#include "core/types.h"
#include "core/defs.h"
#include "core/param.h"
#include "core/date.h"
#include "core/spinlock.h"
#include "core/proc.h"
#include "arch/x86.h"
#include "core/syscall.h"
#include "uapi/posix.h"
#include "core/uaccess.h"
#include "uapi/errno.h"

// Timer values in ticks, rounding a nonzero time up: POSIX says a timer set
// to 1 us goes off, not that it is disarmed.
static uint
tv_ticks(struct timeval *tv)
{
    if (tv->tv_sec < 0 || tv->tv_usec < 0)
        return 0;
    uint64 t = (uint64)tv->tv_sec * HZ +
               ((uint64)tv->tv_usec + USEC_PER_TICK - 1) / USEC_PER_TICK;
    return t > 0x7fffffff ? 0x7fffffff : (uint)t;
}

static void
ticks_tv(uint t, struct timeval *tv)
{
    tv->tv_sec  = t / HZ;
    tv->tv_usec = (t % HZ) * USEC_PER_TICK;
}

// The seconds left on the previous alarm, rounded up, as POSIX asks.
addr_t
sys_alarm(void)
{
    int seconds;
    if (argint(0, &seconds) < 0)
        return -1;
    struct proc *p = myproc();
    uint left = alarm_left(p);
    alarm_arm(p, seconds > 0 ? (uint)seconds * HZ : 0, 0);
    return (left + HZ - 1) / HZ;
}

addr_t
sys_gettimeofday(void)
{
    struct timeval *tv;
    if (argptr(0, (char**)&tv, sizeof(*tv)) < 0)
        return -1;
    if (tv) {
        // Real time, from the hardware clock read at boot plus uptime -- not
        // uptime alone, which is what this used to return and why every machine
        // thought it was 1970. See kernel/core/time.c.
        uint64 sec, usec;
        wallclock(&sec, &usec);
        tv->tv_sec  = (long)sec;
        tv->tv_usec = (long)usec;
    }
    return 0;
}

// Sleep for a timespec, in ticks, rounded up.
//
// Only tv_sec was ever read: `sleep 0.5` returned at once and every
// sub-second sleep -- cmatrix's frame delay, a game loop's -- was no sleep at
// all. And a signal could not end one: Ctrl-Z on `sleep 100` did nothing.
static addr_t
sleep_ticks(uint64 want, addr_t remaddr)
{
    struct proc *p = myproc();
    acquire(&tickslock);
    uint t0 = ticks;
    while ((uint64)(uint)(ticks - t0) < want) {
        if (p->killed || sig_attention(p)) {
            release(&tickslock);
            int e = p->killed ? -EINTR : sig_blocking_check();
            if (e) {
                if (remaddr) {
                    uint64 left = want - (uint)(ticks - t0);
                    struct timespec r = { (long)(left / HZ),
                                          (long)((left % HZ) * (1000000000 / HZ)) };
                    copy_to_user(remaddr, &r, sizeof(r));
                }
                return e;
            }
            acquire(&tickslock);
            continue;
        }
        sleep(&ticks, &tickslock);
    }
    release(&tickslock);
    return 0;
}

static int
timespec_ticks(const struct timespec *ts, uint64 *out)
{
    if (ts->tv_sec < 0 || ts->tv_nsec < 0 || ts->tv_nsec >= 1000000000)
        return -EINVAL;
    uint64 sec = (uint64)ts->tv_sec;
    if (sec > 0xFFFFFFFFULL / HZ)
        sec = 0xFFFFFFFFULL / HZ;          // a few years: forever enough
    *out = sec * HZ + ((uint64)ts->tv_nsec * HZ + 999999999) / 1000000000;
    return 0;
}

addr_t
sys_nanosleep(void)
{
    addr_t tsaddr, remaddr;
    struct timespec ts;
    uint64 want;
    argaddr(0, &tsaddr);
    argaddr(1, &remaddr);
    if (copy_from_user(&ts, tsaddr, sizeof(ts)) < 0)
        return -EFAULT;
    int e = timespec_ticks(&ts, &want);
    if (e)
        return e;
    return sleep_ticks(want, remaddr);
}

addr_t
sys_clock_gettime(void)
{
    int clkid;
    struct timespec *tp;
    argint(0, &clkid);
    if (argptr(1, (char**)&tp, sizeof(*tp)) < 0)
        return -1;
    // CLOCK_MONOTONIC (1) counts from boot; everything else is treated as a
    // realtime clock and counts from the epoch. Returning boot-relative values
    // for CLOCK_REALTIME is what made timestamps land in 1970.
    uint64 sec, usec;
    wallclock(&sec, &usec);
    if (clkid == 1)
        sec -= boot_epoch;
    tp->tv_sec  = (long)sec;
    tp->tv_nsec = (long)(usec * 1000);
    return 0;
}

// ITIMER_REAL only. ITIMER_VIRTUAL and ITIMER_PROF count CPU time, which
// nothing here measures per tick, and are refused rather than accepted and
// never fired -- which is what all three used to be.
static int
itimer_get(struct proc *p, struct itimerval *iv)
{
    ticks_tv(p->alarm_every, &iv->it_interval);
    ticks_tv(alarm_left(p), &iv->it_value);
    return 0;
}

addr_t
sys_getitimer(void)
{
    int which;
    addr_t curp;
    argint(0, &which); argaddr(1, &curp);
    if (which != 0)
        return -EINVAL;
    struct itimerval iv;
    itimer_get(myproc(), &iv);
    if (copy_to_user(curp, &iv, sizeof(iv)) != 0)
        return -EFAULT;
    return 0;
}

addr_t
sys_setitimer(void)
{
    int which;
    addr_t newp, oldp;
    argint(0, &which); argaddr(1, &newp); argaddr(2, &oldp);
    if (which != 0)
        return -EINVAL;
    struct proc *p = myproc();
    struct itimerval iv;
    if (oldp) {
        itimer_get(p, &iv);
        if (copy_to_user(oldp, &iv, sizeof(iv)) != 0)
            return -EFAULT;
    }
    if (newp == 0)
        return 0;
    if (copy_from_user(&iv, newp, sizeof(iv)) != 0)
        return -EFAULT;
    alarm_arm(p, tv_ticks(&iv.it_value), tv_ticks(&iv.it_interval));
    return 0;
}

addr_t
sys_time(void)
{
    addr_t tloc;
    argaddr(0, &tloc);
    uint64 sec;
    wallclock(&sec, 0);
    long t = (long)sec;
    if (tloc)
        put_user(t, tloc);
    return (addr_t)t;
}

addr_t
sys_clock_getres(void)
{
    struct timespec *tp;
    if (argptr(1, (char**)&tp, sizeof(*tp)) < 0) return 0;
    if (tp) { tp->tv_sec = 0; tp->tv_nsec = 10000000L; } // 10ms resolution
    return 0;
}

addr_t
sys_clock_nanosleep(void)
{
    // clock_nanosleep(clockid, flags, rqtp, rmtp). TIMER_ABSTIME (1) makes
    // rqtp a time on that clock rather than an interval.
    int clkid, flags;
    addr_t tsaddr, remaddr;
    struct timespec ts;
    uint64 want;
    argint(0, &clkid);
    argint(1, &flags);
    argaddr(2, &tsaddr);
    argaddr(3, &remaddr);
    if (copy_from_user(&ts, tsaddr, sizeof(ts)) < 0)
        return -EFAULT;
    if (flags & 1) {
        uint64 sec, usec;
        wallclock(&sec, &usec);
        if (clkid == 1)
            sec -= boot_epoch;
        long dsec = ts.tv_sec - (long)sec;
        long dns  = ts.tv_nsec - (long)(usec * 1000);
        if (dns < 0) { dns += 1000000000; dsec--; }
        if (dsec < 0)
            return 0;                       // already past
        ts.tv_sec = dsec;
        ts.tv_nsec = dns;
        remaddr = 0;                        // never written for an absolute sleep
    }
    int e = timespec_ticks(&ts, &want);
    if (e)
        return e;
    return sleep_ticks(want, remaddr);
}