Media utility refactor (#859)

* Move loadImageBase64 into DictionaryImporter

* Convert mediaUtility to a class

* Add getFileExtensionFromImageMediaType to MediaUtility

* Use MediaUtility instead of _getImageExtensionFromMediaType

* Use MediaUtility in ClipboardReader to validate images before reading

4 files changed, 83 insertions, 52 deletions

diff --git a/ext/bg/js/backend.js b/ext/bg/js/backend.js
index b9d85b84..2a90e8e1 100644
--- a/ext/bg/js/backend.js
+++ b/ext/bg/js/backend.js
@@ -24,6 +24,7 @@
  * Environment
  * JsonSchemaValidator
  * Mecab
+ * MediaUtility
  * ObjectPropertyAccessor
  * OptionsUtil
  * ProfileConditions
@@ -39,10 +40,12 @@ class Backend {
         this._translator = new Translator(this._dictionaryDatabase);
         this._anki = new AnkiConnect();
         this._mecab = new Mecab();
+        this._mediaUtility = new MediaUtility();
         this._clipboardReader = new ClipboardReader({
             document: (typeof document === 'object' && document !== null ? document : null),
             pasteTargetSelector: '#clipboard-paste-target',
-            imagePasteTargetSelector: '#clipboard-image-paste-target'
+            imagePasteTargetSelector: '#clipboard-image-paste-target',
+            mediaUtility: this._mediaUtility
         });
         this._clipboardMonitor = new ClipboardMonitor({
             clipboardReader: this._clipboardReader
@@ -1570,7 +1573,8 @@ class Backend {
             const dataUrl = await this._getScreenshot(windowId, tabId, ownerFrameId, format, quality);
 
             const {mediaType, data} = this._getDataUrlInfo(dataUrl);
-            const extension = this._getImageExtensionFromMediaType(mediaType);
+            const extension = this._mediaUtility.getFileExtensionFromImageMediaType(mediaType);
+            if (extension === null) { throw new Error('Unknown image media type'); }
 
             let fileName = `yomichan_browser_screenshot_${reading}_${this._ankNoteDateToString(now)}.${extension}`;
             fileName = this._replaceInvalidFileNameCharacters(fileName);
@@ -1593,7 +1597,8 @@ class Backend {
             }
 
             const {mediaType, data} = this._getDataUrlInfo(dataUrl);
-            const extension = this._getImageExtensionFromMediaType(mediaType);
+            const extension = this._mediaUtility.getFileExtensionFromImageMediaType(mediaType);
+            if (extension === null) { throw new Error('Unknown image media type'); }
 
             let fileName = `yomichan_clipboard_image_${reading}_${this._ankNoteDateToString(now)}.${extension}`;
             fileName = this._replaceInvalidFileNameCharacters(fileName);
@@ -1636,14 +1641,6 @@ class Backend {
         return {mediaType, data};
     }
 
-    _getImageExtensionFromMediaType(mediaType) {
-        switch (mediaType.toLowerCase()) {
-            case 'image/png': return 'png';
-            case 'image/jpeg': return 'jpeg';
-            default: throw new Error('Unknown image media type');
-        }
-    }
-
     _triggerDatabaseUpdated(type, cause) {
         this._translator.clearDatabaseCaches();
         this._sendMessageAllTabs('databaseUpdated', {type, cause});
diff --git a/ext/bg/js/clipboard-reader.js b/ext/bg/js/clipboard-reader.js
index 66cf0c25..d8c80c21 100644
--- a/ext/bg/js/clipboard-reader.js
+++ b/ext/bg/js/clipboard-reader.js
@@ -25,13 +25,14 @@ class ClipboardReader {
      * @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}) {
+    constructor({document=null, pasteTargetSelector=null, imagePasteTargetSelector=null, mediaUtility=null}) {
         this._document = document;
         this._browser = null;
         this._pasteTarget = null;
         this._pasteTargetSelector = pasteTargetSelector;
         this._imagePasteTarget = null;
         this._imagePasteTargetSelector = imagePasteTargetSelector;
+        this._mediaUtility = mediaUtility;
     }
 
     /**
@@ -99,14 +100,20 @@ class ClipboardReader {
      */
     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;
+        if (
+            this._isFirefox() &&
+            this._mediaUtility !== null &&
+            typeof navigator.clipboard !== 'undefined' &&
+            typeof navigator.clipboard.read === 'function'
+        ) {
+            // This function is behind the Firefox flag: dom.events.asyncClipboard.dataTransfer
+            const {files} = await navigator.clipboard.read();
+            for (const file of files) {
+                if (this._mediaUtility.getFileExtensionFromImageMediaType(file.type) !== null) {
+                    return await this._readFileAsDataURL(file);
+                }
             }
+            return null;
         }
 
         const document = this._document;
diff --git a/ext/bg/js/dictionary-importer.js b/ext/bg/js/dictionary-importer.js
index 2ad2ebe4..b641de3a 100644
--- a/ext/bg/js/dictionary-importer.js
+++ b/ext/bg/js/dictionary-importer.js
@@ -18,13 +18,14 @@
 /* global
  * JSZip
  * JsonSchemaValidator
- * mediaUtility
+ * MediaUtility
  */
 
 class DictionaryImporter {
     constructor() {
         this._schemas = new Map();
         this._jsonSchemaValidator = new JsonSchemaValidator();
+        this._mediaUtility = new MediaUtility();
     }
 
     async importDictionary(dictionaryDatabase, archiveSource, details, onProgress) {
@@ -324,14 +325,14 @@ class DictionaryImporter {
         }
 
         const content = await file.async('base64');
-        const mediaType = mediaUtility.getImageMediaTypeFromFileName(path);
+        const mediaType = this._mediaUtility.getImageMediaTypeFromFileName(path);
         if (mediaType === null) {
             throw new Error(`Could not determine media type for image at path ${JSON.stringify(path)} for ${errorSource}`);
         }
 
         let image;
         try {
-            image = await mediaUtility.loadImageBase64(mediaType, content);
+            image = await this._loadImageBase64(mediaType, content);
         } catch (e) {
             throw new Error(`Could not load image at path ${JSON.stringify(path)} for ${errorSource}`);
         }
@@ -380,4 +381,27 @@ class DictionaryImporter {
         }
         return await response.json();
     }
+
+    /**
+     * Attempts to load an image using a base64 encoded content and a media type.
+     * @param mediaType The media type for the image content.
+     * @param content The binary content for the image, encoded in base64.
+     * @returns A Promise which resolves with an HTMLImageElement instance on
+     *   successful load, otherwise an error is thrown.
+     */
+    _loadImageBase64(mediaType, content) {
+        return new Promise((resolve, reject) => {
+            const image = new Image();
+            const eventListeners = new EventListenerCollection();
+            eventListeners.addEventListener(image, 'load', () => {
+                eventListeners.removeAllEventListeners();
+                resolve(image);
+            }, false);
+            eventListeners.addEventListener(image, 'error', () => {
+                eventListeners.removeAllEventListeners();
+                reject(new Error('Image failed to load'));
+            }, false);
+            image.src = `data:${mediaType};base64,${content}`;
+        });
+    }
 }
diff --git a/ext/bg/js/media-utility.js b/ext/bg/js/media-utility.js
index 1f93b2b4..52e32113 100644
--- a/ext/bg/js/media-utility.js
+++ b/ext/bg/js/media-utility.js
@@ -16,9 +16,9 @@
  */
 
 /**
- * mediaUtility is an object containing helper methods related to media processing.
+ * MediaUtility is a class containing helper methods related to media processing.
  */
-const mediaUtility = (() => {
+class MediaUtility {
     /**
      * Gets the file extension of a file path. URL search queries and hash
      * fragments are not handled.
@@ -26,7 +26,7 @@ const mediaUtility = (() => {
      * @returns The file extension, including the '.', or an empty string
      *   if there is no file extension.
      */
-    function getFileNameExtension(path) {
+    getFileNameExtension(path) {
         const match = /\.[^./\\]*$/.exec(path);
         return match !== null ? match[0] : '';
     }
@@ -37,8 +37,8 @@ const mediaUtility = (() => {
      * @returns The media type string if it can be determined from the file path,
      *   otherwise null.
      */
-    function getImageMediaTypeFromFileName(path) {
-        switch (getFileNameExtension(path).toLowerCase()) {
+    getImageMediaTypeFromFileName(path) {
+        switch (this.getFileNameExtension(path).toLowerCase()) {
             case '.apng':
                 return 'image/apng';
             case '.bmp':
@@ -69,30 +69,33 @@ const mediaUtility = (() => {
     }
 
     /**
-     * Attempts to load an image using a base64 encoded content and a media type.
-     * @param mediaType The media type for the image content.
-     * @param content The binary content for the image, encoded in base64.
-     * @returns A Promise which resolves with an HTMLImageElement instance on
-     *   successful load, otherwise an error is thrown.
+     * Gets the file extension for a corresponding media type.
+     * @param mediaType The media type to use.
+     * @returns A file extension including the dot for the media type,
+     *   otherwise null.
      */
-    function loadImageBase64(mediaType, content) {
-        return new Promise((resolve, reject) => {
-            const image = new Image();
-            const eventListeners = new EventListenerCollection();
-            eventListeners.addEventListener(image, 'load', () => {
-                eventListeners.removeAllEventListeners();
-                resolve(image);
-            }, false);
-            eventListeners.addEventListener(image, 'error', () => {
-                eventListeners.removeAllEventListeners();
-                reject(new Error('Image failed to load'));
-            }, false);
-            image.src = `data:${mediaType};base64,${content}`;
-        });
+    getFileExtensionFromImageMediaType(mediaType) {
+        switch (mediaType) {
+            case 'image/apng':
+                return '.apng';
+            case 'image/bmp':
+                return '.bmp';
+            case 'image/gif':
+                return '.gif';
+            case 'image/x-icon':
+                return '.ico';
+            case 'image/jpeg':
+                return '.jpeg';
+            case 'image/png':
+                return '.png';
+            case 'image/svg+xml':
+                return '.svg';
+            case 'image/tiff':
+                return '.tiff';
+            case 'image/webp':
+                return '.webp';
+            default:
+                return null;
+        }
     }
-
-    return {
-        getImageMediaTypeFromFileName,
-        loadImageBase64
-    };
-})();
+}