metamod-r/metamod/include/dlls/hookchains.h

/*
*
*    This program 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; either version 2 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
*    General Public License for more details.
*
*    You should have received a copy of the GNU General Public License
*    along with this program; if not, write to the Free Software Foundation,
*    Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*
*    In addition, as a special exception, the author gives permission to
*    link the code of this program with the Half-Life Game Engine ("HL
*    Engine") and Modified Game Libraries ("MODs") developed by Valve,
*    L.L.C ("Valve").  You must obey the GNU General Public License in all
*    respects for all of the code used other than the HL Engine and MODs
*    from Valve.  If you modify this file, you may extend this exception
*    to your version of the file, but you are not obligated to do so.  If
*    you do not wish to do so, delete this exception statement from your
*    version.
*
*/
#pragma once

template<typename t_ret, typename ...t_args>
class IHookChain {
protected:
	virtual ~IHookChain() {}

public:
	virtual t_ret callNext(t_args... args) = 0;
	virtual t_ret callOriginal(t_args... args) = 0;
};

template<typename t_ret, typename t_class, typename ...t_args>
class IHookChainClass {
protected:
	virtual ~IHookChainClass() {}

public:
	virtual t_ret callNext(t_class *, t_args... args) = 0;
	virtual t_ret callOriginal(t_class *, t_args... args) = 0;
};

template<typename ...t_args>
class IVoidHookChain
{
protected:
	virtual ~IVoidHookChain() {}

public:
	virtual void callNext(t_args... args) = 0;
	virtual void callOriginal(t_args... args) = 0;
};

template<typename t_class, typename ...t_args>
class IVoidHookChainClass
{
protected:
	virtual ~IVoidHookChainClass() {}

public:
	virtual void callNext(t_class *, t_args... args) = 0;
	virtual void callOriginal(t_class *, t_args... args) = 0;
};

// Specifies priorities for hooks call order in the chain.
// For equal priorities first registered hook will be called first.
enum HookChainPriority
{
	HC_PRIORITY_UNINTERRUPTABLE = 255,  // Hook will be called before other hooks.
	HC_PRIORITY_HIGH = 192,             // Hook will be called before hooks with default priority.
	HC_PRIORITY_DEFAULT = 128,          // Default hook call priority.
	HC_PRIORITY_MEDIUM = 64,            // Hook will be called after hooks with default priority.
	HC_PRIORITY_LOW = 0,                // Hook will be called after all other hooks.
};

// Hook chain registry(for hooks [un]registration)
template<typename t_ret, typename ...t_args>
class IHookChainRegistry {
public:
	typedef t_ret(*hookfunc_t)(IHookChain<t_ret, t_args...>*, t_args...);

	virtual void registerHook(hookfunc_t hook, int priority = HC_PRIORITY_DEFAULT) = 0;
	virtual void unregisterHook(hookfunc_t hook) = 0;
};

// Hook chain registry(for hooks [un]registration)
template<typename t_ret, typename t_class, typename ...t_args>
class IHookChainRegistryClass {
public:
	typedef t_ret(*hookfunc_t)(IHookChainClass<t_ret, t_class, t_args...>*, t_class *, t_args...);

	virtual void registerHook(hookfunc_t hook, int priority = HC_PRIORITY_DEFAULT) = 0;
	virtual void unregisterHook(hookfunc_t hook) = 0;
};

// Hook chain registry(for hooks [un]registration)
template<typename ...t_args>
class IVoidHookChainRegistry {
public:
	typedef void(*hookfunc_t)(IVoidHookChain<t_args...>*, t_args...);

	virtual void registerHook(hookfunc_t hook, int priority = HC_PRIORITY_DEFAULT) = 0;
	virtual void unregisterHook(hookfunc_t hook) = 0;
};

// Hook chain registry(for hooks [un]registration)
template<typename t_class, typename ...t_args>
class IVoidHookChainRegistryClass {
public:
	typedef void(*hookfunc_t)(IVoidHookChainClass<t_class, t_args...>*, t_class *, t_args...);

	virtual void registerHook(hookfunc_t hook, int priority = HC_PRIORITY_DEFAULT) = 0;
	virtual void unregisterHook(hookfunc_t hook) = 0;
};