Mark common categories when moving them. Closes #135

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryFragment.kt

@@ -385,10 +385,15 @@ class LibraryFragment : BaseRxFragment<LibraryPresenter>(), ActionMode.Callback
      * @param mangas the manga list to move.
      */
     private fun moveMangasToCategories(mangas: List<Manga>) {
+        val categories = presenter.categories
+        val commonCategoriesIndexes = presenter.getCommonCategories(mangas)
+                .map { categories.indexOf(it) }
+                .toTypedArray()
+
         MaterialDialog.Builder(activity)
                 .title(R.string.action_move_category)
-                .items(presenter.getCategoryNames())
-                .itemsCallbackMultiChoice(null) { dialog, positions, text ->
+                .items(categories.map { it.name })
+                .itemsCallbackMultiChoice(commonCategoriesIndexes) { dialog, positions, text ->
                     presenter.moveMangasToCategories(positions, mangas)
                     destroyActionModeIfNeeded()
                     true

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryPresenter.kt

@@ -220,11 +220,13 @@ class LibraryPresenter : BasePresenter<LibraryFragment>() {
     }
 
     /**
-     * Get the category names as a list.
+     * Returns the common categories for the given list of manga.
+     *
+     * @param mangas the list of manga.
      */
-    fun getCategoryNames(): List<String> {
-        return categories.map { it.name }
-    }
+    fun getCommonCategories(mangas: List<Manga>) = mangas.toSet()
+            .map { db.getCategoriesForManga(it).executeAsBlocking() }
+            .reduce { set1: Iterable<Category>, set2 -> set1.intersect(set2) }
 
     /**
      * Remove the selected manga from the library.