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

Biobuf *
readswap(Biobuf *bp, char *file, Swap *swap)
{
	char *p, *q;

	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';

	if(q = strchr(p, ' ')){
		*q++ = '\0';
		swap->name = q;
	}else
		sysfatal("unexpected swap output");

	if(q = strchr(p, '/')){
		*q++ = '\0';
		swap->m = strtoul(q, nil, 0);
	}
	swap->n = strtoul(p, nil, 0);
	return bp;
}

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

	pp = palloc();
	pp->host = estrdup(hostname);
	pp->interval = interval;
	pp->time = time(nil);
	pp->plugin = estrdup("memory");
	pp->type = estrdup("memory");
	pp->tinst = estrdup(type);
	addgauge(pp, value);

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

void
memoryproc(void *arg)
{
	Channel *c;
	Biobuf *bp;
	Swap swap;
	ulong pagesize;
	double total, free;

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

		pagesize = 0;
		total = free = 0;
		while(bp = readswap(bp, "/dev/swap", &swap)){
			if(strcmp(swap.name, "memory") == 0)
				total = (double)swap.n;

			else if(strcmp(swap.name, "pagesize") == 0)
				pagesize = swap.n;

			/*
			 * To avoid confusion, we only report free
			 * user pages; all other pages (including free
			 * kernel pages) are considered used.
			 */
			else if(strcmp(swap.name, "user") == 0)
				free = (double)(swap.m-swap.n) * pagesize;
		}
		submit(c, "used", total-free);
		submit(c, "free", free);
	}
}