Common: Add class 'FilesystemWatcher' that is used to watch paths and receive callbacks about filesystem level events for anything under that path

Source/Core/Common/FilesystemWatcher.cpp

@@ -0,0 +1,67 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/FilesystemWatcher.h"
+
+#include <wtr/watcher.hpp>
+
+#include "Common/Logging/Log.h"
+#include "Common/StringUtil.h"
+
+namespace Common
+{
+FilesystemWatcher::FilesystemWatcher() = default;
+FilesystemWatcher::~FilesystemWatcher() = default;
+
+void FilesystemWatcher::Watch(const std::string& path)
+{
+  const auto [iter, inserted] = m_watched_paths.try_emplace(path, nullptr);
+  if (inserted)
+  {
+    iter->second = std::make_unique<wtr::watch>(path, [this](wtr::event e) {
+      const auto watched_path = PathToString(e.path_name);
+      if (e.path_type == wtr::event::path_type::watcher)
+      {
+        if (watched_path.starts_with('e'))
+          ERROR_LOG_FMT(COMMON, "Filesystem watcher: '{}'", watched_path);
+        else if (watched_path.starts_with('w'))
+          WARN_LOG_FMT(COMMON, "Filesystem watcher: '{}'", watched_path);
+        return;
+      }
+
+      if (e.effect_type == wtr::event::effect_type::create)
+      {
+        const auto path = WithUnifiedPathSeparators(watched_path);
+        PathAdded(path);
+      }
+      else if (e.effect_type == wtr::event::effect_type::modify)
+      {
+        const auto path = WithUnifiedPathSeparators(watched_path);
+        PathModified(path);
+      }
+      else if (e.effect_type == wtr::event::effect_type::rename)
+      {
+        if (!e.associated)
+        {
+          WARN_LOG_FMT(COMMON, "Rename on path '{}' seen without association!", watched_path);
+          return;
+        }
+
+        const auto old_path = WithUnifiedPathSeparators(watched_path);
+        const auto new_path = WithUnifiedPathSeparators(PathToString(e.associated->path_name));
+        PathRenamed(old_path, new_path);
+      }
+      else if (e.effect_type == wtr::event::effect_type::destroy)
+      {
+        const auto path = WithUnifiedPathSeparators(watched_path);
+        PathDeleted(path);
+      }
+    });
+  }
+}
+
+void FilesystemWatcher::Unwatch(const std::string& path)
+{
+  m_watched_paths.erase(path);
+}
+}  // namespace Common