package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.ExistenceException;
import com.googlecode.prolog_cafe.exceptions.IllegalTypeException;
import com.googlecode.prolog_cafe.exceptions.SystemException;
import com.googlecode.prolog_cafe.lang.IntegerTerm;
import com.googlecode.prolog_cafe.lang.Operation;
import com.googlecode.prolog_cafe.lang.Predicate;
import com.googlecode.prolog_cafe.lang.Prolog;
import com.googlecode.prolog_cafe.lang.StructureTerm;
import com.googlecode.prolog_cafe.lang.SymbolTerm;
import com.googlecode.prolog_cafe.lang.Term;
/**
 * <code>'$call'/2</code><br>
 * @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
 * @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
 * @version 1.0
 */
class PRED_$call_2 extends Predicate.P2 {
    private static final SymbolTerm SYM_SLASH_2 = SymbolTerm.intern("/", 2);
    private static final SymbolTerm SYM_COLON_2 = SymbolTerm.intern(":", 2);

    public PRED_$call_2(Term a1, Term a2, Operation cont) {
	arg1 = a1;
	arg2 = a2;
	this.cont = cont;
    }

    @Override
    public Operation exec(Prolog engine) {
        engine.setB0();
	Term a1, a2;
	a1 = arg1.dereference(); // a1 must be atom of package name
	a2 = arg2.dereference(); // a2 must be callable name

	String functor;
	int arity;
	Term[] args;

	try {
	    if (! (a1 instanceof SymbolTerm))
		throw new IllegalTypeException(this, 1, "atom", a1);
	    if (a2 instanceof SymbolTerm) {
		functor = ((SymbolTerm)a2).name();
		args    = new Term[] {};
		arity   = 0;
	    } else if (a2 instanceof StructureTerm) {
		functor = ((StructureTerm)a2).functor().name();
		args    = ((StructureTerm)a2).args();
		arity   = ((StructureTerm)a2).arity();
	    } else {
		throw new IllegalTypeException(this, 2, "callable", a2);
	    }
	    try {
	      return engine.pcl.predicate(((SymbolTerm)a1).name(), functor, cont, args);
	    } catch (ExistenceException e) {
		try {
            return engine.pcl.predicate(Prolog.BUILTIN, functor, cont, args);
		} catch (ExistenceException e2) {
		    Term what = new StructureTerm(SYM_COLON_2,
		       a1,
		       new StructureTerm(SYM_SLASH_2,
		         SymbolTerm.create(functor),
		         new IntegerTerm(arity)));
		    ExistenceException err = new ExistenceException(this, 0, "procedure", what, e.getMessage());
		    err.initCause(e);
		    throw err;
		}
	    }
	} catch (IllegalArgumentException e) {
	    throw new SystemException(e.toString() + " in " + this.toString());
	}
    }
}