/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2013, 2017-2018, 2020 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2013, 2015 Attila Molnar <attilamolnar@hush.com>
 *   Copyright (C) 2012 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2009-2010 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2009 Uli Schlachter <psychon@inspircd.org>
 *   Copyright (C) 2007 Robin Burchell <robin+git@viroteck.net>
 *   Copyright (C) 2007 Dennis Friis <peavey@inspircd.org>
 *   Copyright (C) 2006 Craig Edwards <brain@inspircd.org>
 *
 * This file is part of InspIRCd.  InspIRCd is free software: you can
 * redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation, version 2.
 *
 * 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 General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "inspircd.h"
#include "modules/whois.h"

enum
{
	// From UnrealIRCd.
	RPL_WHOISHELPOP = 310,

	// From ircd-ratbox.
	ERR_HELPNOTFOUND = 524,
	RPL_HELPSTART = 704,
	RPL_HELPTXT = 705,
	RPL_ENDOFHELP = 706
};

typedef std::vector<std::string> HelpMessage;

struct HelpTopic
{
	// The body of the help topic.
	const HelpMessage body;

	// The title of the help topic.
	const std::string title;

	HelpTopic(const HelpMessage& Body, const std::string& Title)
		: body(Body)
		, title(Title)
	{
	}
};

typedef std::map<std::string, HelpTopic, irc::insensitive_swo> HelpMap;

class CommandHelpop : public Command
{
 private:
	const std::string startkey;

 public:
	HelpMap help;
	std::string nohelp;

	CommandHelpop(Module* Creator)
		: Command(Creator, "HELPOP", 0)
		, startkey("start")
	{
		syntax = "<any-text>";
	}

	CmdResult Handle(User* user, const Params& parameters) CXX11_OVERRIDE
	{
		const std::string& topic = parameters.empty() ? startkey : parameters[0];
		HelpMap::const_iterator titer = help.find(topic);
		if (titer == help.end())
		{
			user->WriteNumeric(ERR_HELPNOTFOUND, topic, nohelp);
			return CMD_FAILURE;
		}

		const HelpTopic& entry = titer->second;
		user->WriteNumeric(RPL_HELPSTART, topic, entry.title);
		for (HelpMessage::const_iterator liter = entry.body.begin(); liter != entry.body.end(); ++liter)
			user->WriteNumeric(RPL_HELPTXT, topic, *liter);
		user->WriteNumeric(RPL_ENDOFHELP, topic, "End of /HELPOP.");
		return CMD_SUCCESS;
	}
};

class ModuleHelpop
	: public Module
	, public Whois::EventListener
{
 private:
		CommandHelpop cmd;
		SimpleUserModeHandler ho;

	public:
		ModuleHelpop()
			: Whois::EventListener(this)
			, cmd(this)
			, ho(this, "helpop", 'h', true)
		{
		}

		void ReadConfig(ConfigStatus& status) CXX11_OVERRIDE
		{
			size_t longestkey = 0;

			HelpMap newhelp;
			ConfigTagList tags = ServerInstance->Config->ConfTags("helpop");
			if (tags.first == tags.second)
				throw ModuleException("You have loaded the helpop module but not configured any help topics!");

			for (ConfigIter i = tags.first; i != tags.second; ++i)
			{
				ConfigTag* tag = i->second;

				// Attempt to read the help key.
				const std::string key = tag->getString("key");
				if (key.empty())
					throw ModuleException(InspIRCd::Format("<helpop:key> is empty at %s", tag->getTagLocation().c_str()));
				else if (irc::equals(key, "index"))
					throw ModuleException(InspIRCd::Format("<helpop:key> is set to \"index\" which is reserved at %s", tag->getTagLocation().c_str()));
				else if (key.length() > longestkey)
					longestkey = key.length();

				// Attempt to read the help value.
				std::string value;
				if (!tag->readString("value", value, true) || value.empty())
					throw ModuleException(InspIRCd::Format("<helpop:value> is empty at %s", tag->getTagLocation().c_str()));

				// Parse the help body. Empty lines are replaced with a single
				// space because some clients are unable to show blank lines.
				HelpMessage helpmsg;
				irc::sepstream linestream(value, '\n', true);
				for (std::string line; linestream.GetToken(line); )
					helpmsg.push_back(line.empty() ? " " : line);

				// Read the help title and store the topic.
				const std::string title = tag->getString("title", InspIRCd::Format("*** Help for %s", key.c_str()), 1);
				if (!newhelp.insert(std::make_pair(key, HelpTopic(helpmsg, title))).second)
				{
					throw ModuleException(InspIRCd::Format("<helpop> tag with duplicate key '%s' at %s",
						key.c_str(), tag->getTagLocation().c_str()));
				}
			}

			// The number of items we can fit on a page.
			HelpMessage indexmsg;
			size_t maxcolumns = 80 / (longestkey + 2);
			for (HelpMap::iterator iter = newhelp.begin(); iter != newhelp.end(); )
			{
				std::string indexline;
				for (size_t column = 0; column != maxcolumns; )
				{
					if (iter == newhelp.end())
						break;

					indexline.append(iter->first);
					if (++column != maxcolumns)
						indexline.append(longestkey - iter->first.length() + 2, ' ');
					iter++;
				}
				indexmsg.push_back(indexline);
			}
			newhelp.insert(std::make_pair("index", HelpTopic(indexmsg, "List of help topics")));
			cmd.help.swap(newhelp);

			ConfigTag* tag = ServerInstance->Config->ConfValue("helpmsg");
			cmd.nohelp = tag->getString("nohelp", "There is no help for the topic you searched for. Please try again.", 1);
		}

		void OnWhois(Whois::Context& whois) CXX11_OVERRIDE
		{
			if (whois.GetTarget()->IsModeSet(ho))
				whois.SendLine(RPL_WHOISHELPOP, "is available for help.");
		}

		Version GetVersion() CXX11_OVERRIDE
		{
			return Version("Adds the /HELPOP command which allows users to view help on various topics and user mode h (helpop) which marks a server operator as being available for help.", VF_VENDOR);
		}
};

MODULE_INIT(ModuleHelpop)