#include "metrics.h"
#include "memory/kmemory.h"

#define AVG_COUNT 30

typedef struct metrics_state {
	u8 frame_avg_counter;
	f64 ms_times[AVG_COUNT];
	f64 ms_avg;
	i32 frames;
	f64 accumulated_frame_ms;
	f64 fps;
} metrics_state;

static metrics_state *state_ptr = 0;

void metrics_initialize (void) {
	if (!state_ptr) {
		state_ptr = kallocate(sizeof(metrics_state), MEMORY_TAG_ENGINE);
	}
}

void metrics_update (f64 frame_elapsed_time) {
	if (!state_ptr) {
		return;
	}

	// Calculate frame ms average
	f64 frame_ms = (frame_elapsed_time * 1000.0);
	state_ptr->ms_times[state_ptr->frame_avg_counter] = frame_ms;
	if (state_ptr->frame_avg_counter == AVG_COUNT - 1) {
		for (u8 i = 0; i < AVG_COUNT; ++i) {
			state_ptr->ms_avg += state_ptr->ms_times[i];
		}

		state_ptr->ms_avg /= AVG_COUNT;
	}
	state_ptr->frame_avg_counter++;
	state_ptr->frame_avg_counter %= AVG_COUNT;

	// Calculate frames per second.
	state_ptr->accumulated_frame_ms += frame_ms;
	if (state_ptr->accumulated_frame_ms > 1000) {
		state_ptr->fps = state_ptr->frames;
		state_ptr->accumulated_frame_ms -= 1000;
		state_ptr->frames = 0;
	}

	// Count all frames.
	state_ptr->frames++;
}

f64 metrics_fps (void) {
	if (!state_ptr) {
		return 0;
	}

	return state_ptr->fps;
}

f64 metrics_frame_time (void) {
	if (!state_ptr) {
		return 0;
	}

	return state_ptr->ms_avg;
}

void metrics_frame (f64 *out_fps, f64 *out_frame_ms) {
	if (!state_ptr) {
		*out_fps = 0;
		*out_frame_ms = 0;
		return;
	}

	*out_fps = state_ptr->fps;
	*out_frame_ms = state_ptr->ms_avg;
}