Create dynamic script/CSS loader utility

1 files changed, 80 insertions, 0 deletions

diff --git a/ext/mixed/js/dynamic-loader.js b/ext/mixed/js/dynamic-loader.js
new file mode 100644
index 00000000..20ed8454
--- /dev/null
+++ b/ext/mixed/js/dynamic-loader.js
@@ -0,0 +1,80 @@
+/*
+ * 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/>.
+ */
+
+const dynamicLoader = (() => {
+    function loadStyles(urls) {
+        const parent = document.head;
+        for (const url of urls) {
+            const node = parent.querySelector(`link[href='${escapeCSSAttribute(url)}']`);
+            if (node !== null) { continue; }
+
+            const style = document.createElement('link');
+            style.rel = 'stylesheet';
+            style.type = 'text/css';
+            style.href = url;
+            parent.appendChild(style);
+        }
+    }
+
+    function loadScripts(urls) {
+        return new Promise((resolve) => {
+            const parent = document.body;
+            for (const url of urls) {
+                const node = parent.querySelector(`script[src='${escapeCSSAttribute(url)}']`);
+                if (node !== null) { continue; }
+
+                const script = document.createElement('script');
+                script.async = false;
+                script.src = url;
+                parent.appendChild(script);
+            }
+
+            loadScriptSentinel(resolve);
+        });
+    }
+
+    function loadScriptSentinel(resolve, reject) {
+        const script = document.createElement('script');
+
+        const sentinelEventName = 'dynamicLoaderSentinel';
+        const sentinelEventCallback = (e) => {
+            if (e.script !== script) { return; }
+            yomichan.off(sentinelEventName, sentinelEventCallback);
+            resolve();
+        };
+        yomichan.on(sentinelEventName, sentinelEventCallback);
+
+        try {
+            script.async = false;
+            script.src = '/mixed/js/dynamic-loader-sentinel.js';
+            document.body.appendChild(script);
+        } catch (e) {
+            yomichan.off(sentinelEventName, sentinelEventCallback);
+            reject(e);
+        }
+    }
+
+    function escapeCSSAttribute(value) {
+        return value.replace(/['\\]/g, (character) => `\\${character}`);
+    }
+
+
+    return {
+        loadStyles,
+        loadScripts
+    };
+})();