From e77054b80568f65aaf8a6201cf8432d000288209 Mon Sep 17 00:00:00 2001
From: ladevieq <ladevie.quentin@gmail.com>
Date: Wed, 20 Jul 2022 00:09:03 +0200
Subject: Add file watching api

---
 src/utils.cpp | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 88 insertions(+), 2 deletions(-)

(limited to 'src/utils.cpp')

diff --git a/src/utils.cpp b/src/utils.cpp
index dc5791c..9994064 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -45,6 +45,92 @@ std::vector<uint8_t> read_file(const char* path) {
     return file_content;
 }
 
-std::vector<uint8_t> read_file(std::string& path) {
-    return read_file(path.c_str());
+
+#ifdef WINDOWS
+void log_last_error() {
+    auto error_code = GetLastError();
+    const char* error_message = nullptr;
+
+    FormatMessageA(
+        FORMAT_MESSAGE_ALLOCATE_BUFFER | 
+        FORMAT_MESSAGE_FROM_SYSTEM |
+        FORMAT_MESSAGE_IGNORE_INSERTS,
+        nullptr,
+        error_code,
+        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+        (LPTSTR) &error_message,
+        0,
+        nullptr
+    );
+
+    std::cerr << error_message << std::endl;
 }
+
+bool watcher::watch_file(std::filesystem::path&& filepath, std::function<void()> callback) {
+    if (!std::filesystem::exists(filepath))
+        return false;
+
+    if (!watcher::watch_dir(filepath.parent_path()))
+        return false;
+
+    auto [_, is_inserted] = watcher::callbacks.emplace(filepath.filename().string(), callback);
+
+    return is_inserted;
+}
+
+bool watcher::watch_dir(std::filesystem::path&& dir_path) {
+    if (!std::filesystem::exists(dir_path))
+        return false;
+
+    if (watcher::watched_dirs.find(dir_path.string()) != watcher::watched_dirs.end())
+        return true;
+
+    HANDLE dir_handle = CreateFileW(
+        dir_path.c_str(),
+        FILE_LIST_DIRECTORY,
+        FILE_SHARE_WRITE | FILE_SHARE_READ,
+        nullptr,
+        OPEN_EXISTING,
+        FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
+        nullptr
+    );
+
+    if(dir_handle == INVALID_HANDLE_VALUE) {
+        log_last_error();
+        return false;
+    }
+
+    auto [dir, _] = watcher::watched_dirs.emplace(dir_path.string(), watch_data{ .dir_handle = dir_handle });
+
+    if (FAILED(ReadDirectoryChangesW(dir_handle, dir->second.buffer, sizeof(watch_data::buffer), FALSE, FILE_NOTIFY_CHANGE_LAST_WRITE, nullptr, &dir->second.overlapped, nullptr))) {
+        log_last_error();
+        return false;
+    }
+
+    return true;
+}
+
+void watcher::pull_changes() {
+    for (auto& dir : watcher::watched_dirs) {
+        auto& watch_data = dir.second;
+        if (!HasOverlappedIoCompleted(&watch_data.overlapped))
+            continue;
+
+        auto* dir_event = (PFILE_NOTIFY_INFORMATION)watch_data.buffer;
+        do {
+            if (dir_event->Action == FILE_ACTION_MODIFIED) {
+                auto w_filename = std::wstring{ dir_event->FileName, dir_event->FileNameLength / sizeof(wchar_t) };
+                auto filename = std::string{w_filename.begin(), w_filename.end()};
+                if (callbacks.contains(filename))
+                    callbacks[filename]();
+            }
+
+            dir_event += dir_event->NextEntryOffset;
+        } while(dir_event->NextEntryOffset != 0);
+
+        if (FAILED(ReadDirectoryChangesW(watch_data.dir_handle, watch_data.buffer, sizeof(watch_data::buffer), FALSE, FILE_NOTIFY_CHANGE_LAST_WRITE, nullptr, &watch_data.overlapped, nullptr))) {
+            log_last_error();
+        }
+    }
+}
+#endif
-- 
cgit v1.3