1 files changed, 97 insertions, 0 deletions
diff --git a/ext/js/display/display-content-manager.js b/ext/js/display/display-content-manager.js
new file mode 100644
index 00000000..a0dd7dd6
--- /dev/null
+++ b/ext/js/display/display-content-manager.js
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2020-2022  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
+ * StringUtil
+ */
+
+class DisplayContentManager {
+    constructor() {
+        this._token = {};
+        this._mediaCache = new Map();
+        this._loadMediaData = [];
+    }
+
+    async loadMedia(path, dictionary, onLoad, onUnload) {
+        const token = this._token;
+        const data = {onUnload, loaded: false};
+
+        this._loadMediaData.push(data);
+
+        const media = await this.getMedia(path, dictionary);
+        if (token !== this._token) { return; }
+
+        onLoad(media.url);
+        data.loaded = true;
+    }
+
+    unloadAll() {
+        for (const {onUnload, loaded} of this._loadMediaData) {
+            if (typeof onUnload === 'function') {
+                onUnload(loaded);
+            }
+        }
+        this._loadMediaData = [];
+
+        for (const map of this._mediaCache.values()) {
+            for (const {url} of map.values()) {
+                if (url !== null) {
+                    URL.revokeObjectURL(url);
+                }
+            }
+        }
+        this._mediaCache.clear();
+
+        this._token = {};
+    }
+
+    async getMedia(path, dictionary) {
+        let cachedData;
+        let dictionaryCache = this._mediaCache.get(dictionary);
+        if (typeof dictionaryCache !== 'undefined') {
+            cachedData = dictionaryCache.get(path);
+        } else {
+            dictionaryCache = new Map();
+            this._mediaCache.set(dictionary, dictionaryCache);
+        }
+
+        if (typeof cachedData === 'undefined') {
+            cachedData = {
+                promise: null,
+                data: null,
+                url: null
+            };
+            dictionaryCache.set(path, cachedData);
+            cachedData.promise = this._getMediaData(path, dictionary, cachedData);
+        }
+
+        return cachedData.promise;
+    }
+
+    async _getMediaData(path, dictionary, cachedData) {
+        const token = this._token;
+        const data = (await yomichan.api.getMedia([{path, dictionary}]))[0];
+        if (token === this._token && data !== null) {
+            const buffer = StringUtil.base64ToArrayBuffer(data.content);
+            const blob = new Blob([buffer], {type: data.mediaType});
+            const url = URL.createObjectURL(blob);
+            cachedData.data = data;
+            cachedData.url = url;
+        }
+        return cachedData;
+    }
+}