/*************************************************************************
*									 *
*	 YAP Prolog 							 *
*									 *
*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
*									 *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
*									 *
**************************************************************************
*									 *
* File:		exo.c							 *
* comments:	Exo compilation						 *
*									 *
* Last rev:     $Date: 2008-07-22 23:34:44 $,$Author: vsc $		 *				 *
* $Log: not supported by cvs2svn $				 	 *
*                                                                        *
*									 *
*************************************************************************/

#include "Yap.h"
#include "clause.h"
#include "yapio.h"
#include "eval.h"
#include "tracer.h"
#ifdef YAPOR
#include "or.macros.h"
#endif	/* YAPOR */
#ifdef TABLING
#include "tab.macros.h"
#endif /* TABLING */
#if HAVE_STRING_H
#include <string.h>
#endif

#define NEXTOP(V,TYPE)    ((yamop *)(&((V)->u.TYPE.next)))

#define MAX_ARITY 256

/* Simple hash function */
static UInt
HASH(UInt j, CELL *cl, struct index_t *it)
{
  return ((cl[j] >> 3) + (3*j*it->nels)/2) % (it->nels*2);
}

/* search for matching elements */
static int 
MATCH(CELL *clp, CELL *kvp, UInt j, UInt bnds[], struct index_t *it)
{
  if ((kvp - it->cls)%it->arity != j)
    return FALSE;
  do {
    if ( bnds[j] && *clp != *kvp)
      return FALSE;
    clp--;
    kvp--;
  } while (j-- != 0);
  return TRUE;
}

static void
ADD_TO_TRY_CHAIN(CELL *kvp, CELL *cl, struct index_t *it)
{
  UInt old = (kvp-it->cls)/it->arity;
  UInt new = (cl-it->cls)/it->arity;
  UInt *links = it->links;
  UInt tmp = links[old]; /* points to the end of the chain */

  if (!tmp) {
    links[old] = links[new] = new;
  } else {
    links[new] = links[tmp];
    links[tmp] = new;
    links[old] = new;
  }
}

static UInt
NEXT(UInt hash, struct index_t *it, UInt j)
{
  return (hash+3) % (it->nels*2);
}

/* This is the critical routine, it builds the hash table *
 * each HT field stores a key pointer which is actually
 * a pointer to the point in the clause where one can find the element.
 *
 * The cls table indexes all elements that can be reached using that key.
 * 
 * Insert:
 * j = first
 * not match cij -> insert, open new chain
 * match ci..j ck..j -> find j = minarg(cij \= c2j), 
 * else j = +inf -> c2+ci
 * Lookup:
 * j= first
 * not match cij -> fail
 * match ci..j ck..j -> find j = minarg(cij \= c2j)
 * else
 */
static void
INSERT(CELL *cl, struct index_t *it, UInt arity, UInt base, UInt bnds[])
{
  UInt j = base;
  CELL *kvp;
  UInt hash;

  /* skip over argument */
  while (!bnds[j]) {
    j++;
  }
  /* j is the firs bound element */
  /* check if we match */
  hash = HASH(j, cl, it);
 next:
  /* loop to insert element */
  kvp = it->key[hash];
  if (kvp == NULL) {
    /* simple case, new entry */
    it->key[hash] = cl+j;
    return;
  } else if (MATCH(cl+j, kvp, j, bnds, it))  {
    /* collision */
    UInt k;
    CELL *target;
    
    for (k =j+1, target = kvp+1; k < arity; k++,target++ ) {
      if (bnds[k]) {
	if (*target != cl[k]) {
	  /* found a new forking point */
	  INSERT(cl, it, arity, k, bnds);
	  return;
	}
      }
    }
    ADD_TO_TRY_CHAIN(kvp, cl, it);
    return;
  } else {
    hash =  NEXT(hash, it, j);
    goto next;
  }
}

static yamop *
LOOKUP(struct index_t *it, UInt arity, UInt bnds[])
{
  UInt j = 0;
  CELL *kvp;
  UInt hash;

  /* skip over argument */
  while (!bnds[j]) {
    j++;
  }
  /* j is the firs bound element */
  /* check if we match */
 hash:
  hash = HASH(j, XREGS+1, it);
 next:
  /* loop to insert element */
  kvp = it->key[hash];
  if (kvp == NULL) {
    /* simple case, no element */
    return FAILCODE;
  } else if (MATCH(XREGS+(j+1), kvp, j, bnds, it))  {
    /* found element */
    UInt k;
    CELL *target;

    for (k =j+1, target = kvp+1; k < arity; k++ ) {
      if (bnds[k]) {
	if (*target != XREGS[k+1]) {
	  j = k;
	  goto hash;
	}
      }
      target++;
    }
    S = target-arity;
    if (it->links[(S-it->cls)/arity])
      return it->code;
    else
      return NEXTOP(NEXTOP(it->code,lp),lp);
  } else {
    /* collision */
    hash =  NEXT(hash, it, j);
    goto next;
  }
}

static void
fill_hash(UInt bmap, UInt bnds[], struct index_t *it)
{
  UInt i;
  UInt arity = it->arity;
  CELL *cl = it->cls;

  for (i=0; i < it->nels; i++) {
    INSERT(cl, it, arity, 0, bnds);
    cl += arity;
  }
  for (i=0; i < it->nels*2; i++) {
    if (it->key[i]) {
      UInt offset = (it->key[i]-it->cls)/arity;
      UInt last = it->links[offset];
      if (last) {
      /* the chain used to point straight to the last, and the last back to the origibal first */
	it->links[offset] = it->links[last];
	it->links[last] = 0;
      }
    }
  }
}

static struct index_t *
add_index(struct index_t **ip, UInt bmap, UInt bndsf[], PredEntry *ap, UInt count)
{
  UInt ncls = ap->cs.p_code.NOfClauses, j;
  CELL *base = NULL;
  struct index_t *i;
  size_t sz;
  yamop *ptr;
  
  if (count) {
    if (!(base = (CELL *)Yap_AllocCodeSpace(3*sizeof(CELL)*ncls))) {
      CACHE_REGS
      save_machine_regs();
      LOCAL_Error_Size = 3*ncls*sizeof(CELL);
      LOCAL_ErrorMessage = "not enough space to index";
      Yap_Error(OUT_OF_HEAP_ERROR, TermNil, LOCAL_ErrorMessage);
      return NULL;
    }
  }
  sz =   (CELL)NEXTOP(NEXTOP((yamop*)NULL,lp),lp)+ap->ArityOfPE*(CELL)NEXTOP((yamop *)NULL,x) +(CELL)NEXTOP(NEXTOP((yamop *)NULL,p),l);
  if (!(i = (struct index_t *)Yap_AllocCodeSpace(sizeof(struct index_t)+sz))) {
    CACHE_REGS
    save_machine_regs();
    LOCAL_Error_Size = 3*ncls*sizeof(CELL);
    LOCAL_ErrorMessage = "not enough space to index";
    Yap_Error(OUT_OF_HEAP_ERROR, TermNil, LOCAL_ErrorMessage);
    return NULL;
  }
  if (count)
    bzero(base, 3*sizeof(CELL)*ncls);
  i->next = *ip;
  i->prev = NULL;
  i->nels = ncls;
  i->arity = ap->ArityOfPE;
  i->ap = ap;
  i->bmap = bmap;
  i->is_key = FALSE;
  i->hsize = 2*ncls;
  i->key = (CELL **)base;
  i->links = (CELL *)(base+2*ncls);
  i->cls = (CELL *)((ADDR)ap->cs.p_code.FirstClause+2*sizeof(struct index_t *)); 
  *ip = i;
  if (count) {
    fill_hash(bmap, bndsf, i);
  }
  ptr = (yamop *)(i+1);
  i->code = ptr;
  if (count)
    ptr->opc = Yap_opcode(_try_exo);
  else
    ptr->opc = Yap_opcode(_try_all_exo);
  ptr->u.lp.l = (yamop *)i;
  ptr->u.lp.p = ap;
  ptr = NEXTOP(ptr, lp);
  if (count)
    ptr->opc = Yap_opcode(_retry_exo);
  else
    ptr->opc = Yap_opcode(_retry_all_exo);
  ptr->u.lp.p = ap;
  ptr->u.lp.l = (yamop *)i;
  ptr = NEXTOP(ptr, lp);
  for (j = 0; j < i->arity; j++) {
    ptr->opc = Yap_opcode(_get_atom_exo);
#if PRECOMPUTE_REGADDRESS
    ptr->u.x.x = (CELL) (XREGS + (j+1));
#else
    ptr->u.x.x = j+1;
#endif
    ptr = NEXTOP(ptr, x);
  }
  ptr->opc = Yap_opcode(_procceed);
  ptr->u.p.p = ap;
  ptr = NEXTOP(ptr, p);
  ptr->opc = Yap_opcode(_Ystop);
  ptr->u.l.l = i->code;
  return i;
}

yamop  *
Yap_ExoLookup(PredEntry *ap) 
{
  UInt arity = ap->ArityOfPE;
  UInt bmap = 0L, bit = 1, count = 0, j;
  struct index_t **ip = (struct index_t **)(ap->cs.p_code.FirstClause);
  struct index_t *i = *ip;
  UInt bnds[MAX_ARITY];
  
  for (j=0; j< arity; j++, bit<<=1) {
    Term t = Deref(XREGS[j+1]);
    if (!IsVarTerm(t)) {
      bmap += bit;
      bnds[j] = TRUE;
      count++;
    } else {
      bnds[j] = FALSE;
    }
    XREGS[j+1] = t;
  }

  while (i) {
    if (i->is_key) {
      if ((i->bmap & bmap) == i->bmap) {
	break;
      }
    } else {
      if (i->bmap == bmap) {
	break;
      }
    }
    ip = &i->next;
    i = i->next;
  }
  if (!i) {
    i = add_index(ip, bmap, bnds, ap, count);
  }
  if (count)
    return LOOKUP(i, arity, bnds);
  else
    return i->code;
}

CELL
Yap_NextExo(choiceptr cptr, struct index_t *it) 
{
  CELL offset = EXO_ADDRESS_TO_OFFSET(it,(CELL *)((CELL *)(B+1))[it->arity]);
  CELL next = it->links[offset];
  ((CELL *)(B+1))[it->arity] = (CELL)EXO_OFFSET_TO_ADDRESS(it, next);
  S = it->cls+it->arity*offset;
  return next;
}

static Int 
p_exodb_get_space( USES_REGS1 )
{				/* '$number_of_clauses'(Predicate,M,N) */
  Term            t = Deref(ARG1);
  Term            mod = Deref(ARG2);
  Term            tn = Deref(ARG3);
  UInt		  arity;
  Prop            pe;
  PredEntry      *ap;
  MegaClause *mcl;
  UInt ncls;
  UInt required;
  struct index_t **li;


  if (IsVarTerm(mod)  || !IsAtomTerm(mod)) {
    return(FALSE);
  }
  if (IsAtomTerm(t)) {
    Atom a = AtomOfTerm(t);
    arity = 0;
    pe = PredPropByAtom(a, mod);
  } else if (IsApplTerm(t)) {
    register Functor f = FunctorOfTerm(t);
    arity = ArityOfFunctor(f);
    pe = PredPropByFunc(f, mod);
  } else {
    return FALSE;
  }
  if (EndOfPAEntr(pe))
    return FALSE;
  ap = RepPredProp(pe);
  if (ap->PredFlags & (DynamicPredFlag|LogUpdatePredFlag
#ifdef TABLING
		       |TabledPredFlag
#endif /* TABLING */
		       )) {
    Yap_Error(PERMISSION_ERROR_MODIFY_STATIC_PROCEDURE,t,"dbload_get_space/4");
    return FALSE;
  }
  if (IsVarTerm(tn)  || !IsIntegerTerm(tn)) {
    return FALSE;
  }
  ncls = IntegerOfTerm(tn);
  if (ncls <= 1) {
    return FALSE;
  }

  required = ncls*sizeof(CELL)+sizeof(MegaClause)+2*sizeof(struct index_t *);
  while (!(mcl = (MegaClause *)Yap_AllocCodeSpace(required))) {
    if (!Yap_growheap(FALSE, required, NULL)) {
      /* just fail, the system will keep on going */
      return FALSE;
    }
  }
  Yap_ClauseSpace += required;
  /* cool, it's our turn to do the conversion */
  mcl->ClFlags = MegaMask;
  mcl->ClSize = required-sizeof(MegaClause);
  mcl->ClPred = ap;
  mcl->ClItemSize = arity*sizeof(CELL);
  mcl->ClNext = NULL;
  li = (struct index_t **)(mcl->ClCode);
  li[0] = li[1] = NULL;
  ap->cs.p_code.FirstClause =
    ap->cs.p_code.LastClause =
    mcl->ClCode;
  ap->PredFlags |= MegaClausePredFlag;
  ap->cs.p_code.NOfClauses = ncls;
  if (ap->PredFlags & (SpiedPredFlag|CountPredFlag|ProfiledPredFlag)) {
    ap->OpcodeOfPred = Yap_opcode(_spy_pred);
  } else {
    ap->OpcodeOfPred = Yap_opcode(_enter_exo);
  }
  ap->CodeOfPred = ap->cs.p_code.TrueCodeOfPred = (yamop *)(&(ap->OpcodeOfPred)); 
  return Yap_unify(ARG4, MkIntegerTerm((Int)mcl));
}

#define DerefAndCheck(t, V)			\
  t = Deref(V); if(IsVarTerm(t) || !(IsAtomOrIntTerm(t))) Yap_Error(TYPE_ERROR_ATOM, t0, "load_db");

static int 
store_exo(yamop *pc, UInt arity, Term t0)
{
  Term t;
  CELL *tp = RepAppl(t0)+1,
    *cpc = (CELL *)pc;
  UInt i;
  for (i = 0; i< arity; i++) {
    DerefAndCheck(t, tp[0]);
    *cpc = t;
    tp++;
    cpc++;
  }
  return TRUE;
}

static Int 
p_exoassert( USES_REGS1 )
{				/* '$number_of_clauses'(Predicate,M,N) */
  Term            thandle = Deref(ARG2);
  Term            tn = Deref(ARG3);
  PredEntry       *pe;
  MegaClause      *mcl;
  Int              n;


  if (IsVarTerm(thandle)  || !IsIntegerTerm(thandle)) {
    return FALSE;
  }
  mcl = (MegaClause *)IntegerOfTerm(thandle);
  if (IsVarTerm(tn)  || !IsIntegerTerm(tn)) {
    return FALSE;
  }
  n = IntegerOfTerm(tn);
  pe = mcl->ClPred;
  return store_exo((yamop *)((ADDR)mcl->ClCode+2*sizeof(struct index_t *)+n*(mcl->ClItemSize)),pe->ArityOfPE, Deref(ARG1));
}

void 
Yap_InitExoPreds(void)
{
  CACHE_REGS
  Term cm = CurrentModule;

  CurrentModule = DBLOAD_MODULE;
  Yap_InitCPred("exo_db_get_space", 4, p_exodb_get_space, 0L);
  Yap_InitCPred("exoassert", 3, p_exoassert, 0L);
  CurrentModule = cm;
}