);
+        });
+ 
+        var oldAttribsAddition = "*" + Changeset.numToString(deletedAttrib) + "*" + Changeset.numToString(authorAttrib);
+ 
+        var textLeftToProcess = textBank;
+ 
+        while(textLeftToProcess.length > 0){
+          //process till the next line break or process only one line break
+          var lengthToProcess = textLeftToProcess.indexOf("\n");
+          var lineBreak = false;
+          switch(lengthToProcess){
+            case -1: 
+              lengthToProcess=textLeftToProcess.length;
+              break;
+            case 0:
+              lineBreak = true;
+              lengthToProcess=1;
+              break;
+          }
+ 
+          //get the text we want to procceed in this step
+          var processText = textLeftToProcess.substr(0, lengthToProcess);
+          textLeftToProcess = textLeftToProcess.substr(lengthToProcess);
+ 
+          if(lineBreak){
+            builder.keep(1, 1); //just skip linebreaks, don't do a insert + keep for a linebreak
+ 
+            //consume the attributes of this linebreak
+            consumeAttribRuns(1, function(){});
+          } else {
+            //add the old text via an insert, but add a deletion attribute + the author attribute of the author who deleted it
+            var textBankIndex = 0;
+            consumeAttribRuns(lengthToProcess, function (len, attribs, endsLine) {
+              //get the old attributes back
+              var attribs = (undoBackToAttribs(attribs) || "") + oldAttribsAddition;
+ 
+              builder.insert(processText.substr(textBankIndex, len), attribs);
+              textBankIndex += len;
+            });
+ 
+            builder.keep(lengthToProcess, 0);
+          }
+        }
+      } else {
+        skip(csOp.chars, csOp.lines);
+        builder.keep(csOp.chars, csOp.lines);
+      }
+    } else if (csOp.opcode == '+') {
+      builder.keep(csOp.chars, csOp.lines);
+    } else if (csOp.opcode == '-') {
+      var textBank = nextText(csOp.chars);
+      var textBankIndex = 0;
+      
+      consumeAttribRuns(csOp.chars, function (len, attribs, endsLine) {
+        builder.insert(textBank.substr(textBankIndex, len), attribs + csOp.attribs);
+        textBankIndex += len;
+      });
+    }
+  }
+ 
+  return Changeset.checkRep(builder.toString());
+};
+ 
+//export the constructor
+module.exports = PadDiff;

src/static/js/Changeset.js

@@ -2182,3 +2182,121 @@ exports.followAttributes = function (att1, att2, pool) {
   }
   return buf.toString();
 };
+
+exports.composeWithDeletions = function (cs1, cs2, pool) {
+  var unpacked1 = exports.unpack(cs1);
+  var unpacked2 = exports.unpack(cs2);
+  var len1 = unpacked1.oldLen;
+  var len2 = unpacked1.newLen;
+  exports.assert(len2 == unpacked2.oldLen, "mismatched composition");
+  var len3 = unpacked2.newLen;
+  var bankIter1 = exports.stringIterator(unpacked1.charBank);
+  var bankIter2 = exports.stringIterator(unpacked2.charBank);
+  var bankAssem = exports.stringAssembler();
+
+  var newOps = exports.applyZip(unpacked1.ops, 0, unpacked2.ops, 0, function (op1, op2, opOut) {
+    var op1code = op1.opcode;
+    var op2code = op2.opcode;
+    if (op1code == '+' && op2code == '-') {
+      bankIter1.skip(Math.min(op1.chars, op2.chars));
+    }
+    exports._slicerZipperFuncWithDeletions(op1, op2, opOut, pool);
+    if (opOut.opcode == '+') {
+      if (op2code == '+') {
+        bankAssem.append(bankIter2.take(opOut.chars));
+      } else {
+        bankAssem.append(bankIter1.take(opOut.chars));
+      }
+    }
+  });
+
+  return exports.pack(len1, len3, newOps, bankAssem.toString());
+};
+
+// This function is 95% like _slicerZipperFunc, we just changed two lines to ensure it merges the attribs of deletions properly. 
+// This is necassary for correct paddiff. But to ensure these changes doesn't affect anything else, we've created a seperate function only used for paddiffs
+exports._slicerZipperFuncWithDeletions= function (attOp, csOp, opOut, pool) {
+  // attOp is the op from the sequence that is being operated on, either an
+  // attribution string or the earlier of two exportss being composed.
+  // pool can be null if definitely not needed.
+  //print(csOp.toSource()+" "+attOp.toSource()+" "+opOut.toSource());
+  if (attOp.opcode == '-') {
+    exports.copyOp(attOp, opOut);
+    attOp.opcode = '';
+  } else if (!attOp.opcode) {
+    exports.copyOp(csOp, opOut);
+    csOp.opcode = '';
+  } else {
+    switch (csOp.opcode) {
+    case '-':
+      {
+        if (csOp.chars <= attOp.chars) {
+          // delete or delete part
+          if (attOp.opcode == '=') {
+            opOut.opcode = '-';
+            opOut.chars = csOp.chars;
+            opOut.lines = csOp.lines;
+            opOut.attribs = csOp.attribs; //changed by yammer
+          }
+          attOp.chars -= csOp.chars;
+          attOp.lines -= csOp.lines;
+          csOp.opcode = '';
+          if (!attOp.chars) {
+            attOp.opcode = '';
+          }
+        } else {
+          // delete and keep going
+          if (attOp.opcode == '=') {
+            opOut.opcode = '-';
+            opOut.chars = attOp.chars;
+            opOut.lines = attOp.lines;
+            opOut.attribs = csOp.attribs; //changed by yammer
+          }
+          csOp.chars -= attOp.chars;
+          csOp.lines -= attOp.lines;
+          attOp.opcode = '';
+        }
+        break;
+      }
+    case '+':
+      {
+        // insert
+        exports.copyOp(csOp, opOut);
+        csOp.opcode = '';
+        break;
+      }
+    case '=':
+      {
+        if (csOp.chars <= attOp.chars) {
+          // keep or keep part
+          opOut.opcode = attOp.opcode;
+          opOut.chars = csOp.chars;
+          opOut.lines = csOp.lines;
+          opOut.attribs = exports.composeAttributes(attOp.attribs, csOp.attribs, attOp.opcode == '=', pool);
+          csOp.opcode = '';
+          attOp.chars -= csOp.chars;
+          attOp.lines -= csOp.lines;
+          if (!attOp.chars) {
+            attOp.opcode = '';
+          }
+        } else {
+          // keep and keep going
+          opOut.opcode = attOp.opcode;
+          opOut.chars = attOp.chars;
+          opOut.lines = attOp.lines;
+          opOut.attribs = exports.composeAttributes(attOp.attribs, csOp.attribs, attOp.opcode == '=', pool);
+          attOp.opcode = '';
+          csOp.chars -= attOp.chars;
+          csOp.lines -= attOp.lines;
+        }
+        break;
+      }
+    case '':
+      {
+        exports.copyOp(attOp, opOut);
+        attOp.opcode = '';
+        break;
+      }
+    }
+  }
+};