Add media controls (#229)

app/src/bridge/components/cast/discovery.ts

@@ -0,0 +1,89 @@
+"use strict";
+
+import mdns from "mdns";
+
+import { ReceiverDevice } from "../../messagingTypes";
+
+/**
+ * Chromecast TXT record
+ */
+interface CastRecord {
+    // Device ID
+    id: string;
+    // Model name (e.g. Chromecast, Google Nest Mini, etc...)
+    md: string;
+    // Friendly name (user-visible)
+    fn: string;
+    // Capabilities
+    ca: string;
+    // Version (?)
+    ve: string;
+    // Icon path (?)
+    ic: string;
+
+    cd: string;
+    rm: string;
+    st: string;
+    bs: string;
+    nf: string;
+    rs: string;
+}
+
+interface DiscoveryOptions {
+    onDeviceFound(device: ReceiverDevice): void;
+    onDeviceDown(deviceId: string): void;
+}
+
+export default class Discovery {
+    browser = mdns.createBrowser(mdns.tcp("googlecast"), {
+        resolverSequence: [
+            mdns.rst.DNSServiceResolve(),
+            "DNSServiceGetAddrInfo" in mdns.dns_sd
+                ? mdns.rst.DNSServiceGetAddrInfo()
+                : // Some issues on Linux with IPv6, so restrict to IPv4
+                  mdns.rst.getaddrinfo({ families: [4] }),
+            mdns.rst.makeAddressesUnique()
+        ]
+    });
+
+    constructor(opts: DiscoveryOptions) {
+        /**
+         * When a service is found, gather device info from service object and
+         * TXT record, then send a `main:receiverDeviceUp` message.
+         */
+        this.browser.on("serviceUp", service => {
+            // Filter invalid results
+            if (!service.txtRecord || !service.name) return;
+
+            const record = service.txtRecord as CastRecord;
+            const device: ReceiverDevice = {
+                id: record.id,
+                friendlyName: record.fn,
+                modelName: record.md,
+                capabilities: parseInt(record.ca),
+                host: service.addresses[0],
+                port: service.port
+            };
+
+            opts.onDeviceFound(device);
+        });
+
+        /**
+         * When a service is lost, send a `main:receiverDeviceDown` message with
+         * the service name as the `deviceId`.
+         */
+        this.browser.on("serviceDown", service => {
+            // Filter invalid results
+            if (!service.name) return;
+
+            opts.onDeviceDown(service.name);
+        });
+    }
+
+    start() {
+        this.browser.start();
+    }
+    stop() {
+        this.browser.stop();
+    }
+}