Fix highlight for multiline elements

* Now highlight should be perfect except for cases where the diff
context is not enough to understant what is the code

sample/index.html

@@ -24,6 +24,20 @@
 
   <script>
     var lineDiffExample =
+      'diff --git a/src/core/init.java b/src/core/init.java\n' +
+      'index e49196a..50f310c 100644\n' +
+      '--- a/src/core/init.java\n' +
+      '+++ b/src/core/init.java\n' +
+      '@@ -101,7 +101,7 @@\n' +
+      ' /**\n' +
+      '   * Setter for property filesize.\n' +
+      '   *\n' +
+      "   * @param filesize value of property 'filesize'.\n" +
+      '   */\n' +
+      '   public void setFilesize(int filesize) {\n' +
+      '-    this.filesizeOld = filesizeOld;\n' +
+      '+    this.filesizeNew = filesizeNew;\n' +
+      '   }\n' +
       'diff --git a/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/coverage.init b/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/coverage.init\n' +
       'index fc56817..e8e7e49 100644\n' +
       '--- a/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/src/very/long/file/path/coverage.init\n' +

src/ui/js/diff2html-ui.js

@@ -8,7 +8,7 @@
  *
  */
 
-/*global $, hljs*/
+/*global $, hljs, Diff2Html*/
 
 (function() {
 
@@ -69,15 +69,28 @@
 
     var $target = that._getTarget(targetId);
 
-    var languages = that._getLanguages($target);
-
-    // pass the languages to the highlightjs plugin
-    hljs.configure({languages: languages});
+    // collect all the diff files and execute the highlight on their lines
+    var $files = $target.find(".d2h-file-wrapper");
+    $files.map(function(i, file) {
+      var state;
+      var $file = $(file);
+      var language = $file.data("lang");
 
       // collect all the code lines and execute the highlight on them
-    var $codeLines = $target.find(".d2h-code-line-ctn");
+      var $codeLines = $file.find(".d2h-code-line-ctn");
       $codeLines.map(function(i, line) {
-      hljs.highlightBlock(line);
+        var text = line.textContent;
+        var result = hljs.getLanguage(language) ? hljs.highlight(language, text, true, state) : hljs.highlightAuto(text);
+        state = result.top;
+
+        var originalStream = nodeStream(line);
+        if (originalStream.length) {
+          var resultNode = document.createElementNS('http://www.w3.org/1999/xhtml', 'div');
+          resultNode.innerHTML = result.value;
+          result.value = mergeStreams(originalStream, nodeStream(resultNode), text);
+        }
+        $(line).html(result.value);
+      });
     });
   };
 
@@ -97,24 +110,6 @@
     return $target;
   };
 
-  Diff2HtmlUI.prototype._getLanguages = function($target) {
-    var allFileLanguages = [];
-
-    if (diffJson) {
-      // collect all the file extensions in the json
-      allFileLanguages = diffJson.map(function(line) {
-        return line.language;
-      });
-    } else {
-      $target.find(".d2h-file-wrapper").map(function(i, file) {
-        allFileLanguages.push($(file).data("lang"));
-      });
-    }
-
-    // return only distinct languages
-    return this._distinct(allFileLanguages);
-  };
-
   Diff2HtmlUI.prototype._getHashTag = function() {
     var docUrl = document.URL;
     var hashTagIndex = docUrl.indexOf('#');
@@ -181,6 +176,129 @@
     return text;
   };
 
+  /*
+   * Copied from Highlight.js Private API
+   * Will be removed when this part of the API is exposed
+   */
+
+  /* Utility functions */
+
+  function escape(value) {
+    return value.replace(/&/gm, '&amp;').replace(/</gm, '&lt;').replace(/>/gm, '&gt;');
+  }
+
+  function tag(node) {
+    return node.nodeName.toLowerCase();
+  }
+
+  /* Stream merging */
+
+  function nodeStream(node) {
+    var result = [];
+    (function _nodeStream(node, offset) {
+      for (var child = node.firstChild; child; child = child.nextSibling) {
+        if (child.nodeType == 3)
+          offset += child.nodeValue.length;
+        else if (child.nodeType == 1) {
+          result.push({
+            event: 'start',
+            offset: offset,
+            node: child
+          });
+          offset = _nodeStream(child, offset);
+          // Prevent void elements from having an end tag that would actually
+          // double them in the output. There are more void elements in HTML
+          // but we list only those realistically expected in code display.
+          if (!tag(child).match(/br|hr|img|input/)) {
+            result.push({
+              event: 'stop',
+              offset: offset,
+              node: child
+            });
+          }
+        }
+      }
+      return offset;
+    })(node, 0);
+    return result;
+  }
+
+  function mergeStreams(original, highlighted, value) {
+    var processed = 0;
+    var result = '';
+    var nodeStack = [];
+
+    function selectStream() {
+      if (!original.length || !highlighted.length) {
+        return original.length ? original : highlighted;
+      }
+      if (original[0].offset != highlighted[0].offset) {
+        return (original[0].offset < highlighted[0].offset) ? original : highlighted;
+      }
+
+      /*
+       To avoid starting the stream just before it should stop the order is
+       ensured that original always starts first and closes last:
+       if (event1 == 'start' && event2 == 'start')
+       return original;
+       if (event1 == 'start' && event2 == 'stop')
+       return highlighted;
+       if (event1 == 'stop' && event2 == 'start')
+       return original;
+       if (event1 == 'stop' && event2 == 'stop')
+       return highlighted;
+       ... which is collapsed to:
+       */
+      return highlighted[0].event == 'start' ? original : highlighted;
+    }
+
+    function open(node) {
+      function attrStr(a) {
+        return ' ' + a.nodeName + '="' + escape(a.value) + '"';
+      }
+
+      result += '<' + tag(node) + Array.prototype.map.call(node.attributes, attrStr).join('') + '>';
+    }
+
+    function close(node) {
+      result += '</' + tag(node) + '>';
+    }
+
+    function render(event) {
+      (event.event == 'start' ? open : close)(event.node);
+    }
+
+    while (original.length || highlighted.length) {
+      var stream = selectStream();
+      result += escape(value.substr(processed, stream[0].offset - processed));
+      processed = stream[0].offset;
+      if (stream == original) {
+        /*
+         On any opening or closing tag of the original markup we first close
+         the entire highlighted node stack, then render the original tag along
+         with all the following original tags at the same offset and then
+         reopen all the tags on the highlighted stack.
+         */
+        nodeStack.reverse().forEach(close);
+        do {
+          render(stream.splice(0, 1)[0]);
+          stream = selectStream();
+        } while (stream == original && stream.length && stream[0].offset == processed);
+        nodeStack.reverse().forEach(open);
+      } else {
+        if (stream[0].event == 'start') {
+          nodeStack.push(stream[0].node);
+        } else {
+          nodeStack.pop();
+        }
+        render(stream.splice(0, 1)[0]);
+      }
+    }
+    return result + escape(value.substr(processed));
+  }
+
+  /* **** Highlight.js Private API **** */
+
   module.exports.Diff2HtmlUI = Diff2HtmlUI;
 
   // Expose diff2html in the browser