/*

Copyright (C) 2015-2018 Night Dive Studios, LLC.

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 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 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/>.
 
*/
#ifndef __OBJECTS_H
#define __OBJECTS_H

/*
** $Header: r:/prj/cit/src/inc/RCS/objects.h 1.18 1994/08/30 07:15:13 xemu Exp $
 * 
*/


// The overriding concept: there is a master array of all objects in the game.
// This is an array of the Obj structure.  Every object has a distinct ID
// which is its index in the array.  The Obj structure contains only
// information which is common to all objects.  Space for extra information is
// allocated separately, as the amount of extra information varies widely
// from object to object.  There are several different classes of objects
// (the typedef ObjClass), each of which has a distinct array storing
// information specific to objects of that class.  This information is kept
// track of in the following manner: the Obj structure contains a "class"
// field, a "subclass" field, and a "specID" field.  The specID field
// specifies what number object of this particular class this object is;
// any given combination of class and specID is unique.  specID is used
// as an index into that class's array to retrieve class-specific information.

// Within a class, there may be many subclasses.  For example, rocks and
// buildings are both static objects, but rocks probably only need one
// field for physical state while a building would more likely want at
// least four.  They do share the same data structure, but may interpret it
// differently.
typedef uchar ObjSubClass;

// An object is ID'd by its position in the Obj array.  For all of these
// arrays, 0 is a null object, and the zeroth element of the array is
// reserved for storing special information.

typedef short ObjID;
#define OBJ_NULL 0		// null object

typedef short ObjRefID;
#define OBJ_REF_NULL 0

typedef short ObjSpecID;
#define OBJ_SPEC_NULL 0

// Now that we have some basic typedef's, we include the application-specific ones.
#ifndef OBJAPP_H
#include "objapp.h"
#endif

// The common data for all objects
typedef struct Obj {
	bool active;								// does this object really exist?
	ObjClass obclass;							// what class this is
	ObjSubClass subclass;					// subclass within that class
	ObjSpecID specID;							// ID within that class
	union {
		ObjRefID ref;							// what refers to this
		ObjID headused;
	};
	union {
		ObjID next;								// next Obj in free chain or used chain
		ObjID headfree;
	};
	ObjID prev;									// prev Obj in used chain
	ObjLoc loc;									// location
	ObjInfo info;								// extra, application-specific information
} Obj;

typedef struct old_Obj {
	bool active;								// does this object really exist?
	ObjClass obclass;							// what class this is
	ObjSubClass subclass;					// subclass within that class
	ObjSpecID specID;							// ID within that class
	union {
		ObjRefID ref;							// what refers to this
		ObjID headused;
	};
	union {
		ObjID next;								// next Obj in free chain or used chain
		ObjID headfree;
	};
	ObjID prev;									// prev Obj in used chain
	ObjLoc loc;									// location
	old_ObjInfo info;								// extra, application-specific information
} old_Obj;

#define FORALLOBJS(pmo) for(pmo = (objs[OBJ_NULL]).headused; \
	pmo != OBJ_NULL; pmo = objs[pmo].next)

// The "next" field of object 0 is the ID of the first element of the chain
// of "free" objects; objects that are not currently in the world.  The "next"
// field of that object points to the next element in the free chain, and so
// on, until a "next" field of 0 means that there are no more free objects.
//
// For an object not in the free chain, the "next" field points to the next
// object in the used chain.  The "ref" field (sorry, next was taken) of the
// zeroth element points to the head of the used chain.  Every element is in
// either the free chain or the used chain.

// The header for an array of class-specific data
typedef struct ObjSpecHeader {
	uchar size;									// size of array
	uchar struct_size;						// size of each element
	char *data;									// pointer to array of class-specific data
} ObjSpecHeader;

// The common part of any class-specific structure.  You can cast any class-specific
// structure to an ObjSpec if you want to write super-general code.
// As with Objs and ObjRefs, the 0th element is reserved, and its next
// field is the head of the free chain, while its id element is the head of the
// used chain.  The next field is the next element in the free chain or used chain,
// as appropriate.

typedef struct ObjSpec {
	union {
		struct {
			ushort tile : 1;					// look in tiled array?
			ObjID id : 15;						// ID in master list
		} bits;	
		ObjSpecID headused;
	};
	union {
		ObjSpecID next;						// next struct in free or used chain
		ObjSpecID headfree;
	};
	ObjSpecID prev;							// prev struct in used chain
} ObjSpec;

// This macro permutes the ObjSpecID pmo through all of the ObjSpecs in the
// used chain of objspec.  "tile" is set to whether it's a tiled object.
// Note that the "tile =" line in the third part refers to the pmo that
// has been set earlier that line.
//
#define FORALLOBJSPECS(pmo,tiled,objspec) for(\
	pmo = (objspec[OBJ_SPEC_NULL]).id, tiled = objspec[pmo].tile;\
	pmo != OBJ_SPEC_NULL;\
	pmo = objspec[pmo].next, tiled = objspec[pmo].tile)

// The master array of objects
extern Obj objs[NUM_OBJECTS];

// The array of class-specific headers.  Index into this array by an ObjClass.
extern /*const*/ ObjSpecHeader objSpecHeaders[NUM_CLASSES];

//////////////////////////////
//
// Now, we get to actual references of objects.  Since a given object can reside
// in more than one map element (if it is large), we need different map elements to be
// able to refer to it.  A map element, then, contains not the object itself
// (an Obj) but rather a reference to an object (an ObjRef).  Each Obj may
// have several different ObjRefs referring to it, each in a different map element.
// All the ObjRefs referring to a given Obj are linked in a circular list by
// the nextref field, and every Obj contains the ID of some ObjRef referring
// to it in its ref field.  As an Obj moves from location to location, at some
// times occupying just one map element and at other times overlapping two or more,
// appropriate ObjRefs will be created and deleted in those map elements.  Note
// that if we implement an Underworld-like "link" field for objects (used to
// specify that one object somehow "contains" another), it can be put in the
// Obj itself and does not need to be put out in the ObjRef.

typedef struct ObjRef {
	ObjRefState state;						// location
	ObjID obj;									// what Obj this refers to
	ObjRefID next;								// next ObjRef in this square, or OBJ_REF_NULL if last
	ObjRefID nextref;							// next ObjRef to refer to the same Obj
} ObjRef;

extern ObjRef objRefs[NUM_REF_OBJECTS];

//////////////////////////////
//
// Routines to make it easy to deal with objects only once

extern uchar objsDealt[NUM_OBJECTS/8];

#define ObjsClearDealt() do {LG_memset (objsDealt, 0, NUM_OBJECTS/8);} while (0)
#define ObjSetDealt(x) do {objsDealt[(x) >> 3] |= (1 << ((x) & 7));} while (0)
#define ObjClearDealt(x) do {objsDealt[(x) >> 3] &= ~(1 << ((x) & 7));} while (0)
#define ObjCheckDealt(x) (objsDealt[(x) >> 3] & (1 << ((x) & 7)))

//////////////////////////////
//
// Here is a structure by which an object's location is specified.
// Physics will use it to tell the object manager how to update the world.

#define MAX_REFS_PER_OBJ 12				// set as appropriate
#define MAX_OBJS_CHANGING 20				// ditto

typedef struct ObjLocState {
	ObjID obj;									// which obj is this?
	ObjLoc loc;
	ObjRefState refs[MAX_REFS_PER_OBJ+1];	// list of points extended into
} ObjLocState;

// refs is a list of map elements that the Obj extends into; i.e., the bins
// that should have ObjRefs referring to that object, along with any
// extra state.  The list is terminated by an ObjRefState with a null bin.

// Physics puts information about objects that have moved in objLocStates.
extern ObjLocState objLocStates[MAX_OBJS_CHANGING];

// numObjLocStates contains the number of entries of objLocStates that are valid.
extern uchar numObjLocStates;

//////////////////////////////
//
// Here is a structure that we use to tell physics what objects are interacting
// with a given object.

#define MAX_REFS_COLLIDING 32

//////////////////////////////
//
// Hashing stuff
//

#ifdef HASH_OBJECTS

typedef short ObjHashElemID;

typedef struct ObjHashElem {
  ObjRefID ref;
  ObjHashElemID next;
} ObjHashElem;

// The entries which can actually be accessed by the hash function
// range from OBJ_HASH_HEAD_ENTRIES_START to that + OBJ_HASH_HEAD_ENTRIES.
// We don't start at zero because we want to reserve the zeroth element
// to be null.

extern ObjHashElem objHashTable[OBJ_HASH_ENTRIES];

// ObjGetHashElem() is called by the macro ObjRefHead(), which tends
// to be called in inner loops.  Thus, making it a function slows things
// down a lot.  The solution used here is to make it a macro that handles
// the simple cases (which happen most of the time) and that calls a function
// when it encounters the complicated case (a chain is hanging off of the
// entry).  This seems to speed up code which calls ObjRefHead() repeatedly
// by a factor of two.
//
// See the full ObjGetHashElem() function in objects.c for a commented
// version of what this is doing.
//
// The global variable is a pain but I don't see a way to get rid of it.

#ifdef USE_FUNCTION_FOR_HASH_GET
ObjHashElemID ObjGetHashElem (ObjRefStateBin thebin, bool create);
#else
extern ObjHashElemID HASHENTRY;	       // global, found in objects.c
#define ObjGetHashElem(thebin,create) \
 (HASHENTRY = OBJ_HASH_FUNC(thebin),\
  (objHashTable[HASHENTRY].ref == OBJ_REF_NULL ?\
    (create ? HASHENTRY : 0) :\
    (ObjRefStateBinEqual(objRefs[objHashTable[HASHENTRY].ref].state.bin,thebin) ?\
      HASHENTRY :\
      ObjGetHashElemFromChain(thebin,create,HASHENTRY))))
ObjHashElemID ObjGetHashElemFromChain (ObjRefStateBin bin, bool create, ObjHashElemID firstentry);
#endif

#endif // HASH_OBJECTS

//////////////////////////////
//
// Public functions
//

void ObjsInit (void);
bool ObjAndSpecGrab (ObjClass obclass, ObjID *id, ObjSpecID *specid);
bool ObjPlace (ObjID id, ObjLoc *loc);
ObjID ObjRefDel (ObjRefID ref);
ObjRefID ObjRefMake (ObjID obj, ObjRefState refstate);
bool ObjDel (ObjID obj);
bool ObjChangeClass (ObjID obj, ObjClass obclass);
bool ObjUpdateLocs (ObjLocState *olsp);
bool ObjsUpdateLocs (void);
void ObjPossibleCollisions (ObjID obj, ObjID *colls);

void ObjBinPrint (ObjRefStateBin bin);
bool ObjSysOkay (void);
void ObjPrintRefs (ObjID obj);

//////////////

bool ObjInstInit (ObjID id, ObjSpecID specid, ObjSubClass subclass);

//////////////////////////////

#endif // __OBJECTS_H