/**

 * vim: set ts=4 :

 * =============================================================================

 * SourceMod

 * Copyright (C) 2004-2008 AlliedModders LLC.  All rights reserved.

 * =============================================================================

 *

 * This program is free software; you can redistribute it and/or modify it under

 * the terms of the GNU General Public License, version 3.0, as published by the

 * Free Software Foundation.

 * 

 * 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/>.

 *

 * As a special exception, AlliedModders LLC gives you permission to link the

 * code of this program (as well as its derivative works) to "Half-Life 2," the

 * "Source Engine," the "SourcePawn JIT," and any Game MODs that run on software

 * by the Valve Corporation.  You must obey the GNU General Public License in

 * all respects for all other code used.  Additionally, AlliedModders LLC grants

 * this exception to all derivative works.  AlliedModders LLC defines further

 * exceptions, found in LICENSE.txt (as of this writing, version JULY-31-2007),

 * or <http://www.sourcemod.net/license.php>.

 *

 * Version: $Id$

 */

#ifndef _INCLUDE_SOURCEMOD_HANDLESYSTEM_INTERFACE_H_

#define _INCLUDE_SOURCEMOD_HANDLESYSTEM_INTERFACE_H_

/**

 * @file IHandleSys.h

 * @brief Defines the interface for creating, reading, and removing Handles.

 * 

 *  The Handle system abstracts generic pointers into typed objects represented by 

 * 32bit codes.  This is extremely useful for verifying data integrity and cross-platform

 * support in SourcePawn scripts.  When a Plugin unloads, all its Handles are freed, ensuring 

 * that no memory leaks are present,  They have reference counts and thus can be duplicated, 

 * or cloned, and are safe to pass between Plugins even if one is unloaded.

 *

 *  Handles are created with a given type (custom types may be created).  They can have

 * per-Identity permissions for deletion, reading, and cloning.  They also support generic

 * operations.  For example, deleting a Handle will call that type's destructor on the generic

 * pointer, making cleanup easier for users and eliminating memory leaks.

 */

#include <IShareSys.h>

#include <sp_vm_types.h>

#define SMINTERFACE_HANDLESYSTEM_NAME			"IHandleSys"

#define SMINTERFACE_HANDLESYSTEM_VERSION		5

/** Specifies no Identity */

#define DEFAULT_IDENTITY			NULL

/** Specifies no Type.  This is invalid for everything but reading a Handle. */

#define NO_HANDLE_TYPE				0

/** Specifies an invalid/NULL Handle */

#define BAD_HANDLE					0

namespace SourceMod

{

	/**

	 * @brief Represents a Handle Type ID.

	 */

	typedef unsigned int HandleType_t;

	/**

	 * @brief Represents a Handle ID.

	 */

	typedef unsigned int Handle_t;

	/*

	 * About type checking:

	 * Types can be inherited - a Parent type ("Supertype") can have child types.

	 * When accessing handles, type checking is done.  This table shows how this is resolved:

	 *

	 * HANDLE		CHECK		->  RESULT

	 * ------		-----			------

	 * Parent		Parent			Success

	 * Parent		Child			Fail

	 * Child		Parent			Success

	 * Child		Child			Success

	 */

	/**

	 * @brief Lists the possible handle error codes.

	 */

	enum HandleError

	{

		HandleError_None = 0,		/**< No error */

		HandleError_Changed,		/**< The handle has been freed and reassigned */

		HandleError_Type,			/**< The handle has a different type registered */

		HandleError_Freed,			/**< The handle has been freed */

		HandleError_Index,			/**< generic internal indexing error */

		HandleError_Access,			/**< No access permitted to free this handle */

		HandleError_Limit,			/**< The limited number of handles has been reached */

		HandleError_Identity,		/**< The identity token was not usable */

		HandleError_Owner,			/**< Owners do not match for this operation */

		HandleError_Version,		/**< Unrecognized security structure version */

		HandleError_Parameter,		/**< An invalid parameter was passed */

		HandleError_NoInherit,		/**< This type cannot be inherited */

	};

	/**

	 * @brief Lists access rights specific to a type.

	 */

	enum HTypeAccessRight

	{

		HTypeAccess_Create = 0,		/**< Handles of this type can be created (DEFAULT=false) */

		HTypeAccess_Inherit,		/**< Sub-types can inherit this type (DEFAULT=false) */

		/* -------------- */

		HTypeAccess_TOTAL,			/**< Total number of type access rights */

	};

	/**

	 * @brief Lists access rights specific to a Handle.  

	 * 

	 * These rights are exclusive. For example, you do not need "read" access to delete or clone.

	 */

	enum HandleAccessRight

	{

		HandleAccess_Read,			/**< Can be read (DEFAULT=ident only) */

		HandleAccess_Delete,		/**< Can be deleted (DEFAULT=owner only) */

		HandleAccess_Clone,			/**< Can be cloned (DEFAULT=any) */

		/* ------------- */

		HandleAccess_TOTAL,			/**< Total number of access rights */

	};

	/** Access is restricted to the identity */

	#define HANDLE_RESTRICT_IDENTITY	(1<<0)	

	/** Access is restricted to the owner */

	#define HANDLE_RESTRICT_OWNER		(1<<1)

	/**

	 * @brief This is used to define per-type access rights.

	 */

	struct TypeAccess

	{

		/** Constructor */

		TypeAccess()

		{

			hsVersion = SMINTERFACE_HANDLESYSTEM_VERSION;

		}

		unsigned int hsVersion;			/**< Handle API version */

		IdentityToken_t *ident;			/**< Identity owning this type */

		bool access[HTypeAccess_TOTAL];	/**< Access array */

	};

	/**

	 * @brief This is used to define per-Handle access rights.

	 */

	struct HandleAccess

	{

		/** Constructor */

		HandleAccess()

		{

			hsVersion = SMINTERFACE_HANDLESYSTEM_VERSION;

		}

		unsigned int hsVersion;						/**< Handle API version */

		unsigned int access[HandleAccess_TOTAL];	/**< Access array */

	};

	/**

	 * @brief This pair of tokens is used for identification.

	 */

	struct HandleSecurity

	{

		HandleSecurity()

		{

		}

		HandleSecurity(IdentityToken_t *owner, IdentityToken_t *identity)

			: pOwner(owner), pIdentity(identity)

		{

		}

		IdentityToken_t *pOwner;			/**< Owner of the Handle */

		IdentityToken_t *pIdentity;			/**< Owner of the Type */

	};

	/**

	 * @brief Hooks type-specific Handle operations.

	 */

	class IHandleTypeDispatch

	{

	public:

		/** Returns the Handle API version */

		virtual unsigned int GetDispatchVersion()

		{

			return SMINTERFACE_HANDLESYSTEM_VERSION;

		}

	public:

		/**

		 * @brief Called when destroying a handle.  Must be implemented.

		 *

		 * @param type		Handle type.

		 * @param object	Handle internal object.

		 */

		virtual void OnHandleDestroy(HandleType_t type, void *object) =0;

		/**

		 * @brief Called to get the size of a handle's memory usage in bytes.

		 * Implementation is optional.

		 *

		 * @param type		Handle type.

		 * @param object	Handle internal object.

		 * @param pSize		Pointer to store the approximate memory usage in bytes.

		 * @return			True on success, false if not implemented.

		 */

		virtual bool GetHandleApproxSize(HandleType_t type, void *object, unsigned int *pSize)

		{

			return false;

		}

	};

	/**

	 * @brief Provides functions for managing Handles.

	 */

	class IHandleSys : public SMInterface

	{

	public:

		virtual unsigned int GetInterfaceVersion()

		{

			return SMINTERFACE_HANDLESYSTEM_VERSION;

		}

		virtual const char *GetInterfaceName()

		{

			return SMINTERFACE_HANDLESYSTEM_NAME;

		}

	public:

		/**

		 * @brief Creates a new Handle type.

		 * NOTE: Currently, a child type may not have its own children.

		 * NOTE: Handle names must be unique if not private.

		 *

		 * @param name		Name of handle type (NULL or "" to be anonymous)

		 * @param dispatch	Pointer to a valid IHandleTypeDispatch object.

		 * @param parent	Parent handle to inherit from, 0 for none.

		 * @param typeAccess	Pointer to a TypeAccess object, NULL to use default 

		 *						or inherited permissions.  Pointer can be temporary.

		 * @param hndlAccess	Pointer to a HandleAccess object to define default

		 *						default permissions on each Handle.  NULL to use default

		 *						permissions.

		 * @param ident		Security token for any permissions.  If typeAccess is NULL, this 

		 *					becomes the owning identity.

		 * @param err		Optional pointer to store an error code on failure (undefined on success).

		 * @return			A new HandleType_t unique ID, or 0 on failure.

		 */

		virtual HandleType_t CreateType(const char *name,

										  IHandleTypeDispatch *dispatch,

										  HandleType_t parent,

										  const TypeAccess *typeAccess,

										  const HandleAccess *hndlAccess,

										  IdentityToken_t *ident,

										  HandleError *err) =0;

		/**

		 * @brief Removes a handle type.

		 * NOTE: This removes all child types.

		 *

		 * @param type		Type chain to remove.

		 * @param ident		Identity token.  Removal fails if the token does not match.

		 * @return			True on success, false on failure.

		 */

		virtual bool RemoveType(HandleType_t type, IdentityToken_t *ident) =0;

		/**

		 * @brief Finds a handle type by name.

		 *

		 * @param name		Name of handle type to find (anonymous not allowed).

		 * @param type		Address to store found handle in (if not found, undefined).

		 * @return			True if found, false otherwise.

		 */

		virtual bool FindHandleType(const char *name, HandleType_t *type) =0;

		/**

		 * @brief Creates a new handle.

		 * 

		 * @param type		Type to use on the handle.

		 * @param object	Object to bind to the handle.

		 * @param owner		Owner of the new Handle (may be NULL).

		 * @param ident		Identity for type access if needed (may be NULL).

		 * @param err		Optional pointer to store an error code on failure (undefined on success).

		 * @return			A new Handle_t, or 0 on failure.

		 */

		virtual Handle_t CreateHandle(HandleType_t type, 

									  void *object,

									  IdentityToken_t *owner,

									  IdentityToken_t *ident,

									  HandleError *err) =0;

		/**

		 * @brief Frees the memory associated with a handle and calls any destructors.

		 * NOTE: This function will decrement the internal reference counter.  It will

		 * only perform any further action if the counter hits 0.

		 *

		 * @param handle	Handle_t identifier to destroy.

		 * @param pSecurity	Security information struct (may be NULL).

		 * @return			A HandleError error code.

		 */

		virtual HandleError FreeHandle(Handle_t handle, const HandleSecurity *pSecurity) =0;

		/**

		 * @brief Clones a handle by adding to its internal reference count.  Its data,

		 * type, and security permissions remain the same.

		 *

		 * @param handle	Handle to duplicate.  Any non-free handle target is valid.

		 * @param newhandle	Stores the duplicated handle in the pointer (must not be NULL).

		 * @param newOwner	New owner of cloned handle.

		 * @param pSecurity	Security information struct (may be NULL).

		 * @return			A HandleError error code.

		 */

		virtual HandleError CloneHandle(Handle_t handle, 

										Handle_t *newhandle, 

										IdentityToken_t *newOwner,

										const HandleSecurity *pSecurity) =0;

		/**

		 * @brief Retrieves the contents of a handle.

		 *

		 * @param handle	Handle_t from which to retrieve contents.

		 * @param type		Expected type to read as.  0 ignores typing rules.

		 * @param pSecurity	Security information struct (may be NULL).

		 * @param object	Optional address to store object in.

		 * @return			HandleError error code.

		 */

		virtual HandleError ReadHandle(Handle_t handle, 

									   HandleType_t type, 

									   const HandleSecurity *pSecurity,

									   void **object) =0;

		/**

		 * @brief Sets access permissions on one or more structures.

		 *

		 * @param pTypeAccess	Optional TypeAccess buffer to initialize with the default values.

		 * @param pHandleAccess	Optional HandleAccess buffer to initialize with the default values.

		 * @return				True on success, false if version is unsupported.

		 */

		virtual bool InitAccessDefaults(TypeAccess *pTypeAccess, HandleAccess *pHandleAccess) =0;

		/**

		 * @brief Creates a new handle.

		 * 

		 * @param type		Type to use on the handle.

		 * @param object	Object to bind to the handle.

		 * @param pSec		Security pointer; pOwner is written as the owner,

		 *					pIdent is used as the parent identity for authorization.

		 * @param pAccess	Access right descriptor for the Handle; NULL for type defaults.

		 * @param err		Optional pointer to store an error code on failure (undefined on success).

		 * @return			A new Handle_t, or 0 on failure.

		 */

		virtual Handle_t CreateHandleEx(HandleType_t type, 

										void *object,

										const HandleSecurity *pSec,

										const HandleAccess *pAccess,

										HandleError *err) =0;

		/**

		 * @brief Clones a handle, bypassing security checks.

		 *

		 * @return          A new Handle_t, or 0 on failure.

		 */

		virtual Handle_t FastCloneHandle(Handle_t hndl) =0;

		/**

		 * @brief Type checks two handles.

		 *

		 * @param given		Type to test.

		 * @param actual	Type to check for.

		 * @return			True if "given" is a subtype of "actual", false otherwise.

		 */

		virtual bool TypeCheck(HandleType_t given, HandleType_t actual) = 0;

	};

}

#endif //_INCLUDE_SOURCEMOD_HANDLESYSTEM_INTERFACE_H_