Add Basilisk

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diff --git a/application/basilisk/components/translation/TranslationDocument.jsm b/application/basilisk/components/translation/TranslationDocument.jsm
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+++ b/application/basilisk/components/translation/TranslationDocument.jsm
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
+
+this.EXPORTED_SYMBOLS = [ "TranslationDocument" ];
+
+const SHOW_ELEMENT = Ci.nsIDOMNodeFilter.SHOW_ELEMENT;
+const SHOW_TEXT = Ci.nsIDOMNodeFilter.SHOW_TEXT;
+const TEXT_NODE = Ci.nsIDOMNode.TEXT_NODE;
+
+Cu.import("resource://services-common/utils.js");
+Cu.import("resource://gre/modules/Task.jsm");
+
+/**
+ * This class represents a document that is being translated,
+ * and it is responsible for parsing the document,
+ * generating the data structures translation (the list of
+ * translation items and roots), and managing the original
+ * and translated texts on the translation items.
+ *
+ * @param document  The document to be translated
+ */
+this.TranslationDocument = function(document) {
+  this.itemsMap = new Map();
+  this.roots = [];
+  this._init(document);
+};
+
+this.TranslationDocument.prototype = {
+  translatedFrom: "",
+  translatedTo: "",
+  translationError: false,
+  originalShown: true,
+
+  /**
+   * Initializes the object and populates
+   * the roots lists.
+   *
+   * @param document  The document to be translated
+   */
+  _init(document) {
+    let window = document.defaultView;
+    let winUtils = window.QueryInterface(Ci.nsIInterfaceRequestor)
+                         .getInterface(Ci.nsIDOMWindowUtils);
+
+    // Get all the translation nodes in the document's body:
+    // a translation node is a node from the document which
+    // contains useful content for translation, and therefore
+    // must be included in the translation process.
+    let nodeList = winUtils.getTranslationNodes(document.body);
+
+    let length = nodeList.length;
+
+    for (let i = 0; i < length; i++) {
+      let node = nodeList.item(i);
+      let isRoot = nodeList.isTranslationRootAtIndex(i);
+
+      // Create a TranslationItem object for this node.
+      // This function will also add it to the this.roots array.
+      this._createItemForNode(node, i, isRoot);
+    }
+
+    // At first all roots are stored in the roots list, and only after
+    // the process has finished we're able to determine which roots are
+    // simple, and which ones are not.
+
+    // A simple root is defined by a root with no children items, which
+    // basically represents an element from a page with only text content
+    // inside.
+
+    // This distinction is useful for optimization purposes: we treat a
+    // simple root as plain-text in the translation process and with that
+    // we are able to reduce their data payload sent to the translation service.
+
+    for (let root of this.roots) {
+      if (root.children.length == 0 &&
+          root.nodeRef.childElementCount == 0) {
+        root.isSimpleRoot = true;
+      }
+    }
+  },
+
+  /**
+   * Creates a TranslationItem object, which should be called
+   * for each node returned by getTranslationNodes.
+   *
+   * @param node        The DOM node for this item.
+   * @param id          A unique, numeric id for this item.
+   * @parem isRoot      A boolean saying whether this item is a root.
+   *
+   * @returns           A TranslationItem object.
+   */
+  _createItemForNode(node, id, isRoot) {
+    if (this.itemsMap.has(node)) {
+      return this.itemsMap.get(node);
+    }
+
+    let item = new TranslationItem(node, id, isRoot);
+
+    if (isRoot) {
+      // Root items do not have a parent item.
+      this.roots.push(item);
+    } else {
+      let parentItem = this.itemsMap.get(node.parentNode);
+      if (parentItem) {
+        parentItem.children.push(item);
+      }
+    }
+
+    this.itemsMap.set(node, item);
+    return item;
+  },
+
+  /**
+   * Generate the text string that represents a TranslationItem object.
+   * Besides generating the string, it's also stored in the "original"
+   * field of the TranslationItem object, which needs to be stored for
+   * later to be used in the "Show Original" functionality.
+   * If this function had already been called for the given item (determined
+   * by the presence of the "original" array in the item), the text will
+   * be regenerated from the "original" data instead of from the related
+   * DOM nodes (because the nodes might contain translated data).
+   *
+   * @param item     A TranslationItem object
+   *
+   * @returns        A string representation of the TranslationItem.
+   */
+  generateTextForItem(item) {
+    if (item.original) {
+      return regenerateTextFromOriginalHelper(item);
+    }
+
+    if (item.isSimpleRoot) {
+      let text = item.nodeRef.firstChild.nodeValue.trim();
+      item.original = [text];
+      return text;
+    }
+
+    let str = "";
+    item.original = [];
+    let wasLastItemPlaceholder = false;
+
+    for (let child of item.nodeRef.childNodes) {
+      if (child.nodeType == TEXT_NODE) {
+        let x = child.nodeValue.trim();
+        if (x != "") {
+          item.original.push(x);
+          str += x;
+          wasLastItemPlaceholder = false;
+        }
+        continue;
+      }
+
+      let objInMap = this.itemsMap.get(child);
+      if (objInMap && !objInMap.isRoot) {
+        // If this childNode is present in the itemsMap, it means
+        // it's a translation node: it has useful content for translation.
+        // In this case, we need to stringify this node.
+        // However, if this item is a root, we should skip it here in this
+        // object's child list (and just add a placeholder for it), because
+        // it will be stringfied separately for being a root.
+        item.original.push(objInMap);
+        str += this.generateTextForItem(objInMap);
+        wasLastItemPlaceholder = false;
+      } else if (!wasLastItemPlaceholder) {
+        // Otherwise, if this node doesn't contain any useful content,
+        // or if it is a root itself, we can replace it with a placeholder node.
+        // We can't simply eliminate this node from our string representation
+        // because that could change the HTML structure (e.g., it would
+        // probably merge two separate text nodes).
+        // It's not necessary to add more than one placeholder in sequence;
+        // we can optimize them away.
+        item.original.push(TranslationItem_NodePlaceholder);
+        str += "<br>";
+        wasLastItemPlaceholder = true;
+      }
+    }
+
+    return generateTranslationHtmlForItem(item, str);
+  },
+
+  /**
+   * Changes the document to display its translated
+   * content.
+   */
+  showTranslation() {
+    this.originalShown = false;
+    this._swapDocumentContent("translation");
+  },
+
+  /**
+   * Changes the document to display its original
+   * content.
+   */
+  showOriginal() {
+    this.originalShown = true;
+    this._swapDocumentContent("original");
+  },
+
+  /**
+   * Swap the document with the resulting translation,
+   * or back with the original content.
+   *
+   * @param target   A string that is either "translation"
+   *                 or "original".
+   */
+  _swapDocumentContent(target) {
+    Task.spawn(function *() {
+      // Let the event loop breath on every 100 nodes
+      // that are replaced.
+      const YIELD_INTERVAL = 100;
+      let count = YIELD_INTERVAL;
+
+      for (let root of this.roots) {
+        root.swapText(target);
+        if (count-- == 0) {
+          count = YIELD_INTERVAL;
+          yield CommonUtils.laterTickResolvingPromise();
+        }
+      }
+    }.bind(this));
+  }
+};
+
+/**
+ * This class represents an item for translation. It's basically our
+ * wrapper class around a node returned by getTranslationNode, with
+ * more data and structural information on it.
+ *
+ * At the end of the translation process, besides the properties below,
+ * a TranslationItem will contain two other properties: one called "original"
+ * and one called "translation". They are twin objects, one which reflect
+ * the structure of that node in its original state, and the other in its
+ * translated state.
+ *
+ * The "original" array is generated in the generateTextForItem function,
+ * and the "translation" array is generated when the translation results
+ * are parsed.
+ *
+ * They are both arrays, which contain a mix of strings and references to
+ * child TranslationItems. The references in both arrays point to the * same *
+ * TranslationItem object, but they might appear in different orders between the
+ * "original" and "translation" arrays.
+ *
+ * An example:
+ *
+ *  English: <div id="n1">Welcome to <b id="n2">Mozilla's</b> website</div>
+ *  Portuguese: <div id="n1">Bem vindo a pagina <b id="n2">da Mozilla</b></div>
+ *
+ *  TranslationItem n1 = {
+ *    id: 1,
+ *    original: ["Welcome to", ptr to n2, "website"]
+ *    translation: ["Bem vindo a pagina", ptr to n2]
+ *  }
+ *
+ *  TranslationItem n2 = {
+ *    id: 2,
+ *    original: ["Mozilla's"],
+ *    translation: ["da Mozilla"]
+ *  }
+ */
+function TranslationItem(node, id, isRoot) {
+  this.nodeRef = node;
+  this.id = id;
+  this.isRoot = isRoot;
+  this.children = [];
+}
+
+TranslationItem.prototype = {
+  isRoot: false,
+  isSimpleRoot: false,
+
+  toString() {
+    let rootType = "";
+    if (this.isRoot) {
+      if (this.isSimpleRoot) {
+        rootType = " (simple root)";
+      } else {
+        rootType = " (non simple root)";
+      }
+    }
+    return "[object TranslationItem: <" + this.nodeRef.localName + ">"
+           + rootType + "]";
+  },
+
+  /**
+   * This function will parse the result of the translation of one translation
+   * item. If this item was a simple root, all we sent was a plain-text version
+   * of it, so the result is also straightforward text.
+   *
+   * For non-simple roots, we sent a simplified HTML representation of that
+   * node, and we'll first parse that into an HTML doc and then call the
+   * parseResultNode helper function to parse it.
+   *
+   * While parsing, the result is stored in the "translation" field of the
+   * TranslationItem, which will be used to display the final translation when
+   * all items are finished. It remains stored too to allow back-and-forth
+   * switching between the "Show Original" and "Show Translation" functions.
+   *
+   * @param result    A string with the textual result received from the server,
+   *                  which can be plain-text or a serialized HTML doc.
+   */
+  parseResult(result) {
+    if (this.isSimpleRoot) {
+      this.translation = [result];
+      return;
+    }
+
+    let domParser = Cc["@mozilla.org/xmlextras/domparser;1"]
+                      .createInstance(Ci.nsIDOMParser);
+
+    let doc = domParser.parseFromString(result, "text/html");
+    parseResultNode(this, doc.body.firstChild);
+  },
+
+  /**
+   * This function finds a child TranslationItem
+   * with the given id.
+   * @param id        The id to look for, in the format "n#"
+   * @returns         A TranslationItem with the given id, or null if
+   *                  it was not found.
+   */
+  getChildById(id) {
+    for (let child of this.children) {
+      if (("n" + child.id) == id) {
+        return child;
+      }
+    }
+    return null;
+  },
+
+  /**
+   * Swap the text of this TranslationItem between
+   * its original and translated states.
+   *
+   * @param target   A string that is either "translation"
+   *                 or "original".
+   */
+  swapText(target) {
+    swapTextForItem(this, target);
+  }
+};
+
+/**
+ * This object represents a placeholder item for translation. It's similar to
+ * the TranslationItem class, but it represents nodes that have no meaningful
+ * content for translation. These nodes will be replaced by "<br>" in a
+ * translation request. It's necessary to keep them to use it as a mark
+ * for correct positioning and spliting of text nodes.
+ */
+const TranslationItem_NodePlaceholder = {
+  toString() {
+    return "[object TranslationItem_NodePlaceholder]";
+  }
+};
+
+/**
+ * Generate the outer HTML representation for a given item.
+ *
+ * @param   item       A TranslationItem object.
+ * param    content    The inner content for this item.
+ * @returns string     The outer HTML needed for translation
+ *                     of this item.
+ */
+function generateTranslationHtmlForItem(item, content) {
+  let localName = item.isRoot ? "div" : "b";
+  return "<" + localName + " id=n" + item.id + ">" +
+         content +
+         "</" + localName + ">";
+}
+
+ /**
+ * Regenerate the text string that represents a TranslationItem object,
+ * with data from its "original" array. The array must have already
+ * been created by TranslationDocument.generateTextForItem().
+ *
+ * @param item     A TranslationItem object
+ *
+ * @returns        A string representation of the TranslationItem.
+ */
+function regenerateTextFromOriginalHelper(item) {
+  if (item.isSimpleRoot) {
+    return item.original[0];
+  }
+
+  let str = "";
+  for (let child of item.original) {
+    if (child instanceof TranslationItem) {
+      str += regenerateTextFromOriginalHelper(child);
+    } else if (child === TranslationItem_NodePlaceholder) {
+      str += "<br>";
+    } else {
+      str += child;
+    }
+  }
+
+  return generateTranslationHtmlForItem(item, str);
+}
+
+/**
+ * Helper function to parse a HTML doc result.
+ * How it works:
+ *
+ * An example result string is:
+ *
+ * <div id="n1">Hello <b id="n2">World</b> of Mozilla.</div>
+ *
+ * For an element node, we look at its id and find the corresponding
+ * TranslationItem that was associated with this node, and then we
+ * walk down it repeating the process.
+ *
+ * For text nodes we simply add it as a string.
+ */
+function parseResultNode(item, node) {
+  item.translation = [];
+  for (let child of node.childNodes) {
+    if (child.nodeType == TEXT_NODE) {
+      item.translation.push(child.nodeValue);
+    } else if (child.localName == "br") {
+      item.translation.push(TranslationItem_NodePlaceholder);
+    } else {
+      let translationItemChild = item.getChildById(child.id);
+
+      if (translationItemChild) {
+        item.translation.push(translationItemChild);
+        parseResultNode(translationItemChild, child);
+      }
+    }
+  }
+}
+
+/**
+ * Helper function to swap the text of a TranslationItem
+ * between its original and translated states.
+ * How it works:
+ *
+ * The function iterates through the target array (either the `original` or
+ * `translation` array from the TranslationItem), while also keeping a pointer
+ * to a current position in the child nodes from the actual DOM node that we
+ * are modifying. This pointer is moved forward after each item of the array
+ * is translated. If, at any given time, the pointer doesn't match the expected
+ * node that was supposed to be seen, it means that the original and translated
+ * contents have a different ordering, and thus we need to adjust that.
+ *
+ * A full example of the reordering process, swapping from Original to
+ * Translation:
+ *
+ *    Original (en): <div>I <em>miss</em> <b>you</b></div>
+ *
+ * Translation (fr): <div><b>Tu</b> me <em>manques</em></div>
+ *
+ * Step 1:
+ *   pointer points to firstChild of the DOM node, textnode "I "
+ *   first item in item.translation is [object TranslationItem <b>]
+ *
+ *   pointer does not match the expected element, <b>. So let's move <b> to the
+ *   pointer position.
+ *
+ *   Current state of the DOM:
+ *     <div><b>you</b>I <em>miss</em> </div>
+ *
+ * Step 2:
+ *   pointer moves forward to nextSibling, textnode "I " again.
+ *   second item in item.translation is the string " me "
+ *
+ *   pointer points to a text node, and we were expecting a text node. Match!
+ *   just replace the text content.
+ *
+ *   Current state of the DOM:
+ *     <div><b>you</b> me <em>miss</em> </div>
+ *
+ * Step 3:
+ *   pointer moves forward to nextSibling, <em>miss</em>
+ *   third item in item.translation is [object TranslationItem <em>]
+ *
+ *   pointer points to the expected node. Match! Nothing to do.
+ *
+ * Step 4:
+ *   all items in this item.translation were transformed. The remaining
+ *   text nodes are cleared to "", and domNode.normalize() removes them.
+ *
+ *   Current state of the DOM:
+ *     <div><b>you</b> me <em>miss</em></div>
+ *
+ * Further steps:
+ *   After that, the function will visit the child items (from the visitStack),
+ *   and the text inside the <b> and <em> nodes will be swapped as well,
+ *   yielding the final result:
+ *
+ *     <div><b>Tu</b> me <em>manques</em></div>
+ *
+ *
+ * @param item     A TranslationItem object
+ * @param target   A string that is either "translation"
+ *                 or "original".
+ */
+function swapTextForItem(item, target) {
+  // visitStack is the stack of items that we still need to visit.
+  // Let's start the process by adding the root item.
+  let visitStack = [ item ];
+
+  while (visitStack.length > 0) {
+    let curItem = visitStack.shift();
+
+    let domNode = curItem.nodeRef;
+    if (!domNode) {
+      // Skipping this item due to a missing node.
+      continue;
+    }
+
+    if (!curItem[target]) {
+      // Translation not found for this item. This could be due to
+      // an error in the server response. For example, if a translation
+      // was broken in various chunks, and one of the chunks failed,
+      // the items from that chunk will be missing its "translation"
+      // field.
+      continue;
+    }
+
+    domNode.normalize();
+
+    // curNode points to the child nodes of the DOM node that we are
+    // modifying. During most of the process, while the target array is
+    // being iterated (in the for loop below), it should walk together with
+    // the array and be pointing to the correct node that needs to modified.
+    // If it's not pointing to it, that means some sort of node reordering
+    // will be necessary to produce the correct translation.
+    // Note that text nodes don't need to be reordered, as we can just replace
+    // the content of one text node with another.
+    //
+    // curNode starts in the firstChild...
+    let curNode = domNode.firstChild;
+
+    // ... actually, let's make curNode start at the first useful node (either
+    // a non-blank text node or something else). This is not strictly necessary,
+    // as the reordering algorithm would correctly handle this case. However,
+    // this better aligns the resulting translation with the DOM content of the
+    // page, avoiding cases that would need to be unecessarily reordered.
+    //
+    // An example of how this helps:
+    //
+    // ---- Original: <div>                <b>Hello </b> world.</div>
+    //                       ^textnode 1      ^item 1      ^textnode 2
+    //
+    // - Translation: <div><b>Hallo </b> Welt.</div>
+    //
+    // Transformation process without this optimization:
+    //   1 - start pointer at textnode 1
+    //   2 - move item 1 to first position inside the <div>
+    //
+    //       Node now looks like: <div><b>Hello </b>[         ][ world.]</div>
+    //                                         textnode 1^       ^textnode 2
+    //
+    //   3 - replace textnode 1 with " Welt."
+    //   4 - clear remaining text nodes (in this case, textnode 2)
+    //
+    // Transformation process with this optimization:
+    //   1 - start pointer at item 1
+    //   2 - item 1 is already in position
+    //   3 - replace textnode 2 with " Welt."
+    //
+    // which completely avoids any node reordering, and requires only one
+    // text change instead of two (while also leaving the page closer to
+    // its original state).
+    while (curNode &&
+           curNode.nodeType == TEXT_NODE &&
+           curNode.nodeValue.trim() == "") {
+      curNode = curNode.nextSibling;
+    }
+
+    // Now let's walk through all items in the `target` array of the
+    // TranslationItem. This means either the TranslationItem.original or
+    // TranslationItem.translation array.
+    for (let targetItem of curItem[target]) {
+
+      if (targetItem instanceof TranslationItem) {
+        // If the array element is another TranslationItem object, let's
+        // add it to the stack to be visited.
+        visitStack.push(targetItem);
+
+        let targetNode = targetItem.nodeRef;
+
+            // If the node is not in the expected position, let's reorder
+            // it into position...
+        if (curNode != targetNode &&
+            // ...unless the page has reparented this node under a totally
+            // different node (or removed it). In this case, all bets are off
+            // on being able to do anything correctly, so it's better not to
+            // bring back the node to this parent.
+            targetNode.parentNode == domNode) {
+
+          // We don't need to null-check curNode because insertBefore(..., null)
+          // does what we need in that case: reorder this node to the end
+          // of child nodes.
+          domNode.insertBefore(targetNode, curNode);
+          curNode = targetNode;
+        }
+
+        // Move pointer forward. Since we do not add empty text nodes to the
+        // list of translation items, we must skip them here too while
+        // traversing the DOM in order to get better alignment between the
+        // text nodes and the translation items.
+        if (curNode) {
+          curNode = getNextSiblingSkippingEmptyTextNodes(curNode);
+        }
+
+      } else if (targetItem === TranslationItem_NodePlaceholder) {
+        // If the current item is a placeholder node, we need to move
+        // our pointer "past" it, jumping from one side of a block of
+        // elements + empty text nodes to the other side. Even if
+        // non-placeholder elements exists inside the jumped block,
+        // they will be pulled correctly later in the process when the
+        // targetItem for those nodes are handled.
+
+        while (curNode &&
+               (curNode.nodeType != TEXT_NODE ||
+                curNode.nodeValue.trim() == "")) {
+          curNode = curNode.nextSibling;
+        }
+
+      } else {
+        // Finally, if it's a text item, we just need to find the next
+        // text node to use. Text nodes don't need to be reordered, so
+        // the first one found can be used.
+        while (curNode && curNode.nodeType != TEXT_NODE) {
+          curNode = curNode.nextSibling;
+        }
+
+        // If none was found and we reached the end of the child nodes,
+        // let's create a new one.
+        if (!curNode) {
+          // We don't know if the original content had a space or not,
+          // so the best bet is to create the text node with " " which
+          // will add one space at the beginning and one at the end.
+          curNode = domNode.appendChild(domNode.ownerDocument.createTextNode(" "));
+        }
+
+        // A trailing and a leading space must be preserved because
+        // they are meaningful in HTML.
+        let preSpace = /^\s/.test(curNode.nodeValue) ? " " : "";
+        let endSpace = /\s$/.test(curNode.nodeValue) ? " " : "";
+
+        curNode.nodeValue = preSpace + targetItem + endSpace;
+        curNode = getNextSiblingSkippingEmptyTextNodes(curNode);
+      }
+    }
+
+    // The translated version of a node might have less text nodes than its
+    // original version. If that's the case, let's clear the remaining nodes.
+    if (curNode) {
+      clearRemainingNonEmptyTextNodesFromElement(curNode);
+    }
+
+    // And remove any garbage "" nodes left after clearing.
+    domNode.normalize();
+  }
+}
+
+function getNextSiblingSkippingEmptyTextNodes(startSibling) {
+  let item = startSibling.nextSibling;
+  while (item &&
+         item.nodeType == TEXT_NODE &&
+         item.nodeValue.trim() == "") {
+    item = item.nextSibling;
+  }
+  return item;
+}
+
+function clearRemainingNonEmptyTextNodesFromElement(startSibling) {
+  let item = startSibling;
+  while (item) {
+    if (item.nodeType == TEXT_NODE &&
+        item.nodeValue != "") {
+      item.nodeValue = "";
+    }
+    item = item.nextSibling;
+  }
+}