Add a helper for app <-> browser communication.

git-svn-id: https://www.unprompted.com/svn/projects/tildefriends/trunk@3908 ed5197a5-7fde-0310-b194-c3ffbd925b24

core/tfrpc.js

@@ -0,0 +1,78 @@
+const k_is_browser = get_is_browser();
+let g_api = {};
+let g_next_id = 1;
+let g_calls = {};
+
+function get_is_browser() {
+	try { return window !== undefined && console !== undefined; } catch { return false; }
+}
+
+if (k_is_browser) {
+	print = console.log;
+}
+
+function make_rpc(target, prop, receiver) {
+	return function() {
+		let id = g_next_id++;
+		let promise = new Promise(function(resolve, reject) {
+			g_calls[id] = {resolve: resolve, reject: reject};
+		});
+		if (k_is_browser) {
+			window.parent.postMessage({message: 'tfrpc', method: prop, params: [...arguments], id: id}, '*');
+			return promise;
+		} else {
+			return app.postMessage({message: 'tfrpc', method: prop, params: [...arguments], id: id}).then(x => promise);
+		}
+	}
+}
+
+function call_rpc(message) {
+	if (message && message.message === 'tfrpc') {
+		if (message.method) {
+			let method = g_api[message.method];
+			if (method) {
+				let response = {message: 'tfrpc', id: message.id};
+				try {
+					response.result = method(...message.params);
+				} catch (error) {
+					response.error = error;
+				}
+				if (k_is_browser) {
+					window.parent.postMessage(response, '*');
+				} else {
+					app.postMessage(response);
+				}
+			} else {
+				throw new Error(message.method + ' not found.');
+			}
+		} else if (message.result !== undefined) {
+			if (g_calls[message.id]) {
+				g_calls[message.id].resolve(message.result);
+			} else {
+				throw new Error(message.id + ' not found to reply.');
+			}
+		} else if (message.error !== undefined) {
+			if (g_calls[message.id]) {
+				g_calls[message.id].reject(message.error);
+			} else {
+				throw new Error(message.id + ' not found to reply.');
+			}
+		}
+	}
+}
+
+if (k_is_browser) {
+	window.addEventListener('message', function(event) {
+		call_rpc(event.data);
+	});
+} else {
+	core.register('message', function(message) {
+		call_rpc(message?.message);
+	});
+}
+
+export let rpc = new Proxy({}, {get: make_rpc});
+
+export function register(method) {
+	g_api[method.name] = method;
+}