#include <stdio.h>
#include <unistd.h>
#include <error.h>

#define TRIMz(x)  ((tz = (SIC_t)(x)) < 0 ? 0 : tz)
typedef unsigned long long TIC_t;
typedef          long long SIC_t;
static int Cpu_tot;

typedef struct CPU_t {
	TIC_t u, n, s, i, w, x, y, z; // as represented in /proc/stat
	TIC_t u_sav, s_sav, n_sav, i_sav, w_sav, x_sav, y_sav, z_sav; // in the order of our display
	unsigned id;  // the CPU ID number
} CPU_t;

static CPU_t *cpus_refresh (CPU_t *cpus)
{
	static FILE *fp = NULL;
	int i;
	int num;
	// enough for a /proc/stat CPU line (not the intr line)
	char buf[SMLBUFSIZ];

	/* by opening this file once, we'll avoid the hit on minor page faults
	(sorry Linux, but you'll have to close it for us) */
	if (!fp) {
		if (!(fp = fopen("/proc/stat", "r")))
			std_err(fmtmk("Failed /proc/stat open: %s", strerror(errno)));
		/* note: we allocate one more CPU_t than Cpu_tot so that the last slot
		can hold tics representing the /proc/stat cpu summary (the first
		line read) -- that slot supports our View_CPUSUM toggle */
		cpus = alloc_c((1 + Cpu_tot) * sizeof(CPU_t));
	}
	rewind(fp);
	fflush(fp);

	// first value the last slot with the cpu summary line
	if (!fgets(buf, sizeof(buf), fp)) std_err("failed /proc/stat read");
	cpus[Cpu_tot].x = 0;  // FIXME: can't tell by kernel version number
	cpus[Cpu_tot].y = 0;  // FIXME: can't tell by kernel version number
	cpus[Cpu_tot].z = 0;  // FIXME: can't tell by kernel version number
	num = sscanf(buf, "cpu %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu",
		&cpus[Cpu_tot].u,
		&cpus[Cpu_tot].n,
		&cpus[Cpu_tot].s,
		&cpus[Cpu_tot].i,
		&cpus[Cpu_tot].w,
		&cpus[Cpu_tot].x,
		&cpus[Cpu_tot].y,
		&cpus[Cpu_tot].z
		);
	if (num < 4)
		std_err("failed /proc/stat read");

	// and just in case we're 2.2.xx compiled without SMP support...
	if (Cpu_tot == 1) {
		cpus[1].id = 0;
		memcpy(cpus, &cpus[1], sizeof(CPU_t));
	}

	// now value each separate cpu's tics
	for (i = 0; 1 < Cpu_tot && i < Cpu_tot; i++) {
		if (!fgets(buf, sizeof(buf), fp)) std_err("failed /proc/stat read");
		cpus[i].x = 0;  // FIXME: can't tell by kernel version number
		cpus[i].y = 0;  // FIXME: can't tell by kernel version number
		cpus[i].z = 0;  // FIXME: can't tell by kernel version number
		num = sscanf(buf, "cpu%u %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu",
			&cpus[i].id,
			&cpus[i].u, &cpus[i].n, &cpus[i].s, &cpus[i].i, &cpus[i].w, &cpus[i].x, &cpus[i].y, &cpus[i].z
			);
		if (num < 4)
			std_err("failed /proc/stat read");
	}
	return cpus;
}

static void summaryhlp (CPU_t *cpu, const char *pfx)
{
	// we'll trim to zero if we get negative time ticks,
	// which has happened with some SMP kernels (pre-2.4?)
#define TRIMz(x)  ((tz = (SIC_t)(x)) < 0 ? 0 : tz)
	SIC_t u_frme, s_frme, n_frme, i_frme, w_frme, x_frme, y_frme, z_frme, tot_frme, tz;
	float scale;

	u_frme = cpu->u - cpu->u_sav;
	s_frme = cpu->s - cpu->s_sav;
	n_frme = cpu->n - cpu->n_sav;
	i_frme = TRIMz(cpu->i - cpu->i_sav);
	w_frme = cpu->w - cpu->w_sav;
	x_frme = cpu->x - cpu->x_sav;
	y_frme = cpu->y - cpu->y_sav;
	z_frme = cpu->z - cpu->z_sav;
	tot_frme = u_frme + s_frme + n_frme + i_frme + w_frme + x_frme + y_frme + z_frme;
	if (tot_frme < 1) tot_frme = 1;
	scale = 100.0 / (float)tot_frme;

	// display some kinda' cpu state percentages
	// (who or what is explained by the passed prefix)
	show_special(
		0,
		fmtmk(
		States_fmts,
		pfx,
		(float)u_frme * scale,
		(float)s_frme * scale,
		(float)n_frme * scale,
		(float)i_frme * scale,
		(float)w_frme * scale,
		(float)x_frme * scale,
		(float)y_frme * scale,
		(float)z_frme * scale
		)
		);
	Msg_row += 1;

	// remember for next time around
	cpu->u_sav = cpu->u;
	cpu->s_sav = cpu->s;
	cpu->n_sav = cpu->n;
	cpu->i_sav = cpu->i;
	cpu->w_sav = cpu->w;
	cpu->x_sav = cpu->x;
	cpu->y_sav = cpu->y;
	cpu->z_sav = cpu->z;

#undef TRIMz
}

static const char *fmtmk (const char *fmts, ...) __attribute__((format(printf,1,2)));
static const char *fmtmk (const char *fmts, ...)
{
	static char buf[BIGBUFSIZ];          // with help stuff, our buffer
	va_list va;                          // requirements exceed 1k

	va_start(va, fmts);
	vsnprintf(buf, sizeof(buf), fmts, va);
	va_end(va);
	return (const char *)buf;
}