feat: implemented consumer thread, all tests pass

README.md

@@ -34,3 +34,14 @@ The reader never throws on I/O errors; every outcome is expressed through the en
 `UnixIpcBridge` ([include/UnixIpcBridge.hpp](include/UnixIpcBridge.hpp), [src/core/UnixIpcBridge.cxx](src/core/UnixIpcBridge.cxx)) is a small helper that connects to a UNIX domain socket and sends a single `int` per call. It opens a new connection for each value, which keeps the protocol stateless and simple.
 
 **Tests:** [tests/test_unix_ipc.cxx](tests/test_unix_ipc.cxx) — spins up a fake socket server, sends values through the bridge, and asserts they arrive correctly.
+
+## ConsumerThread
+
+`ConsumerThread` ([include/ConsumerThread.hpp](include/ConsumerThread.hpp), [src/core/ConsumerThread.cxx](src/core/ConsumerThread.cxx)) is a `QObject` that listens on a UNIX domain socket in a background `std::thread`. On each received integer it:
+
+1. Prints the value to `stdout`.
+2. Emits the `valueReceived(int)` Qt signal.
+
+The server socket is created and bound inside `start()` **before** the thread is spawned, so the socket is guaranteed to be ready by the time `start()` returns — eliminating race conditions with the producer. Graceful shutdown is handled by `stop()`, which shuts down the file descriptor to unblock the blocking `accept()` call.
+
+**Tests:** [tests/test_consumer_thread.cxx](tests/test_consumer_thread.cxx) — uses `QSignalSpy` to verify single-value, multi-value, negative, and zero reception.

src/core/Consumer.cxx

@@ -0,0 +1,104 @@
+// ConsumerThread.cxx
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Author: Unai Blazquez <unaibg2000@gmail.com>
+
+#include "Consumer.hpp"
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include <cstring>
+#include <iostream>
+#include <stdexcept>
+
+ConsumerThread::ConsumerThread(const std::string& socket_path, QObject* parent)
+    : QObject(parent), m_socket_path(socket_path)
+{
+}
+
+ConsumerThread::~ConsumerThread() { stop(); }
+
+void ConsumerThread::start()
+{
+  // Remove stale socket from previous runs
+  unlink(m_socket_path.c_str());
+
+  // Create, bind and listen BEFORE spawning the thread so the socket
+  // is guaranteed ready when start() returns — no race with the producer.
+  m_server_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+  if (m_server_fd < 0)
+  {
+    throw std::runtime_error("ConsumerThread: socket() failed");
+  }
+
+  struct sockaddr_un addr = {};
+  addr.sun_family = AF_UNIX;
+  std::strncpy(addr.sun_path, m_socket_path.c_str(), sizeof(addr.sun_path) - 1);
+
+  if (bind(m_server_fd, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) < 0)
+  {
+    close(m_server_fd);
+    m_server_fd = -1;
+    throw std::runtime_error("ConsumerThread: bind() failed");
+  }
+
+  if (listen(m_server_fd, 5) < 0)
+  {
+    close(m_server_fd);
+    m_server_fd = -1;
+    throw std::runtime_error("ConsumerThread: listen() failed");
+  }
+
+  m_running.store(true);
+  m_thread = std::thread(&ConsumerThread::run_loop, this);
+}
+
+void ConsumerThread::stop()
+{
+  if (!m_running.exchange(false))
+  {
+    return;  // already stopped or never started
+  }
+
+  // Shutdown the server fd to unblock the blocking accept() call
+  if (m_server_fd >= 0)
+  {
+    shutdown(m_server_fd, SHUT_RDWR);
+    close(m_server_fd);
+    m_server_fd = -1;
+  }
+
+  if (m_thread.joinable())
+  {
+    m_thread.join();
+  }
+
+  unlink(m_socket_path.c_str());
+}
+
+void ConsumerThread::run_loop()
+{
+  while (m_running.load())
+  {
+    int client_fd = accept(m_server_fd, nullptr, nullptr);
+    if (client_fd < 0)
+    {
+      // accept() failed — most likely stop() closed the fd
+      break;
+    }
+
+    int value = 0;
+    ssize_t n = recv(client_fd, &value, sizeof(value), MSG_WAITALL);
+    close(client_fd);
+
+    if (n == static_cast<ssize_t>(sizeof(value)))
+    {
+      // 1) Print to console (spec requirement)
+      std::cout << "ConsumerThread received: " << value << std::endl;
+
+      // 2) Emit Qt signal (spec requirement)
+      emit valueReceived(value);
+    }
+  }
+}

tests/test_consumer.cxx

@@ -0,0 +1,120 @@
+#include <gtest/gtest.h>
+
+#include <QCoreApplication>
+#include <QSignalSpy>
+
+#include "Consumer.hpp"
+#include "UnixIpcBridge.hpp"
+
+// QSignalSpy needs a QCoreApplication to dispatch queued signals
+static int argc_ = 0;
+static QCoreApplication app_(argc_, nullptr);
+
+TEST(ConsumerThreadTest, ReceivesSingleValue)
+{
+  const std::string sock = "/tmp/test_ct_single.sock";
+
+  ConsumerThread consumer(sock);
+
+  // QSignalSpy records every emission of the given signal
+  QSignalSpy spy(&consumer, &ConsumerThread::valueReceived);
+  consumer.start();
+
+  UnixIpcBridge bridge(sock);
+  bridge.send(42);
+
+  // spy.wait() pumps the event loop for up to 1s until a signal arrives
+  spy.wait(1000);
+  consumer.stop();
+
+  ASSERT_EQ(spy.count(), 1);
+  EXPECT_EQ(spy.at(0).at(0).toInt(), 42);
+}
+
+TEST(ConsumerThreadTest, ReceivesMultipleValues)
+{
+  const std::string sock = "/tmp/test_ct_multi.sock";
+
+  ConsumerThread consumer(sock);
+  QSignalSpy spy(&consumer, &ConsumerThread::valueReceived);
+  consumer.start();
+
+  constexpr int kMessages = 5;
+  for (int i = 0; i < kMessages; ++i)
+  {
+    UnixIpcBridge bridge(sock);
+    bridge.send(i * 10);
+    // Small delay so the consumer can re-enter accept() between sends
+    std::this_thread::sleep_for(std::chrono::milliseconds(10));
+  }
+
+  // Wait until all signals arrive (or timeout after 5s)
+  for (int attempt = 0; spy.count() < kMessages && attempt < 50; ++attempt)
+  {
+    spy.wait(100);
+  }
+
+  consumer.stop();
+
+  ASSERT_EQ(spy.count(), kMessages);
+  for (int i = 0; i < kMessages; ++i)
+  {
+    EXPECT_EQ(spy.at(i).at(0).toInt(), i * 10);
+  }
+}
+
+TEST(ConsumerThreadTest, ReceivesNegativeAndZero)
+{
+  // Zero
+  {
+    const std::string sock = "/tmp/test_ct_zero.sock";
+    ConsumerThread consumer(sock);
+    QSignalSpy spy(&consumer, &ConsumerThread::valueReceived);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(0);
+
+    spy.wait(1000);
+    consumer.stop();
+
+    ASSERT_EQ(spy.count(), 1);
+    EXPECT_EQ(spy.at(0).at(0).toInt(), 0);
+  }
+
+  // Negative
+  {
+    const std::string sock = "/tmp/test_ct_neg.sock";
+    ConsumerThread consumer(sock);
+    QSignalSpy spy(&consumer, &ConsumerThread::valueReceived);
+    consumer.start();
+
+    UnixIpcBridge bridge(sock);
+    bridge.send(-999);
+
+    spy.wait(1000);
+    consumer.stop();
+
+    ASSERT_EQ(spy.count(), 1);
+    EXPECT_EQ(spy.at(0).at(0).toInt(), -999);
+  }
+}
+
+TEST(ConsumerThreadTest, StopsCleanlyWithoutDeadlock)
+{
+  const std::string sock = "/tmp/test_ct_stop.sock";
+
+  ConsumerThread consumer(sock);
+  consumer.start();
+  // stop() must return without hanging, even with no connections
+  consumer.stop();
+}
+
+TEST(ConsumerThreadTest, StopsCleanlyWhenNeverStarted)
+{
+  const std::string sock = "/tmp/test_ct_nostart.sock";
+
+  ConsumerThread consumer(sock);
+  // stop() on a consumer that was never started must not crash
+  consumer.stop();
+}