#include <stdio.h>
#include <stdlib.h>
#include <sys/poll.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <sched.h>

static int set_realtime_priority( void )
{
    struct sched_param schp;

    memset( &schp, 0, sizeof( schp ) );
    schp.sched_priority = sched_get_priority_max( SCHED_FIFO );

    if( sched_setscheduler( 0, SCHED_FIFO, &schp ) != 0 ) {
        return -1;
    }

    return 0;
}

int main( int argc, char **argv )
{
    int outchan = 1;
    int mfd;

    /**
     * We try to set ourselves at realtime priority,
     * but we can still run if we don't get it.
     */
    if( set_realtime_priority() < 0 ) {
        fprintf( stderr, "miditool: Can't set realtime priority, "
                         "latency may suffer.\n"
                         "miditool: You can run as root to fix this.\n" );
    }

    mfd = open( "/dev/midi0", O_RDWR );
    if( mfd < 0 ) {
        fprintf( stderr, "miditool: Can't open device /dev/midi0.\n" );
        return 1;
    }

    if( argc > 1 ) {
        outchan = atoi( argv[ 1 ] ) - 1;
        if( outchan <  0 ) outchan = 0;
        if( outchan > 15 ) outchan = 15;
    }

    fprintf( stderr, "miditool: Converting all messages to MIDI channel %d\n",
             outchan + 1 );
    for(;;) {
        unsigned char buff;
        int command;

        /**
         * Only need one byte at a time.
         * (that's all my driver gives me anyway)
         */
        if( read( mfd, &buff, 1 ) < 0 ) break;

        /* Drop active sensing messages */
        if( buff == 0xfe ) continue;

        /* Grab command information. */
        command = buff >> 4;

        /* Only act on the few MIDI messages I care about */
        if( command >= 8 && command <= 11 ) {
            buff = (command << 4) | outchan;
        }

        /* Output our (potentially modified) byte. */
        write( mfd, &buff, 1 );
    }

    return 0;
}