/**
 * collectd - src/contextswitch.c
 * Copyright (C) 2009  Patrik Weiskircher
 * Copyright (C) 2010  Kimo Rosenbaum
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; only version 2 of the License is applicable.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * Authors:
 *   Patrik Weiskircher <weiskircher at inqnet.at>
 *   Kimo Rosenbaum <http://github.com/kimor79>
 **/

#include "collectd.h"

#include "plugin.h"
#include "utils/common/common.h"

#if defined(HAVE_SYSCTLBYNAME) && defined(HAVE_SYS_SYSCTL_H)
#include <sys/sysctl.h>
/* no global variables */
/* #endif HAVE_SYSCTLBYNAME */

#elif KERNEL_LINUX
/* no global variables */
/* #endif KERNEL_LINUX */

#elif HAVE_PERFSTAT
#include <libperfstat.h>
#include <sys/protosw.h>
/* #endif HAVE_PERFSTAT */

#else
#error "No applicable input method."
#endif

static void cs_submit(derive_t context_switches) {
  value_list_t vl = VALUE_LIST_INIT;

  vl.values = &(value_t){.derive = context_switches};
  vl.values_len = 1;
  sstrncpy(vl.plugin, "contextswitch", sizeof(vl.plugin));
  sstrncpy(vl.type, "contextswitch", sizeof(vl.type));

  plugin_dispatch_values(&vl);
}

static int cs_read(void) {
#if HAVE_SYSCTLBYNAME
  int value = 0;
  size_t value_len = sizeof(value);
  int status;

  status = sysctlbyname("vm.stats.sys.v_swtch", &value, &value_len,
                        /* new pointer = */ NULL, /* new length = */ 0);
  if (status != 0) {
    ERROR("contextswitch plugin: sysctlbyname "
          "(vm.stats.sys.v_swtch) failed");
    return -1;
  }

  cs_submit(value);
  /* #endif HAVE_SYSCTLBYNAME */

#elif KERNEL_LINUX
  FILE *fh;
  char buffer[64];
  int numfields;
  char *fields[3];
  derive_t result = 0;
  int status = -2;

  fh = fopen("/proc/stat", "r");
  if (fh == NULL) {
    ERROR("contextswitch plugin: unable to open /proc/stat: %s", STRERRNO);
    return -1;
  }

  while (fgets(buffer, sizeof(buffer), fh) != NULL) {
    char *endptr;

    numfields = strsplit(buffer, fields, STATIC_ARRAY_SIZE(fields));
    if (numfields != 2)
      continue;

    if (strcmp("ctxt", fields[0]) != 0)
      continue;

    errno = 0;
    endptr = NULL;
    result = (derive_t)strtoll(fields[1], &endptr, /* base = */ 10);
    if ((endptr == fields[1]) || (errno != 0)) {
      ERROR("contextswitch plugin: Cannot parse ctxt value: %s", fields[1]);
      status = -1;
      break;
    }

    cs_submit(result);
    status = 0;
    break;
  }
  fclose(fh);

  if (status == -2)
    ERROR("contextswitch plugin: Unable to find context switch value.");
    /* #endif  KERNEL_LINUX */

#elif HAVE_PERFSTAT
  int status = 0;
  perfstat_cpu_total_t perfcputotal;

  status =
      perfstat_cpu_total(NULL, &perfcputotal, sizeof(perfstat_cpu_total_t), 1);
  if (status < 0) {
    ERROR("contextswitch plugin: perfstat_cpu_total: %s", STRERRNO);
    return -1;
  }

  cs_submit(perfcputotal.pswitch);
  status = 0;
#endif /* defined(HAVE_PERFSTAT) */

  return status;
}

void module_register(void) {
  plugin_register_read("contextswitch", cs_read);
} /* void module_register */