/*
 * Copyright (c) 2018 Alastair Roy Poole <netstar@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#if defined(__OpenBSD__)
# define CPU_STATES      6
#else
# define CPU_STATES      5
#endif

static int
cpu_count(void)
{
   static int cores = 0;

   if (cores != 0)
     return cores;

#if defined(__linux__)
   char buf[4096];
   FILE *f;
   int line = 0;

   f = fopen("/proc/stat", "r");
   if (!f) return 0;

   while (fgets(buf, sizeof(buf), f))
     {
        if (line)
          {
             if (!strncmp(buf, "cpu", 3))
               cores++;
             else
               break;
          }
        line++;
     }

   fclose(f);
#elif defined(__MacOS__) || defined(__FreeBSD__) || defined(__DragonFly__) || defined(__OpenBSD__)
   size_t len;
   int mib[2] = { CTL_HW, HW_NCPU };

   len = sizeof(cores);
   if (sysctl(mib, 2, &cores, &len, NULL, 0) < 0)
     return 0;
#endif
   return cores;
}

int
system_cpu_count_get(void)
{
   return cpu_count();
}

int
system_cpu_online_count_get(void)
{
#if defined(__OpenBSD__)
   static int cores = 0;

   if (cores != 0) return cores;

   size_t len;
   int mib[2] = { CTL_HW, HW_NCPUONLINE };

   len = sizeof(cores);
   if (sysctl(mib, 2, &cores, &len, NULL, 0) < 0)
     return cpu_count();

   return cores;
#else
   return cpu_count();
#endif
}

static void
_cpu_state_get(cpu_core_t **cores, int ncpu)
{
   int diff_total, diff_idle;
   double ratio, percent;
   unsigned long total, idle, used;
   cpu_core_t *core;
#if defined(__FreeBSD__) || defined(__DragonFly__)
   size_t size;
   int i, j;

   if (!ncpu)
     return;
   size = sizeof(unsigned long) * (CPU_STATES * ncpu);
   unsigned long cpu_times[ncpu][CPU_STATES];

   if (sysctlbyname("kern.cp_times", cpu_times, &size, NULL, 0) < 0)
     return;

   for (i = 0; i < ncpu; i++) {
        core = cores[i];
        unsigned long *cpu = cpu_times[i];

        total = 0;
        for (j = 0; j < CPU_STATES; j++)
          total += cpu[j];

        idle = cpu[4];

        diff_total = total - core->total;
        diff_idle = idle - core->idle;
        if (diff_total == 0) diff_total = 1;

        ratio = diff_total / 100.0;
        used = diff_total - diff_idle;
        percent = used / ratio;

        if (percent > 100) percent = 100;
        else if (percent < 0)
          percent = 0;

        core->percent = percent;
        core->total = total;
        core->idle = idle;
     }
#elif defined(__OpenBSD__)
   static struct cpustats cpu_times[CPU_STATES];
   static int cpu_time_mib[] = { CTL_KERN, KERN_CPUSTATS, 0 };
   size_t size;
   int i, j;

   memset(&cpu_times, 0, CPU_STATES * sizeof(struct cpustats));
   if (!ncpu)
     return;

   for (i = 0; i < ncpu; i++) {
        core = cores[i];
        size = sizeof(struct cpustats);
        cpu_time_mib[2] = i;
        if (sysctl(cpu_time_mib, 3, &cpu_times[i], &size, NULL, 0) < 0)
          return;

        total = 0;
        for (j = 0; j < CPU_STATES; j++)
          total += cpu_times[i].cs_time[j];

        idle = cpu_times[i].cs_time[CP_IDLE];

        diff_total = total - core->total;
        if (diff_total == 0) diff_total = 1;

        diff_idle = idle - core->idle;
        ratio = diff_total / 100.0;
        used = diff_total - diff_idle;
        percent = used / ratio;

        if (percent > 100) percent = 100;
        else if (percent < 0)
          percent = 0;

        core->percent = percent;
        core->total = total;
        core->idle = idle;
     }
#elif defined(__linux__)
   char *buf, name[128];
   int i;

   buf = file_contents("/proc/stat");
   if (!buf) return;

   for (i = 0; i < ncpu; i++) {
        core = cores[i];
        snprintf(name, sizeof(name), "cpu%d", i);
        char *line = strstr(buf, name);
        if (line)
          {
             line = strchr(line, ' ') + 1;
             unsigned long cpu_times[4] = { 0 };

             if (4 != sscanf(line, "%lu %lu %lu %lu", &cpu_times[0],
                   &cpu_times[1], &cpu_times[2], &cpu_times[3]))
               return;

             total = cpu_times[0] + cpu_times[1] + cpu_times[2] + cpu_times[3];
             idle = cpu_times[3];
             diff_total = total - core->total;
             if (diff_total == 0) diff_total = 1;

             diff_idle = idle - core->idle;
             ratio = diff_total / 100.0;
             used = diff_total - diff_idle;
             percent = used / ratio;

             if (percent > 100) percent = 100;
             else if (percent < 0)
               percent = 0;

             core->percent = percent;
             core->total = total;
             core->idle = idle;
          }
     }
   free(buf);
#elif defined(__MacOS__)
   mach_msg_type_number_t count;
   processor_cpu_load_info_t load;
   mach_port_t mach_port;
   unsigned int cpu_count;
   int i;

   cpu_count = ncpu;

   count = HOST_CPU_LOAD_INFO_COUNT;
   mach_port = mach_host_self();
   if (host_processor_info(mach_port, PROCESSOR_CPU_LOAD_INFO, &cpu_count,
                (processor_info_array_t *)&load, &count) != KERN_SUCCESS)
     exit(-1);

   for (i = 0; i < ncpu; i++) {
        core = cores[i];

        total = load[i].cpu_ticks[CPU_STATE_USER] +
           load[i].cpu_ticks[CPU_STATE_SYSTEM] +
           load[i].cpu_ticks[CPU_STATE_IDLE] +
           load[i].cpu_ticks[CPU_STATE_NICE];
        idle = load[i].cpu_ticks[CPU_STATE_IDLE];

        diff_total = total - core->total;
        if (diff_total == 0) diff_total = 1;
        diff_idle = idle - core->idle;
        ratio = diff_total / 100.0;
        used = diff_total - diff_idle;
        percent = used / ratio;

        if (percent > 100) percent = 100;
        else if (percent < 0)
          percent = 0;

        core->percent = percent;
        core->total = total;
        core->idle = idle;
     }
#endif
}

cpu_core_t **
system_cpu_usage_delayed_get(int *ncpu, int usecs)
{
   cpu_core_t **cores;
   int i;

   *ncpu = cpu_count();

   cores = malloc((*ncpu) * sizeof(cpu_core_t *));

   for (i = 0; i < *ncpu; i++)
     cores[i] = calloc(1, sizeof(cpu_core_t));

   _cpu_state_get(cores, *ncpu);
   usleep(usecs);
   _cpu_state_get(cores, *ncpu);

   return cores;
}

cpu_core_t **
system_cpu_usage_get(int *ncpu)
{
   return system_cpu_usage_delayed_get(ncpu, 1000000);
}

int
system_cpu_frequency_get(void)
{
   int freq = -1;

#if defined(__FreeBSD__) || defined(__DragonFly__)
   size_t len = sizeof(freq);
   if (sysctlbyname("dev.cpu.0.freq", &freq, &len, NULL, 0) != -1)
     freq *= 1000;
#elif defined(__OpenBSD__)
   int mib[2] = { CTL_HW, HW_CPUSPEED };
   size_t len = sizeof(freq);
   if (sysctl(mib, sizeof(mib), &freq, &len, NULL, 0) != -1)
     freq *= 1000;
#elif defined(__linux__)

#else

#endif
   return freq;
}