4 files changed, 94 insertions, 6 deletions
diff --git a/src/base/Base.cpp b/src/base/Base.cpp
index 1704f8a9..c6d9ac07 100644
--- a/src/base/Base.cpp
+++ b/src/base/Base.cpp
@@ -4,4 +4,5 @@
 
 namespace cru {
 void UnreachableCode() { std::terminate(); }
+void NotImplemented() { std::terminate(); }
 }  // namespace cru
diff --git a/src/base/CMakeLists.txt b/src/base/CMakeLists.txt
index 300898af..7e7b0127 100644
--- a/src/base/CMakeLists.txt
+++ b/src/base/CMakeLists.txt
@@ -24,8 +24,8 @@ target_compile_definitions(CruBase PUBLIC $<$<CONFIG:Debug>:CRU_DEBUG>)
 
 if (UNIX AND NOT EMSCRIPTEN)
 	target_sources(CruBase PRIVATE
+		platform/unix/EventLoop.cpp
 		platform/unix/PosixSpawnSubProcess.cpp
-		platform/unix/Timer.cpp
 		platform/unix/UnixFile.cpp
 		platform/unix/UnixFileStream.cpp
 	)
diff --git a/src/base/platform/unix/EventLoop.cpp b/src/base/platform/unix/EventLoop.cpp
new file mode 100644
index 00000000..337d8a44
--- /dev/null
+++ b/src/base/platform/unix/EventLoop.cpp
@@ -0,0 +1,92 @@
+#include "cru/base/platform/unix/EventLoop.h"
+#include "cru/base/Exception.h"
+
+#include <poll.h>
+#include <algorithm>
+#include <chrono>
+#include <thread>
+
+namespace cru::platform::unix {
+int UnixTimerFile::GetReadFd() const { return this->read_fd_; }
+
+UnixEventLoop::UnixEventLoop() : timer_tag_(1) {}
+
+int UnixEventLoop::Run() {
+  running_thread_ = std::this_thread::get_id();
+
+  pollfd poll_fds[1];
+
+  while (!exit_code_) {
+    int poll_timeout = -1;
+
+    auto iter = std::ranges::find_if(timers_, [](const TimerData &timer) {
+      return timer.timeout <= std::chrono::milliseconds::zero();
+    });
+    if (iter != timers_.end()) {
+      auto &timer = *iter;
+      if (timer.repeat) {
+        while (timer.timeout <= std::chrono::milliseconds::zero()) {
+          timer.timeout += timer.original_timeout;
+          timer.action();
+        }
+      } else {
+        auto action = timer.action;
+        timers_.erase(iter);
+        action();
+      }
+      continue;
+    }
+
+    if (!timers_.empty()) {
+      poll_timeout =
+          std::ranges::min_element(timers_, [](const TimerData &left,
+                                               const TimerData &right) {
+            return left.timeout < right.timeout;
+          })->timeout.count();
+    }
+
+    auto start = std::chrono::steady_clock::now();
+
+    ::poll(poll_fds, sizeof poll_fds / sizeof *poll_fds, poll_timeout);
+
+    // TODO: A Big Implement to handle X events.
+
+    auto end = std::chrono::steady_clock::now();
+    auto time =
+        std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
+
+    for (auto &timer : timers_) {
+      timer.timeout -= time;
+    }
+  }
+
+  return exit_code_.value();
+}
+
+void UnixEventLoop::RequestQuit(int exit_code) {}
+
+int UnixEventLoop::SetTimer(std::function<void()> action,
+                            std::chrono::milliseconds timeout, bool repeat) {
+  if (repeat) {
+    if (timeout <= std::chrono::milliseconds::zero()) {
+      throw Exception("Interval must be bigger than 0.");
+    }
+  } else {
+    if (timeout < std::chrono::milliseconds::zero()) {
+      throw Exception("Timeout must be at least 0.");
+    }
+  }
+
+  auto tag = timer_tag_++;
+
+  if (std::this_thread::get_id() == running_thread_) {
+    timers_.push_back(
+        TimerData(tag, std::move(timeout), repeat, std::move(action)));
+  } else {
+    // TODO: Implement
+  }
+
+  return tag;
+}
+
+}  // namespace cru::platform::unix
diff --git a/src/base/platform/unix/Timer.cpp b/src/base/platform/unix/Timer.cpp
deleted file mode 100644
index 25264dc8..00000000
--- a/src/base/platform/unix/Timer.cpp
+++ /dev/null
@@ -1,5 +0,0 @@
-#include "cru/base/platform/unix/Timer.h"
-
-namespace cru::platform::unix {
-int UnixTimerFile::GetReadFd() const { return this->read_fd_; }
-}  // namespace cru::platform::unix