/*
    
    07.08.1999 by Thomas Koch <no-return@gmx.net>
    Einfache (externe) lautstaerkereglung...
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
    
    1.9.1999: code ueberarbeitet
    8.9.1999: nochmals komplett ueberarbeitet. ein und ausfaden moeglich.
    
*/

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>

#include <sys/ioctl.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/soundcard.h>


#define MAXVOL 25700          // maximale lautstaerke
#define MINVOL 0	      // minimale lautstaerke
#define MIXER "/dev/mixer"    // mixerdevice
#define SERDEV "/dev/ttyS0"   // serialdevice

// globale variablen
int mixerfd, serialfd;



// wert lesen
int readvalue() {

    int flags;
    
    // daten von device holen	
    ioctl(mixerfd, MIXER_READ(0), &flags);

    return(flags);

}


// wert schreiben
int writevalue(int flags) {

    // wert schreiben
    ioctl(mixerfd, MIXER_WRITE(0), &flags);
    
    return(0);

}


// laut/leise
int volume(int volume) {
    
    int status;
    
    status = readvalue();
    
    if(volume) {
	if(status < MAXVOL) {
    	    status = readvalue();
    	    status += 514;
	    writevalue(status);
	}
    } else {
	if(status > MINVOL) {
    	    status = readvalue();
    	    status -= 514;
	    writevalue(status);
	}
    }

    return(0);
}


int main(int argc, char *argv[]) {
    
    int flags, i, status, oldstatus;
	
    // mixerdevice oeffnen   (/dev/mixer z.b.) 
    if((mixerfd = open(MIXER, O_RDWR | O_NDELAY)) < 0) {
	printf("mixer konnte nicht geoeffnet werden\n");
    	exit(1);
    } 
    
    // serialdevice oeffnen    
    if((serialfd = open(SERDEV, O_RDWR | O_NDELAY)) < 0) {
	printf("serial device konnte nicht geoeffnet werden\n");
    	exit(1);
    } 


    // into loop...        
    while(1) {

	ioctl(serialfd, TIOCMGET, &flags);
    
	if(flags & TIOCM_CTS) { 	// leiser
	    volume(0);
	}
	if(flags & TIOCM_DSR) { 	// lauter
	    volume(1);	
	}
	if(flags & TIOCM_CAR) { 	// ausfaden
	    oldstatus = readvalue();    // derzeitige lautstaerke besorgen (zum wiederherstellen	
	    for(i = 0; i < 50; i++) {   // beim wiedereinfaden)
		volume(0);
		usleep(10000);
	    }
	}
	if(flags & TIOCM_RNG) {		// einfaden
	    for(i = 0; i < 50; i++) {
		status = readvalue();
		if(status < MAXVOL) {
    		    status = readvalue();
		    if(status < oldstatus) { // alte lautstaerke wieder herstellen
	        	status += 514;
			writevalue(status);
			usleep(10000);
		    }
		}
    	    }
	}
	
	usleep(100000);
	
    } // end while(1)



    // devices schliesen
    close(mixerfd);
    close(serialfd);
    
    return(0); // schrecklich, alles muss immer irgendwas zurueckgeben
    	
}