1 files changed, 139 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..ce946109
--- /dev/null
+++ b/ext/mixed/js/dynamic-loader.js
@@ -0,0 +1,139 @@
+/*
+ * 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/>.
+ */
+
+/* global
+ * apiInjectStylesheet
+ */
+
+const dynamicLoader = (() => {
+    const injectedStylesheets = new Map();
+
+    async function loadStyle(id, type, value, useWebExtensionApi=false) {
+        if (useWebExtensionApi && yomichan.isExtensionUrl(window.location.href)) {
+            // Permissions error will occur if trying to use the WebExtension API to inject into an extension page
+            useWebExtensionApi = false;
+        }
+
+        let styleNode = injectedStylesheets.get(id);
+        if (typeof styleNode !== 'undefined') {
+            if (styleNode === null) {
+                // Previously injected via WebExtension API
+                throw new Error(`Stylesheet with id ${id} has already been injected using the WebExtension API`);
+            }
+        } else {
+            styleNode = null;
+        }
+
+        if (useWebExtensionApi) {
+            // Inject via WebExtension API
+            if (styleNode !== null && styleNode.parentNode !== null) {
+                styleNode.parentNode.removeChild(styleNode);
+            }
+
+            injectedStylesheets.set(id, null);
+            await apiInjectStylesheet(type, value);
+            return null;
+        }
+
+        // Create node in document
+        const parentNode = document.head;
+        if (parentNode === null) {
+            throw new Error('No parent node');
+        }
+
+        // Create or reuse node
+        const isFile = (type === 'file');
+        const tagName = isFile ? 'link' : 'style';
+        if (styleNode === null || styleNode.nodeName.toLowerCase() !== tagName) {
+            if (styleNode !== null && styleNode.parentNode !== null) {
+                styleNode.parentNode.removeChild(styleNode);
+            }
+            styleNode = document.createElement(tagName);
+        }
+
+        // Update node style
+        if (isFile) {
+            styleNode.rel = 'stylesheet';
+            styleNode.href = value;
+        } else {
+            styleNode.textContent = value;
+        }
+
+        // Update parent
+        if (styleNode.parentNode !== parentNode) {
+            parentNode.appendChild(styleNode);
+        }
+
+        // Add to map
+        injectedStylesheets.set(id, styleNode);
+        return styleNode;
+    }
+
+    function loadScripts(urls) {
+        return new Promise((resolve, reject) => {
+            const parent = document.body;
+            if (parent === null) {
+                reject(new Error('Missing body'));
+                return;
+            }
+
+            for (const url of urls) {
+                const node = parent.querySelector(`script[src='${escapeCSSAttribute(url)}']`);
+                if (node !== null) { continue; }
+
+                const script = document.createElement('script');
+                script.async = false;
+                script.src = url;
+                parent.appendChild(script);
+            }
+
+            loadScriptSentinel(parent, resolve, reject);
+        });
+    }
+
+    function loadScriptSentinel(parent, resolve, reject) {
+        const script = document.createElement('script');
+
+        const sentinelEventName = 'dynamicLoaderSentinel';
+        const sentinelEventCallback = (e) => {
+            if (e.script !== script) { return; }
+            yomichan.off(sentinelEventName, sentinelEventCallback);
+            parent.removeChild(script);
+            resolve();
+        };
+        yomichan.on(sentinelEventName, sentinelEventCallback);
+
+        try {
+            script.async = false;
+            script.src = '/mixed/js/dynamic-loader-sentinel.js';
+            parent.appendChild(script);
+        } catch (e) {
+            yomichan.off(sentinelEventName, sentinelEventCallback);
+            reject(e);
+        }
+    }
+
+    function escapeCSSAttribute(value) {
+        return value.replace(/['\\]/g, (character) => `\\${character}`);
+    }
+
+
+    return {
+        loadStyle,
+        loadScripts
+    };
+})();