package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.ExistenceException;
import com.googlecode.prolog_cafe.exceptions.IllegalDomainException;
import com.googlecode.prolog_cafe.exceptions.PInstantiationException;
import com.googlecode.prolog_cafe.exceptions.PermissionException;
import com.googlecode.prolog_cafe.lang.JavaObjectTerm;
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.SymbolTerm;
import com.googlecode.prolog_cafe.lang.Term;
import com.googlecode.prolog_cafe.lang.VariableTerm;

import java.io.PrintWriter;
/**
 * <code>flush_output/1</code><br>
 * @author Mutsunori Banbara (banbara@kobe-u.ac.jp)
 * @author Naoyuki Tamura (tamura@kobe-u.ac.jp)
 * @version 1.0
*/
public class PRED_flush_output_1 extends Predicate.P1 {
    public PRED_flush_output_1(Term a1, Operation cont) {
        arg1 = a1;
        this.cont = cont;
    }

    @Override
    public Operation exec(Prolog engine) {
        engine.setB0();
        Term a1;
        a1 = arg1;
	Object stream = null;

	a1 = a1.dereference();
	if (a1 instanceof VariableTerm) {
	    throw new PInstantiationException(this, 1);
	} else if (a1 instanceof SymbolTerm) {
	    if (! engine.getStreamManager().containsKey(a1))
		throw new ExistenceException(this, 1, "stream", a1, "");
	    stream = ((JavaObjectTerm) engine.getStreamManager().get(a1)).object();
	} else if (a1 instanceof JavaObjectTerm) {
	    stream = ((JavaObjectTerm) a1).object();
	} else {
	    throw new IllegalDomainException(this, 1, "stream_or_alias", a1);
	}
	if (! (stream instanceof PrintWriter))
	    throw new PermissionException(this, "output", "stream", a1, "");
	((PrintWriter)stream).flush();
        return cont;
    }
}