<?php
/*
 * StatusNet - the distributed open-source microblogging tool
 * Copyright (C) 2008, 2009, 2010 StatusNet, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

if (!defined('GNUSOCIAL')) { exit(1); }

require_once(INSTALLDIR.'/lib/channel.php');

class Command
{
    protected $scoped = null;   // The Profile of the user performing the command
    var $user = null;

    function __construct($user=null)
    {
        $this->scoped = empty($user)?null:$user->getProfile();
        $this->user = $user;
    }

    /**
     * Execute the command and send success or error results
     * back via the given communications channel.
     *
     * @param Channel
     */
    public function execute($channel)
    {
        try {
            $this->handle($channel);
        } catch (CommandException $e) {
            $channel->error($this->user, $e->getMessage());
        } catch (Exception $e) {
            common_log(LOG_ERR, "Error handling " . get_class($this) . ": " . $e->getMessage());
            $channel->error($this->user, $e->getMessage());
        }
    }

    /**
     * Override this with the meat!
     *
     * An error to send back to the user may be sent by throwing
     * a CommandException with a formatted message.
     *
     * @param Channel
     * @throws CommandException
     */
    function handle($channel)
    {
        return false;
    }

    /**
     * Look up a notice from an argument, by poster's name to get last post
     * or notice_id prefixed with #.
     *
     * @return Notice
     * @throws CommandException
     */
    function getNotice($arg)
    {
        $notice = null;
        if (Event::handle('StartCommandGetNotice', array($this, $arg, &$notice))) {
            if(substr($this->other,0,1)=='#'){
                // A specific notice_id #123

                $notice = Notice::getKV(substr($arg,1));
                if (!$notice) {
                    // TRANS: Command exception text shown when a notice ID is requested that does not exist.
                    throw new CommandException(_('Notice with that id does not exist.'));
                }
            }

            if (Validate::uri($this->other)) {
                // A specific notice by URI lookup
                $notice = Notice::getKV('uri', $arg);
            }

            if (!$notice) {
                // Local or remote profile name to get their last notice.
                // May throw an exception and report 'no such user'
                $recipient = $this->getProfile($arg);

                $notice = $recipient->getCurrentNotice();
                if (!$notice) {
                    // TRANS: Command exception text shown when a last user notice is requested and it does not exist.
                    throw new CommandException(_('User has no last notice.'));
                }
            }
        }
        Event::handle('EndCommandGetNotice', array($this, $arg, &$notice));
        if (!$notice) {
            // TRANS: Command exception text shown when a notice ID is requested that does not exist.
            throw new CommandException(_('Notice with that id does not exist.'));
        }
        return $notice;
    }

    /**
     * Look up a local or remote profile by nickname.
     *
     * @return Profile
     * @throws CommandException
     */
    function getProfile($arg)
    {
        $profile = null;
        if (Event::handle('StartCommandGetProfile', array($this, $arg, &$profile))) {
            $profile =
              common_relative_profile($this->user, common_canonical_nickname($arg));
        }
        Event::handle('EndCommandGetProfile', array($this, $arg, &$profile));
        if (!$profile) {
            // TRANS: Message given requesting a profile for a non-existing user.
            // TRANS: %s is the nickname of the user for which the profile could not be found.
            throw new CommandException(sprintf(_('Could not find a user with nickname %s.'), $arg));
        }
        return $profile;
    }

    /**
     * Get a local user by name
     * @return User
     * @throws CommandException
     */
    function getUser($arg)
    {
        $user = null;
        if (Event::handle('StartCommandGetUser', array($this, $arg, &$user))) {
            $user = User::getKV('nickname', Nickname::normalize($arg));
        }
        Event::handle('EndCommandGetUser', array($this, $arg, &$user));
        if (!$user){
            // TRANS: Message given getting a non-existing user.
            // TRANS: %s is the nickname of the user that could not be found.
            throw new CommandException(sprintf(_('Could not find a local user with nickname %s.'),
                               $arg));
        }
        return $user;
    }

    /**
     * Get a local or remote group by name.
     * @return User_group
     * @throws CommandException
     */
    function getGroup($arg)
    {
        $group = null;
        if (Event::handle('StartCommandGetGroup', array($this, $arg, &$group))) {
            $group = User_group::getForNickname($arg, $this->user->getProfile());
        }
        Event::handle('EndCommandGetGroup', array($this, $arg, &$group));
        if (!$group) {
            // TRANS: Command exception text shown when a group is requested that does not exist.
            throw new CommandException(_('No such group.'));
        }
        return $group;
    }
}

class CommandException extends Exception
{
}

class UnimplementedCommand extends Command
{
    function handle($channel)
    {
        // TRANS: Error text shown when an unimplemented command is given.
        $channel->error($this->user, _('Sorry, this command is not yet implemented.'));
    }
}

class TrackingCommand extends UnimplementedCommand
{
}

class TrackOffCommand extends UnimplementedCommand
{
}

class TrackCommand extends UnimplementedCommand
{
    var $word = null;
    function __construct($user, $word)
    {
        parent::__construct($user);
        $this->word = $word;
    }
}

class UntrackCommand extends UnimplementedCommand
{
    var $word = null;
    function __construct($user, $word)
    {
        parent::__construct($user);
        $this->word = $word;
    }
}

class NudgeCommand extends Command
{
    var $other = null;
    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        $recipient = $this->getUser($this->other);
        if ($recipient->id == $this->user->id) {
            // TRANS: Command exception text shown when a user tries to nudge themselves.
            throw new CommandException(_('It does not make a lot of sense to nudge yourself!'));
        } else {
            if ($recipient->email && $recipient->emailnotifynudge) {
                mail_notify_nudge($this->user, $recipient);
            }
            // XXX: notify by IM
            // XXX: notify by SMS
            // TRANS: Message given having nudged another user.
            // TRANS: %s is the nickname of the user that was nudged.
            $channel->output($this->user, sprintf(_('Nudge sent to %s.'),
                           $recipient->nickname));
        }
    }
}

class InviteCommand extends UnimplementedCommand
{
    var $other = null;
    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }
}

class StatsCommand extends Command
{
    function handle($channel)
    {
        $profile = $this->user->getProfile();

        $subs_count   = $profile->subscriptionCount();
        $subbed_count = $profile->subscriberCount();
        $notice_count = $profile->noticeCount();

        // TRANS: User statistics text.
        // TRANS: %1$s is the number of other user the user is subscribed to.
        // TRANS: %2$s is the number of users that are subscribed to the user.
        // TRANS: %3$s is the number of notices the user has sent.
        $channel->output($this->user, sprintf(_("Subscriptions: %1\$s\n".
                                   "Subscribers: %2\$s\n".
                                   "Notices: %3\$s"),
                                 $subs_count,
                                 $subbed_count,
                                 $notice_count));
    }
}

class JoinCommand extends Command
{
    var $other = null;

    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        $group = $this->getGroup($this->other);
        $cur   = $this->user;

        if ($cur->isMember($group)) {
            // TRANS: Error text shown a user tries to join a group they already are a member of.
            $channel->error($cur, _('You are already a member of that group.'));
            return;
        }
        if (Group_block::isBlocked($group, $cur->getProfile())) {
            // TRANS: Error text shown when a user tries to join a group they are blocked from joining.
          $channel->error($cur, _('You have been blocked from that group by the admin.'));
            return;
        }

        try {
            $cur->joinGroup($group);
        } catch (Exception $e) {
            // TRANS: Message given having failed to add a user to a group.
            // TRANS: %1$s is the nickname of the user, %2$s is the nickname of the group.
            $channel->error($cur, sprintf(_('Could not join user %1$s to group %2$s.'),
                                          $cur->nickname, $group->nickname));
            return;
        }

        // TRANS: Message given having added a user to a group.
        // TRANS: %1$s is the nickname of the user, %2$s is the nickname of the group.
        $channel->output($cur, sprintf(_('%1$s joined group %2$s.'),
                                              $cur->nickname,
                                              $group->nickname));
    }
}

class DropCommand extends Command
{
    var $other = null;

    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        $group = $this->getGroup($this->other);
        $cur   = $this->user;

        if (!$group) {
            // TRANS: Error text shown when trying to leave a group that does not exist.
            $channel->error($cur, _('No such group.'));
            return;
        }

        if (!$cur->isMember($group)) {
            // TRANS: Error text shown when trying to leave an existing group the user is not a member of.
            $channel->error($cur, _('You are not a member of that group.'));
            return;
        }

        try {
            $cur->leaveGroup($group);
        } catch (Exception $e) {
            // TRANS: Message given having failed to remove a user from a group.
            // TRANS: %1$s is the nickname of the user, %2$s is the nickname of the group.
            $channel->error($cur, sprintf(_('Could not remove user %1$s from group %2$s.'),
                                          $cur->nickname, $group->nickname));
            return;
        }

        // TRANS: Message given having removed a user from a group.
        // TRANS: %1$s is the nickname of the user, %2$s is the nickname of the group.
        $channel->output($cur, sprintf(_('%1$s left group %2$s.'),
                                              $cur->nickname,
                                              $group->nickname));
    }
}

class TagCommand extends Command
{
    var $other = null;
    var $tags = null;
    function __construct($user, $other, $tags)
    {
        parent::__construct($user);
        $this->other = $other;
        $this->tags = $tags;
    }

    function handle($channel)
    {
        $profile = $this->getProfile($this->other);
        $cur     = $this->user->getProfile();

        if (!$profile) {
            // TRANS: Client error displayed trying to perform an action related to a non-existing profile.
            $channel->error($cur, _('No such profile.'));
            return;
        }
        if (!$cur->canTag($profile)) {
            // TRANS: Error displayed when trying to tag a user that cannot be tagged.
            $channel->error($cur, _('You cannot tag this user.'));
            return;
        }

        $privs = array();
        $tags = preg_split('/[\s,]+/', $this->tags);
        $clean_tags = array();

        foreach ($tags as $tag) {
            $private = @$tag[0] === '.';
            $tag = $clean_tags[] = common_canonical_tag($tag);

            if (!common_valid_profile_tag($tag)) {
                // TRANS: Error displayed if a given tag is invalid.
                // TRANS: %s is the invalid tag.
                $channel->error($cur, sprintf(_('Invalid tag: "%s".'), $tag));
                return;
            }
            $privs[$tag] = $private;
        }

        try {
            foreach ($clean_tags as $tag) {
                Profile_tag::setTag($cur->id, $profile->id, $tag, null, $privs[$tag]);
            }
        } catch (Exception $e) {
            // TRANS: Error displayed if tagging a user fails.
            // TRANS: %1$s is the tagged user, %2$s is the error message (no punctuation).
            $channel->error($cur, sprintf(_('Error tagging %1$s: %2$s'),
                                          $profile->nickname, $e->getMessage()));
            return;
        }

        // TRANS: Succes message displayed if tagging a user succeeds.
        // TRANS: %1$s is the tagged user's nickname, %2$s is a list of tags.
        // TRANS: Plural is decided based on the number of tags added (not part of message).
        $channel->output($cur, sprintf(_m('%1$s was tagged %2$s',
                                          '%1$s was tagged %2$s',
                                          count($clean_tags)),
                                       $profile->nickname,
                                       // TRANS: Separator for list of tags.
                                       implode(_(', '), $clean_tags)));
    }
}

class UntagCommand extends TagCommand
{
    function handle($channel)
    {
        $profile = $this->getProfile($this->other);
        $cur     = $this->user->getProfile();

        if (!$profile) {
            // TRANS: Client error displayed trying to perform an action related to a non-existing profile.
            $channel->error($cur, _('No such profile.'));
            return;
        }
        if (!$cur->canTag($profile)) {
            // TRANS: Error displayed when trying to tag a user that cannot be tagged.
            $channel->error($cur, _('You cannot tag this user.'));
            return;
        }

        $tags = array_map('common_canonical_tag', preg_split('/[\s,]+/', $this->tags));

        foreach ($tags as $tag) {
            if (!common_valid_profile_tag($tag)) {
                // TRANS: Error displayed if a given tag is invalid.
                // TRANS: %s is the invalid tag.
                $channel->error($cur, sprintf(_('Invalid tag: "%s"'), $tag));
                return;
            }
        }

        try {
            foreach ($tags as $tag) {
                Profile_tag::unTag($cur->id, $profile->id, $tag);
            }
        } catch (Exception $e) {
            // TRANS: Error displayed if untagging a user fails.
            // TRANS: %1$s is the untagged user, %2$s is the error message (no punctuation).
            $channel->error($cur, sprintf(_('Error untagging %1$s: %2$s'),
                                          $profile->nickname, $e->getMessage()));
            return;
        }

        // TRANS: Succes message displayed if untagging a user succeeds.
        // TRANS: %1$s is the untagged user's nickname, %2$s is a list of tags.
        // TRANS: Plural is decided based on the number of tags removed (not part of message).
        $channel->output($cur, sprintf(_m('The following tag was removed from user %1$s: %2$s.',
                                         'The following tags were removed from user %1$s: %2$s.',
                                         count($tags)),
                                       $profile->nickname,
                                       // TRANS: Separator for list of tags.
                                       implode(_(', '), $tags)));
    }
}

class WhoisCommand extends Command
{
    var $other = null;
    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        $recipient = $this->getProfile($this->other);

        // TRANS: Whois output.
        // TRANS: %1$s nickname of the queried user, %2$s is their profile URL.
        $whois = sprintf(_m('WHOIS',"%1\$s (%2\$s)"), $recipient->nickname,
                         $recipient->profileurl);
        if ($recipient->fullname) {
            // TRANS: Whois output. %s is the full name of the queried user.
            $whois .= "\n" . sprintf(_('Fullname: %s'), $recipient->fullname);
        }
        if ($recipient->location) {
            // TRANS: Whois output. %s is the location of the queried user.
            $whois .= "\n" . sprintf(_('Location: %s'), $recipient->location);
        }
        if ($recipient->homepage) {
            // TRANS: Whois output. %s is the homepage of the queried user.
            $whois .= "\n" . sprintf(_('Homepage: %s'), $recipient->homepage);
        }
        if ($recipient->bio) {
            // TRANS: Whois output. %s is the bio information of the queried user.
            $whois .= "\n" . sprintf(_('About: %s'), $recipient->bio);
        }
        $channel->output($this->user, $whois);
    }
}

class ReplyCommand extends Command
{
    var $other = null;
    var $text = null;
    function __construct($user, $other, $text)
    {
        parent::__construct($user);
        $this->other = $other;
        $this->text = $text;
    }

    function handle($channel)
    {
        $notice = $this->getNotice($this->other);
        $recipient = $notice->getProfile();

        $len = mb_strlen($this->text);

        if ($len == 0) {
            // TRANS: Command exception text shown when trying to reply to a notice without providing content for the reply.
            $channel->error($this->user, _('No content!'));
            return;
        }

        $this->text = $this->user->shortenLinks($this->text);

        if (Notice::contentTooLong($this->text)) {
            // XXX: i18n. Needs plural support.
            // TRANS: Message given if content of a notice for a reply is too long. %1$d is used for plural.
            // TRANS: %1$d is the maximum number of characters, %2$d is the number of submitted characters.
            $channel->error($this->user, sprintf(_m('Notice too long - maximum is %1$d character, you sent %2$d.',
                                                    'Notice too long - maximum is %1$d characters, you sent %2$d.',
                                                    Notice::maxContent()),
                                                 Notice::maxContent(), mb_strlen($this->text)));
            return;
        }

        $notice = Notice::saveNew($this->user->id, $this->text, $channel->source(),
                                  array('reply_to' => $notice->id));

        if ($notice) {
            // TRANS: Text shown having sent a reply to a notice successfully.
            // TRANS: %s is the nickname of the user of the notice the reply was sent to.
            $channel->output($this->user, sprintf(_('Reply to %s sent.'), $recipient->nickname));
        } else {
            // TRANS: Error text shown when a reply to a notice fails with an unknown reason.
            $channel->error($this->user, _('Error saving notice.'));
        }

    }
}

class GetCommand extends Command
{
    var $other = null;

    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        $target = $this->getProfile($this->other);

        $notice = $target->getCurrentNotice();
        if (!$notice) {
            // TRANS: Error text shown when a last user notice is requested and it does not exist.
            $channel->error($this->user, _('User has no last notice.'));
            return;
        }
        $notice_content = $notice->content;

        $channel->output($this->user, $target->nickname . ": " . $notice_content);
    }
}

class SubCommand extends Command
{
    var $other = null;

    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {

        if (!$this->other) {
            // TRANS: Error text shown when no username was provided when issuing a subscribe command.
            $channel->error($this->user, _('Specify the name of the user to subscribe to.'));
            return;
        }

        $target = $this->getProfile($this->other);

        try {
            Subscription::start($this->user->getProfile(), $target);
            // TRANS: Text shown after having subscribed to another user successfully.
            // TRANS: %s is the name of the user the subscription was requested for.
            $channel->output($this->user, sprintf(_('Subscribed to %s.'), $this->other));
        } catch (Exception $e) {
            $channel->error($this->user, $e->getMessage());
        }
    }
}

class UnsubCommand extends Command
{
    var $other = null;

    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        if(!$this->other) {
            // TRANS: Error text shown when no username was provided when issuing an unsubscribe command.
            $channel->error($this->user, _('Specify the name of the user to unsubscribe from.'));
            return;
        }

        $target = $this->getProfile($this->other);

        try {
            Subscription::cancel($this->user->getProfile(), $target);
            // TRANS: Text shown after having unsubscribed from another user successfully.
            // TRANS: %s is the name of the user the unsubscription was requested for.
            $channel->output($this->user, sprintf(_('Unsubscribed from %s.'), $this->other));
        } catch (Exception $e) {
            $channel->error($this->user, $e->getMessage());
        }
    }
}

class OffCommand extends Command
{
    var $other = null;

    function __construct($user, $other=null)
    {
        parent::__construct($user);
        $this->other = $other;
    }
    function handle($channel)
    {
        if ($this->other) {
            // TRANS: Error text shown when issuing the command "off" with a setting which has not yet been implemented.
            $channel->error($this->user, _("Command not yet implemented."));
        } else {
            if ($channel->off($this->user)) {
                // TRANS: Text shown when issuing the command "off" successfully.
                $channel->output($this->user, _('Notification off.'));
            } else {
                // TRANS: Error text shown when the command "off" fails for an unknown reason.
                $channel->error($this->user, _('Can\'t turn off notification.'));
            }
        }
    }
}

class OnCommand extends Command
{
    var $other = null;
    function __construct($user, $other=null)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function handle($channel)
    {
        if ($this->other) {
            // TRANS: Error text shown when issuing the command "on" with a setting which has not yet been implemented.
            $channel->error($this->user, _("Command not yet implemented."));
        } else {
            if ($channel->on($this->user)) {
                // TRANS: Text shown when issuing the command "on" successfully.
                $channel->output($this->user, _('Notification on.'));
            } else {
                // TRANS: Error text shown when the command "on" fails for an unknown reason.
                $channel->error($this->user, _('Can\'t turn on notification.'));
            }
        }
    }
}

class LoginCommand extends Command
{
    function handle($channel)
    {
        $disabled = common_config('logincommand','disabled');
        $disabled = isset($disabled) && $disabled;
        if($disabled) {
            // TRANS: Error text shown when issuing the login command while login is disabled.
            $channel->error($this->user, _('Login command is disabled.'));
            return;
        }

        try {
            $login_token = Login_token::makeNew($this->user);
        } catch (Exception $e) {
            $channel->error($this->user, $e->getMessage());
        }

        $channel->output($this->user,
            // TRANS: Text shown after issuing the login command successfully.
            // TRANS: %s is a logon link..
            sprintf(_('This link is useable only once and is valid for only 2 minutes: %s.'),
                    common_local_url('otp',
                        array('user_id' => $login_token->user_id, 'token' => $login_token->token))));
    }
}

class LoseCommand extends Command
{
    var $other = null;

    function __construct($user, $other)
    {
        parent::__construct($user);
        $this->other = $other;
    }

    function execute($channel)
    {
        if(!$this->other) {
            // TRANS: Error text shown when no username was provided when issuing the command.
            $channel->error($this->user, _('Specify the name of the user to unsubscribe from.'));
            return;
        }

        $result = Subscription::cancel($this->getProfile($this->other), $this->user->getProfile());

        if ($result) {
            // TRANS: Text shown after issuing the lose command successfully (stop another user from following the current user).
            // TRANS: %s is the name of the user the unsubscription was requested for.
            $channel->output($this->user, sprintf(_('Unsubscribed %s.'), $this->other));
        } else {
            $channel->error($this->user, $result);
        }
    }
}

class SubscriptionsCommand extends Command
{
    function handle($channel)
    {
        $profile = $this->user->getSubscribed(0);
        $nicknames=array();
        while ($profile->fetch()) {
            $nicknames[]=$profile->nickname;
        }
        if(count($nicknames)==0){
            // TRANS: Text shown after requesting other users a user is subscribed to without having any subscriptions.
            $out=_('You are not subscribed to anyone.');
        }else{
            // TRANS: Text shown after requesting other users a user is subscribed to.
            // TRANS: This message supports plural forms. This message is followed by a
            // TRANS: hard coded space and a comma separated list of subscribed users.
            $out = _m('You are subscribed to this person:',
                'You are subscribed to these people:',
                count($nicknames));
            $out .= ' ';
            $out .= implode(', ',$nicknames);
        }
        $channel->output($this->user,$out);
    }
}

class SubscribersCommand extends Command
{
    function handle($channel)
    {
        $profile = $this->user->getSubscribers();
        $nicknames=array();
        while ($profile->fetch()) {
            $nicknames[]=$profile->nickname;
        }
        if(count($nicknames)==0){
            // TRANS: Text shown after requesting other users that are subscribed to a user
            // TRANS: (followers) without having any subscribers.
            $out=_('No one is subscribed to you.');
        }else{
            // TRANS: Text shown after requesting other users that are subscribed to a user (followers).
            // TRANS: This message supports plural forms. This message is followed by a
            // TRANS: hard coded space and a comma separated list of subscribing users.
            $out = _m('This person is subscribed to you:',
                'These people are subscribed to you:',
                count($nicknames));
            $out .= ' ';
            $out .= implode(', ',$nicknames);
        }
        $channel->output($this->user,$out);
    }
}

class GroupsCommand extends Command
{
    function handle($channel)
    {
        $group = $this->user->getGroups();
        $groups=array();
        while ($group instanceof User_group && $group->fetch()) {
            $groups[]=$group->nickname;
        }
        if(count($groups)==0){
            // TRANS: Text shown after requesting groups a user is subscribed to without having
            // TRANS: any group subscriptions.
            $out=_('You are not a member of any groups.');
        }else{
            // TRANS: Text shown after requesting groups a user is subscribed to.
            // TRANS: This message supports plural forms. This message is followed by a
            // TRANS: hard coded space and a comma separated list of subscribed groups.
            $out = _m('You are a member of this group:',
                'You are a member of these groups:',
                count($nicknames));
            $out.=implode(', ',$groups);
        }
        $channel->output($this->user,$out);
    }
}

class HelpCommand extends Command
{
    function handle($channel)
    {
        // TRANS: Header line of help text for commands.
        $out = array(_m('COMMANDHELP', "Commands:"));
        $commands = array(// TRANS: Help message for IM/SMS command "on".
                          "on" => _m('COMMANDHELP', "turn on notifications"),
                          // TRANS: Help message for IM/SMS command "off".
                          "off" => _m('COMMANDHELP', "turn off notifications"),
                          // TRANS: Help message for IM/SMS command "help".
                          "help" => _m('COMMANDHELP', "show this help"),
                          // TRANS: Help message for IM/SMS command "follow <nickname>".
                          "follow <nickname>" => _m('COMMANDHELP', "subscribe to user"),
                          // TRANS: Help message for IM/SMS command "groups".
                          "groups" => _m('COMMANDHELP', "lists the groups you have joined"),
                          // TRANS: Help message for IM/SMS command "tag".
                          "tag <nickname> <tags>" => _m('COMMANDHELP',"tag a user"),
                          // TRANS: Help message for IM/SMS command "untag".
                          "untag <nickname> <tags>" => _m('COMMANDHELP',"untag a user"),
                          // TRANS: Help message for IM/SMS command "subscriptions".
                          "subscriptions" => _m('COMMANDHELP', "list the people you follow"),
                          // TRANS: Help message for IM/SMS command "subscribers".
                          "subscribers" => _m('COMMANDHELP', "list the people that follow you"),
                          // TRANS: Help message for IM/SMS command "leave <nickname>".
                          "leave <nickname>" => _m('COMMANDHELP', "unsubscribe from user"),
                          // TRANS: Help message for IM/SMS command "d <nickname> <text>".
                          "d <nickname> <text>" => _m('COMMANDHELP', "direct message to user"),
                          // TRANS: Help message for IM/SMS command "get <nickname>".
                          "get <nickname>" => _m('COMMANDHELP', "get last notice from user"),
                          // TRANS: Help message for IM/SMS command "whois <nickname>".
                          "whois <nickname>" => _m('COMMANDHELP', "get profile info on user"),
                          // TRANS: Help message for IM/SMS command "lose <nickname>".
                          "lose <nickname>" => _m('COMMANDHELP', "force user to stop following you"),
                          // TRANS: Help message for IM/SMS command "reply #<notice_id>".
                          "reply #<notice_id>" => _m('COMMANDHELP', "reply to notice with a given id"),
                          // TRANS: Help message for IM/SMS command "reply <nickname>".
                          "reply <nickname>" => _m('COMMANDHELP', "reply to the last notice from user"),
                          // TRANS: Help message for IM/SMS command "join <group>".
                          "join <group>" => _m('COMMANDHELP', "join group"),
                          // TRANS: Help message for IM/SMS command "login".
                          "login" => _m('COMMANDHELP', "Get a link to login to the web interface"),
                          // TRANS: Help message for IM/SMS command "drop <group>".
                          "drop <group>" => _m('COMMANDHELP', "leave group"),
                          // TRANS: Help message for IM/SMS command "stats".
                          "stats" => _m('COMMANDHELP', "get your stats"),
                          // TRANS: Help message for IM/SMS command "stop".
                          "stop" => _m('COMMANDHELP', "same as 'off'"),
                          // TRANS: Help message for IM/SMS command "quit".
                          "quit" => _m('COMMANDHELP', "same as 'off'"),
                          // TRANS: Help message for IM/SMS command "sub <nickname>".
                          "sub <nickname>" => _m('COMMANDHELP', "same as 'follow'"),
                          // TRANS: Help message for IM/SMS command "unsub <nickname>".
                          "unsub <nickname>" => _m('COMMANDHELP', "same as 'leave'"),
                          // TRANS: Help message for IM/SMS command "last <nickname>".
                          "last <nickname>" => _m('COMMANDHELP', "same as 'get'"),
                          // TRANS: Help message for IM/SMS command "on <nickname>".
                          "on <nickname>" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "off <nickname>".
                          "off <nickname>" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "nudge <nickname>".
                          "nudge <nickname>" => _m('COMMANDHELP', "remind a user to update."),
                          // TRANS: Help message for IM/SMS command "invite <phone number>".
                          "invite <phone number>" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "track <word>".
                          "track <word>" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "untrack <word>".
                          "untrack <word>" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "track off".
                          "track off" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "untrack all".
                          "untrack all" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "tracks".
                          "tracks" => _m('COMMANDHELP', "not yet implemented."),
                          // TRANS: Help message for IM/SMS command "tracking".
                          "tracking" => _m('COMMANDHELP', "not yet implemented."));

        // Give plugins a chance to add or override...
        Event::handle('HelpCommandMessages', array($this, &$commands));

        ksort($commands);
        foreach ($commands as $command => $help) {
            $out[] = "$command - $help";
        }
        $channel->output($this->user, implode("\n", $out));
    }
}
