refactor: modernize Cast discovery and app activation

Checks/cast-session.swift

@@ -366,6 +366,87 @@ private func testIdentity() throws -> (SecIdentity, URL) {
 @main
 @MainActor
 struct CastSessionCheck {
+    static func discovery() async throws {
+        let prefix = "terebi-discovery-" + UUID().uuidString
+        let firstID = prefix + "-first", secondID = prefix + "-second"
+        let discovery = CastDiscovery()
+        var listeners: [NWListener] = []
+        var accepted: [NWConnection] = []
+        defer {
+            discovery.stop()
+            for listener in listeners { listener.cancel() }
+            for connection in accepted { connection.cancel() }
+        }
+        func advertise(_ suffix: String, id: String, name: String) throws -> NWListener {
+            let listener = try NWListener(using: .tcp)
+            listener.service = .init(name: prefix + suffix, type: "_googlecast._tcp",
+                                     txtRecord: NWTXTRecord(["id": id, "fn": name]))
+            listener.newConnectionHandler = { connection in
+                MainActor.assumeIsolated {
+                    accepted.append(connection)
+                    connection.start(queue: .main)
+                }
+            }
+            listener.start(queue: .main)
+            listeners.append(listener)
+            return listener
+        }
+        let first = try advertise("-a", id: firstID, name: "TV 10")
+        let second = try advertise("-b", id: secondID, name: "TV 2")
+        let duplicate = try advertise("-c", id: firstID, name: "TV 10")
+        let fallback = try advertise("-fallback", id: "", name: "")
+        try await until("Bonjour publishers are ready") { listeners.allSatisfy { $0.state == .ready } }
+        let duplicatePort = duplicate.port!.rawValue
+        discovery.start()
+        discovery.start() // Repeated menu requests must not replace a running search.
+        func ownDevices() -> [CastDevice] {
+            discovery.devices.filter { $0.id == firstID || $0.id == secondID }
+        }
+        try await until("Bonjour TXT identity/name, deduplication and natural device order", attempts: 1500) {
+            ownDevices().map(\.id) == [secondID, firstID] &&
+                ownDevices().map(\.name) == ["TV 2", "TV 10"]
+        }
+        try await until("Empty TXT values fall back to the service name and identity", attempts: 1500) {
+            discovery.devices.contains { $0.name == prefix + "-fallback" && $0.port == fallback.port?.rawValue }
+        }
+        let fallbackID = discovery.devices.first { $0.name == prefix + "-fallback" }!.id
+        let device = ownDevices()[0]
+        require(device.port == second.port?.rawValue, "Discovery preserves the advertised Cast port")
+        let connection = NWConnection(host: NWEndpoint.Host(device.host),
+                                      port: NWEndpoint.Port(rawValue: device.port)!, using: .tcp)
+        defer { connection.cancel() }
+        connection.start(queue: .main)
+        try await until("Resolved host/port connects to the advertised receiver") {
+            connection.state == .ready && !accepted.isEmpty
+        }
+        second.service = .init(name: prefix + "-b", type: "_googlecast._tcp",
+                               txtRecord: NWTXTRecord(["id": secondID, "fn": "TV 1"]))
+        try await until("TXT changes update the device without changing its identity", attempts: 1500) {
+            ownDevices().map(\.id) == [secondID, firstID] && ownDevices()[0].name == "TV 1"
+        }
+        first.cancel()
+        try await until("A duplicate advertisement keeps the receiver available", attempts: 1500) {
+            ownDevices().first(where: { $0.id == firstID })?.port == duplicatePort
+        }
+        duplicate.cancel()
+        try await until("Removing the last advertisement removes the receiver", attempts: 1500) {
+            ownDevices().map(\.id) == [secondID]
+        }
+        discovery.stop()
+        require(discovery.devices.isEmpty, "Stop clears published receivers")
+        discovery.start()
+        try await until("Restart ignores cancelled browser/resolver callbacks and rediscovers the receiver", attempts: 1500) {
+            ownDevices().map(\.id) == [secondID] && ownDevices()[0].name == "TV 1"
+        }
+        try await until("Service identity without TXT stays stable across restart", attempts: 1500) {
+            discovery.devices.contains { $0.id == fallbackID && $0.name == prefix + "-fallback" }
+        }
+        second.cancel()
+        try await until("Receiver removal after restart", attempts: 1500) { ownDevices().isEmpty }
+        require(discovery.error == nil, "Successful browsing leaves no permission/network error")
+        print("PASS: Bonjour discovery TXT identity/name/update, natural order, duplicate removal, routable host/port, stop/restart")
+    }
+
     static func codec() throws {
         let payload = Data("{\"type\":\"PING\"}".utf8)
         let message = CastWire.Message(source: "sender-0", destination: "receiver-0",
@@ -921,10 +1002,15 @@ struct CastSessionCheck {
     }
 
     static func main() async throws {
+        if CommandLine.arguments.count == 2, CommandLine.arguments[1] == "--discovery" {
+            try await discovery()
+            return
+        }
         if CommandLine.arguments.count == 6, CommandLine.arguments[1] == "--peer" {
             try await realPeer(CommandLine.arguments)
             return
         }
+        try await discovery()
         try codec()
         let (identity, directory) = try testIdentity()
         defer { try? FileManager.default.removeItem(at: directory) }