/* mini man implementation for busybox
 * Copyright (C) 2008 Denys Vlasenko <vda.linux@googlemail.com>
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

//usage:#define man_trivial_usage
//usage:       "[-aw] [MANPAGE]..."
//usage:#define man_full_usage "\n\n"
//usage:       "Format and display manual page\n"
//usage:     "\n        -a      Display all pages"
//usage:     "\n        -w      Show page locations"

#include "libbb.h"

enum {
        OPT_a = 1, /* all */
        OPT_w = 2, /* print path */
};

/* This is what I see on my desktop system being executed:

(
echo ".ll 12.4i"
echo ".nr LL 12.4i"
echo ".pl 1100i"
gunzip -c '/usr/man/man1/bzip2.1.gz'
echo ".\\\""
echo ".pl \n(nlu+10"
) | gtbl | nroff -Tlatin1 -mandoc | less

*/

static int show_manpage(const char *pager, char *man_filename, int man, int level);

static int run_pipe(const char *pager, char *man_filename, int man, int level)
{
        char *cmd;

        /* Prevent man page link loops */
        if (level > 10)
                return 0;

        if (access(man_filename, R_OK) != 0)
                return 0;

        if (option_mask32 & OPT_w) {
                puts(man_filename);
                return 1;
        }

        if (man) { /* man page, not cat page */
                /* Is this a link to another manpage? */
                /* The link has the following on the first line: */
                /* ".so another_man_page" */

                struct stat sb;
                char *line;
                char *linkname, *p;

                /* On my system:
                 * man1/genhostid.1.gz: 203 bytes - smallest real manpage
                 * man2/path_resolution.2.gz: 114 bytes - largest link
                 */
                xstat(man_filename, &sb);
                if (sb.st_size > 300) /* err on the safe side */
                        goto ordinary_manpage;

                line = xmalloc_open_zipped_read_close(man_filename, NULL);
                if (!line || strncmp(line, ".so ", 4) != 0) {
                        free(line);
                        goto ordinary_manpage;
                }
                /* Example: man2/path_resolution.2.gz contains
                 * ".so man7/path_resolution.7\n<junk>"
                 */
                *strchrnul(line, '\n') = '\0';
                linkname = skip_whitespace(&line[4]);

                /* If link has no slashes, we just replace man page name.
                 * If link has slashes (however many), we go back *once*.
                 * ".so zzz/ggg/page.3" does NOT go back two levels. */
                p = strrchr(man_filename, '/');
                if (!p)
                        goto ordinary_manpage;
                *p = '\0';
                if (strchr(linkname, '/')) {
                        p = strrchr(man_filename, '/');
                        if (!p)
                                goto ordinary_manpage;
                        *p = '\0';
                }

                /* Links do not have .gz extensions, even if manpage
                 * is compressed */
                man_filename = xasprintf("%s/%s", man_filename, linkname);
                free(line);
                /* Note: we leak "new" man_filename string as well... */
                if (show_manpage(pager, man_filename, man, level + 1))
                        return 1;
                /* else: show the link, it's better than nothing */
        }

 ordinary_manpage:
        close(STDIN_FILENO);
        open_zipped(man_filename); /* guaranteed to use fd 0 (STDIN_FILENO) */
        /* "2>&1" is added so that nroff errors are shown in pager too.
         * Otherwise it may show just empty screen */
        cmd = xasprintf(
                man ? "gtbl | nroff -Tlatin1 -mandoc 2>&1 | %s"
                    : "%s",
                pager);
        system(cmd);
        free(cmd);
        return 1;
}

/* man_filename is of the form "/dir/dir/dir/name.s" */
static int show_manpage(const char *pager, char *man_filename, int man, int level)
{
#if SEAMLESS_COMPRESSION
        /* We leak this allocation... */
        char *filename_with_zext = xasprintf("%s.lzma", man_filename);
        char *ext = strrchr(filename_with_zext, '.') + 1;
#endif

#if ENABLE_FEATURE_SEAMLESS_LZMA
        if (run_pipe(pager, filename_with_zext, man, level))
                return 1;
#endif
#if ENABLE_FEATURE_SEAMLESS_XZ
        strcpy(ext, "xz");
        if (run_pipe(pager, man_filename, man, level))
                return 1;
#endif
#if ENABLE_FEATURE_SEAMLESS_BZ2
        strcpy(ext, "bz2");
        if (run_pipe(pager, man_filename, man, level))
                return 1;
#endif
#if ENABLE_FEATURE_SEAMLESS_GZ
        strcpy(ext, "gz");
        if (run_pipe(pager, man_filename, man, level))
                return 1;
#endif

#if SEAMLESS_COMPRESSION
        ext[-1] = '\0';
#endif
        if (run_pipe(pager, man_filename, man, level))
                return 1;

        return 0;
}

int man_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int man_main(int argc UNUSED_PARAM, char **argv)
{
        parser_t *parser;
        const char *pager;
        char **man_path_list;
        char *sec_list;
        char *cur_path, *cur_sect;
        int count_mp, cur_mp;
        int opt, not_found;
        char *token[2];

        opt_complementary = "-1"; /* at least one argument */
        opt = getopt32(argv, "+aw");
        argv += optind;

        sec_list = xstrdup("1:2:3:4:5:6:7:8:9");
        /* Last valid man_path_list[] is [0x10] */
        count_mp = 0;
        man_path_list = xzalloc(0x11 * sizeof(man_path_list[0]));
        man_path_list[0] = getenv("MANPATH");
        if (!man_path_list[0]) /* default, may be overridden by /etc/man.conf */
                man_path_list[0] = (char*)"/usr/man";
        else
                count_mp++;
        pager = getenv("MANPAGER");
        if (!pager) {
                pager = getenv("PAGER");
                if (!pager)
                        pager = "more";
        }

        /* Parse man.conf[ig] or man_db.conf */
        /* man version 1.6f uses man.config */
        /* man-db implementation of man uses man_db.conf */
        parser = config_open2("/etc/man.config", fopen_for_read);
        if (!parser)
                parser = config_open2("/etc/man.conf", fopen_for_read);
        if (!parser)
                parser = config_open2("/etc/man_db.conf", fopen_for_read);

        while (config_read(parser, token, 2, 0, "# \t", PARSE_NORMAL)) {
                if (!token[1])
                        continue;
                if (strcmp("MANDATORY_MANPATH"+10, token[0]) == 0 /* "MANPATH"? */
                 || strcmp("MANDATORY_MANPATH", token[0]) == 0
                ) {
                        char *path = token[1];
                        while (*path) {
                                char *next_path;
                                char **path_element;

                                next_path = strchr(path, ':');
                                if (next_path) {
                                        *next_path = '\0';
                                        if (next_path++ == path) /* "::"? */
                                                goto next;
                                }
                                /* Do we already have path? */
                                path_element = man_path_list;
                                while (*path_element) {
                                        if (strcmp(*path_element, path) == 0)
                                                goto skip;
                                        path_element++;
                                }
                                man_path_list = xrealloc_vector(man_path_list, 4, count_mp);
                                man_path_list[count_mp] = xstrdup(path);
                                count_mp++;
                                /* man_path_list is NULL terminated */
                                /*man_path_list[count_mp] = NULL; - xrealloc_vector did it */
 skip:
                                if (!next_path)
                                        break;
 next:
                                path = next_path;
                        }
                }
                if (strcmp("MANSECT", token[0]) == 0) {
                        free(sec_list);
                        sec_list = xstrdup(token[1]);
                }
        }
        config_close(parser);

        not_found = 0;
        do { /* for each argv[] */
                int found = 0;
                cur_mp = 0;

                if (strchr(*argv, '/')) {
                        found = show_manpage(pager, *argv, /*man:*/ 1, 0);
                        goto check_found;
                }
                while ((cur_path = man_path_list[cur_mp++]) != NULL) {
                        /* for each MANPATH */
                        cur_sect = sec_list;
                        do { /* for each section */
                                char *next_sect = strchrnul(cur_sect, ':');
                                int sect_len = next_sect - cur_sect;
                                char *man_filename;
                                int cat0man1 = 0;

                                /* Search for cat, then man page */
                                while (cat0man1 < 2) {
                                        int found_here;
                                        man_filename = xasprintf("%s/%s%.*s/%s.%.*s",
                                                        cur_path,
                                                        "cat\0man" + (cat0man1 * 4),
                                                        sect_len, cur_sect,
                                                        *argv,
                                                        sect_len, cur_sect);
                                        found_here = show_manpage(pager, man_filename, cat0man1, 0);
                                        found |= found_here;
                                        cat0man1 += found_here + 1;
                                        free(man_filename);
                                }

                                if (found && !(opt & OPT_a))
                                        goto next_arg;
                                cur_sect = next_sect;
                                while (*cur_sect == ':')
                                        cur_sect++;
                        } while (*cur_sect);
                }
 check_found:
                if (!found) {
                        bb_error_msg("no manual entry for '%s'", *argv);
                        not_found = 1;
                }
 next_arg:
                argv++;
        } while (*argv);

        return not_found;
}