#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;
}

addr_t
sys_nanosleep(void)
{
    addr_t tsaddr, raw;
    if (argaddr(0, &tsaddr) < 0 || fetchaddr(tsaddr, &raw) < 0)
        return -1;
    int64 sec = (int64)raw;
    if (sec > 0) {
        acquire(&tickslock);
        uint t0 = ticks;
        while (ticks - t0 < (uint)(sec * HZ)) {
            if (myproc()->killed) { release(&tickslock); return -EINTR; }
            sleep(&ticks, &tickslock);
        }
        release(&tickslock);
    }
    return 0;
}

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)
{
    // Treat the same as nanosleep: arg2 is the timespec, arg1 is flags.
    // Linux: clock_nanosleep(clockid, flags, rqtp, rmtp)
    addr_t tsaddr, raw;
    if (argaddr(2, &tsaddr) < 0 || fetchaddr(tsaddr, &raw) < 0)
        return -1;
    int64 sec = (int64)raw;
    if (sec > 0) {
        acquire(&tickslock);
        uint t0 = ticks;
        while (ticks - t0 < (uint)(sec * HZ)) {
            if (myproc()->killed) { release(&tickslock); return -EINTR; }
            sleep(&ticks, &tickslock);
        }
        release(&tickslock);
    }
    return 0;
}