DictionaryImporterMediaLoader (#1860)

* Rename param for consistency

* Move media loading functionality into DictionaryImporterMediaLoader

* Create test class for media loading

* Remove unnecessary Blob/Image/URL functionality

1 files changed, 57 insertions, 0 deletions

diff --git a/ext/js/language/dictionary-importer-media-loader.js b/ext/js/language/dictionary-importer-media-loader.js
new file mode 100644
index 00000000..bbcc5476
--- /dev/null
+++ b/ext/js/language/dictionary-importer-media-loader.js
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2021  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/>.
+ */
+
+/* global
+ * MediaUtil
+ */
+
+/**
+ * Class used for loading and validating media during the dictionary import process.
+ */
+class DictionaryImporterMediaLoader {
+    /**
+     * Attempts to load an image using a base64 encoded content and a media type
+     * and returns its resolution.
+     * @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 {width, height} on success,
+     *   otherwise an error is thrown.
+     */
+    getImageResolution(mediaType, content) {
+        return new Promise((resolve, reject) => {
+            const image = new Image();
+            const eventListeners = new EventListenerCollection();
+            const cleanup = () => {
+                image.removeAttribute('src');
+                URL.revokeObjectURL(url);
+                eventListeners.removeAllEventListeners();
+            };
+            eventListeners.addEventListener(image, 'load', () => {
+                const {naturalWidth: width, naturalHeight: height} = image;
+                cleanup();
+                resolve({width, height});
+            }, false);
+            eventListeners.addEventListener(image, 'error', () => {
+                cleanup();
+                reject(new Error('Image failed to load'));
+            }, false);
+            const blob = MediaUtil.createBlobFromBase64Content(content, mediaType);
+            const url = URL.createObjectURL(blob);
+            image.src = url;
+        });
+    }
+}