/* vi: set sw=4 ts=4: */
/*
 * Mini more implementation for busybox
 *
 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 *
 * Latest version blended together by Erik Andersen <andersen@codepoet.org>,
 * based on the original more implementation by Bruce, and code from the
 * Debian boot-floppies team.
 *
 * Termios corrects by Vladimir Oleynik <dzo@simtreas.ru>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//config:config MORE
//config:       bool "more (7 kb)"
//config:       default y
//config:       help
//config:       more is a simple utility which allows you to read text one screen
//config:       sized page at a time. If you want to read text that is larger than
//config:       the screen, and you are using anything faster than a 300 baud modem,
//config:       you will probably find this utility very helpful. If you don't have
//config:       any need to reading text files, you can leave this disabled.

//applet:IF_MORE(APPLET(more, BB_DIR_BIN, BB_SUID_DROP))

//kbuild:lib-$(CONFIG_MORE) += more.o

//usage:#define more_trivial_usage
//usage:       "[FILE]..."
//usage:#define more_full_usage "\n\n"
//usage:       "View FILE (or stdin) one screenful at a time"
//usage:
//usage:#define more_example_usage
//usage:       "$ dmesg | more\n"

#include "libbb.h"
#include "common_bufsiz.h"

struct globals {
        int tty_fileno;
        unsigned terminal_width;
        unsigned terminal_height;
        struct termios initial_settings;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { setup_common_bufsiz(); } while (0)

static void get_wh(void)
{
        /* never returns w, h <= 1 */
        get_terminal_width_height(G.tty_fileno, &G.terminal_width, &G.terminal_height);
        G.terminal_height -= 1;
}

static void tcsetattr_tty_TCSANOW(struct termios *settings)
{
        tcsetattr(G.tty_fileno, TCSANOW, settings);
}

static void gotsig(int sig UNUSED_PARAM)
{
        /* bb_putchar_stderr doesn't use stdio buffering,
         * therefore it is safe in signal handler */
        bb_putchar_stderr('\n');
        tcsetattr_tty_TCSANOW(&G.initial_settings);
        _exit(EXIT_FAILURE);
}

#define CONVERTED_TAB_SIZE 8

int more_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int more_main(int argc UNUSED_PARAM, char **argv)
{
        int c = c; /* for compiler */
        int input = 0;
        int spaces = 0;
        int please_display_more_prompt;
        FILE *tty;

        INIT_G();

        /* Parse options */
        /* Accepted but ignored: */
        /* -d   Display help instead of ringing bell */
        /* -e   Exit immediately after writing the last line */
        /* -f   Count logical lines (IOW: long lines are not folded) */
        /* -l   Do not pause after any line containing a ^L (form feed) */
        /* -s   Squeeze blank lines into one */
        /* -u   Suppress underlining */
        getopt32(argv, "deflsu");
        argv += optind;

        /* Another popular pager, most, detects when stdout
         * is not a tty and turns into cat. This makes sense. */
        if (!isatty(STDOUT_FILENO))
                return bb_cat(argv);
        tty = fopen_for_read(CURRENT_TTY);
        if (!tty)
                return bb_cat(argv);

        G.tty_fileno = fileno(tty);

        /* Turn on unbuffered input; turn off echoing */
        set_termios_to_raw(G.tty_fileno, &G.initial_settings, 0);
        bb_signals(BB_FATAL_SIGS, gotsig);

        do {
                struct stat st;
                FILE *file;
                int len;
                int lines;

                file = stdin;
                if (*argv) {
                        file = fopen_or_warn(*argv, "r");
                        if (!file)
                                continue;
                }
                st.st_size = 0;
                fstat(fileno(file), &st);

                get_wh();

                please_display_more_prompt = 0;
                len = 0;
                lines = 0;
                for (;;) {
                        int wrap;

                        if (spaces)
                                spaces--;
                        else {
                                c = getc(file);
                                if (c == EOF) break;
                        }
 loop_top:
                        if (input != 'r' && please_display_more_prompt) {
                                len = printf("--More-- ");
                                if (st.st_size != 0) {
                                        uoff_t d = (uoff_t)st.st_size / 100;
                                        if (d == 0)
                                                d = 1;
                                        len += printf("(%u%% of %"OFF_FMT"u bytes)",
                                                (int) ((uoff_t)ftello(file) / d),
                                                st.st_size);
                                }

                                /*
                                 * We've just displayed the "--More--" prompt, so now we need
                                 * to get input from the user.
                                 */
                                for (;;) {
                                        fflush_all();
                                        input = getc(tty);
                                        input = tolower(input);
                                        /* Erase the last message */
                                        printf("\r%*s\r", len, "");

                                        if (input == 'q')
                                                goto end;
                                        /* Due to various multibyte escape
                                         * sequences, it's not ok to accept
                                         * any input as a command to scroll
                                         * the screen. We only allow known
                                         * commands, else we show help msg. */
                                        if (input == ' ' || input == '\n' || input == 'r')
                                                break;
                                        len = printf("(Enter:next line Space:next page Q:quit R:show the rest)");
                                }
                                len = 0;
                                lines = 0;
                                please_display_more_prompt = 0;

                                /* The user may have resized the terminal.
                                 * Re-read the dimensions. */
                                get_wh();
                        }

                        /* Crudely convert tabs into spaces, which are
                         * a bajillion times easier to deal with. */
                        if (c == '\t') {
                                spaces = ((unsigned)~len) % CONVERTED_TAB_SIZE;
                                c = ' ';
                        }

                        /*
                         * There are two input streams to worry about here:
                         *
                         * c    : the character we are reading from the file being "mored"
                         * input: a character received from the keyboard
                         *
                         * If we hit a newline in the _file_ stream, we want to test and
                         * see if any characters have been hit in the _input_ stream. This
                         * allows the user to quit while in the middle of a file.
                         */
                        wrap = (++len > G.terminal_width);
                        if (c == '\n' || wrap) {
                                /* Then outputting this character
                                 * will move us to a new line. */
                                if (++lines >= G.terminal_height || input == '\n')
                                        please_display_more_prompt = 1;
                                len = 0;
                        }
                        if (c != '\n' && wrap) {
                                /* Then outputting this will also put a character on
                                 * the beginning of that new line. Thus we first want to
                                 * display the prompt (if any), so we skip the putchar()
                                 * and go back to the top of the loop, without reading
                                 * a new character. */
                                goto loop_top;
                        }
                        /* My small mind cannot fathom backspaces and UTF-8 */
                        putchar(c);
                        die_if_ferror_stdout(); /* if tty was destroyed (closed xterm, etc) */
                }
                fclose(file);
                fflush_all();
        } while (*argv && *++argv);
 end:
        tcsetattr_tty_TCSANOW(&G.initial_settings);
        return 0;
}