/*
PURPOSE:
    ( gettimeofday clock )
PROGRAMMERS:
    (((Robert W. Bailey) (LinCom) (April 1992) (--) (Realtime.))
     ((Robert W. Bailey) (LinCom) (7/22/92) (--) (--))
     ((Eddie J. Paddock) (MDSSC) (Oct 1992) (--) (Realtime.)))
     ((Alex Lin) (NASA) (April 2009) (--) (c++ port)))
*/

#include <iostream>
#include <sstream>

#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <math.h>
#include <signal.h>
#include <sys/types.h>
#include <unistd.h>

#include "trick/ITimer.hh"
#include "trick/exec_proto.h"
#include "trick/message_proto.h"

Trick::ITimer * the_itimer ;

Trick::ITimer::ITimer() : Timer() {

    the_itimer = this ;

#if ! ( __APPLE__ | __INTERIX )
    clock_getres(CLOCK_REALTIME, &res);
#else
    res.tv_nsec = 10000000;
    res.tv_sec = 0;
#endif

    return ;
}

Trick::ITimer::~ITimer() {
    return ;
}

void Trick::ITimer::semaphore_post() {
    sem_post(semaphore) ;
}

/**
@details
-# Set the SIGALRM signal handler to the ITimer signal handler routine.
-# Open a unique named semaphore
*/
int Trick::ITimer::init() {

    static struct sigaction sigact;
    std::stringstream sem_name_stream ;

    sigact.sa_handler = (void (*)(int)) it_handler;
    if (sigaction(SIGALRM, &sigact, NULL) < 0) {
        perror("sigaction() failed for SIGALRM");
    }

    // Initialize the itimer semaphore used by SIGALRM handler to
    // wake up the sim_exec_loop from its underrun sleepy time.

    sem_name_stream << "itimersepmaphore_" << getpid() ;
    sem_name = sem_name_stream.str() ;

    semaphore = sem_open(sem_name.c_str(), O_CREAT, S_IRWXU , 0);

    return (0) ;
}

/**
@details
-# If the timer is enabled
   -# If the frame time is valid
      -# Set the system itimer to expire one time at the desired frame period.
   -# Else termiate the simulation with the error message stating that the
      itimer frame period is invalid.
*/
int Trick::ITimer::start(double in_frame_time) {

    struct itimerval ivalue;
    int ret ;
    unsigned long long frame_sec ;
    unsigned int frame_usec ;

    if ( enabled ) {

        // clear out any built up signals.
        while ( (ret = sem_trywait(semaphore)) == 0 ) ;

        frame_sec = ( unsigned long long )in_frame_time ;
        frame_usec = (unsigned int)((in_frame_time - frame_sec) * 1000000) ;

        // check minimum time > 10ms
        if ( frame_sec == 0 && frame_usec < 10000 ) {
            active = false ;
            return(0) ;
        } else if ( frame_usec < 2000 && frame_sec > 0 ) {
            // adjust times with usec < 2000 , we'll be subtracting 2ms from the frame_usec
            frame_sec  -= 1 ;
            frame_usec += 1000000 ;
        }
        frame_usec -= 2000 ;

        if ( in_frame_time > 0 ) {
            /* Set timer interval in micro-seconds */
            ivalue.it_interval.tv_sec = 0;
            ivalue.it_interval.tv_usec = 0;
            ivalue.it_value.tv_sec = frame_sec;
            ivalue.it_value.tv_usec = (long) frame_usec;

            setitimer(ITIMER_REAL, &ivalue, NULL);
            active = true ;
        } else {
            char error_message[256];
            sprintf(error_message, "itimer frame_time is not set\n" ) ;
            exec_terminate_with_return(-1, __FILE__, __LINE__ , error_message);
        }
    }
    return (0) ;

}

/*
@details
-# Call the start function
*/
int Trick::ITimer::reset(double in_frame_time) {
    start(in_frame_time) ;
    return (0) ;
}

/**
@details
-# Set the system itimer with the expiriation time of 0.
*/
int Trick::ITimer::stop() {

    static struct itimerval ivalue, ovalue;

    /* Turn off itimer */
    ivalue.it_interval.tv_usec = 0;
    ivalue.it_interval.tv_sec = 0;

    ivalue.it_value.tv_usec = 0;
    ivalue.it_value.tv_sec = 0;

    (void) setitimer(ITIMER_REAL, &ivalue, &ovalue);

    active = false ;

    return (0) ;

}

/**
@details
-# If the timer is enabled
   -# Call sem_wait to decrement the semaphore.  sem_wait will sleep and wait
      for the semaphore to be posted from the signal handler.
   -# If sem_wait returns an error, write an error message
*/
int Trick::ITimer::pause() {

    int sem_ret;

    if ( enabled and active ) {

        do {
            sem_ret = sem_wait(semaphore);
            //TODO: I'd like to use sem_timedwait
            //sem_ret = sem_timedwait(semaphore, &timeout);
        } while ((sem_ret < 0 && errno == EINTR) && (errno != EDEADLK));

        if (sem_ret != 0) {
            // Prepend info to the error message string (given by errno)
            perror( "ITimer call to sem_wait()" );
        }

    }

    return (0) ;

}

/**
@details
-# Unlink the semaphore
*/
int Trick::ITimer::shutdown() {
    sem_unlink(sem_name.c_str()) ;
    return(0) ;
}

Trick::ITimer * get_itimer() {
    return (the_itimer) ;
}