// Shared helper for the per-backend present-thread overhead guards.
//
// The capture path (Present / SwapBuffers hook, or the Vulkan read-back) runs on the game's present
// thread. If it stalls there, it caps the game's frame rate -- the Vulkan layer did exactly this,
// dropping a 144 FPS game to ~3 FPS by spending ~370 ms per present reading write-combined memory.
// Each GPU backend's in-process hook test measures the wall time its present spends with the hook
// live vs. removed and asserts the added cost stays under one display frame, so a future regression
// that puts a synchronous read-back / stall back on the present thread fails the test.
#pragma once

#include <windows.h>

namespace cooptest {
inline double now_ms()
{
	LARGE_INTEGER f, c;
	QueryPerformanceFrequency(&f);
	QueryPerformanceCounter(&c);
	return 1000.0 * static_cast<double>(c.QuadPart) / static_cast<double>(f.QuadPart);
}

// Average wall time of `present()` over n frames, calling `render()` (untimed) before each so a
// fresh frame is produced. Returns milliseconds per present.
template <class RenderFn, class PresentFn>
double avg_present_ms(int n, RenderFn render, PresentFn present)
{
	render();
	present(); // warm (first present/resource setup)
	double total = 0;
	for (int i = 0; i < n; ++i) {
		render();
		const double a = now_ms();
		present();
		total += now_ms() - a;
	}
	return n > 0 ? total / n : 0.0;
}

// One 60 Hz display frame. The capture's added present-thread cost must stay well under this or it
// throttles the game; the Vulkan bug added ~370 ms (22x over budget). Generous on purpose -- the
// guard targets the catastrophic-stall class, not micro-overhead, so it never flakes on jitter.
inline constexpr double kPresentOverheadBudgetMs = 16.7;
} // namespace cooptest