/*
 * builtin-help.c
 *
 * Builtin help-related commands (help, usage, version)
 */
#include "cache.h"
#include "builtin.h"
#include "exec_cmd.h"
#include "common-cmds.h"
#include "parse-options.h"
#include "run-command.h"
#include "help.h"

static struct man_viewer_list {
        struct man_viewer_list *next;
        char name[FLEX_ARRAY];
} *man_viewer_list;

static struct man_viewer_info_list {
        struct man_viewer_info_list *next;
        const char *info;
        char name[FLEX_ARRAY];
} *man_viewer_info_list;

enum help_format {
        HELP_FORMAT_MAN,
        HELP_FORMAT_INFO,
        HELP_FORMAT_WEB,
};

static int show_all = 0;
static enum help_format help_format = HELP_FORMAT_MAN;
static struct option builtin_help_options[] = {
        OPT_BOOLEAN('a', "all", &show_all, "print all available commands"),
        OPT_SET_INT('m', "man", &help_format, "show man page", HELP_FORMAT_MAN),
        OPT_SET_INT('w', "web", &help_format, "show manual in web browser",
                        HELP_FORMAT_WEB),
        OPT_SET_INT('i', "info", &help_format, "show info page",
                        HELP_FORMAT_INFO),
        OPT_END(),
};

static const char * const builtin_help_usage[] = {
        "git help [--all] [--man|--web|--info] [command]",
        NULL
};

static enum help_format parse_help_format(const char *format)
{
        if (!strcmp(format, "man"))
                return HELP_FORMAT_MAN;
        if (!strcmp(format, "info"))
                return HELP_FORMAT_INFO;
        if (!strcmp(format, "web") || !strcmp(format, "html"))
                return HELP_FORMAT_WEB;
        die("unrecognized help format '%s'", format);
}

static const char *get_man_viewer_info(const char *name)
{
        struct man_viewer_info_list *viewer;

        for (viewer = man_viewer_info_list; viewer; viewer = viewer->next)
        {
                if (!strcasecmp(name, viewer->name))
                        return viewer->info;
        }
        return NULL;
}

static int check_emacsclient_version(void)
{
        struct strbuf buffer = STRBUF_INIT;
        struct child_process ec_process;
        const char *argv_ec[] = { "emacsclient", "--version", NULL };
        int version;

        /* emacsclient prints its version number on stderr */
        memset(&ec_process, 0, sizeof(ec_process));
        ec_process.argv = argv_ec;
        ec_process.err = -1;
        ec_process.stdout_to_stderr = 1;
        if (start_command(&ec_process)) {
                fprintf(stderr, "Failed to start emacsclient.\n");
                return -1;
        }
        strbuf_read(&buffer, ec_process.err, 20);
        close(ec_process.err);

        /*
         * Don't bother checking return value, because "emacsclient --version"
         * seems to always exits with code 1.
         */
        finish_command(&ec_process);

        if (prefixcmp(buffer.buf, "emacsclient")) {
                fprintf(stderr, "Failed to parse emacsclient version.\n");
                strbuf_release(&buffer);
                return -1;
        }

        strbuf_remove(&buffer, 0, strlen("emacsclient"));
        version = atoi(buffer.buf);

        if (version < 22) {
                fprintf(stderr,
                        "emacsclient version '%d' too old (< 22).\n",
                        version);
                strbuf_release(&buffer);
                return -1;
        }

        strbuf_release(&buffer);
        return 0;
}

static void exec_woman_emacs(const char* path, const char *page)
{
        if (!check_emacsclient_version()) {
                /* This works only with emacsclient version >= 22. */
                struct strbuf man_page = STRBUF_INIT;

                if (!path)
                        path = "emacsclient";
                strbuf_addf(&man_page, "(woman \"%s\")", page);
                execlp(path, "emacsclient", "-e", man_page.buf, NULL);
                warning("failed to exec '%s': %s", path, strerror(errno));
        }
}

static void exec_man_konqueror(const char* path, const char *page)
{
        const char *display = getenv("DISPLAY");
        if (display && *display) {
                struct strbuf man_page = STRBUF_INIT;
                const char *filename = "kfmclient";

                /* It's simpler to launch konqueror using kfmclient. */
                if (path) {
                        const char *file = strrchr(path, '/');
                        if (file && !strcmp(file + 1, "konqueror")) {
                                char *new = xstrdup(path);
                                char *dest = strrchr(new, '/');

                                /* strlen("konqueror") == strlen("kfmclient") */
                                strcpy(dest + 1, "kfmclient");
                                path = new;
                        }
                        if (file)
                                filename = file;
                } else
                        path = "kfmclient";
                strbuf_addf(&man_page, "man:%s(1)", page);
                execlp(path, filename, "newTab", man_page.buf, NULL);
                warning("failed to exec '%s': %s", path, strerror(errno));
        }
}

static void exec_man_man(const char* path, const char *page)
{
        if (!path)
                path = "man";
        execlp(path, "man", page, NULL);
        warning("failed to exec '%s': %s", path, strerror(errno));
}

static void exec_man_cmd(const char *cmd, const char *page)
{
        struct strbuf shell_cmd = STRBUF_INIT;
        strbuf_addf(&shell_cmd, "%s %s", cmd, page);
        execl("/bin/sh", "sh", "-c", shell_cmd.buf, NULL);
        warning("failed to exec '%s': %s", cmd, strerror(errno));
}

static void add_man_viewer(const char *name)
{
        struct man_viewer_list **p = &man_viewer_list;
        size_t len = strlen(name);

        while (*p)
                p = &((*p)->next);
        *p = xcalloc(1, (sizeof(**p) + len + 1));
        strncpy((*p)->name, name, len);
}

static int supported_man_viewer(const char *name, size_t len)
{
        return (!strncasecmp("man", name, len) ||
                !strncasecmp("woman", name, len) ||
                !strncasecmp("konqueror", name, len));
}

static void do_add_man_viewer_info(const char *name,
                                   size_t len,
                                   const char *value)
{
        struct man_viewer_info_list *new = xcalloc(1, sizeof(*new) + len + 1);

        strncpy(new->name, name, len);
        new->info = xstrdup(value);
        new->next = man_viewer_info_list;
        man_viewer_info_list = new;
}

static int add_man_viewer_path(const char *name,
                               size_t len,
                               const char *value)
{
        if (supported_man_viewer(name, len))
                do_add_man_viewer_info(name, len, value);
        else
                warning("'%s': path for unsupported man viewer.\n"
                        "Please consider using 'man.<tool>.cmd' instead.",
                        name);

        return 0;
}

static int add_man_viewer_cmd(const char *name,
                              size_t len,
                              const char *value)
{
        if (supported_man_viewer(name, len))
                warning("'%s': cmd for supported man viewer.\n"
                        "Please consider using 'man.<tool>.path' instead.",
                        name);
        else
                do_add_man_viewer_info(name, len, value);

        return 0;
}

static int add_man_viewer_info(const char *var, const char *value)
{
        const char *name = var + 4;
        const char *subkey = strrchr(name, '.');

        if (!subkey)
                return error("Config with no key for man viewer: %s", name);

        if (!strcmp(subkey, ".path")) {
                if (!value)
                        return config_error_nonbool(var);
                return add_man_viewer_path(name, subkey - name, value);
        }
        if (!strcmp(subkey, ".cmd")) {
                if (!value)
                        return config_error_nonbool(var);
                return add_man_viewer_cmd(name, subkey - name, value);
        }

        warning("'%s': unsupported man viewer sub key.", subkey);
        return 0;
}

static int git_help_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "help.format")) {
                if (!value)
                        return config_error_nonbool(var);
                help_format = parse_help_format(value);
                return 0;
        }
        if (!strcmp(var, "man.viewer")) {
                if (!value)
                        return config_error_nonbool(var);
                add_man_viewer(value);
                return 0;
        }
        if (!prefixcmp(var, "man."))
                return add_man_viewer_info(var, value);

        return git_default_config(var, value, cb);
}

/* most GUI terminals set COLUMNS (although some don't export it) */
static int term_columns(void)
{
        char *col_string = getenv("COLUMNS");
        int n_cols;

        if (col_string && (n_cols = atoi(col_string)) > 0)
                return n_cols;

#ifdef TIOCGWINSZ
        {
                struct winsize ws;
                if (!ioctl(1, TIOCGWINSZ, &ws)) {
                        if (ws.ws_col)
                                return ws.ws_col;
                }
        }
#endif

        return 80;
}

static inline void mput_char(char c, unsigned int num)
{
        while(num--)
                putchar(c);
}

struct cmdnames main_cmds, other_cmds;

void add_cmdname(struct cmdnames *cmds, const char *name, int len)
{
        struct cmdname *ent = xmalloc(sizeof(*ent) + len + 1);

        ent->len = len;
        memcpy(ent->name, name, len);
        ent->name[len] = 0;

        ALLOC_GROW(cmds->names, cmds->cnt + 1, cmds->alloc);
        cmds->names[cmds->cnt++] = ent;
}

static int cmdname_compare(const void *a_, const void *b_)
{
        struct cmdname *a = *(struct cmdname **)a_;
        struct cmdname *b = *(struct cmdname **)b_;
        return strcmp(a->name, b->name);
}

static void uniq(struct cmdnames *cmds)
{
        int i, j;

        if (!cmds->cnt)
                return;

        for (i = j = 1; i < cmds->cnt; i++)
                if (strcmp(cmds->names[i]->name, cmds->names[i-1]->name))
                        cmds->names[j++] = cmds->names[i];

        cmds->cnt = j;
}

void exclude_cmds(struct cmdnames *cmds, struct cmdnames *excludes)
{
        int ci, cj, ei;
        int cmp;

        ci = cj = ei = 0;
        while (ci < cmds->cnt && ei < excludes->cnt) {
                cmp = strcmp(cmds->names[ci]->name, excludes->names[ei]->name);
                if (cmp < 0)
                        cmds->names[cj++] = cmds->names[ci++];
                else if (cmp == 0)
                        ci++, ei++;
                else if (cmp > 0)
                        ei++;
        }

        while (ci < cmds->cnt)
                cmds->names[cj++] = cmds->names[ci++];

        cmds->cnt = cj;
}

static void pretty_print_string_list(struct cmdnames *cmds, int longest)
{
        int cols = 1, rows;
        int space = longest + 1; /* min 1 SP between words */
        int max_cols = term_columns() - 1; /* don't print *on* the edge */
        int i, j;

        if (space < max_cols)
                cols = max_cols / space;
        rows = (cmds->cnt + cols - 1) / cols;

        for (i = 0; i < rows; i++) {
                printf("  ");

                for (j = 0; j < cols; j++) {
                        int n = j * rows + i;
                        int size = space;
                        if (n >= cmds->cnt)
                                break;
                        if (j == cols-1 || n + rows >= cmds->cnt)
                                size = 1;
                        printf("%-*s", size, cmds->names[n]->name);
                }
                putchar('\n');
        }
}

static int is_executable(const char *name)
{
        struct stat st;

        if (stat(name, &st) || /* stat, not lstat */
            !S_ISREG(st.st_mode))
                return 0;

#ifdef __MINGW32__
        /* cannot trust the executable bit, peek into the file instead */
        char buf[3] = { 0 };
        int n;
        int fd = open(name, O_RDONLY);
        st.st_mode &= ~S_IXUSR;
        if (fd >= 0) {
                n = read(fd, buf, 2);
                if (n == 2)
                        /* DOS executables start with "MZ" */
                        if (!strcmp(buf, "#!") || !strcmp(buf, "MZ"))
                                st.st_mode |= S_IXUSR;
                close(fd);
        }
#endif
        return st.st_mode & S_IXUSR;
}

static unsigned int list_commands_in_dir(struct cmdnames *cmds,
                                         const char *path,
                                         const char *prefix)
{
        unsigned int longest = 0;
        int prefix_len;
        DIR *dir = opendir(path);
        struct dirent *de;
        struct strbuf buf = STRBUF_INIT;
        int len;

        if (!dir)
                return 0;
        if (!prefix)
                prefix = "git-";
        prefix_len = strlen(prefix);

        strbuf_addf(&buf, "%s/", path);
        len = buf.len;

        while ((de = readdir(dir)) != NULL) {
                int entlen;

                if (prefixcmp(de->d_name, prefix))
                        continue;

                strbuf_setlen(&buf, len);
                strbuf_addstr(&buf, de->d_name);
                if (!is_executable(buf.buf))
                        continue;

                entlen = strlen(de->d_name) - prefix_len;
                if (has_extension(de->d_name, ".exe"))
                        entlen -= 4;

                if (longest < entlen)
                        longest = entlen;

                add_cmdname(cmds, de->d_name + prefix_len, entlen);
        }
        closedir(dir);
        strbuf_release(&buf);

        return longest;
}

unsigned int load_command_list(const char *prefix,
                struct cmdnames *main_cmds,
                struct cmdnames *other_cmds)
{
        unsigned int longest = 0;
        unsigned int len;
        const char *env_path = getenv("PATH");
        char *paths, *path, *colon;
        const char *exec_path = git_exec_path();

        if (exec_path)
                longest = list_commands_in_dir(main_cmds, exec_path, prefix);

        if (!env_path) {
                fprintf(stderr, "PATH not set\n");
                exit(1);
        }

        path = paths = xstrdup(env_path);
        while (1) {
                if ((colon = strchr(path, PATH_SEP)))
                        *colon = 0;

                len = list_commands_in_dir(other_cmds, path, prefix);
                if (len > longest)
                        longest = len;

                if (!colon)
                        break;
                path = colon + 1;
        }
        free(paths);

        qsort(main_cmds->names, main_cmds->cnt,
              sizeof(*main_cmds->names), cmdname_compare);
        uniq(main_cmds);

        qsort(other_cmds->names, other_cmds->cnt,
              sizeof(*other_cmds->names), cmdname_compare);
        uniq(other_cmds);
        exclude_cmds(other_cmds, main_cmds);

        return longest;
}

void list_commands(const char *title, unsigned int longest,
                struct cmdnames *main_cmds, struct cmdnames *other_cmds)
{
        const char *exec_path = git_exec_path();

        if (main_cmds->cnt) {
                printf("available %s in '%s'\n", title, exec_path);
                printf("----------------");
                mput_char('-', strlen(title) + strlen(exec_path));
                putchar('\n');
                pretty_print_string_list(main_cmds, longest);
                putchar('\n');
        }

        if (other_cmds->cnt) {
                printf("%s available from elsewhere on your $PATH\n", title);
                printf("---------------------------------------");
                mput_char('-', strlen(title));
                putchar('\n');
                pretty_print_string_list(other_cmds, longest);
                putchar('\n');
        }
}

void list_common_cmds_help(void)
{
        int i, longest = 0;

        for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
                if (longest < strlen(common_cmds[i].name))
                        longest = strlen(common_cmds[i].name);
        }

        puts("The most commonly used git commands are:");
        for (i = 0; i < ARRAY_SIZE(common_cmds); i++) {
                printf("   %s   ", common_cmds[i].name);
                mput_char(' ', longest - strlen(common_cmds[i].name));
                puts(common_cmds[i].help);
        }
}

int is_in_cmdlist(struct cmdnames *c, const char *s)
{
        int i;
        for (i = 0; i < c->cnt; i++)
                if (!strcmp(s, c->names[i]->name))
                        return 1;
        return 0;
}

static int is_git_command(const char *s)
{
        return is_in_cmdlist(&main_cmds, s) ||
                is_in_cmdlist(&other_cmds, s);
}

static const char *prepend(const char *prefix, const char *cmd)
{
        size_t pre_len = strlen(prefix);
        size_t cmd_len = strlen(cmd);
        char *p = xmalloc(pre_len + cmd_len + 1);
        memcpy(p, prefix, pre_len);
        strcpy(p + pre_len, cmd);
        return p;
}

static const char *cmd_to_page(const char *git_cmd)
{
        if (!git_cmd)
                return "git";
        else if (!prefixcmp(git_cmd, "git"))
                return git_cmd;
        else if (is_git_command(git_cmd))
                return prepend("git-", git_cmd);
        else
                return prepend("git", git_cmd);
}

static void setup_man_path(void)
{
        struct strbuf new_path;
        const char *old_path = getenv("MANPATH");

        strbuf_init(&new_path, 0);

        /* We should always put ':' after our path. If there is no
         * old_path, the ':' at the end will let 'man' to try
         * system-wide paths after ours to find the manual page. If
         * there is old_path, we need ':' as delimiter. */
        strbuf_addstr(&new_path, GIT_MAN_PATH);
        strbuf_addch(&new_path, ':');
        if (old_path)
                strbuf_addstr(&new_path, old_path);

        setenv("MANPATH", new_path.buf, 1);

        strbuf_release(&new_path);
}

static void exec_viewer(const char *name, const char *page)
{
        const char *info = get_man_viewer_info(name);

        if (!strcasecmp(name, "man"))
                exec_man_man(info, page);
        else if (!strcasecmp(name, "woman"))
                exec_woman_emacs(info, page);
        else if (!strcasecmp(name, "konqueror"))
                exec_man_konqueror(info, page);
        else if (info)
                exec_man_cmd(info, page);
        else
                warning("'%s': unknown man viewer.", name);
}

static void show_man_page(const char *git_cmd)
{
        struct man_viewer_list *viewer;
        const char *page = cmd_to_page(git_cmd);

        setup_man_path();
        for (viewer = man_viewer_list; viewer; viewer = viewer->next)
        {
                exec_viewer(viewer->name, page); /* will return when unable */
        }
        exec_viewer("man", page);
        die("no man viewer handled the request");
}

static void show_info_page(const char *git_cmd)
{
        const char *page = cmd_to_page(git_cmd);
        setenv("INFOPATH", GIT_INFO_PATH, 1);
        execlp("info", "info", "gitman", page, NULL);
}

static void get_html_page_path(struct strbuf *page_path, const char *page)
{
        struct stat st;
        const char *html_path = system_path(GIT_HTML_PATH);

        /* Check that we have a git documentation directory. */
        if (stat(mkpath("%s/git.html", html_path), &st)
            || !S_ISREG(st.st_mode))
                die("'%s': not a documentation directory.", html_path);

        strbuf_init(page_path, 0);
        strbuf_addf(page_path, "%s/%s.html", html_path, page);
}

/*
 * If open_html is not defined in a platform-specific way (see for
 * example compat/mingw.h), we use the script web--browse to display
 * HTML.
 */
#ifndef open_html
void open_html(const char *path)
{
        execl_git_cmd("web--browse", "-c", "help.browser", path, NULL);
}
#endif

static void show_html_page(const char *git_cmd)
{
        const char *page = cmd_to_page(git_cmd);
        struct strbuf page_path; /* it leaks but we exec bellow */

        get_html_page_path(&page_path, page);

        open_html(page_path.buf);
}

void help_unknown_cmd(const char *cmd)
{
        fprintf(stderr, "git: '%s' is not a git-command. See 'git --help'.\n", cmd);
        exit(1);
}

int cmd_version(int argc, const char **argv, const char *prefix)
{
        printf("git version %s\n", git_version_string);
        return 0;
}

int cmd_help(int argc, const char **argv, const char *prefix)
{
        int nongit;
        const char *alias;
        unsigned int longest = load_command_list("git-", &main_cmds, &other_cmds);

        setup_git_directory_gently(&nongit);
        git_config(git_help_config, NULL);

        argc = parse_options(argc, argv, builtin_help_options,
                        builtin_help_usage, 0);

        if (show_all) {
                printf("usage: %s\n\n", git_usage_string);
                list_commands("git commands", longest, &main_cmds, &other_cmds);
                printf("%s\n", git_more_info_string);
                return 0;
        }

        if (!argv[0]) {
                printf("usage: %s\n\n", git_usage_string);
                list_common_cmds_help();
                printf("\n%s\n", git_more_info_string);
                return 0;
        }

        alias = alias_lookup(argv[0]);
        if (alias && !is_git_command(argv[0])) {
                printf("`git %s' is aliased to `%s'\n", argv[0], alias);
                return 0;
        }

        switch (help_format) {
        case HELP_FORMAT_MAN:
                show_man_page(argv[0]);
                break;
        case HELP_FORMAT_INFO:
                show_info_page(argv[0]);
                break;
        case HELP_FORMAT_WEB:
                show_html_page(argv[0]);
                break;
        }

        return 0;
}