ClipboardReader class (#854)

* Create ClipboardReader class

* Use ClipboardReader in Backend

* Update ClipboardMonitor to use ClipboardReader

* Replace _onApiClipboardImageGet call

* Assign clipboard reader browser

4 files changed, 170 insertions, 82 deletions

diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index f656adbd..91188fdc 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -20,6 +20,7 @@
  * AudioSystem
  * AudioUriBuilder
  * ClipboardMonitor
+ * ClipboardReader
  * DictionaryDatabase
  * Environment
  * JsonSchemaValidator
@@ -39,7 +40,14 @@ class Backend {
         this._translator = new Translator(this._dictionaryDatabase);
         this._anki = new AnkiConnect();
         this._mecab = new Mecab();
-        this._clipboardMonitor = new ClipboardMonitor({getClipboard: this._onApiClipboardGet.bind(this)});
+        this._clipboardReader = new ClipboardReader({
+            document: (typeof document === 'object' && document !== null ? document : null),
+            pasteTargetSelector: '#clipboard-paste-target',
+            imagePasteTargetSelector: '#clipboard-image-paste-target'
+        });
+        this._clipboardMonitor = new ClipboardMonitor({
+            clipboardReader: this._clipboardReader
+        });
         this._options = null;
         this._profileConditionsSchemaValidator = new JsonSchemaValidator();
         this._profileConditionsSchemaCache = [];
@@ -56,11 +64,6 @@ class Backend {
         });
         this._optionsUtil = new OptionsUtil();
 
-        this._clipboardPasteTarget = null;
-        this._clipboardPasteTargetInitialized = false;
-        this._clipboardImagePasteTarget = null;
-        this._clipboardImagePasteTargetInitialized = false;
-
         this._searchPopupTabId = null;
         this._searchPopupTabCreatePromise = null;
 
@@ -179,6 +182,8 @@ class Backend {
             yomichan.on('log', this._onLog.bind(this));
 
             await this._environment.prepare();
+            this._clipboardReader.browser = this._environment.getInfo().browser;
+
             try {
                 await this._dictionaryDatabase.prepare();
             } catch (e) {
@@ -577,78 +582,11 @@ class Backend {
     }
 
     async _onApiClipboardGet() {
-        /*
-        Notes:
-            document.execCommand('paste') doesn't work on Firefox.
-            This may be a bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1603985
-            Therefore, navigator.clipboard.readText() is used on Firefox.
-
-            navigator.clipboard.readText() can't be used in Chrome for two reasons:
-            * Requires page to be focused, else it rejects with an exception.
-            * When the page is focused, Chrome will request clipboard permission, despite already
-              being an extension with clipboard permissions. It effectively asks for the
-              non-extension permission for clipboard access.
-        */
-        const {browser} = this._environment.getInfo();
-        if (browser === 'firefox' || browser === 'firefox-mobile') {
-            return await navigator.clipboard.readText();
-        }
-
-        if (!this._environmentHasDocument()) {
-            throw new Error('Reading the clipboard is not supported in this context');
-        }
-
-        if (!this._clipboardPasteTargetInitialized) {
-            this._clipboardPasteTarget = document.querySelector('#clipboard-paste-target');
-            this._clipboardPasteTargetInitialized = true;
-        }
-
-        const target = this._clipboardPasteTarget;
-        if (target === null) {
-            throw new Error('Clipboard paste target does not exist');
-        }
-
-        target.value = '';
-        target.focus();
-        this._executePasteCommand();
-        const result = target.value;
-        target.value = '';
-        return result;
+        return this._clipboardReader.getText();
     }
 
     async _onApiClipboardImageGet() {
-        // See browser-specific notes in _onApiClipboardGet
-        const {browser} = this._environment.getInfo();
-        if (browser === 'firefox' || browser === 'firefox-mobile') {
-            if (typeof navigator.clipboard !== 'undefined' && typeof navigator.clipboard.read === 'function') {
-                // This function is behind the flag: dom.events.asyncClipboard.dataTransfer
-                const {files} = await navigator.clipboard.read();
-                if (files.length === 0) { return null; }
-                const result = await this._readFileAsDataURL(files[0]);
-                return result;
-            }
-        }
-
-        if (!this._environmentHasDocument()) {
-            throw new Error('Reading the clipboard is not supported in this context');
-        }
-
-        if (!this._clipboardImagePasteTargetInitialized) {
-            this._clipboardImagePasteTarget = document.querySelector('#clipboard-image-paste-target');
-            this._clipboardImagePasteTargetInitialized = true;
-        }
-
-        const target = this._clipboardImagePasteTarget;
-        if (target === null) {
-            throw new Error('Clipboard paste target does not exist');
-        }
-
-        target.focus();
-        this._executePasteCommand();
-        const image = target.querySelector('img[src^="data:"]');
-        const result = (image !== null ? image.getAttribute('src') : null);
-        target.textContent = '';
-        return result;
+        return this._clipboardReader.getImage();
     }
 
     async _onApiGetDisplayTemplatesHtml() {
@@ -1655,7 +1593,7 @@ class Backend {
         try {
             const now = new Date(timestamp);
 
-            const dataUrl = await this._onApiClipboardImageGet();
+            const dataUrl = await this._clipboardReader.getImage();
             if (dataUrl === null) {
                 throw new Error('No clipboard image');
             }
diff --git a/ext/bg/js/clipboard-monitor.js b/ext/bg/js/clipboard-monitor.js
index e7e7378c..4d980e11 100644
--- a/ext/bg/js/clipboard-monitor.js
+++ b/ext/bg/js/clipboard-monitor.js
@@ -20,28 +20,28 @@
  */
 
 class ClipboardMonitor extends EventDispatcher {
-    constructor({getClipboard}) {
+    constructor({clipboardReader}) {
         super();
         this._timerId = null;
         this._timerToken = null;
         this._interval = 250;
         this._previousText = null;
-        this._getClipboard = getClipboard;
+        this._clipboardReader = clipboardReader;
     }
 
     start() {
         this.stop();
 
         // The token below is used as a unique identifier to ensure that a new clipboard monitor
-        // hasn't been started during the await call. The check below the await this._getClipboard()
-        // call will exit early if the reference has changed.
+        // hasn't been started during the await call. The check below the await call
+        // will exit early if the reference has changed.
         const token = {};
         const intervalCallback = async () => {
             this._timerId = null;
 
             let text = null;
             try {
-                text = await this._getClipboard();
+                text = await this._clipboardReader.getText();
             } catch (e) {
                 // NOP
             }
diff --git a/ext/bg/js/clipboard-reader.js b/ext/bg/js/clipboard-reader.js
new file mode 100644
index 00000000..66cf0c25
--- /dev/null
+++ b/ext/bg/js/clipboard-reader.js
@@ -0,0 +1,148 @@
+/*
+ * Copyright (C) 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 which can read text and images from the clipboard.
+ */
+class ClipboardReader {
+    /**
+     * Creates a new instances of a clipboard reader.
+     * @param document The Document object to be used, or null for no support.
+     * @param pasteTargetSelector The selector for the paste target element.
+     * @param imagePasteTargetSelector The selector for the image paste target element.
+     */
+    constructor({document=null, pasteTargetSelector=null, imagePasteTargetSelector=null}) {
+        this._document = document;
+        this._browser = null;
+        this._pasteTarget = null;
+        this._pasteTargetSelector = pasteTargetSelector;
+        this._imagePasteTarget = null;
+        this._imagePasteTargetSelector = imagePasteTargetSelector;
+    }
+
+    /**
+     * Gets the browser being used.
+     */
+    get browser() {
+        return this._browser;
+    }
+
+    /**
+     * Assigns the browser being used.
+     */
+    set browser(value) {
+        this._browser = value;
+    }
+
+    /**
+     * Gets the text in the clipboard.
+     * @returns A string containing the clipboard text.
+     * @throws Error if not supported.
+     */
+    async getText() {
+        /*
+        Notes:
+            document.execCommand('paste') doesn't work on Firefox.
+            This may be a bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1603985
+            Therefore, navigator.clipboard.readText() is used on Firefox.
+
+            navigator.clipboard.readText() can't be used in Chrome for two reasons:
+            * Requires page to be focused, else it rejects with an exception.
+            * When the page is focused, Chrome will request clipboard permission, despite already
+              being an extension with clipboard permissions. It effectively asks for the
+              non-extension permission for clipboard access.
+        */
+        if (this._isFirefox()) {
+            return await navigator.clipboard.readText();
+        }
+
+        const document = this._document;
+        if (document === null) {
+            throw new Error('Not supported');
+        }
+
+        let target = this._pasteTarget;
+        if (target === null) {
+            target = document.querySelector(this._pasteTargetSelector);
+            if (target === null) {
+                throw new Error('Clipboard paste target does not exist');
+            }
+            this._pasteTarget = target;
+        }
+
+        target.value = '';
+        target.focus();
+        document.execCommand('paste');
+        const result = target.value;
+        target.value = '';
+        return (typeof result === 'string' ? result : '');
+    }
+
+    /**
+     * Gets the first image in the clipboard.
+     * @returns A string containing a data URL of the image file, or null if no image was found.
+     * @throws Error if not supported.
+     */
+    async getImage() {
+        // See browser-specific notes in getText
+        if (this._isFirefox()) {
+            if (typeof navigator.clipboard !== 'undefined' && typeof navigator.clipboard.read === 'function') {
+                // This function is behind the flag: dom.events.asyncClipboard.dataTransfer
+                const {files} = await navigator.clipboard.read();
+                if (files.length === 0) { return null; }
+                const result = await this._readFileAsDataURL(files[0]);
+                return result;
+            }
+        }
+
+        const document = this._document;
+        if (document === null) {
+            throw new Error('Not supported');
+        }
+
+        let target = this._imagePasteTarget;
+        if (target === null) {
+            target = document.querySelector(this._imagePasteTargetSelector);
+            if (target === null) {
+                throw new Error('Clipboard paste target does not exist');
+            }
+            this._imagePasteTarget = target;
+        }
+
+        target.focus();
+        document.execCommand('paste');
+        const image = target.querySelector('img[src^="data:"]');
+        const result = (image !== null ? image.getAttribute('src') : null);
+        target.textContent = '';
+        return result;
+    }
+
+    // Private
+
+    _isFirefox() {
+        return (this._browser === 'firefox' || this._browser === 'firefox-mobile');
+    }
+
+    _readFileAsDataURL(file) {
+        return new Promise((resolve, reject) => {
+            const reader = new FileReader();
+            reader.onload = () => resolve(reader.result);
+            reader.onerror = () => reject(reader.error);
+            reader.readAsDataURL(file);
+        });
+    }
+}
diff --git a/ext/bg/js/search.js b/ext/bg/js/search.js
index 2aa6d249..f5b4a671 100644
--- a/ext/bg/js/search.js
+++ b/ext/bg/js/search.js
@@ -36,7 +36,9 @@ class DisplaySearch extends Display {
         this._introAnimationTimer = null;
         this._clipboardMonitorEnabled = false;
         this._clipboardMonitor = new ClipboardMonitor({
-            getClipboard: api.clipboardGet.bind(api)
+            clipboardReader: {
+                getText: async () => (await api.clipboardGet())
+            }
         });
         this._onKeyDownIgnoreKeys = new Map([
             ['ANY_MOD', new Set([