/*  more02b.c  - version 0.2b of more
 *	read and print 24 lines then pause for a few special commands
 *	v02b: reads user control cmds from /dev/tty using read
 *	      and uses tcgetattr tcsetattr to change input processing
 *	prob: if interrupted or killed, does not reset terminal
 *	note: run this under dash to get the correct effect (bash is too smart)
 */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <signal.h>

#define  PAGELEN	23		/* leave one for the prompt */
#define  ERROR		1
#define  SUCCESS	0
#define  has_more_data(x)   (!feof(x))
#define	CTL_DEV	"/dev/tty"		/* source of control commands	*/

int  do_more(FILE *, int);
int  how_much_more(int);
void print_one_line(FILE *);
int  setup_tty(int);
int  reset_tty(int);
void ouch(int);

void ouch(int s)
{
	printf("ouch!\n");
	exit(1);
}
int main( int ac , char *av[] )
{
	FILE	*fp;			/* stream to view with more	*/
	int	result = SUCCESS;	/* return status from main	*/
	int	term_fd;		/* fd for keyboard		*/

	// signal(SIGINT, ouch);
	if ( (term_fd = open(CTL_DEV, O_RDONLY)) == -1 ){
		perror(CTL_DEV);
		return ERROR;
	}
	if ( setup_tty(term_fd) == -1 )	/* set program mode		*/
		return ERROR;

	if ( ac == 1 )
		result = do_more( stdin, term_fd );
	else
		while ( result == SUCCESS && --ac )
			if ( (fp = fopen( *++av , "r" )) != NULL ) {
				result = do_more( fp, term_fd) ; 
				fclose( fp );
			}
			else
				result = ERROR;

	if ( reset_tty(term_fd) == -1 || close(term_fd) == -1 )
		return ERROR;

	return result;
}
/*  do_more -- show a page of text, then call how_much_more() for instructions
 *      args: FILE * opened to text to display
 *      rets: SUCCESS if ok, ERROR if not
 */
int do_more( FILE *fp , int term_fd )
{
	int	space_left = PAGELEN ;		/* space left on screen */
	int	reply;				/* user request		*/

	while ( has_more_data( fp ) ) {		/* more input	*/
		if ( space_left <= 0 ) {		/* screen full?	*/
			reply = how_much_more(term_fd);	/* ask user	*/
			if ( reply == 0 )		/*    n: done   */
				break;
			space_left = reply;		/* reset count	*/
		}
		print_one_line( fp );
		space_left--;				/* count it	*/
	}
	return SUCCESS;				/* EOF => done		*/
}

/*  print_one_line(fp) -- copy data from input to stdout until \n or EOF */
void print_one_line( FILE *fp )
{
	int	c;

	while( ( c = getc(fp) ) != EOF && c != '\n' )
		putchar( c ) ;
	putchar('\n');
}

/*  how_much_more -- ask user how much more to show
 *      args: none
 *      rets: number of additional lines to show: 0 => all done
 *	note: space => screenful, 'q' => quit, '\n' => one line
 */
int how_much_more(int term_fd)
{
	char	c;
	int	nread;

	while( 1 )
	{
		printf("\033[7m more? \033[m");	/* reverse on a vt100	*/
		fflush(stdout);
		nread = read(term_fd, &c, 1);
		printf("\r       \r");		/* clear more?		*/
		if ( nread != 1 )		/* error or EOF		*/
			return 0;
		if ( c == 'q' )			/* q -> N		*/
			return 0;
		if ( c == ' ' )			/* ' ' => next page	*/
			return PAGELEN;		/* how many to show	*/
		if ( c == '\n' )		/* Enter key => 1 line	*/
			return 1;		
	}
}

/*
 * terminal mode control: setup_tty, reset_tty
 * uses a static copy of the original settings to reset to what they were
 */

static struct termios orig_settings;
static int	      have_orig = 0;	/* is orig_settings valid */

/*
 * setup_tty: get settings, change them for program mode, return fd or -1
 */
int setup_tty(int fd)
{
	struct termios settings;
	if ( tcgetattr(fd, &settings) == -1 ){
		perror("cannot get terminal settings");
		return -1;
	}
	orig_settings = settings;		/* make copy		*/
	have_orig     = 1;

	settings.c_lflag   &= ~ICANON;		/* no buffering		*/
	settings.c_lflag   &= ~ECHO;		/* no echoing please	*/
	settings.c_cc[VMIN] = 1;		/* read chars 1-by-1	*/
	if ( tcsetattr(fd, TCSANOW, &settings) == -1 ){
		perror("cannot set terminal settings");
		return -1;
	}
	return fd;
}

/*
 * reset_tty: restore original driver settings if stored, 
 * rets: 0 for ok, -1 for error
 */
int reset_tty(int fd)
{
	if ( have_orig && tcsetattr(fd, TCSANOW, &orig_settings) != -1 )
		return 0;
	return -1;
}