feat: connect clients from validated assignments

Game/scripts/control_plane_client.gd

@@ -9,6 +9,8 @@ signal session_expired()
 signal session_changed(player_id: String)
 signal websocket_event(event: Dictionary)
 signal websocket_status_changed(status: String)
+signal assignment_connection_started(assignment: AssignmentState)
+signal assignment_connection_failed(detail: String)
 
 const DEFAULT_BASE_URL := "http://127.0.0.1:8080"
 const PERSIST_PATH := "user://matchmaking_state.cfg"
@@ -178,6 +180,47 @@ func fetch_assignment(match_id: String) -> Error:
 	return _start_request("assignment", HTTPClient.METHOD_GET, "/v1/assignments/" + match_id, {}, "")
 
 
+# Starts the assigned game transport only after AssignmentState has validated
+# the complete player-scoped manifest. The signed authorisation is passed to
+# MatchNet's hello RPC, never appended to the endpoint URL or logged. Server
+# admission remains authoritative; this method only owns the client-side
+# readiness/transport boundary.
+func connect_to_assignment() -> Error:
+	if assignment == null or not assignment.available or not _assignment_is_fresh(assignment):
+		var unavailable_detail := "Match assignment is unavailable or expired"
+		assignment_connection_failed.emit(unavailable_detail)
+		return ERR_UNAUTHORIZED
+	var endpoint := _split_assignment_endpoint(assignment.endpoint)
+	if endpoint.is_empty():
+		var invalid_detail := "Match assignment endpoint is invalid"
+		assignment_connection_failed.emit(invalid_detail)
+		return ERR_INVALID_PARAMETER
+	var transport := NetworkManager.TRANSPORT_ENET if assignment.transport == "enet" else NetworkManager.TRANSPORT_STEAM
+	MatchNet.join_authorisation = assignment.join_authorisation
+	state.mark_connecting()
+	var err := NetworkManager.join(String(endpoint["host"]), int(endpoint["port"]), transport)
+	if err != OK:
+		MatchNet.join_authorisation = ""
+		assignment_connection_failed.emit("Unable to connect to match server")
+		return err
+	assignment_connection_started.emit(assignment)
+	return OK
+
+
+static func _assignment_is_fresh(value: AssignmentState) -> bool:
+	if value == null or value.expires_at.is_empty():
+		return false
+	var expiry := Time.get_unix_time_from_datetime_string(value.expires_at)
+	return expiry > Time.get_unix_time_from_system()
+
+
+static func _split_assignment_endpoint(value: String) -> Dictionary:
+	if not AssignmentState._valid_endpoint(value):
+		return {}
+	var separator := value.rfind(":")
+	return {"host": value.substr(0, separator), "port": int(value.substr(separator + 1))}
+
+
 func heartbeat(ticket_id: String, expected_revision: int) -> Error:
 	if ticket_id.is_empty() or expected_revision < 0:
 		return ERR_INVALID_PARAMETER