titan_client/tcp/

tcp_client_blocking.rs

use std::{
    io::{BufRead, BufReader, Write},
    net::{TcpStream, ToSocketAddrs},
    sync::{
        atomic::{AtomicBool, Ordering},
        mpsc, Arc, Mutex,
    },
    thread::{self, JoinHandle},
    time::Duration,
};

use serde_json;
use thiserror::Error;
use titan_types_api::TcpSubscriptionRequest;
use titan_types_core::Event;
use tracing::{debug, error, info, warn};

use crate::tcp::reconnection::ReconnectionManager;

use super::{
    connection_status::{ConnectionStatus, ConnectionStatusTracker},
    reconnection,
};

#[derive(Debug, Error)]
pub enum TcpClientError {
    #[error("io error: {0}")]
    IOError(#[from] std::io::Error),
    #[error("serde error: {0}")]
    SerdeError(#[from] serde_json::Error),
    #[error("address parse error: {0}")]
    AddrParseError(String),
}
/// Configuration for TCP client reconnection.
#[derive(Debug, Clone)]
pub struct TcpClientConfig {
    /// Base duration for reconnect interval (will be used with exponential backoff)
    pub base_reconnect_interval: Duration,
    /// Maximum reconnect interval (cap for exponential backoff)
    pub max_reconnect_interval: Duration,
    /// Maximum number of reconnection attempts.
    /// Use `None` for unlimited attempts.
    pub max_reconnect_attempts: Option<u32>,
    /// Connection timeout.
    pub connection_timeout: Duration,
    /// Initial capacity of the read buffer (in bytes)
    pub read_buffer_capacity: usize,
    /// Maximum allowed size for the read buffer (in bytes)
    pub max_buffer_size: usize,
    /// Interval between ping messages
    pub ping_interval: Duration,
    /// Timeout for waiting for pong responses
    pub pong_timeout: Duration,
}

impl Default for TcpClientConfig {
    fn default() -> Self {
        TcpClientConfig {
            base_reconnect_interval: Duration::from_secs(1),
            max_reconnect_interval: Duration::from_secs(60),
            max_reconnect_attempts: None,
            connection_timeout: Duration::from_secs(30),
            read_buffer_capacity: 4096,             // 4KB initial capacity
            max_buffer_size: 10 * 1024 * 1024,      // 10MB max buffer size
            ping_interval: Duration::from_secs(30), // Send ping every 30 seconds
            pong_timeout: Duration::from_secs(10),  // Wait 10 seconds for pong response
        }
    }
}

/// Synchronous TCP subscription listener with reconnection support.
///
/// Connects to the TCP server at `addr` and sends the given subscription request
/// (encoded as JSON). It then spawns a dedicated thread that reads lines from the TCP
/// connection. If the connection drops or an error occurs, it will attempt to reconnect
/// according to the configuration settings.
///
/// # Thread Management
///
/// This client spawns a background thread to handle the TCP connection and event processing.
/// To ensure proper cleanup, you should call `shutdown_and_join()` when you're done with the
/// client. If you don't call this method, the background thread will be automatically
/// signaled to shut down when the `TcpClient` is dropped, but the thread may continue
/// running briefly after the client is dropped.
///
/// ```
/// # use client::tcp_client_blocking::{TcpClient, TcpClientConfig};
/// # fn main() {
/// let client = TcpClient::new(TcpClientConfig::default());
/// // Use the client...
///
/// // When done, ensure clean shutdown
/// client.shutdown_and_join();
/// # }
/// ```
#[cfg(feature = "tcp_client_blocking")]
pub struct TcpClient {
    shutdown_flag: Arc<AtomicBool>,
    config: TcpClientConfig,
    status_tracker: ConnectionStatusTracker,
    worker_thread: Mutex<Option<JoinHandle<()>>>,
}

#[cfg(feature = "tcp_client_blocking")]
impl TcpClient {
    /// Creates a new TCP client with the given configuration.
    pub fn new(config: TcpClientConfig) -> Self {
        Self {
            shutdown_flag: Arc::new(AtomicBool::new(false)),
            config,
            status_tracker: ConnectionStatusTracker::new(),
            worker_thread: Mutex::new(None),
        }
    }

    /// Get the current connection status
    pub fn get_status(&self) -> ConnectionStatus {
        self.status_tracker.get_status()
    }

    /// Get whether the client was disconnected at any point in time
    pub fn create_status_subscriber(&self) -> mpsc::Receiver<ConnectionStatus> {
        let (tx, rx) = mpsc::channel();
        self.status_tracker.register_listener(tx);
        rx
    }

    /// Checks if there is an active worker thread.
    ///
    /// Returns true if a worker thread is currently running.
    pub fn has_active_thread(&self) -> bool {
        match self.worker_thread.lock() {
            Ok(lock) => lock.is_some(),
            Err(_) => {
                error!("Failed to acquire worker thread lock");
                false
            }
        }
    }

    /// Subscribe to events from the given address.
    ///
    /// This will spawn a background thread that connects to the server and
    /// listens for events. The events will be sent to the returned channel.
    ///
    /// If there's already an active worker thread, it will be shut down and
    /// a new one will be created.
    pub fn subscribe(
        &self,
        addr: String,
        subscription_request: TcpSubscriptionRequest,
    ) -> Result<mpsc::Receiver<Event>, TcpClientError> {
        // Check if we already have a worker thread running
        let mut worker_lock = self.worker_thread.lock().map_err(|_| {
            TcpClientError::IOError(std::io::Error::new(
                std::io::ErrorKind::Other,
                "Failed to acquire worker thread lock",
            ))
        })?;

        // Reset shutdown flag in case it was previously set
        self.shutdown_flag.store(false, Ordering::SeqCst);

        let shutdown_flag = self.shutdown_flag.clone();
        let config = self.config.clone();
        let status_tracker = self.status_tracker.clone();

        // Call the subscribe function which returns both the receiver and thread handle
        let (rx, handle) = subscribe(
            addr,
            subscription_request,
            shutdown_flag,
            config,
            status_tracker,
        )?;

        // Store the thread handle for later joining
        *worker_lock = Some(handle);

        Ok(rx)
    }

    /// Signals the client to shut down and stop any reconnection attempts.
    /// Does not wait for the worker thread to complete.
    pub fn shutdown(&self) {
        self.status_tracker
            .update_status(ConnectionStatus::Disconnected);
        self.shutdown_flag.store(true, Ordering::SeqCst);
    }

    /// Signals the client to shut down and waits for the worker thread to complete.
    /// Returns true if the thread was successfully joined, false otherwise.
    pub fn shutdown_and_join(&self) -> bool {
        // Signal shutdown
        self.shutdown();

        // Try to join the thread
        self.join()
    }

    /// Waits for the worker thread to complete.
    /// Returns true if the thread was successfully joined, false otherwise.
    pub fn join(&self) -> bool {
        // Acquire the lock on the worker thread
        let mut worker_lock = match self.worker_thread.lock() {
            Ok(lock) => lock,
            Err(e) => {
                error!("Failed to acquire worker thread lock: {}", e);
                return false;
            }
        };

        // Take the thread handle out (replacing it with None)
        if let Some(handle) = worker_lock.take() {
            match handle.join() {
                Ok(_) => {
                    info!("Successfully joined worker thread");
                    true
                }
                Err(e) => {
                    error!("Failed to join worker thread: {:?}", e);
                    false
                }
            }
        } else {
            // No thread to join
            false
        }
    }
}

#[cfg(feature = "tcp_client_blocking")]
impl Drop for TcpClient {
    fn drop(&mut self) {
        // Signal thread to terminate
        self.shutdown();

        // Attempt to join the thread directly in the destructor
        // This is safe because we're taking ownership of the JoinHandle
        if let Ok(mut worker_lock) = self.worker_thread.lock() {
            if let Some(handle) = worker_lock.take() {
                // Don't block for too long in a destructor - it's generally not good practice
                // Just log that we're not waiting for the thread
                info!("TcpClient dropped, thread will continue running until shutdown completes");
            }
        }
        // The shutdown flag has been set, so the thread will terminate naturally
    }
}

fn subscribe(
    addr: String,
    subscription_request: TcpSubscriptionRequest,
    shutdown_flag: Arc<AtomicBool>,
    config: TcpClientConfig,
    status_tracker: ConnectionStatusTracker,
) -> Result<(mpsc::Receiver<Event>, JoinHandle<()>), TcpClientError> {
    // Create a standard mpsc channel to forward events.
    let (tx, rx) = mpsc::channel::<Event>();

    let address = addr
        .to_socket_addrs()
        .map_err(|_| TcpClientError::AddrParseError(format!("Invalid address: {}", addr)))?
        .next()
        .ok_or(TcpClientError::AddrParseError(format!(
            "Invalid address: {}",
            addr
        )))?;

    // Set initial status to Connecting
    status_tracker.update_status(ConnectionStatus::Connecting);

    // Create the reconnection manager
    let reconnection_config = reconnection::from_tcp_client_config(&config);

    let handle = thread::spawn(move || {
        // Create a status updater for use in the thread
        let update_status = status_tracker.create_updater();

        // Create the reconnection manager
        let mut reconnection_manager = ReconnectionManager::new(reconnection_config);

        loop {
            if shutdown_flag.load(Ordering::SeqCst) {
                info!("Shutdown flag set. Exiting subscription thread.");
                // Set status to disconnected
                update_status(ConnectionStatus::Disconnected);
                break;
            }

            // Try to connect to the server.
            info!("Attempting to connect to {}...", addr);
            // Ensure status is set to Connecting
            update_status(ConnectionStatus::Connecting);

            let connect_result = TcpStream::connect_timeout(&address, config.connection_timeout);

            match connect_result {
                Ok(mut stream) => {
                    info!("Connected to server at {}", addr);
                    // Update status to Connected
                    update_status(ConnectionStatus::Connected);

                    // Reset reconnection attempts after successful connection
                    reconnection_manager.reset();

                    // Set read timeout - use shorter timeout to allow for ping checks
                    if let Err(e) = stream.set_read_timeout(Some(Duration::from_millis(500))) {
                        error!("Failed to set read timeout: {}", e);
                        continue;
                    }

                    // Set write timeout
                    if let Err(e) = stream.set_write_timeout(Some(Duration::from_secs(5))) {
                        error!("Failed to set write timeout: {}", e);
                        continue;
                    }

                    // Clone the stream for reading.
                    let reader_stream = match stream.try_clone() {
                        Ok(rs) => rs,
                        Err(e) => {
                            error!("Failed to clone stream: {}", e);
                            continue;
                        }
                    };
                    let mut reader = BufReader::new(reader_stream);

                    // Serialize and send the subscription request.
                    match serde_json::to_string(&subscription_request) {
                        Ok(req_json) => {
                            if let Err(e) = stream.write_all(req_json.as_bytes()) {
                                error!("Failed to send subscription request: {}", e);
                                continue;
                            }
                            if let Err(e) = stream.write_all(b"\n") {
                                error!("Failed to send newline: {}", e);
                                continue;
                            }
                            if let Err(e) = stream.flush() {
                                error!("Failed to flush stream: {}", e);
                                continue;
                            }
                        }
                        Err(e) => {
                            error!("Failed to serialize subscription request: {}", e);
                            break;
                        }
                    }

                    // Initialize the byte buffer with the configured capacity
                    let mut byte_buf = Vec::with_capacity(config.read_buffer_capacity);

                    // Ping-pong state tracking
                    let mut last_ping_time = std::time::Instant::now();
                    let mut last_pong_time = std::time::Instant::now();
                    let mut awaiting_pong = false;

                    // Inner loop: read events from the connection with ping/pong support
                    loop {
                        if shutdown_flag.load(Ordering::SeqCst) {
                            info!("Shutdown flag set. Exiting inner read loop.");
                            update_status(ConnectionStatus::Disconnected);
                            break;
                        }

                        // Current time
                        let now = std::time::Instant::now();

                        // Handle ping-pong logic
                        if now.duration_since(last_ping_time) >= config.ping_interval {
                            if awaiting_pong {
                                // Check if we've exceeded the pong timeout
                                if now.duration_since(last_pong_time) >= config.pong_timeout {
                                    warn!("Pong response timed out after {:?}, considering connection dead",
                                          now.duration_since(last_pong_time));
                                    update_status(ConnectionStatus::Reconnecting);
                                    break;
                                }
                            } else {
                                // Time to send a ping
                                match stream.write_all(b"PING\n") {
                                    Ok(_) => {
                                        if let Err(e) = stream.flush() {
                                            error!("Failed to flush after PING: {}", e);
                                            update_status(ConnectionStatus::Reconnecting);
                                            break;
                                        }
                                        last_ping_time = now;
                                        awaiting_pong = true;
                                    }
                                    Err(e) => {
                                        error!("Failed to send PING: {}", e);
                                        update_status(ConnectionStatus::Reconnecting);
                                        break;
                                    }
                                }
                            }
                        }

                        // Set read timeout to allow for ping checks and shutdown signals
                        if let Err(e) = stream.set_read_timeout(Some(Duration::from_millis(50))) {
                            error!("Failed to set read timeout: {}", e);
                            update_status(ConnectionStatus::Reconnecting);
                            break;
                        }

                        // Try to read until newline
                        match reader.read_until(b'\n', &mut byte_buf) {
                            Ok(0) => {
                                // Connection closed by server
                                warn!("TCP connection closed by server. Attempting to reconnect.");
                                update_status(ConnectionStatus::Reconnecting);
                                break;
                            }
                            Ok(n) if n > 0 => {
                                // Note: read_until includes the delimiter in the buffer.
                                // Trim whitespace and the trailing newline before processing.
                                let message_bytes = byte_buf.trim_ascii_end();

                                if !message_bytes.is_empty() {
                                    // Check if this is a PONG response
                                    if message_bytes == b"PONG" {
                                        if awaiting_pong {
                                            awaiting_pong = false;
                                            last_pong_time = std::time::Instant::now();
                                            debug!("Received PONG");
                                        } else {
                                            warn!("Received unexpected PONG");
                                        }
                                    } else {
                                        // Check if message size exceeds limit *before* parsing JSON
                                        if message_bytes.len() > config.max_buffer_size {
                                            error!(
                                                "Received message exceeds maximum allowed size ({}), skipping. Message starts with: {:?}",
                                                config.max_buffer_size,
                                                String::from_utf8_lossy(&message_bytes[..std::cmp::min(message_bytes.len(), 50)]) // Log first 50 bytes
                                            );
                                            // Don't break, just clear buffer and continue reading the next message.
                                        } else {
                                            // Try to parse as an event from the byte slice
                                            match serde_json::from_slice::<Event>(message_bytes) {
                                                Ok(event) => {
                                                    // Any successful message means the connection is alive
                                                    last_pong_time = std::time::Instant::now();
                                                    awaiting_pong = false; // Reset awaiting_pong if we received a valid event

                                                    if tx.send(event).is_err() {
                                                        error!("Receiver dropped. Exiting subscription thread.");
                                                        update_status(
                                                            ConnectionStatus::Disconnected,
                                                        ); // Set status before returning
                                                        return; // Exit the thread
                                                    }
                                                }
                                                Err(e) => {
                                                    error!(
                                                        "Failed to parse event: {}. Raw data (first 100 bytes): {:?}",
                                                        e,
                                                        String::from_utf8_lossy(&message_bytes[..std::cmp::min(message_bytes.len(), 100)])
                                                    );
                                                    // Consider if this error should cause a reconnect or just skip
                                                    // For now, let's try reconnecting on parse error for safety
                                                    update_status(ConnectionStatus::Reconnecting);
                                                    break; // Trigger reconnect on parse error
                                                }
                                            }
                                        }
                                    }
                                }
                                // Clear the buffer for the next message AFTER processing the current one
                                byte_buf.clear();
                            }
                            Ok(_) => {
                                // n == 0, should be handled by Ok(0) case, safety belt
                                byte_buf.clear();
                            }
                            Err(e) => {
                                if e.kind() == std::io::ErrorKind::TimedOut
                                    || e.kind() == std::io::ErrorKind::WouldBlock
                                {
                                    // Expected timeout - continue the loop to check ping/shutdown
                                    continue;
                                } else {
                                    // Real error
                                    error!("Error reading from TCP socket using read_until: {}", e);
                                    update_status(ConnectionStatus::Reconnecting);
                                    break; // Break inner loop to trigger reconnect
                                }
                            }
                        }

                        // Check if buffer capacity is exceeding limits (less critical with clear(), but good safety)
                        if byte_buf.capacity() > config.max_buffer_size {
                            error!("Buffer capacity exceeded maximum allowed size ({}), resetting connection.", config.max_buffer_size);
                            update_status(ConnectionStatus::Reconnecting);
                            break;
                        }
                    } // end inner loop for current connection

                    // When we exit the inner loop (connection lost or shutdown)
                    // Update status to reconnecting only if not shutting down
                    if !shutdown_flag.load(Ordering::SeqCst) {
                        update_status(ConnectionStatus::Reconnecting);
                    }
                }
                Err(e) => {
                    error!("Failed to connect to {}: {}", addr, e);
                    // Set status to reconnecting since we're going to try again
                    update_status(ConnectionStatus::Reconnecting);
                }
            }

            // Before attempting reconnect, check shutdown flag again
            if shutdown_flag.load(Ordering::SeqCst) {
                update_status(ConnectionStatus::Disconnected);
                break;
            }

            // Get the next delay from the reconnection manager
            match reconnection_manager.next_delay() {
                Some(wait_time) => {
                    info!(
                        "Reconnecting in {:?}... (attempt {}/{:?})",
                        wait_time,
                        reconnection_manager.current_attempt(),
                        reconnection_manager.config().max_attempts
                    );
                    // Use a flag-aware sleep
                    let sleep_start = std::time::Instant::now();
                    while sleep_start.elapsed() < wait_time {
                        if shutdown_flag.load(Ordering::SeqCst) {
                            info!("Shutdown detected during reconnect wait.");
                            update_status(ConnectionStatus::Disconnected);
                            return; // Exit thread immediately
                        }
                        thread::sleep(Duration::from_millis(50)); // Check flag periodically
                    }
                }
                None => {
                    error!(
                        "Reached maximum reconnection attempts ({}). Exiting.",
                        reconnection_manager.config().max_attempts.unwrap_or(0)
                    );
                    // Set status to disconnected when max attempts reached
                    update_status(ConnectionStatus::Disconnected);
                    break;
                }
            }
        }
        info!("Exiting TCP subscription thread.");
        // Ensure status is Disconnected when thread exits naturally
        update_status(ConnectionStatus::Disconnected);
    });

    Ok((rx, handle))
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::{BufRead, Read, Write};
    use std::net::{SocketAddr, TcpListener};
    use std::thread;
    use std::time::Duration;
    use titan_types_core::EventType;

    // Helper function to create a test TCP server
    fn start_test_server(ready_tx: std::sync::mpsc::Sender<SocketAddr>) -> JoinHandle<()> {
        thread::spawn(move || {
            // Bind to a random available port
            let listener = TcpListener::bind("127.0.0.1:0").unwrap();
            let addr = listener.local_addr().unwrap();

            // Notify the test that we're ready and send the address
            ready_tx.send(addr).unwrap();

            // Accept one connection
            if let Ok((mut stream, _)) = listener.accept() {
                let mut reader = BufReader::new(stream.try_clone().unwrap());
                let mut request_buf = Vec::new();

                // Read the subscription request
                match reader.read_until(b'\n', &mut request_buf) {
                    Ok(n) if n > 0 => {
                        let request_bytes = request_buf.trim_ascii_end();
                        println!(
                            "Server received request: {}",
                            String::from_utf8_lossy(request_bytes)
                        );

                        // Add a small delay to ensure the client is ready to receive
                        thread::sleep(Duration::from_millis(50));

                        // Send a sample event - using correct format for Event
                        let event = r#"{"type":"TransactionsAdded","data": {"txids":["1111111111111111111111111111111111111111111111111111111111111111"]}}"#;
                        if let Err(e) = stream.write_all(event.as_bytes()) {
                            println!("Server write error: {}", e);
                            return;
                        }
                        if let Err(e) = stream.write_all(b"\n") {
                            println!("Server write error: {}", e);
                            return;
                        }
                        if let Err(e) = stream.flush() {
                            println!("Server flush error: {}", e);
                            return;
                        }

                        // Keep the connection open for a while to ensure the client can read the response
                        thread::sleep(Duration::from_millis(500));
                    }
                    Ok(0) => println!("Server: Client disconnected before sending request"),
                    Err(e) => println!("Test server read error: {}", e),
                    _ => println!("Server: Unexpected read result for request"),
                }
            }
        })
    }

    #[test]
    fn test_connection_status_transitions() {
        // Create a channel to sync with the test server
        let (ready_tx, ready_rx) = std::sync::mpsc::channel();

        // Start a test server
        let server_handle = start_test_server(ready_tx);

        // Wait for the server to be ready and get its address
        let server_addr = ready_rx.recv_timeout(Duration::from_secs(5)).unwrap();

        // Create a client with short timeout
        let config = TcpClientConfig {
            connection_timeout: Duration::from_secs(1),
            max_reconnect_attempts: Some(1),
            base_reconnect_interval: Duration::from_millis(100),
            ..TcpClientConfig::default()
        };
        let client = TcpClient::new(config);

        // Initially disconnected
        assert_eq!(client.get_status(), ConnectionStatus::Disconnected);

        // Subscribe - this should connect
        let subscription_request = TcpSubscriptionRequest {
            subscribe: vec![EventType::TransactionsAdded],
        };

        let rx = client
            .subscribe(format!("{}", server_addr), subscription_request)
            .unwrap();

        // Give it time to connect
        thread::sleep(Duration::from_millis(100));

        // Should be connected now
        assert_eq!(client.get_status(), ConnectionStatus::Connected);

        // Shutdown the client
        client.shutdown_and_join();

        // Check the client is disconnected
        assert_eq!(client.get_status(), ConnectionStatus::Disconnected);

        // Wait for the server to finish
        server_handle.join().unwrap();
    }

    #[test]
    fn test_receive_events() {
        // Create a channel to sync with the test server
        let (ready_tx, ready_rx) = std::sync::mpsc::channel();

        // Start a test server
        let server_handle = start_test_server(ready_tx);

        // Wait for the server to be ready and get its address
        let server_addr = ready_rx.recv_timeout(Duration::from_secs(5)).unwrap();

        // Create a client with short timeout
        let config = TcpClientConfig {
            connection_timeout: Duration::from_secs(1),
            max_reconnect_attempts: Some(1),
            base_reconnect_interval: Duration::from_millis(100),
            ..TcpClientConfig::default()
        };
        let client = TcpClient::new(config);

        // Subscribe to receive events
        let subscription_request = TcpSubscriptionRequest {
            subscribe: vec![EventType::TransactionsAdded],
        };

        let rx = client
            .subscribe(format!("{}", server_addr), subscription_request)
            .unwrap();

        // Give it time to establish connection
        thread::sleep(Duration::from_millis(200));

        // Try to receive an event with timeout
        let event = rx.recv_timeout(Duration::from_secs(2));
        assert!(event.is_ok(), "Should have received an event");

        match event.unwrap() {
            Event::TransactionsAdded { txids } => {
                assert_eq!(txids.len(), 1);
                assert_eq!(
                    txids[0].to_string(),
                    "1111111111111111111111111111111111111111111111111111111111111111"
                );
            }
            other => panic!("Received unexpected event type: {:?}", other),
        }

        // Shutdown the client
        client.shutdown_and_join();

        // Wait for the server to finish
        server_handle.join().unwrap();
    }

    #[test]
    fn test_connection_error_handling() {
        // Create a client with short timeout
        let config = TcpClientConfig {
            connection_timeout: Duration::from_secs(1),
            max_reconnect_attempts: Some(2),
            base_reconnect_interval: Duration::from_millis(100),
            ..TcpClientConfig::default()
        };
        let client = TcpClient::new(config);

        // Initially disconnected
        assert_eq!(client.get_status(), ConnectionStatus::Disconnected);

        // Try to connect to a non-existent server
        let subscription_request = TcpSubscriptionRequest {
            subscribe: vec![EventType::TransactionsAdded],
        };

        let _rx = client
            .subscribe("127.0.0.1:1".to_string(), subscription_request)
            .unwrap();

        // Give it time to attempt connection and reconnection
        thread::sleep(Duration::from_millis(500));

        // Should be in reconnecting state or disconnected if it already gave up
        let status = client.get_status();
        assert!(
            status == ConnectionStatus::Reconnecting || status == ConnectionStatus::Disconnected,
            "Expected Reconnecting or Disconnected state, got {:?}",
            status
        );

        // Shutdown the client
        client.shutdown_and_join();

        // Check the client is disconnected
        assert_eq!(client.get_status(), ConnectionStatus::Disconnected);
    }

    #[test]
    fn test_resource_cleanup() {
        // Create a client
        let client = TcpClient::new(TcpClientConfig::default());

        // Subscribe to a non-existent server
        let subscription_request = TcpSubscriptionRequest {
            subscribe: vec![EventType::TransactionsAdded],
        };

        let rx = client
            .subscribe("127.0.0.1:1".to_string(), subscription_request)
            .unwrap();

        // Verify we have an active thread
        assert!(client.has_active_thread());

        // Drop the receiver channel
        drop(rx);

        // Give the thread a moment to notice the receiver is dropped (if applicable)
        thread::sleep(Duration::from_millis(50));

        // Shutdown and join the client
        let joined = client.shutdown_and_join();
        assert!(joined, "Should have successfully joined the worker thread");

        // Verify we no longer have an active thread
        assert!(!client.has_active_thread());
    }

    // Helper function to create a test TCP server that handles ping/pong
    fn start_ping_pong_server(ready_tx: std::sync::mpsc::Sender<SocketAddr>) -> JoinHandle<()> {
        thread::spawn(move || {
            // Bind to a random available port
            let listener = TcpListener::bind("127.0.0.1:0").unwrap();
            let addr = listener.local_addr().unwrap();

            // Notify the test that we're ready and send the address
            ready_tx.send(addr).unwrap();

            // Accept one connection
            if let Ok((mut stream, _)) = listener.accept() {
                // Set a read timeout so we don't block forever
                stream
                    .set_read_timeout(Some(Duration::from_millis(200)))
                    .unwrap();

                // Create a buffer reader
                let mut reader = BufReader::new(stream.try_clone().unwrap());
                let mut line_buf = Vec::new(); // Use Vec<u8> for read_until

                // Read the subscription request
                match reader.read_until(b'\n', &mut line_buf) {
                    Ok(n) if n > 0 => {
                        let request_bytes = line_buf.trim_ascii_end();
                        println!(
                            "Ping-pong server received request: {}",
                            String::from_utf8_lossy(request_bytes)
                        );

                        // Send a sample event
                        let event = r#"{"type":"TransactionsAdded","data": {"txids":["1111111111111111111111111111111111111111111111111111111111111111"]}}"#;
                        if let Err(e) = stream.write_all(event.as_bytes()) {
                            println!("Server write error: {}", e);
                            return;
                        }
                        if let Err(e) = stream.write_all(b"\n") {
                            println!("Server write error: {}", e);
                            return;
                        }
                        if let Err(e) = stream.flush() {
                            println!("Server flush error: {}", e);
                            return;
                        }
                        println!("Ping-pong server sent initial event");
                    }
                    Ok(0) => {
                        println!("Ping-pong server: Client disconnected early");
                        return;
                    }
                    _ => {
                        println!("Ping-pong server failed to read subscription request");
                        return;
                    }
                }

                // Clear line for next reads
                line_buf.clear();

                // Keep handling ping/pong for a while
                let start = std::time::Instant::now();
                let timeout = Duration::from_secs(5); // Run for 5 seconds

                while start.elapsed() < timeout {
                    match reader.read_until(b'\n', &mut line_buf) {
                        // Use read_until here too
                        Ok(0) => {
                            println!("Ping-pong server: client closed connection");
                            break;
                        }
                        Ok(n) if n > 0 => {
                            let trimmed_line = line_buf.trim_ascii_end(); // Trim bytes
                            println!(
                                "Ping-pong server received: {}",
                                String::from_utf8_lossy(trimmed_line)
                            );

                            if trimmed_line == b"PING" {
                                // Compare bytes
                                println!("Ping-pong server sending PONG");
                                if let Err(e) = stream.write_all(b"PONG\n") {
                                    println!("Ping-pong server failed to send PONG: {}", e);
                                    break;
                                }
                                if let Err(e) = stream.flush() {
                                    println!("Ping-pong server failed to flush PONG: {}", e);
                                    break;
                                }
                            }
                            line_buf.clear(); // Clear buffer after processing
                        }
                        Ok(_) => {
                            /* n==0 case handled above */
                            line_buf.clear();
                        }
                        Err(e)
                            if e.kind() == std::io::ErrorKind::WouldBlock
                                || e.kind() == std::io::ErrorKind::TimedOut =>
                        {
                            // Expected timeout - continue
                            line_buf.clear(); // Ensure buffer is cleared even on timeout
                        }
                        Err(e) => {
                            println!("Ping-pong server error: {}", e);
                            break;
                        }
                    }

                    // Small sleep to prevent tight loop
                    thread::sleep(Duration::from_millis(50));
                }

                println!("Ping-pong server shutting down");
            }
        })
    }

    #[test]
    fn test_ping_pong_mechanism() {
        // Create a channel to sync with the test server
        let (ready_tx, ready_rx) = std::sync::mpsc::channel();

        // Start a ping-pong test server
        let server_handle = start_ping_pong_server(ready_tx);

        // Wait for the server to be ready and get its address
        let server_addr = ready_rx.recv_timeout(Duration::from_secs(5)).unwrap();

        // Create a client with short ping interval for faster testing
        let config = TcpClientConfig {
            connection_timeout: Duration::from_secs(1),
            max_reconnect_attempts: Some(1),
            base_reconnect_interval: Duration::from_millis(100),
            ping_interval: Duration::from_millis(500), // Short ping interval for testing
            pong_timeout: Duration::from_millis(1000), // 1 second timeout
            ..TcpClientConfig::default()
        };
        let client = TcpClient::new(config);

        // Subscribe to receive events
        let subscription_request = TcpSubscriptionRequest {
            subscribe: vec![EventType::TransactionsAdded],
        };

        let _rx = client
            .subscribe(format!("{}", server_addr), subscription_request)
            .unwrap();

        // Give it time to establish connection
        thread::sleep(Duration::from_millis(200));

        // Verify connection status is connected
        assert_eq!(
            client.get_status(),
            ConnectionStatus::Connected,
            "Client should be connected"
        );

        // Wait long enough for multiple ping/pong cycles
        thread::sleep(Duration::from_secs(2));

        // Verify still connected after ping/pong cycles
        assert_eq!(
            client.get_status(),
            ConnectionStatus::Connected,
            "Client should remain connected after ping/pong exchanges"
        );

        // Shutdown the client
        client.shutdown_and_join();

        // Wait for the server to finish
        server_handle.join().unwrap();
    }
}