Mendeley import: Reuse existing collections

If "Place imported collections and items into new collection" is
unchecked, previously imported collections will be reused when they're
in the right place in the hierarchy rather than creating new ones.

chrome/content/zotero/fileInterface.js

@@ -336,6 +336,7 @@ var Zotero_File_Interface = new function() {
 			// Mendeley import doesn't use the real translation architecture, but we create a
 			// translation object with the same interface
 			translation = yield _getMendeleyTranslation();
+			translation.createNewCollection = createNewCollection;
 			defaultNewCollectionPrefix = "Mendeley Import";
 		}
 		else {

chrome/content/zotero/import/mendeley/mendeleyImport.js

@@ -5,6 +5,7 @@ Components.utils.import("resource://gre/modules/osfile.jsm");
 Services.scriptloader.loadSubScript("chrome://zotero/content/include.js");
 
 var Zotero_Import_Mendeley = function () {
+	this.createNewCollection = null;
 	this.newItems = [];
 	
 	this._db;
@@ -84,7 +85,7 @@ Zotero_Import_Mendeley.prototype.translate = async function (options) {
 		let folders = await this._getFolders(mendeleyGroupID);
 		let collectionJSON = this._foldersToAPIJSON(folders, rootCollectionKey);
 		let folderKeys = this._getFolderKeys(collectionJSON);
-		await this._saveCollections(libraryID, collectionJSON);
+		await this._saveCollections(libraryID, collectionJSON, folderKeys);
 		
 		//
 		// Items
@@ -253,14 +254,31 @@ Zotero_Import_Mendeley.prototype._getFolderKeys = function (collections) {
  * @param {Integer} libraryID
  * @param {Object[]} json
  */
-Zotero_Import_Mendeley.prototype._saveCollections = async function (libraryID, json) {
-	var idMap = new Map();
-	for (let collectionJSON of json) {
-		let collection = new Zotero.Collection;
-		collection.libraryID = libraryID;
-		if (collectionJSON.key) {
-			collection.key = collectionJSON.key;
-			await collection.loadPrimaryData();
+Zotero_Import_Mendeley.prototype._saveCollections = async function (libraryID, json, folderKeys) {
+	var keyMap = new Map();
+	for (let i = 0; i < json.length; i++) {
+		let collectionJSON = json[i];
+		
+		// Check if the collection was previously imported
+		let collection = this._findExistingCollection(
+			libraryID,
+			collectionJSON,
+			collectionJSON.parentCollection ? keyMap.get(collectionJSON.parentCollection) : null
+		);
+		if (collection) {
+			// Update any child collections to point to the existing collection's key instead of
+			// the new generated one
+			this._updateParentKeys('collection', json, i + 1, collectionJSON.key, collection.key);
+			// And update the map of Mendeley folderIDs to Zotero collection keys
+			folderKeys.set(collectionJSON.folderID, collection.key);
+		}
+		else {
+			collection = new Zotero.Collection;
+			collection.libraryID = libraryID;
+			if (collectionJSON.key) {
+				collection.key = collectionJSON.key;
+				await collection.loadPrimaryData();
+			}
 		}
 		
 		// Remove external ids before saving
@@ -272,12 +290,37 @@ Zotero_Import_Mendeley.prototype._saveCollections = async function (libraryID, j
 		await collection.saveTx({
 			skipSelect: true
 		});
-		idMap.set(collectionJSON.folderID, collection.id);
 	}
-	return idMap;
 };
 
 
+Zotero_Import_Mendeley.prototype._findExistingCollection = function (libraryID, collectionJSON, parentCollection) {
+	// Don't use existing collections if the import is creating a top-level collection
+	if (this.createNewCollection || !collectionJSON.relations) {
+		return false;
+	}
+	
+	var predicate = 'mendeleyDB:remoteFolderUUID';
+	var uuid = collectionJSON.relations[predicate];
+	
+	var collections = Zotero.Relations.getByPredicateAndObject('collection', predicate, uuid)
+		.filter((c) => {
+			if (c.libraryID != libraryID) {
+				return false;
+			}
+			// If there's a parent collection it has to be the one we've already used
+			return parentCollection ? c.parentID == parentCollection.id : true;
+		});
+	if (!collections.length) {
+		return false;
+	}
+	
+	Zotero.debug(`Found existing collection ${collections[0].libraryKey} for `
+		+ `${predicate} ${collectionJSON.relations[predicate]}`);
+	return collections[0];
+}
+
+
 //
 // Items
 //
@@ -756,14 +799,14 @@ Zotero_Import_Mendeley.prototype._saveItems = async function (libraryID, json) {
 			let itemJSON = json[i];
 			
 			// Check if the item has been previously imported
-			let item = await this._findExistingItem(libraryID, itemJSON, lastExistingParentItem);
+			let item = this._findExistingItem(libraryID, itemJSON, lastExistingParentItem);
 			if (item) {
 				if (item.isRegularItem()) {
 					lastExistingParentItem = item;
 					
 					// Update any child items to point to the existing item's key instead of the
 					// new generated one
-					this._updateParentItemKey(json, i + 1, itemJSON.key, item.key);
+					this._updateParentKeys('item', json, i + 1, itemJSON.key, item.key);
 					
 					// Leave item in any collections it's in
 					itemJSON.collections = item.getCollections()
@@ -800,7 +843,7 @@ Zotero_Import_Mendeley.prototype._saveItems = async function (libraryID, json) {
 };
 
 
-Zotero_Import_Mendeley.prototype._findExistingItem = async function (libraryID, itemJSON, existingParentItem) {
+Zotero_Import_Mendeley.prototype._findExistingItem = function (libraryID, itemJSON, existingParentItem) {
 	var predicate;
 	
 	//
@@ -890,22 +933,9 @@ Zotero_Import_Mendeley.prototype._findExistingItem = async function (libraryID,
 }
 
 
-Zotero_Import_Mendeley.prototype._updateParentItemKey = function (json, i, oldKey, newKey) {
-	for (; i < json.length; i++) {
-		let x = json[i];
-		if (x.parentItem == oldKey) {
-			x.parentItem = newKey;
-		}
-		else {
-			break;
-		}
-	}
-}
-
-
 Zotero_Import_Mendeley.prototype._getItemByRelation = function (libraryID, predicate, object) {
-	var items = Zotero.Relations.getByPredicateAndObject('item', predicate, object);
-	items = items.filter(item => item.libraryID == libraryID && !item.deleted);
+	var items = Zotero.Relations.getByPredicateAndObject('item', predicate, object)
+		.filter(item => item.libraryID == libraryID && !item.deleted);
 	if (!items.length) {
 		return false;
 	}
@@ -1088,3 +1118,28 @@ Zotero_Import_Mendeley.prototype._saveAnnotations = async function (annotations,
 		skipSelect: true
 	});
 };
+
+
+Zotero_Import_Mendeley.prototype._updateParentKeys = function (objectType, json, i, oldKey, newKey) {
+	var prop = 'parent' + objectType[0].toUpperCase() + objectType.substr(1);
+	
+	for (; i < json.length; i++) {
+		let x = json[i];
+		if (x[prop] == oldKey) {
+			x[prop] = newKey;
+		}
+		// Child items are grouped together, so we can stop as soon as we stop seeing the prop
+		else if (objectType == 'item') {
+			break;
+		}
+	}
+}
+
+Zotero_Import_Mendeley.prototype._updateItemCollectionKeys = function (json, oldKey, newKey) {
+	for (; i < json.length; i++) {
+		let x = json[i];
+		if (x[prop] == oldKey) {
+			x[prop] = newKey;
+		}
+	}
+}