Add select inverse action

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

@@ -133,6 +133,15 @@ class LibraryCategoryView @JvmOverloads constructor(context: Context, attrs: Att
                     }
                     controller.invalidateActionMode()
                 }
+
+        subscriptions += controller.selectInverseRelay
+            .filter { it == category.id }
+            .subscribe {
+                adapter.currentItems.forEach { item ->
+                    controller.toggleSelection(item.manga)
+                }
+                controller.invalidateActionMode()
+            }
     }
 
     fun onRecycle() {

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

@@ -100,6 +100,11 @@ class LibraryController(
      */
     val selectAllRelay: PublishRelay<Int> = PublishRelay.create()
 
+    /**
+     * Relay to notify the library's viewpager to select the inverse
+     */
+    val selectInverseRelay: PublishRelay<Int> = PublishRelay.create()
+
     /**
      * Number of manga per row in grid mode.
      */
@@ -407,6 +412,7 @@ class LibraryController(
             R.id.action_move_to_category -> showChangeMangaCategoriesDialog()
             R.id.action_delete -> showDeleteMangaDialog()
             R.id.action_select_all -> selectAllCategoryManga()
+            R.id.action_select_inverse -> selectInverseCategoryManga()
             else -> return false
         }
         return true
@@ -445,6 +451,19 @@ class LibraryController(
         }
     }
 
+    /**
+     * Toggles the current selection state for a given manga.
+     *
+     * @param manga the manga whose selection to change.
+     */
+    fun toggleSelection(manga: Manga) {
+        if (selectedMangas.add(manga)) {
+            selectionRelay.call(LibrarySelectionEvent.Selected(manga))
+        } else if (selectedMangas.remove(manga)) {
+            selectionRelay.call(LibrarySelectionEvent.Unselected(manga))
+        }
+    }
+
     /**
      * Move the selected manga to a list of categories.
      */
@@ -501,6 +520,12 @@ class LibraryController(
         }
     }
 
+    private fun selectInverseCategoryManga() {
+        adapter?.categories?.getOrNull(library_pager.currentItem)?.id?.let {
+            selectInverseRelay.call(it)
+        }
+    }
+
     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
         if (requestCode == REQUEST_IMAGE_OPEN) {
             if (data == null || resultCode != Activity.RESULT_OK) return