#include <u.h>
#include <libc.h>
#include <bio.h>
#include <thread.h>
#include "collectd.h"

#define	MAXCPU	32

Biobuf *
readsysstat(Biobuf *bp, char *file, Sysstat *sysstat)
{
	char *p, *f[10];
	int nf;

	if(bp == nil){
		bp = Bopen(file, OREAD);
		if(bp == nil)
			sysfatal("couldn't open %s: %r", file);
	}
	p = Brdline(bp, '\n');
	if(p == nil){
		Bterm(bp);
		return nil;
	}
	p[Blinelen(bp)-1] = '\0';

	nf = tokenize(p, f, nelem(f));
	if(nf < nelem(f))
		sysfatal("unexpected sysstat output");

	sysstat->id = strtoul(f[0], nil, 0);
	sysstat->cs = strtoul(f[1], nil, 0);
	sysstat->intr = strtoul(f[2], nil, 0);
	sysstat->syscall = strtoul(f[3], nil, 0);
	sysstat->pfault = strtoul(f[4], nil, 0);
	sysstat->tlbfault = strtoul(f[5], nil, 0);
	sysstat->tlbpurge = strtoul(f[6], nil, 0);
	sysstat->load = strtoul(f[7], nil, 0);
	sysstat->idlepct = strtoul(f[8], nil, 0);
	sysstat->intrpct = strtoul(f[9], nil, 0);

	return bp;
}

static void
submit(Channel *c, ulong id, char *type, uvlong value)
{
	Packet *pp;

	pp = palloc();
	pp->host = estrdup(hostname);
	pp->interval = interval;
	pp->time = time(nil);
	pp->plugin = estrdup("cpu");
	pp->pinst = smprint("%uld", id);
#ifdef USE_JIFFIES
	pp->type = estrdup("cpu");
#else
	pp->type = estrdup("percent");
#endif
	pp->tinst = estrdup(type);
	addcounter(pp, value);

	if(nbsendp(c, pp) < 1)
		pfree(pp);
}

static uvlong counter[MAXCPU][3];	/* idle, interrupt, user */

void
cpuproc(void *arg)
{
	Channel *c;
	Biobuf *bp;
	Sysstat sysstat;
	ulong userpct;

	c = arg;
	bp = nil;
	for(;;){
		snooze();

		while(bp = readsysstat(bp, "/dev/sysstat", &sysstat)){
			/*
			 * Unfortunately, syscall usage is not exposed
			 * via sysstat, so we are unable to distinguish
			 * between system and user.  Rather than report
			 * nothing, we submit the remainder as user.
			 */
			userpct = 100 - sysstat.idlepct - sysstat.intrpct;

#ifdef USE_JIFFIES
			/*
			 * Older versions of collectd expect that cpu
			 * usage is reported in terms of "jiffies".
			 * We simulate this nonsense by incrementing
			 * each counter with usage multiplied by the
			 * interval to match expectations.
			 */
			counter[sysstat.id][0] += sysstat.idlepct*interval;
			submit(c, sysstat.id, "idle", counter[sysstat.id][0]);

			counter[sysstat.id][1] += sysstat.intrpct*interval;
			submit(c, sysstat.id, "interrupt", counter[sysstat.id][1]);

			counter[sysstat.id][2] += userpct*interval;
			submit(c, sysstat.id, "user", counter[sysstat.id][2]);
#else
			submit(c, sysstat.id, "idle", sysstat.idlepct);
			submit(c, sysstat.id, "interrupt", sysstat.intrpct);
			submit(c, sysstat.id, "user", userpct);
#endif
		}
	}
}