Move layout reload policy into platform api

src/platform_api/asset_file_load_policy.cpp

@@ -0,0 +1,33 @@
+#include "platform_api/asset_file_load_policy.h"
+
+#include <string>
+#include <sys/stat.h>
+
+namespace pp::platform {
+
+AssetFileLoadDecision plan_asset_file_load(
+    std::string_view absolute_path,
+    bool already_loaded,
+    std::int64_t previous_last_write_time)
+{
+#if defined(_WIN32) || defined(__OSX__)
+    struct stat file_info {};
+    const std::string path(absolute_path);
+    if (stat(path.c_str(), &file_info) != 0)
+        return { false, false, previous_last_write_time };
+
+    const auto current_last_write_time = static_cast<std::int64_t>(file_info.st_mtime);
+    if (current_last_write_time <= previous_last_write_time)
+        return { false, false, previous_last_write_time };
+
+    return { true, true, current_last_write_time };
+#else
+    if (already_loaded)
+        return { false, true, previous_last_write_time };
+
+    (void)absolute_path;
+    return { true, true, previous_last_write_time };
+#endif
+}
+
+}