InvocationOnWhateverExpression.java

/*
Copyright (c) 2008 Arno Haase, Andr� Arnold.
All rights reserved. This program and the accompanying materials
are made available under the terms of the Eclipse Public License v1.0
which accompanies this distribution, and is available at
http://www.eclipse.org/legal/epl-v10.html

Contributors:
    Arno Haase - initial API and implementation
    Andr� Arnold
 */
package org.eclipse.xtend.backend.expr;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.eclipse.xtend.backend.common.ExecutionContext;
import org.eclipse.xtend.backend.common.ExpressionBase;
import org.eclipse.xtend.backend.common.QualifiedName;
import org.eclipse.xtend.backend.common.SourcePos;
import org.eclipse.xtend.backend.common.SyntaxConstants;
import org.eclipse.xtend.backend.syslib.CollectionOperations;


//TODO refactor: middle ends only use this, and a subsequent step differentiates / optimizes to the other two


/**
 * This expression invokes a function on the first argument, deciding at runtime whether to do the "collection magic" of
 *  invoking the function on every member of the collection that is the first argument and returning the collection of
 *  all the arguments.<br>
 *  
 * This expression does *not* do implicit "this" resolution - it is the responsibility of the initializing code, e.g. in the
 *  middle end, to statically resolve that.
 * 
 * @author Arno Haase (http://www.haase-consulting.com)
 * @author Andr� Arnold
 */
public final class InvocationOnWhateverExpression extends ExpressionBase {
    private final QualifiedName _functionName;
    private final List<? extends ExpressionBase> _params;
    private final boolean _nullIfFirstParamIsNull;
    
    public InvocationOnWhateverExpression (QualifiedName functionName, List<? extends ExpressionBase> params, boolean nullIfFirstParamIsNull, SourcePos sourcePos) {
        super (sourcePos);
        
        _functionName = functionName;
        _params = params;
        _nullIfFirstParamIsNull = nullIfFirstParamIsNull;
    }
    
    public QualifiedName getFunctionName() {
		return _functionName;
	}

	public List<? extends ExpressionBase> getParams() {
		return _params;
	}

	public boolean isNullIfFirstParamIsNull() {
		return _nullIfFirstParamIsNull;
	}

	@Override
    protected Object evaluateInternal(ExecutionContext ctx) {
        final List<Object> params = new ArrayList<Object> ();
        boolean firstParamIsThis = false;
        if (_params.size() > 0 && _params.get(0) instanceof LocalVarEvalExpression)
        	if (((LocalVarEvalExpression)_params.get(0)).getLocalVarName().equals(SyntaxConstants.THIS))
        		firstParamIsThis = true;
        for (ExpressionBase expr: _params)
        	params.add (expr.evaluate(ctx));

        if (_nullIfFirstParamIsNull && params.get(0) == null) {
            ctx.logNullDeRef (getPos());
            return null;
        }
        
        if (params.get (0) instanceof Collection<?>) {
            // check if this is a function on Collection itself
            if (ctx.getFunctionDefContext().hasMatch (ctx, _functionName, params))
                return ctx.getFunctionDefContext().invoke (ctx, _functionName, params, firstParamIsThis);

            final Collection<?> coll = (Collection<?>) params.get (0);
            
            final Collection<Object> result = CollectionOperations.createMatchingCollection (coll);
            
            for (Object o: coll) {
                params.set (0, o);
                
                CollectionOperations.addFlattened (result, ctx.getFunctionDefContext().invoke (ctx, _functionName, params, firstParamIsThis));
            }
            
            return result;

        }
        else 
            return ctx.getFunctionDefContext().invoke (ctx, _functionName, params, firstParamIsThis);
    }
}