/**
 * \file
 * UWP proclib support for Mono.
 *
 * Copyright 2016 Microsoft
 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
*/
#include <config.h>
#include <glib.h>
#include "mono/utils/mono-compiler.h"

#if G_HAVE_API_SUPPORT(HAVE_UWP_WINAPI_SUPPORT)
#include <windows.h>
#include <mono/utils/mono-proclib.h>

gint32
mono_cpu_usage (MonoCpuUsageState *prev)
{
	gint32 cpu_usage = 0;
	gint64 cpu_total_time;
	gint64 cpu_busy_time;
	guint64 idle_time;
	guint64 kernel_time;
	guint64 user_time;
	guint64 current_time;
	guint64 creation_time;
	guint64 exit_time;

	GetSystemTimeAsFileTime ((FILETIME*)&current_time);
	if (!GetProcessTimes (GetCurrentProcess (), (FILETIME*)&creation_time, (FILETIME*)&exit_time, (FILETIME*)&kernel_time, (FILETIME*)&user_time)) {
		g_error ("GetProcessTimes() failed, error code is %d\n", GetLastError ());
		return -1;
	}

	// GetProcessTimes user_time is a sum of user time spend by all threads in the process.
	// This means that the total user time can be more than real time. In order to adjust for this
	// the total available time that we can be scheduled depends on the number of available cores.
	// For example, having 2 threads running 100% on a 2 core system for 100 ms will return a user_time of 200ms
	// but the current_time - creation_time will only be 100ms but by adjusting the available time based on number of
	// of availalbe cores will gives use the total load of the process.
	guint64 total_available_time = (current_time - creation_time) * mono_cpu_count ();

	idle_time = total_available_time - (kernel_time + user_time);

	cpu_total_time = (gint64)((idle_time - (prev ? prev->idle_time : 0)) + (user_time - (prev ? prev->user_time : 0)) + (kernel_time - (prev ? prev->kernel_time : 0)));
	cpu_busy_time = (gint64)(cpu_total_time - (idle_time - (prev ? prev->idle_time : 0)));

	if (prev) {
		prev->idle_time = idle_time;
		prev->kernel_time = kernel_time;
		prev->user_time = user_time;
	}

	if (cpu_total_time > 0 && cpu_busy_time > 0)
		cpu_usage = (gint32)(cpu_busy_time * 100 / cpu_total_time);

	return cpu_usage;
}

#else /* G_HAVE_API_SUPPORT(HAVE_UWP_WINAPI_SUPPORT) */

MONO_EMPTY_SOURCE_FILE (mono_proclib_windows_uwp);
#endif /* G_HAVE_API_SUPPORT(HAVE_UWP_WINAPI_SUPPORT) */