/*
 * 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);
}