/*
 * Builtin help command
 */
#include "cache.h"
#include "builtin.h"
#include "exec_cmd.h"
#include "parse-options.h"
#include "run-command.h"
#include "column.h"
#include "help.h"

#ifndef DEFAULT_HELP_FORMAT
#define DEFAULT_HELP_FORMAT "man"
#endif

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_NONE,
        HELP_FORMAT_MAN,
        HELP_FORMAT_INFO,
        HELP_FORMAT_WEB
};

static const char *html_path;

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

static const char * const builtin_help_usage[] = {
        N_("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))
                return error(_("Failed to start emacsclient."));

        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")) {
                strbuf_release(&buffer);
                return error(_("Failed to parse emacsclient version."));
        }

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

        if (version < 22) {
                strbuf_release(&buffer);
                return error(_("emacsclient version '%d' too old (< 22)."),
                        version);
        }

        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, (char *)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, (char *)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, (char *)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, (char *)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 0;

        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);
        }

        return 0;
}

static int git_help_config(const char *var, const char *value, void *cb)
{
        if (!prefixcmp(var, "column."))
                return git_column_config(var, value, "help", &colopts);
        if (!strcmp(var, "help.format")) {
                if (!value)
                        return config_error_nonbool(var);
                help_format = parse_help_format(value);
                return 0;
        }
        if (!strcmp(var, "help.htmlpath")) {
                if (!value)
                        return config_error_nonbool(var);
                html_path = xstrdup(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);
}

static struct cmdnames main_cmds, other_cmds;

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 = STRBUF_INIT;
        const char *old_path = getenv("MANPATH");

        /* 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, system_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);
        const char *fallback = getenv("GIT_MAN_VIEWER");

        setup_man_path();
        for (viewer = man_viewer_list; viewer; viewer = viewer->next)
        {
                exec_viewer(viewer->name, page); /* will return when unable */
        }
        if (fallback)
                exec_viewer(fallback, page);
        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", system_path(GIT_INFO_PATH), 1);
        execlp("info", "info", "gitman", page, (char *)NULL);
        die(_("no info viewer handled the request"));
}

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

        /* Check that we have a git documentation directory. */
        if (!strstr(html_path, "://")) {
                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
static void open_html(const char *path)
{
        execl_git_cmd("web--browse", "-c", "help.browser", path, (char *)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);
}

int cmd_help(int argc, const char **argv, const char *prefix)
{
        int nongit;
        const char *alias;
        enum help_format parsed_help_format;
        load_command_list("git-", &main_cmds, &other_cmds);

        argc = parse_options(argc, argv, prefix, builtin_help_options,
                        builtin_help_usage, 0);
        parsed_help_format = help_format;

        if (show_all) {
                git_config(git_help_config, NULL);
                printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
                list_commands(colopts, &main_cmds, &other_cmds);
                printf("%s\n", _(git_more_info_string));
                return 0;
        }

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

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

        if (parsed_help_format != HELP_FORMAT_NONE)
                help_format = parsed_help_format;
        if (help_format == HELP_FORMAT_NONE)
                help_format = parse_help_format(DEFAULT_HELP_FORMAT);

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

        switch (help_format) {
        case HELP_FORMAT_NONE:
        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;
}