/* rotate.c : map a->b, b->c, .. z->a
 *   purpose: useful for showing tty modes
 */

#include   <stdio.h>
#include   <ctype.h>

int main()
{
    int c;
    while ( ( c=getchar() ) != EOF ){
        if ( c == 'z' )  
            c = 'a';
        else if (islower(c))
            c++;
        putchar(c);
    }
}

/* play_again4.c
 *  purpose: ask if user wants another transaction
 *   method: set tty into chr-by-chr, no-echo mode
 *       set tty into no-delay mode
 *       read char, return result
 *       resets terminal modes on SIGINT, ignores SIGQUIT
 *  returns: 0=>yes, 1=>no, 2=>timeout
 *   better: reset terminal mode on Interrupt
 */
#include    <stdio.h>
#include    <termios.h>
#include    <fcntl.h>
#include    <string.h>
#include    <signal.h>
#include        <stdlib.h>
#include        <unistd.h>
#include        <ctype.h>

#define ASK     "Do you want another transaction"
#define TRIES      3                                       /* max tries */
#define SLEEPTIME  2                                       /* time per try */
#define BEEP       putchar('\a')                           /* alert user */

/*
 *  skip over non-legal chars and return y,Y,n,N or EOF
 */
char get_ok_char()
{
        int c;
        while( ( c = getchar() ) != EOF && strchr("yYnN",c) == NULL )
                ;
        return c;
}


int get_response( char *question , int maxtries)
/*
 * purpose: ask a question and wait for a y/n answer or timeout
 *  method: use getchar and complain about non-y/n input
 * returns: 0=>yes, 1=>no
 */
{
    int input;

    printf("%s (y/n)?", question);          /* ask      */
    fflush(stdout);                 /* force output */
    while ( 1 ){
        sleep(SLEEPTIME);           /* wait a bit   */
        input = tolower(get_ok_char());         /* get next chr */
        if ( input == 'y' )
            return 0;
        if ( input == 'n' )
            return 1;
        if ( maxtries-- == 0 )          /* outatime?    */
            return 2;           /* sayso    */
        BEEP;
    }
}

void set_cr_noecho_mode()
/* 
 * purpose: put file descriptor 0 into chr-by-chr mode and noecho mode
 *  method: use bits in termios
 */
{
    struct  termios ttystate;

    tcgetattr( 0, &ttystate);       /* read curr. setting   */
    ttystate.c_lflag        &= ~ICANON; /* no buffering     */
    ttystate.c_lflag        &= ~ECHO;   /* no echo either   */
    ttystate.c_cc[VMIN]     =  1;       /* get 1 char at a time */
    tcsetattr( 0 , TCSANOW, &ttystate); /* install settings */
}

void set_nodelay_mode()
/*
 * purpose: put file descriptor 0 into no-delay mode
 *  method: use fcntl to set bits
 *   notes: tcsetattr() will do something similar, but it is complicated
 */
{
    int termflags;

    termflags = fcntl(0, F_GETFL);      /* read curr. settings  */
    termflags |= O_NONBLOCK;            /* flip on nodelay bit  */
    fcntl(0, F_SETFL, termflags);       /* and install 'em  */
}

/* how == 0 => save current mode,  how == 1 => restore mode */
/* this version handles termios and fcntl flags             */

void tty_mode(int how)
{
    static struct termios original_mode;
    static int            original_flags;
    static int            stored = 0;

    if ( how == 0 ){
        tcgetattr(0, &original_mode);
        original_flags = fcntl(0, F_GETFL);
        stored = 1;
    }
    else if ( stored ) {
        tcsetattr(0, TCSANOW, &original_mode); 
        fcntl( 0, F_SETFL, original_flags); 
    }
}

void ctrl_c_handler(int signum)
/*
 * purpose: called if SIGINT is detected
 *  action: reset tty and scram
 */
{
    tty_mode(1);
    exit(2);
}

int main()
{
        int     response;
        void    ctrl_c_handler(int);

        tty_mode(0);                            /* save current mode    */
        set_cr_noecho_mode();                   /* set -icanon, -echo   */
        set_nodelay_mode();                     /* noinput => EOF       */
        signal( SIGINT, ctrl_c_handler );       /* handle INT           */
        signal( SIGQUIT, SIG_IGN );             /* ignore QUIT signals  */
        response = get_response(ASK, TRIES);    /* get some answer      */
        tty_mode(1);                            /* reset orig mode      */
        return response;
}