/*
 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * Simple paged-output and paged-viewing functions
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <unistd.h>
#include <stropts.h>

static int p_maxlines = -1;
static int p_freelines;

static struct termios orig_termios;
static char *pager_prompt1 = \
	" --more--  <space> page down <enter> line down <q> quit ";
static char *pager_blank = \
	"                                                        ";

/*
 * 'open' the pager
 */
void
pager_open(void)
{
	int	nlines;
	char *cp, *lp;
	struct termios raw;
	struct winsize ws;

	(void) tcgetattr(0, &orig_termios);
	raw = orig_termios;
	raw.c_lflag &= ~(ICANON | ECHO);
	raw.c_cc[VMIN] = 1;
	raw.c_cc[VTIME] = 0;
	(void) tcsetattr(0, TCSAFLUSH, &raw);

	nlines = 24;		/* sensible default */
	if (ioctl(1, TIOCGWINSZ, &ws) == -1 || ws.ws_row == 0) {
		if ((cp = getenv("screen-#rows")) != NULL) {
			nlines = strtol(cp, &lp, 0);
		}
	} else
		nlines = ws.ws_row;

	p_maxlines = nlines - 1;
	if (p_maxlines < 1)
		p_maxlines = 1;
	p_freelines = p_maxlines;
}

/*
 * 'close' the pager
 */
void
pager_close(void)
{
	(void) fflush(stdout);
	p_maxlines = -1;
	(void) tcsetattr(0, TCSAFLUSH, &orig_termios);
}

/*
 * Emit lines to the pager; may not return until the user
 * has responded to the prompt.
 *
 * Will return nonzero if the user enters 'q' or 'Q' at the prompt.
 *
 * XXX note that this watches outgoing newlines (and eats them), but
 *     does not handle wrap detection (req. count of columns).
 */
int
pager_output(const char *cp)
{
	int action;

	if (cp == NULL)
		return (0);

	for (;;) {
		if (*cp == 0)
			return (0);

		(void) putchar(*cp);		/* always emit character */

		if (*(cp++) == '\n') {	/* got a newline? */
			p_freelines--;
			if (p_freelines <= 0) {
				printf("%s", pager_prompt1);
				action = 0;
				while (action == 0) {
					switch (getchar()) {
					case '\r':
					case '\n':
						p_freelines = 1;
						action = 1;
					break;
					case ' ':
						p_freelines = p_maxlines;
						action = 1;
					break;
					case 'q':
					case 'Q':
						action = 2;
					break;
					default:
					break;
					}
				}
				printf("\r%s\r", pager_blank);
				if (action == 2)
					return (1);
			}
		}
	}
}

/*
 * Display from (fd).
 */
int
pager_file(const char *fname)
{
	char buf[80];
	size_t hmuch;
	int fd;
	int result;

	if ((fd = open(fname, O_RDONLY)) == -1) {
		printf("can't open '%s': %s\n", fname, strerror(errno));
		return (-1);
	}

	for (;;) {
		hmuch = read(fd, buf, sizeof (buf) - 1);
		if (hmuch == -1) {
			result = -1;
			break;
		}
		if (hmuch == 0) {
			result = 0;
			break;
		}
		buf[hmuch] = 0;
		if (pager_output(buf)) {
			result = 1;
			break;
		}
	}
	(void) close(fd);
	return (result);
}