#include <config.h>

#include <sys/types.h>
#include <unistd.h>

#include <glib.h>
#include <glibtop.h>
#include <glibtop/proctime.h>
#include <glibtop/cpu.h>

#include <algorithm>

#include "smooth_refresh.h"
#include "procman.h"
#include "util.h"


const string SmoothRefresh::KEY("smooth-refresh");


unsigned SmoothRefresh::get_own_cpu_usage()
{
    glibtop_cpu cpu;
    glibtop_proc_time proctime;
    guint64 elapsed;
    unsigned usage = PCPU_LO;

    glibtop_get_cpu (&cpu);
    elapsed = cpu.total - this->last_total_time;

    if (elapsed) { // avoid division by 0
        glibtop_get_proc_time(&proctime, getpid());
        usage = (proctime.rtime - this->last_cpu_time) * 100 / elapsed;
        this->last_cpu_time = proctime.rtime;
    }

    usage = MIN (usage, 100);

    this->last_total_time = cpu.total;

    return usage;
}



void SmoothRefresh::status_changed(GSettings *settings,
                                   const gchar *key,
                                   gpointer user_data)
{
    static_cast<SmoothRefresh*>(user_data)->load_settings_value(key);
}

void SmoothRefresh::load_settings_value(const gchar *key)
{
    this->active = g_settings_get_boolean(settings, key);

    if (this->active)
        procman_debug("smooth_refresh is enabled");
}

SmoothRefresh::SmoothRefresh(GSettings *a_settings)
    :
    settings(a_settings)
{
    this->connection = g_signal_connect(G_OBJECT(settings),
                                        "changed::smooth-refresh",
                                        G_CALLBACK(status_changed),
                                        this);

  this->reset();
  this->load_settings_value(KEY.c_str());
}



void SmoothRefresh::reset()
{
    glibtop_cpu cpu;
    glibtop_proc_time proctime;

    glibtop_get_cpu(&cpu);
    glibtop_get_proc_time(&proctime, getpid());

    this->interval = ProcData::get_instance()->config.update_interval;
    this->last_pcpu = PCPU_LO;
    this->last_total_time = cpu.total;
    this->last_cpu_time = proctime.rtime;
}



SmoothRefresh::~SmoothRefresh()
{
    if (this->connection)
        g_signal_handler_disconnect(G_OBJECT(settings), this->connection);
}



bool
SmoothRefresh::get(guint &new_interval)
{
    const unsigned config_interval = ProcData::get_instance()->config.update_interval;

    g_assert(this->interval >= config_interval);

    if (not this->active)
        return false;


    const unsigned pcpu = this->get_own_cpu_usage();
    /*
      invariant: MAX_UPDATE_INTERVAL >= interval >= config_interval >= MIN_UPDATE_INTERVAL

      i see 3 cases:

      a) interval is too big (CPU usage < 10%)
      -> increase interval

      b) interval is too small (CPU usage > 10%) AND interval != config_interval
      >
      -> decrease interval

      c) interval is config_interval (start or interval is perfect)

    */

    if (pcpu > PCPU_HI && this->last_pcpu > PCPU_HI)
        new_interval = this->interval * 11 / 10;
    else if (this->interval != config_interval && pcpu < PCPU_LO && this->last_pcpu < PCPU_LO)
        new_interval = this->interval * 9 / 10;
    else
        new_interval = this->interval;

    new_interval = CLAMP(new_interval, config_interval, config_interval * 2);
    new_interval = CLAMP(new_interval, MIN_UPDATE_INTERVAL, MAX_UPDATE_INTERVAL);

    bool changed = this->interval != new_interval;

    if (changed)
        this->interval = new_interval;

    this->last_pcpu = pcpu;


    if (changed) {
        procman_debug("CPU usage is %3u%%, changed refresh_interval to %u (config %u)",
                      this->last_pcpu,
                      this->interval,
                      config_interval);
    }

    g_assert(this->interval == new_interval);
    g_assert(this->interval >= config_interval);

    return changed;
}

