1 files changed, 153 insertions, 0 deletions
diff --git a/ext/bg/js/template-renderer-proxy.js b/ext/bg/js/template-renderer-proxy.js
new file mode 100644
index 00000000..f08efdd6
--- /dev/null
+++ b/ext/bg/js/template-renderer-proxy.js
@@ -0,0 +1,153 @@
+/*
+ * 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/>.
+ */
+
+class TemplateRendererProxy {
+    constructor() {
+        this._frame = null;
+        this._frameNeedsLoad = true;
+        this._frameLoading = false;
+        this._frameLoadPromise = null;
+        this._frameUrl = chrome.runtime.getURL('/bg/template-renderer.html');
+        this._invocations = new Set();
+    }
+
+    async render(template, data, marker) {
+        await this._prepareFrame();
+        return await this._invoke('renderHandlebarsTemplate', {template, data, marker});
+    }
+
+    // Private
+
+    async _prepareFrame() {
+        if (this._frame === null) {
+            this._frame = document.createElement('iframe');
+            this._frame.addEventListener('load', this._onFrameLoad.bind(this), false);
+            const style = this._frame.style;
+            style.opacity = '0';
+            style.width = '0';
+            style.height = '0';
+            style.position = 'absolute';
+        }
+        if (this._frameNeedsLoad) {
+            this._frameNeedsLoad = false;
+            this._frameLoading = true;
+            this._frameLoadPromise = this._loadFrame(this._frame, this._frameUrl)
+                .finally(() => { this._frameLoading = false; });
+        }
+        await this._frameLoadPromise;
+    }
+
+    _loadFrame(frame, url, timeout=5000) {
+        return new Promise((resolve, reject) => {
+            let ready = false;
+            const cleanup = () => {
+                frame.removeEventListener('load', onLoad, false);
+                if (timer !== null) {
+                    clearTimeout(timer);
+                    timer = null;
+                }
+            };
+            const onLoad = () => {
+                if (!ready) { return; }
+                cleanup();
+                resolve();
+            };
+
+            let timer = setTimeout(() => {
+                cleanup();
+                reject(new Error('Timeout'));
+            }, timeout);
+
+            frame.removeAttribute('src');
+            frame.removeAttribute('srcdoc');
+            frame.addEventListener('load', onLoad, false);
+            try {
+                document.body.appendChild(frame);
+                ready = true;
+                frame.contentDocument.location.href = url;
+            } catch (e) {
+                cleanup();
+                reject(e);
+            }
+        });
+    }
+
+    _invoke(action, params, timeout=null) {
+        return new Promise((resolve, reject) => {
+            const frameWindow = (this._frame !== null ? this._frame.contentWindow : null);
+            if (frameWindow === null) {
+                reject(new Error('Frame not set up'));
+                return;
+            }
+
+            const id = generateId(16);
+            const invocation = {
+                cancel: () => {
+                    cleanup();
+                    reject(new Error('Terminated'));
+                }
+            };
+
+            const cleanup = () => {
+                this._invocations.delete(invocation);
+                window.removeEventListener('message', onMessage, false);
+                if (timer !== null) {
+                    clearTimeout(timer);
+                    timer = null;
+                }
+            };
+            const onMessage = (e) => {
+                if (
+                    e.source !== frameWindow ||
+                    e.data.id !== id ||
+                    e.data.action !== `${action}.response`
+                ) {
+                    return;
+                }
+
+                const response = e.data.params;
+                cleanup();
+                const {error} = response;
+                if (error) {
+                    reject(jsonToError(error));
+                } else {
+                    resolve(response.result);
+                }
+            };
+
+            let timer = (typeof timeout === 'number' ? setTimeout(() => {
+                cleanup();
+                reject(new Error('Timeout'));
+            }, timeout) : null);
+
+            this._invocations.add(invocation);
+
+            window.addEventListener('message', onMessage, false);
+            frameWindow.postMessage({action, params, id}, '*');
+        });
+    }
+
+    _onFrameLoad() {
+        if (this._frameLoading) { return; }
+        this._frameNeedsLoad = true;
+
+        for (const invocation of this._invocations) {
+            invocation.cancel();
+        }
+        this._invocations.clear();
+    }
+}