// SPDX-License-Identifier: GPL-3.0-or-later
//
// This file is part of CProof.
// See LICENSE for the full GPLv3 text and the special OpenSSL linking exception.

#include "bench_common.h"

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>

double
bench_now_ms(void)
{
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return (double)ts.tv_sec * 1000.0 + (double)ts.tv_nsec / 1.0e6;
}

char*
bench_fmt_bytes(uint64_t bytes)
{
    static const char* units[] = { "B", "KB", "MB", "GB", "TB" };
    int u = 0;
    double v = (double)bytes;
    while (v >= 1024.0 && u < 4) {
        v /= 1024.0;
        u++;
    }
    if (u == 0)
        return g_strdup_printf("%" G_GUINT64_FORMAT " %s", bytes, units[u]);
    return g_strdup_printf("%.2f %s", v, units[u]);
}

char*
bench_fmt_ms(double ms)
{
    if (ms < 1.0)
        return g_strdup_printf("%.0f us", ms * 1000.0);
    if (ms < 1000.0)
        return g_strdup_printf("%.1f ms", ms);
    if (ms < 60000.0)
        return g_strdup_printf("%.2f s", ms / 1000.0);
    return g_strdup_printf("%.1f min", ms / 60000.0);
}

bench_volume_t
bench_volume_from_env(void)
{
    const char* v = getenv("BENCH_VOLUME");
    if (!v || !v[0])
        return BENCH_VOLUME_MEDIUM;
    if (g_ascii_strcasecmp(v, "small") == 0)
        return BENCH_VOLUME_SMALL;
    if (g_ascii_strcasecmp(v, "medium") == 0)
        return BENCH_VOLUME_MEDIUM;
    if (g_ascii_strcasecmp(v, "max") == 0)
        return BENCH_VOLUME_MAX;
    fprintf(stderr, "WARN: unknown BENCH_VOLUME='%s', defaulting to medium\n", v);
    return BENCH_VOLUME_MEDIUM;
}

const char*
bench_volume_name(bench_volume_t v)
{
    switch (v) {
    case BENCH_VOLUME_SMALL:
        return "small";
    case BENCH_VOLUME_MEDIUM:
        return "medium";
    case BENCH_VOLUME_MAX:
        return "max";
    }
    return "?";
}

gboolean
bench_drop_page_cache(const char* path)
{
    int fd = open(path, O_RDONLY);
    if (fd < 0)
        return FALSE;
#ifdef POSIX_FADV_DONTNEED
    // Best-effort: kernel may ignore but typically honours.
    posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
#endif
    close(fd);
    return TRUE;
}

int64_t
bench_fs_free_bytes(const char* path)
{
    struct statvfs vfs;
    if (statvfs(path, &vfs) != 0)
        return -1;
    return (int64_t)vfs.f_bavail * (int64_t)vfs.f_frsize;
}

long
bench_peak_rss_kb(void)
{
    struct rusage ru;
    if (getrusage(RUSAGE_SELF, &ru) != 0)
        return -1;
    return ru.ru_maxrss; // already KB on Linux
}

double
bench_run_best_of(int runs, bench_fn_t fn, void* arg, long* peak_rss_kb)
{
    if (runs < 1)
        runs = 1;
    double best = 0.0;
    long max_rss = 0;
    for (int i = 0; i < runs; i++) {
        double t0 = bench_now_ms();
        fn(arg);
        double dt = bench_now_ms() - t0;
        if (i == 0 || dt < best)
            best = dt;
        long rss = bench_peak_rss_kb();
        if (rss > max_rss)
            max_rss = rss;
    }
    if (peak_rss_kb)
        *peak_rss_kb = max_rss;
    return best;
}