Page exit prevention refactor (#637)

* Add page exit prevention functionality to SettingsController

* Update dictionary controller to use new page exit prevention system

* Remove page-exit-prevention.js

4 files changed, 42 insertions, 68 deletions

diff --git a/ext/bg/js/page-exit-prevention.js b/ext/bg/js/page-exit-prevention.js
deleted file mode 100644
index f55cf024..00000000
--- a/ext/bg/js/page-exit-prevention.js
+++ /dev/null
@@ -1,59 +0,0 @@
-/*
- * Copyright (C) 2019-2020  Yomichan Authors
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <https://www.gnu.org/licenses/>.
- */
-
-
-class PageExitPrevention {
-    constructor() {
-    }
-
-    start() {
-        PageExitPrevention._addInstance(this);
-    }
-
-    end() {
-        PageExitPrevention._removeInstance(this);
-    }
-
-    static _addInstance(instance) {
-        const size = PageExitPrevention._instances.size;
-        PageExitPrevention._instances.set(instance, true);
-        if (size === 0) {
-            window.addEventListener('beforeunload', PageExitPrevention._onBeforeUnload);
-        }
-    }
-
-    static _removeInstance(instance) {
-        if (
-            PageExitPrevention._instances.delete(instance) &&
-            PageExitPrevention._instances.size === 0
-        ) {
-            window.removeEventListener('beforeunload', PageExitPrevention._onBeforeUnload);
-        }
-    }
-
-    static _onBeforeUnload(e) {
-        if (PageExitPrevention._instances.size === 0) {
-            return;
-        }
-
-        e.preventDefault();
-        e.returnValue = '';
-        return '';
-    }
-}
-
-PageExitPrevention._instances = new Map();
diff --git a/ext/bg/js/settings/dictionaries.js b/ext/bg/js/settings/dictionaries.js
index 94a71233..1e780909 100644
--- a/ext/bg/js/settings/dictionaries.js
+++ b/ext/bg/js/settings/dictionaries.js
@@ -16,7 +16,6 @@
  */
 
 /* global
- * PageExitPrevention
  * api
  * utilBackgroundIsolate
  */
@@ -156,6 +155,11 @@ class SettingsDictionaryListUI extends EventDispatcher {
         // Overwrite
     }
 
+    preventPageExit() {
+        // Overwrite
+        return {end: () => {}};
+    }
+
     onDictionaryConfirmDelete(e) {
         e.preventDefault();
         const n = document.querySelector('#dict-delete-modal');
@@ -286,10 +290,8 @@ class SettingsDictionaryEntryUI {
         const progressBar = this.content.querySelector('.progress-bar');
         this.isDeleting = true;
 
-        const prevention = new PageExitPrevention();
+        const prevention = this.parent.preventPageExit();
         try {
-            prevention.start();
-
             const onProgress = ({processed, count, storeCount, storesProcesed}) => {
                 let percent = 0.0;
                 if (count > 0 && storesProcesed > 0) {
@@ -409,6 +411,7 @@ class DictionaryController {
             document.querySelector('#dict-extra-template')
         );
         this._dictionaryUI.save = () => this._settingsController.save();
+        this._dictionaryUI.preventPageExit = this._preventPageExit.bind(this);
         this._dictionaryUI.on('databaseUpdated', this._onDatabaseUpdated.bind(this));
 
         document.querySelector('#dict-purge-button').addEventListener('click', this._onPurgeButtonClick.bind(this), false);
@@ -610,10 +613,9 @@ class DictionaryController {
         const dictProgress = document.querySelector('#dict-purge');
         dictProgress.hidden = false;
 
-        const prevention = new PageExitPrevention();
+        const prevention = this._preventPageExit();
 
         try {
-            prevention.start();
             this._dictionaryErrorsShow(null);
             this._dictionarySpinnerShow(true);
 
@@ -649,10 +651,9 @@ class DictionaryController {
         const dictProgress = $('#dict-import-progress').show();
         const dictImportInfo = document.querySelector('#dict-import-info');
 
-        const prevention = new PageExitPrevention();
+        const prevention = this._preventPageExit();
 
         try {
-            prevention.start();
             this._dictionaryErrorsShow(null);
             this._dictionarySpinnerShow(true);
 
@@ -718,4 +719,8 @@ class DictionaryController {
         optionsFull.global.database.prefixWildcardsSupported = !!e.target.checked;
         await this._settingsController.save();
     }
+
+    _preventPageExit() {
+        return this.settingsController.preventPageExit();
+    }
 }
diff --git a/ext/bg/js/settings/settings-controller.js b/ext/bg/js/settings/settings-controller.js
index 87dea408..6479714d 100644
--- a/ext/bg/js/settings/settings-controller.js
+++ b/ext/bg/js/settings/settings-controller.js
@@ -26,6 +26,8 @@ class SettingsController extends EventDispatcher {
         super();
         this._profileIndex = profileIndex;
         this._source = yomichan.generateId(16);
+        this._pageExitPreventions = new Set();
+        this._pageExitPreventionEventListeners = new EventListenerCollection();
     }
 
     get source() {
@@ -109,6 +111,16 @@ class SettingsController extends EventDispatcher {
         return {index: this._profileIndex};
     }
 
+    preventPageExit() {
+        const obj = {end: null};
+        obj.end = this._endPreventPageExit.bind(this, obj);
+        if (this._pageExitPreventionEventListeners.size === 0) {
+            this._pageExitPreventionEventListeners.addEventListener(window, 'beforeunload', this._onBeforeUnload.bind(this), false);
+        }
+        this._pageExitPreventions.add(obj);
+        return obj;
+    }
+
     // Private
 
     _setProfileIndex(value) {
@@ -147,4 +159,21 @@ class SettingsController extends EventDispatcher {
         targets = this._setupTargets(targets, extraFields);
         return await api.modifySettings(targets, this._source);
     }
+
+    _onBeforeUnload(e) {
+        if (this._pageExitPreventions.size === 0) {
+            return;
+        }
+
+        e.preventDefault();
+        e.returnValue = '';
+        return '';
+    }
+
+    _endPreventPageExit(obj) {
+        this._pageExitPreventions.delete(obj);
+        if (this._pageExitPreventions.size === 0) {
+            this._pageExitPreventionEventListeners.removeAllEventListeners();
+        }
+    }
 }
diff --git a/ext/bg/settings.html b/ext/bg/settings.html
index 6fa54e23..260c1b46 100644
--- a/ext/bg/settings.html
+++ b/ext/bg/settings.html
@@ -1146,7 +1146,6 @@
         <script src="/bg/js/dictionary.js"></script>
         <script src="/bg/js/handlebars.js"></script>
         <script src="/bg/js/options.js"></script>
-        <script src="/bg/js/page-exit-prevention.js"></script>
         <script src="/bg/js/profile-conditions.js"></script>
         <script src="/bg/js/util.js"></script>
         <script src="/mixed/js/audio-system.js"></script>