#pragma once

/*
 * Lightweight per-stream statistics tracker.
 * Header-only; include wherever stream send/receive happens.
 *
 * Usage:
 *   Stream_Stats s;
 *   stream_stats_init(&s, stream_id);
 *
 *   // on each frame:
 *   stream_stats_record_frame(&s, byte_count);
 *
 *   // periodically (e.g. after every frame):
 *   if (stream_stats_tick(&s)) {
 *       printf("%.1f fps  %.2f Mbps\n", s.fps, s.mbps);
 *   }
 */

#include <stdint.h>
#include <string.h>
#include <time.h>

#define STREAM_STATS_INTERVAL 0.5   /* recompute rates every 0.5 s */

typedef struct {
	uint16_t        stream_id;

	/* Lifetime counters — never reset. */
	uint64_t        total_frames;
	uint64_t        total_bytes;

	/* Rolling window — reset each time rates are computed. */
	uint64_t        window_frames;
	uint64_t        window_bytes;
	struct timespec window_start;

	/* Last computed rates. */
	float           fps;
	float           mbps;
} Stream_Stats;

static inline void stream_stats_init(Stream_Stats *s, uint16_t stream_id)
{
	memset(s, 0, sizeof(*s));
	s->stream_id = stream_id;
	clock_gettime(CLOCK_MONOTONIC, &s->window_start);
}

/* Call once per received/sent frame. */
static inline void stream_stats_record_frame(Stream_Stats *s, uint32_t nbytes)
{
	s->total_frames++;
	s->total_bytes  += nbytes;
	s->window_frames++;
	s->window_bytes += nbytes;
}

/*
 * Recompute fps and mbps if enough time has elapsed.
 * Returns 1 when rates were updated, 0 otherwise.
 */
static inline int stream_stats_tick(Stream_Stats *s)
{
	struct timespec now;
	clock_gettime(CLOCK_MONOTONIC, &now);
	double elapsed = (double)(now.tv_sec  - s->window_start.tv_sec) +
	                 (double)(now.tv_nsec - s->window_start.tv_nsec) * 1e-9;
	if (elapsed < STREAM_STATS_INTERVAL) { return 0; }
	s->fps  = (float)((double)s->window_frames / elapsed);
	s->mbps = (float)((double)s->window_bytes * 8.0 / elapsed / 1e6);
	s->window_frames = 0;
	s->window_bytes  = 0;
	s->window_start  = now;
	return 1;
}