/*************************************************************************
*									 *
*	 YAP Prolog 							 *
*									 *
*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
*									 *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997	 *
*									 *
**************************************************************************
*									 *
* File:		corout.c						 *
* Last rev:								 *
* mods:									 *
* comments:	Co-routining from within YAP				 *
*									 *
*************************************************************************/
#ifdef SCCS
static char SccsId[]="%W% %G%";
#endif

#include "Yap.h"
#include "Yatom.h"
#include "YapHeap.h"
#include "heapgc.h"
#include "attvar.h"
#ifndef NULL
#define NULL (void *)0
#endif

#ifdef COROUTINING

/* check if variable was there */
static Term AddVarIfNotThere(Term var , Term dest USES_REGS)
{
  Term test = dest;
  while (test != TermNil) {
    if ((RepPair(test))[0] == var) return(dest);
    else test = (RepPair(test))[1];
  }
  return(MkPairTerm(var,dest));
}


/* This routine verifies whether two complex structures can unify. */
static int can_unify_complex(register CELL *pt0,
		register CELL *pt0_end,
		register CELL *pt1,
		Term  *Vars USES_REGS)
{

  /* This is really just unification, folks */
  tr_fr_ptr saved_TR;
  CELL *saved_HB;
  choiceptr saved_B;

  register CELL **to_visit = (CELL **)Yap_PreAllocCodeSpace();
  CELL **to_visit_base = to_visit;

  /* make sure to trail all bindings */
  saved_TR = TR;
  saved_B = B;
  saved_HB = HB;
  HB = HR;

 loop:
  while (pt0 < pt0_end) {
    register CELL d0, d1;
    ++ pt0;
    ++ pt1;
    d0 = Derefa(pt0);
    d1 = Derefa(pt1);
    if (IsVarTerm(d0)) {
      if (IsVarTerm(d1)) {
	if (d0 != d1) {
	  /* we need to suspend on both variables ! */
	  *Vars = AddVarIfNotThere(d0, AddVarIfNotThere(d1,*Vars PASS_REGS) PASS_REGS);
	  /* bind the two variables, we would have to do that to unify
	     them */
	  if (d1 > d0) { /* youngest */
	    /* we don't want to wake up goals */
	    Bind_Global((CELL *)d1, d0);
	  } else {
	    Bind_Global((CELL *)d0, d1);
	  }
	}
	/* continue the loop */
	continue;
      }
      else {
	/* oh no, some more variables! */
	*Vars = AddVarIfNotThere(d0, *Vars PASS_REGS);
      }
      /* now bind it */
      Bind_Global((CELL *)d0, d1);
      /* continue the loop */
    } else if (IsVarTerm(d1))  {
      *Vars = AddVarIfNotThere(d1, *Vars PASS_REGS);
      /* and bind it */
      Bind_Global((CELL *)d1, d0);
      /* continue the loop */
    } else {
      if (d0 == d1) continue;
      if (IsAtomOrIntTerm(d0) || IsAtomOrIntTerm(d1)) {
	  if (d0 != d1) goto comparison_failed;
	/* else continue the loop */
      }
      else if (IsPairTerm(d0)) {
	if (!IsPairTerm(d1)) goto comparison_failed;
#ifdef RATIONAL_TREES
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = pt1;
	to_visit[3] = (CELL *)*pt0;
	to_visit += 4;
	*pt0 = d1;
#else
	/* store the terms to visit */
	if (pt0 < pt0_end) {
	  to_visit[0] = pt0;
	  to_visit[1] = pt0_end;
	  to_visit[2] = pt1;
	  to_visit += 3;
	}
#endif
	pt0 = RepPair(d0) - 1;
	pt0_end = RepPair(d0) + 1;
	pt1 = RepPair(d1) - 1;
	continue;
      }
      else if (IsApplTerm(d0)) {
	register Functor f;
	register CELL *ap2, *ap3;
	if (!IsApplTerm(d1)) {
	  goto comparison_failed;
	} else {
	  /* store the terms to visit */
	  ap2 = RepAppl(d0);
	  ap3 = RepAppl(d1);
	  f = (Functor)(*ap2);
	  /* compare functors */
	  if (f != (Functor)*ap3) {
	    goto comparison_failed;
	  }
	  if (IsExtensionFunctor(f)) {
	    switch((CELL)f) {
	    case (CELL)FunctorDBRef:
	      if (d0 == d1) continue;
	      goto comparison_failed;
	    case (CELL)FunctorLongInt:
	      if (ap2[1] == ap3[1]) continue;
	      goto comparison_failed;
	    case (CELL)FunctorDouble:
	      if (FloatOfTerm(d0) == FloatOfTerm(d1)) continue;
	      goto comparison_failed;
	    case (CELL)FunctorString:
	      if (strcmp((char *)StringOfTerm(d0), (char *)StringOfTerm(d1)) == 0) continue;
	      goto comparison_failed;
#ifdef USE_GMP
	    case (CELL)FunctorBigInt:
	      if (Yap_gmp_tcmp_big_big(d0,d1) == 0) continue;
	      goto comparison_failed;
#endif /* USE_GMP */
	    default:
	      goto comparison_failed;
	    }
	  }
#ifdef RATIONAL_TREES
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit[2] = pt1;
	to_visit[3] = (CELL *)*pt0;
	to_visit += 4;
	*pt0 = d1;
#else
	  /* store the terms to visit */
	  if (pt0 < pt0_end) {
	    to_visit[0] = pt0;
	    to_visit[1] = pt0_end;
	    to_visit[2] = pt1;
	    to_visit += 3;
	  }
#endif
	  d0 = ArityOfFunctor(f);
	  pt0 = ap2;
	  pt0_end = ap2 + d0;
	  pt1 = ap3;
	  continue;
	}
      }

    }

  }
  /* Do we still have compound terms to visit */
  if (to_visit > (CELL **)to_visit_base) {
#ifdef RATIONAL_TREES
    to_visit -= 4;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
#else
    to_visit -= 3;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
#endif
    goto loop;
  }
  /* success */
  Yap_ReleasePreAllocCodeSpace((ADDR)to_visit);
  /* restore B, and later HB */
  B = saved_B;
  HB = saved_HB;
  /* untrail all bindings made by IUnify */
  while (TR != saved_TR) {
    pt1 = (CELL *)(TrailTerm(--TR));
    RESET_VARIABLE(pt1);
  }
  return(TRUE);

 comparison_failed:
  /* failure */
  Yap_ReleasePreAllocCodeSpace((ADDR)to_visit);
#ifdef RATIONAL_TREES
  while (to_visit > (CELL **)to_visit_base) {
    to_visit -= 4;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    pt1 = to_visit[2];
    *pt0 = (CELL)to_visit[3];
  }
#endif
  /* restore B, and later HB */
  B  = saved_B;
  HB = saved_HB;
  /* the system will take care of TR for me, no need to worry here! */
  return(FALSE);
}

static int
can_unify(Term t1, Term t2, Term *Vars USES_REGS)
{
  t1 = Deref(t1);
  t2 = Deref(t2);
  if (t1 == t2) {
    *Vars = TermNil;
    return TRUE;
  }
  if (IsVarTerm(t1)) {
    /* we know for sure  they can't be different */
    if (IsVarTerm(t2)) {
      /* we need to suspend on both variables because otherwise
	 Y = susp(_) would not wakeup susp ! */
      *Vars = MkPairTerm(t1,MkPairTerm(t2,TermNil));
      return TRUE;
    } else {
      *Vars = MkPairTerm(t1,TermNil);
      return TRUE;
    }
  } else if (IsVarTerm(t2)) {
    /* wait until t2 is bound */
    *Vars = MkPairTerm(t2,TermNil);
    return TRUE;
  }
  /* Two standard terms at last! */
  if (IsAtomOrIntTerm(t1) || IsAtomOrIntTerm(t2)) {
    /* Two primitive terms can only be equal if they are
       the same. If they are, $eq succeeds without further ado.
       */
    if (t1 != t2)
      return FALSE;
    else {
      *Vars = TermNil;
      return TRUE;
    }
  } else if (IsPairTerm(t1)) {
    if (IsPairTerm(t2)) {
      return(can_unify_complex(RepPair(t1)-1, RepPair(t1)+1,
			       RepPair(t2)-1, Vars PASS_REGS));
    } else return FALSE;
  } else {
    Functor f = FunctorOfTerm(t1);
    if (f != FunctorOfTerm(t2))
      return FALSE;
    if (IsExtensionFunctor(f)) {
      switch((CELL)f) {
      case (CELL)FunctorDBRef:
	if (t1 == t2) return FALSE;
	return FALSE;
      case (CELL)FunctorLongInt:
	if (RepAppl(t1)[1] == RepAppl(t2)[1]) return(TRUE);
	return FALSE;
      case (CELL)FunctorString:
	if (strcmp((char *)StringOfTerm(t1), (char *)StringOfTerm(t2)) == 0) return(TRUE);
	return FALSE;
      case (CELL)FunctorDouble:
	if (FloatOfTerm(t1) == FloatOfTerm(t2)) return(TRUE);
	return FALSE;
#ifdef USE_GMP
      case (CELL)FunctorBigInt:
	if (Yap_gmp_tcmp_big_big(t1,t2) == 0) return(TRUE);
	return(FALSE);
#endif /* USE_GMP */
      default:
	return FALSE;
      }
    }
    /* Two complex terms with the same functor */
    return can_unify_complex(RepAppl(t1),
			     RepAppl(t1)+ArityOfFunctor(f),
			     RepAppl(t2), Vars PASS_REGS);
  }
}

/* This routine verifies whether a complex has variables. */
static int non_ground_complex(register CELL *pt0,
		register CELL *pt0_end,
		Term  *Var USES_REGS)
{

  register CELL **to_visit = (CELL **)Yap_PreAllocCodeSpace();
  CELL **to_visit_base = to_visit;

 loop:
  while (pt0 < pt0_end) {
    register CELL d0;
    ++ pt0;
    d0 = Derefa(pt0);
    if (IsVarTerm(d0)) {
      *Var = d0;
      goto var_found;
    }
    if (IsPairTerm(d0)) {
      if (to_visit + 1024 >= (CELL **)AuxSp) {
	goto aux_overflow;
      }
#ifdef RATIONAL_TREES
      to_visit[0] = pt0;
      to_visit[1] = pt0_end;
      to_visit[2] = (CELL *)*pt0;
      to_visit += 3;
      *pt0 = TermNil;
#else
      /* store the terms to visit */
      if (pt0 < pt0_end) {
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit += 2;
      }
#endif
      pt0 = RepPair(d0) - 1;
      pt0_end = RepPair(d0) + 1;
    }
    else if (IsApplTerm(d0)) {
      register Functor f;
      register CELL *ap2;

      /* store the terms to visit */
      ap2 = RepAppl(d0);
      f = (Functor)(*ap2);

      if (IsExtensionFunctor(f)) {
	continue;
      }
      if (to_visit + 1024 >= (CELL **)AuxSp) {
	goto aux_overflow;
      }
#ifdef RATIONAL_TREES
      to_visit[0] = pt0;
      to_visit[1] = pt0_end;
      to_visit[2] = (CELL *)*pt0;
      to_visit += 3;
      *pt0 = TermNil;
#else
      /* store the terms to visit */
      if (pt0 < pt0_end) {
	to_visit[0] = pt0;
	to_visit[1] = pt0_end;
	to_visit += 2;
      }
#endif
      d0 = ArityOfFunctor(f);
      pt0 = ap2;
      pt0_end = ap2 + d0;
    }
    /* just continue the loop */
  }

  /* Do we still have compound terms to visit */
  if (to_visit > (CELL **)to_visit_base) {
#ifdef RATIONAL_TREES
    to_visit -= 3;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    *pt0 = (CELL)to_visit[2];
#else
    to_visit -= 2;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
#endif
    goto loop;
  }

  /* the term is ground */
  Yap_ReleasePreAllocCodeSpace((ADDR)to_visit);
  return FALSE;

 var_found:
  /* the term is non-ground */
  Yap_ReleasePreAllocCodeSpace((ADDR)to_visit);
#ifdef RATIONAL_TREES
  while (to_visit > (CELL **)to_visit_base) {
    to_visit -= 3;
    pt0 = to_visit[0];
    pt0_end = to_visit[1];
    *pt0 = (CELL)to_visit[2];
  }
#endif
  /* the system will take care of TR for me, no need to worry here! */
  return TRUE;

 aux_overflow:
  /* unwind stack */
  Yap_ReleasePreAllocCodeSpace((ADDR)to_visit);
#ifdef RATIONAL_TREES
  while (to_visit > (CELL **)to_visit_base) {
    to_visit -= 3;
    pt0 = to_visit[0];
    *pt0 = (CELL)to_visit[2];
  }
#endif
  return -1;
}

static int
non_ground(Term t, Term *Var USES_REGS)
{
  int out = -1;
  while (out < 0) {
    t = Deref(t);
    if (IsVarTerm(t)) {
      /* we found a variable */
      *Var = t;
      return TRUE;
    }
    if (IsPrimitiveTerm(t)) {
      return FALSE;
    } else if (IsPairTerm(t)) {
      out = non_ground_complex(RepPair(t)-1, RepPair(t)+1, Var PASS_REGS);
      if (out >= 0)
	return out;
    } else {
      Functor f = FunctorOfTerm(t);
      if (IsExtensionFunctor(f)) {
	return FALSE;
      }
      out = non_ground_complex(RepAppl(t),
			       RepAppl(t)+ArityOfFunctor(FunctorOfTerm(t)),
			       Var PASS_REGS);
      if (out >= 0)
	return out;
    }
    if (!Yap_ExpandPreAllocCodeSpace(0, NULL, TRUE)) {
      Yap_Error(OUT_OF_AUXSPACE_ERROR, ARG1, "overflow in ground");
      return FALSE;
    }      
  }
  return FALSE;
}

#endif

/* check whether the two terms unify and return what variables should
   be bound before the terms are exactly equal */
static Int p_can_unify( USES_REGS1 )
{
#ifdef COROUTINING
  Term r = TermNil;
  if (!can_unify(ARG1, ARG2, &r PASS_REGS))
    return FALSE;
  return Yap_unify(ARG3, r);
#else
  return FALSE;
#endif
}

/* if the term is not ground return a variable in the term */
static Int p_non_ground( USES_REGS1 )
{
#ifdef COROUTINING
  Term r = TermNil;
  if (!non_ground(ARG1, &r PASS_REGS))
    return(FALSE);
  return (Yap_unify(ARG2, r));
#else
  return(FALSE);
#endif
}

/* if the term is not ground return a variable in the term */
static Int p_coroutining( USES_REGS1 )
{
#ifdef COROUTINING
  return(TRUE);
#else
  return(FALSE);
#endif
}

#if COROUTINING
static Term
ListOfWokenGoals( USES_REGS1 ) {
  return Yap_ReadTimedVar(LOCAL_WokenGoals);
}

Term
Yap_ListOfWokenGoals(void) {
  CACHE_REGS
  return ListOfWokenGoals( PASS_REGS1 );
}
#endif

/* return a list of awoken goals */
static Int p_awoken_goals( USES_REGS1 )
{
#ifdef COROUTINING
  Term WGs = Yap_ReadTimedVar(LOCAL_WokenGoals);
  if (WGs == TermNil) {
    return(FALSE);
  }
  WGs = ListOfWokenGoals( PASS_REGS1 );
  Yap_UpdateTimedVar(LOCAL_WokenGoals, TermNil);
  return(Yap_unify(ARG1,WGs));
#else
  return(FALSE);
#endif
}

static Int
p_yap_has_rational_trees( USES_REGS1 )
{
#if RATIONAL_TREES
  return TRUE;
#else
  return FALSE;
#endif
}

static Int
p_yap_has_coroutining( USES_REGS1 )
{
#if COROUTINING
  return TRUE;
#else
  return FALSE;
#endif
}

void
Yap_InitCoroutPreds( void )
{
#ifdef COROUTINING
  Atom            at;
  PredEntry      *pred;

  at = AtomWakeUpGoal;
  pred = RepPredProp(PredPropByFunc(Yap_MkFunctor(at, 2),0));
  WakeUpCode = pred;
#endif
  Yap_InitAttVarPreds();
  Yap_InitCPred("$yap_has_rational_trees", 0, p_yap_has_rational_trees, SafePredFlag);
  Yap_InitCPred("$yap_has_coroutining", 0, p_yap_has_coroutining, SafePredFlag);
  Yap_InitCPred("$can_unify", 3, p_can_unify, SafePredFlag);
  Yap_InitCPred("$non_ground", 2, p_non_ground, SafePredFlag);
  Yap_InitCPred("$coroutining", 0, p_coroutining, SafePredFlag);
  Yap_InitCPred("$awoken_goals", 1, p_awoken_goals, SafePredFlag);
}