move frame offset forwarding code to a class

1 files changed, 94 insertions, 0 deletions

diff --git a/ext/fg/js/frame-offset-forwarder.js b/ext/fg/js/frame-offset-forwarder.js
new file mode 100644
index 00000000..b3715c2a
--- /dev/null
+++ b/ext/fg/js/frame-offset-forwarder.js
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2020  Alex Yatskov <alex@foosoft.net>
+ * Author: Alex Yatskov <alex@foosoft.net>
+ *
+ * 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
+ * apiForward
+ */
+
+class FrameOffsetForwarder {
+    constructor() {
+        this._forwardFrameOffset = window !== window.parent ?
+            this._forwardFrameOffsetParent.bind(this) :
+            this._forwardFrameOffsetOrigin.bind(this);
+
+        this._windowMessageHandlers = new Map([
+            ['getFrameOffset', ({offset, uniqueId}, e) => { return this._onGetFrameOffset(offset, uniqueId, e); }]
+        ]);
+
+        window.addEventListener('message', this.onMessage.bind(this), false);
+    }
+
+    async applyOffset(x, y) {
+        const uniqueId = yomichan.generateId(16);
+
+        let frameOffsetResolve = null;
+        const frameOffsetPromise = new Promise((resolve) => (frameOffsetResolve = resolve));
+
+        const runtimeMessageCallback = ({action, params}, sender, callback) => {
+            if (action === 'frameOffset' && isObject(params) && params.uniqueId === uniqueId) {
+                chrome.runtime.onMessage.removeListener(runtimeMessageCallback);
+                callback();
+                frameOffsetResolve(params);
+                return false;
+            }
+        };
+        chrome.runtime.onMessage.addListener(runtimeMessageCallback);
+
+        window.parent.postMessage({
+            action: 'getFrameOffset',
+            params: {
+                uniqueId,
+                offset: [x, y]
+            }
+        }, '*');
+
+        const {offset} = await frameOffsetPromise;
+        return offset;
+    }
+
+    onMessage(e) {
+        const {action, params} = e.data;
+        const handler = this._windowMessageHandlers.get(action);
+        if (typeof handler !== 'function') { return; }
+        handler(params, e);
+    }
+
+    _onGetFrameOffset(offset, uniqueId, e) {
+        let sourceFrame = null;
+        for (const frame of document.querySelectorAll('frame, iframe:not(.yomichan-float)')) {
+            if (frame.contentWindow !== e.source) { continue; }
+            sourceFrame = frame;
+            break;
+        }
+        if (sourceFrame === null) { return; }
+
+        const [forwardedX, forwardedY] = offset;
+        const {x, y} = sourceFrame.getBoundingClientRect();
+        offset = [forwardedX + x, forwardedY + y];
+
+        this._forwardFrameOffset(offset, uniqueId);
+    }
+
+    _forwardFrameOffsetParent(offset, uniqueId) {
+        window.parent.postMessage({action: 'getFrameOffset', params: {offset, uniqueId}}, '*');
+    }
+
+    _forwardFrameOffsetOrigin(offset, uniqueId) {
+        apiForward('frameOffset', {offset, uniqueId});
+    }
+}