/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2021 Dominic Hamon
 *   Copyright (C) 2020-2023 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2019 Robby <robby@chatbelgie.be>
 *   Copyright (C) 2013, 2016 Attila Molnar <attilamolnar@hush.com>
 *
 * 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/>.
 */


#pragma once

class StreamSocket;

class IOHookProvider
	: public std::enable_shared_from_this<IOHookProvider>
	, public ServiceProvider
{
	const bool middlehook;

public:
	enum Type
	{
		IOH_UNKNOWN,
		IOH_SSL
	};

	const Type type;

	/** Constructor
	 * @param mod Module that owns the IOHookProvider
	 * @param Name Name of the provider
	 * @param hooktype One of IOHookProvider::Type
	 * @param middle True if the IOHook instances created by this hook are subclasses of IOHookMiddle, false otherwise
	 */
	IOHookProvider(Module* mod, const std::string& Name, Type hooktype = IOH_UNKNOWN, bool middle = false)
		: ServiceProvider(mod, Name, SERVICE_IOHOOK)
		, middlehook(middle)
		, type(hooktype)
	{
	}

	/** Check if the IOHook provided can appear in the non-last position of a hook chain.
	 * That is the case if and only if the IOHook instances created are subclasses of IOHookMiddle.
	 * @return True if the IOHooks provided are subclasses of IOHookMiddle
	 */
	bool IsMiddle() const { return middlehook; }

	/** Called when the provider should hook an incoming connection and act as being on the server-side of the connection.
	 * This occurs when a bind block has a hook configured and the listener accepts a connection.
	 * @param sock Socket to hook
	 * @param client Client IP address and port
	 * @param server Server IP address and port
	 */
	virtual void OnAccept(StreamSocket* sock, const irc::sockets::sockaddrs& client, const irc::sockets::sockaddrs& server) = 0;

	/** Called when the provider should hook an outgoing connection and act as being on the client side of the connection.
	 * @param sock Socket to hook
	 */
	virtual void OnConnect(StreamSocket* sock) = 0;
};

class IOHook
	: public Cullable
{
public:
	/** The IOHookProvider for this hook, contains information about the hook,
	 * such as the module providing it and the hook type.
	 */
	std::shared_ptr<IOHookProvider> prov;

	/** Constructor
	 * @param provider IOHookProvider that creates this object
	 */
	IOHook(const std::shared_ptr<IOHookProvider>& provider)
		: prov(provider)
	{
	}

	/** Determines whether this I/O hook is ready to send and receive data. */
	virtual bool IsHookReady() const { return true; }

	/**
	 * Called when the hooked socket has data to write, or when the socket engine returns it as writable
	 * @param sock Hooked socket
	 * @param sendq Send queue to send data from
	 * @return 1 if the sendq has been completely emptied, 0 if there is
	 *  still data to send, and -1 if there was an error
	 */
	virtual ssize_t OnStreamSocketWrite(StreamSocket* sock, StreamSocket::SendQueue& sendq) = 0;

	/** Called immediately before the hooked socket is closed. When this event is called, shutdown()
	 * has not yet been called on the socket.
	 * @param sock Hooked socket
	 */
	virtual void OnStreamSocketClose(StreamSocket* sock) = 0;

	/**
	 * Called when the hooked socket has data to read
	 * @param sock Hooked socket
	 * @param recvq The receive queue that new data should be appended to
	 * @return 1 if new data has been read, 0 if no new data is ready (but the
	 *  socket is still connected), -1 if there was an error or close
	 */
	virtual ssize_t OnStreamSocketRead(StreamSocket* sock, std::string& recvq) = 0;

	/** Sends a ping to the remote client to check whether it is still connected.
	 * @return True if the client was pinged; otherwise, false.
	 */
	virtual bool Ping() { return false; }
};

class IOHookMiddle
	: public IOHook
{
	/** Data already processed by the IOHook waiting to go down the chain
	 */
	StreamSocket::SendQueue sendq;

	/** Data waiting to go up the chain
	 */
	std::string precvq;

	/** Next IOHook in the chain
	 */
	IOHook* nexthook = nullptr;

protected:
	/** Get all queued up data which has not yet been passed up the hook chain
	 * @return RecvQ containing the data
	 */
	std::string& GetRecvQ() { return precvq; }

	/** Get all queued up data which is ready to go down the hook chain
	 * @return SendQueue containing all data waiting to go down the hook chain
	 */
	StreamSocket::SendQueue& GetSendQ() { return sendq; }

public:
	/** Constructor
	 * @param provider IOHookProvider that creates this object
	 */
	IOHookMiddle(const std::shared_ptr<IOHookProvider>& provider)
		: IOHook(provider)
	{
	}

	/** @copydoc IOHook::OnStreamSocketClose */
	void OnStreamSocketClose(StreamSocket* sock) override { }

	/** Get all queued up data which is ready to go down the hook chain
	 * @return SendQueue containing all data waiting to go down the hook chain
	 */
	const StreamSocket::SendQueue& GetSendQ() const { return sendq; }

	/** Get the next IOHook in the chain
	 * @return Next hook in the chain or NULL if this is the last hook
	 */
	IOHook* GetNextHook() const { return nexthook; }

	/** Set the next hook in the chain
	 * @param hook Hook to set as the next hook in the chain
	 */
	void SetNextHook(IOHook* hook) { nexthook = hook; }

	/** Check if a hook is capable of being the non-last hook in a hook chain and if so, cast it to an IOHookMiddle object.
	 * @param hook IOHook to check
	 * @return IOHookMiddle referring to the same hook or NULL
	 */
	static IOHookMiddle* ToMiddleHook(IOHook* hook)
	{
		if (hook->prov->IsMiddle())
			return static_cast<IOHookMiddle*>(hook);
		return nullptr;
	}

	friend class StreamSocket;
};