From 7d59c2743d4c63f9e6c83de6a245f9bf3b3c2902 Mon Sep 17 00:00:00 2001
From: iwubcode <iwubcode@users.noreply.github.com>
Date: Sun, 2 Mar 2025 23:57:13 -0600
Subject: [PATCH] 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/CMakeLists.txt        |  3 ++
 Source/Core/Common/FilesystemWatcher.cpp | 67 ++++++++++++++++++++++++
 Source/Core/Common/FilesystemWatcher.h   | 47 +++++++++++++++++
 Source/Core/DolphinLib.props             |  2 +
 4 files changed, 119 insertions(+)
 create mode 100644 Source/Core/Common/FilesystemWatcher.cpp
 create mode 100644 Source/Core/Common/FilesystemWatcher.h

diff --git a/Source/Core/Common/CMakeLists.txt b/Source/Core/Common/CMakeLists.txt
index bbc3721a19..6d1b6908f3 100644
--- a/Source/Core/Common/CMakeLists.txt
+++ b/Source/Core/Common/CMakeLists.txt
@@ -64,6 +64,8 @@ add_library(common
   FatFsUtil.h
   FileSearch.cpp
   FileSearch.h
+  FilesystemWatcher.cpp
+  FilesystemWatcher.h
   FileUtil.cpp
   FileUtil.h
   FixedSizeQueue.h
@@ -184,6 +186,7 @@ PRIVATE
   FatFs
   Iconv::Iconv
   spng::spng
+  watcher
   ${VTUNE_LIBRARIES}
 )
 
diff --git a/Source/Core/Common/FilesystemWatcher.cpp b/Source/Core/Common/FilesystemWatcher.cpp
new file mode 100644
index 0000000000..646e2467ed
--- /dev/null
+++ b/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
diff --git a/Source/Core/Common/FilesystemWatcher.h b/Source/Core/Common/FilesystemWatcher.h
new file mode 100644
index 0000000000..ad1c822e2b
--- /dev/null
+++ b/Source/Core/Common/FilesystemWatcher.h
@@ -0,0 +1,47 @@
+// Copyright 2025 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+#include <string_view>
+
+namespace wtr
+{
+inline namespace watcher
+{
+class watch;
+}
+}  // namespace wtr
+
+namespace Common
+{
+// A class that can watch a path and receive callbacks
+// when files or directories underneath that path receive events
+class FilesystemWatcher
+{
+public:
+  FilesystemWatcher();
+  virtual ~FilesystemWatcher();
+
+  void Watch(const std::string& path);
+  void Unwatch(const std::string& path);
+
+private:
+  // A new file or folder was added to one of the watched paths
+  virtual void PathAdded(std::string_view path) {}
+
+  // A file or folder was modified in one of the watched paths
+  virtual void PathModified(std::string_view path) {}
+
+  // A file or folder was renamed in one of the watched paths
+  virtual void PathRenamed(std::string_view old_path, std::string_view new_path) {}
+
+  // A file or folder was deleted in one of the watched paths
+  virtual void PathDeleted(std::string_view path) {}
+
+  std::map<std::string, std::unique_ptr<wtr::watch>> m_watched_paths;
+};
+}  // namespace Common
diff --git a/Source/Core/DolphinLib.props b/Source/Core/DolphinLib.props
index b21f1791d4..931207fbce 100644
--- a/Source/Core/DolphinLib.props
+++ b/Source/Core/DolphinLib.props
@@ -59,6 +59,7 @@
     <ClInclude Include="Common\Event.h" />
     <ClInclude Include="Common\FatFsUtil.h" />
     <ClInclude Include="Common\FileSearch.h" />
+    <ClInclude Include="Common\FilesystemWatcher.h" />
     <ClInclude Include="Common\FileUtil.h" />
     <ClInclude Include="Common\FixedSizeQueue.h" />
     <ClInclude Include="Common\Flag.h" />
@@ -813,6 +814,7 @@
     <ClCompile Include="Common\ENet.cpp" />
     <ClCompile Include="Common\FatFsUtil.cpp" />
     <ClCompile Include="Common\FileSearch.cpp" />
+    <ClCompile Include="Common\FilesystemWatcher.cpp" />
     <ClCompile Include="Common\FileUtil.cpp" />
     <ClCompile Include="Common\FloatUtils.cpp" />
     <ClCompile Include="Common\GekkoDisassembler.cpp" />