RPC Support

/**
 * Simple RPC client for making calls to RPC servers
 */
public class RpcClient implements AutoCloseable {
    
    /**
     * Create RPC client with default exchange and routing
     * @param channel - Channel to use for RPC calls
     * @param exchange - Exchange to publish requests to
     * @param routingKey - Routing key for requests
     */
    public RpcClient(Channel channel, String exchange, String routingKey) throws IOException;
    
    /**
     * Create RPC client with custom timeout
     * @param channel - Channel to use for RPC calls
     * @param exchange - Exchange to publish requests to  
     * @param routingKey - Routing key for requests
     * @param timeout - Request timeout in milliseconds
     */
    public RpcClient(Channel channel, String exchange, String routingKey, int timeout) throws IOException;
    
    /**
     * Make RPC call with byte array request and response
     * @param message - Request message as bytes
     * @return Response message as bytes
     */
    public byte[] primitiveCall(byte[] message) throws IOException, ShutdownSignalException, TimeoutException;
    
    /**
     * Make RPC call with string request and response
     * @param message - Request message as string
     * @return Response message as string
     */
    public String stringCall(String message) throws IOException, ShutdownSignalException, TimeoutException;
    
    /**
     * Make RPC call with Map request and response
     * @param message - Request message as Map
     * @return Response message as Map
     */
    public Map<String, Object> mapCall(Map<String, Object> message) throws IOException, ShutdownSignalException, TimeoutException;
    
    /**
     * Make RPC call with Map request and response with custom timeout
     * @param message - Request message as Map
     * @param timeout - Request timeout in milliseconds
     * @return Response message as Map
     */
    public Map<String, Object> mapCall(Map<String, Object> message, int timeout) throws IOException, ShutdownSignalException, TimeoutException;
    
    /**
     * Close the RPC client and clean up resources
     */
    @Override
    public void close() throws IOException;
}

// Basic RPC client usage
Channel channel = connection.createChannel();
RpcClient rpcClient = new RpcClient(channel, "", "rpc_queue");

// String-based RPC call
String response = rpcClient.stringCall("Hello RPC");
System.out.println("Response: " + response);

// Byte array RPC call
byte[] request = "binary request".getBytes();
byte[] responseBytes = rpcClient.primitiveCall(request);

// Map-based RPC call  
Map<String, Object> requestMap = new HashMap<>();
requestMap.put("method", "fibonacci");
requestMap.put("number", 30);
Map<String, Object> responseMap = rpcClient.mapCall(requestMap);

rpcClient.close();

/**
 * Abstract base class for RPC servers
 */
public abstract class RpcServer implements AutoCloseable {
    
    /**
     * Create RPC server on specified queue
     * @param channel - Channel to use for RPC operations
     * @param queueName - Queue name to consume requests from
     */
    public RpcServer(Channel channel, String queueName) throws IOException;
    
    /**
     * Handle incoming RPC call - implement this method
     * @param requestBody - Request message body
     * @param replyProperties - Properties for reply message
     * @return Response message body
     */
    public abstract byte[] handleCall(byte[] requestBody, AMQP.BasicProperties replyProperties);
    
    /**
     * Start processing RPC calls (blocking call)
     */
    public void mainloop() throws IOException;
    
    /**
     * Process a single request and send response
     * @param requestBody - Request message body
     * @param properties - Request message properties
     * @return Response message body
     */
    public byte[] processRequest(byte[] requestBody, AMQP.BasicProperties properties) throws IOException;
    
    /**
     * Close the RPC server and clean up resources
     */
    @Override
    public void close() throws IOException;
}

/**
 * RPC server that handles string-based requests and responses
 */
public abstract class StringRpcServer extends RpcServer {
    
    /**
     * Create string RPC server
     * @param channel - Channel to use
     * @param queueName - Queue to consume from
     */
    public StringRpcServer(Channel channel, String queueName) throws IOException;
    
    /**
     * Handle string-based RPC call - implement this method
     * @param request - Request message as string
     * @return Response message as string
     */
    public abstract String handleStringCall(String request);
}

/**
 * RPC server that handles Map-based requests and responses
 */
public abstract class MapRpcServer extends RpcServer {
    
    /**
     * Create Map RPC server
     * @param channel - Channel to use
     * @param queueName - Queue to consume from
     */
    public MapRpcServer(Channel channel, String queueName) throws IOException;
    
    /**
     * Handle Map-based RPC call - implement this method
     * @param request - Request message as Map
     * @return Response message as Map
     */
    public abstract Map<String, Object> handleMapCall(Map<String, Object> request);
}

// String RPC Server implementation
public class FibonacciRpcServer extends StringRpcServer {
    public FibonacciRpcServer(Channel channel, String queueName) throws IOException {
        super(channel, queueName);
    }
    
    @Override
    public String handleStringCall(String request) {
        int n = Integer.parseInt(request);
        int result = fibonacci(n);
        return String.valueOf(result);
    }
    
    private int fibonacci(int n) {
        if (n <= 1) return n;
        return fibonacci(n - 1) + fibonacci(n - 2);
    }
}

// Start the RPC server
Channel channel = connection.createChannel();
FibonacciRpcServer server = new FibonacciRpcServer(channel, "rpc_queue");
server.mainloop(); // Blocks and processes requests

// Map RPC Server implementation
public class CalculatorRpcServer extends MapRpcServer {
    public CalculatorRpcServer(Channel channel, String queueName) throws IOException {
        super(channel, queueName);
    }
    
    @Override
    public Map<String, Object> handleMapCall(Map<String, Object> request) {
        String operation = (String) request.get("operation");
        double a = ((Number) request.get("a")).doubleValue();
        double b = ((Number) request.get("b")).doubleValue();
        
        double result;
        switch (operation) {
            case "add": result = a + b; break;
            case "subtract": result = a - b; break;
            case "multiply": result = a * b; break;
            case "divide": result = a / b; break;
            default: throw new IllegalArgumentException("Unknown operation");
        }
        
        Map<String, Object> response = new HashMap<>();
        response.put("result", result);
        return response;
    }
}

/**
 * Parameters for configuring RPC client behavior
 */
public class RpcClientParams {
    
    /**
     * Set request timeout in milliseconds
     * @param timeout - Timeout value
     */
    public RpcClientParams setTimeout(int timeout);
    
    /**
     * Set whether to use publisher confirms
     * @param useConfirms - Whether to enable confirms
     */
    public RpcClientParams setUseConfirms(boolean useConfirms);
    
    /**
     * Set whether requests should be mandatory
     * @param mandatory - Whether requests are mandatory
     */
    public RpcClientParams setMandatory(boolean mandatory);
    
    /**
     * Get configured timeout
     */
    public int getTimeout();
    
    /**
     * Check if confirms are enabled
     */
    public boolean isUseConfirms();
    
    /**
     * Check if requests are mandatory
     */
    public boolean isMandatory();
}