#include <sys/types.h>

#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "lxcstats.h"
#include "_lxcstats.h"

static inline uint32_t
nsecs_to_user_hz(uint64_t counter)
{
    /*
     * XXX I don't know if it will work for custom values of HZ in the kernel.
     */
    return (counter / (NSEC_PER_SEC / sysconf(_SC_CLK_TCK)));
}

static int
read_stat(struct lxcst *c)
{
    char    path[PATH_MAX];
    char    *values;
    char    *fields[4];
    int     ret;

    _lxcst_join_path(path, sizeof(path), c->cgroup_dir, "cpuacct.stat");
    ret = _lxcst_read_file(path, &values);
    if (ret > 0) {
        values[ret - 1] = '\0'; /* Replace the last \n by a \0 */
        if (_lxcst_strsplit(values, fields, ARRAY_SIZE(fields)) == ARRAY_SIZE(fields)) {
            errno = 0;
            c->cpuacct.user = strtoul(fields[1], NULL, 10);
            c->cpuacct.system = strtoul(fields[3], NULL, 10);
            if (!errno) {
                free(values);
                return (0);
            }
        }
        free(values);
    }

    c->cpuacct.user = 0;
    c->cpuacct.system = 0;
    return (1);
}

static int
read_usage_percpu(struct lxcst *c)
{
    char    path[PATH_MAX];
    char    *values;
    int     ret;
    char    *p;
    int     ncpus;
    int     i;

    _lxcst_join_path(path, sizeof(path), c->cgroup_dir, "cpuacct.usage_percpu");
    ret = _lxcst_read_file(path, &values);
    if (ret > 0) {
        values[ret - 1] = '\0';

        p = values;
        for (ncpus = 0; ; ncpus++) {
            p = strchr(p + 1, ' ');
            if (!p)
                break ;
        }

        if (ncpus)
            c->cpuacct.percpu = calloc(ncpus + 1, sizeof(*c->cpuacct.percpu));

        if (c->cpuacct.percpu) {
            errno = 0;
            p = values;
            for (i = 0; i != ncpus && *p; ++i) {
                c->cpuacct.percpu[i] = nsecs_to_user_hz(strtoul(p, &p, 10));
                if (errno)
                    goto err;
                p += strcspn(p, "0123456789");
            }

            free(values);
            return (0);
        }

err:
        free(c->cpuacct.percpu);
        c->cpuacct.percpu = NULL;
        free(values);
    }

    return (1);
}

int
_lxcst_probe_cpuacct(struct lxcst *c)
{
    assert(c);

    return (read_stat(c)
            || read_usage_percpu(c));
}