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Groovy: A powerful, dynamic language for the JVM
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/*
 * Copyright 2003-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package groovy.transform.stc;

import org.codehaus.groovy.ast.ASTNode;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.MethodNode;
import org.codehaus.groovy.control.CompilationUnit;
import org.codehaus.groovy.control.SourceUnit;

/**
 * Base class for hints which use the type of a parameter of the annotated method as the signature.
 * This can optionally use a generic type of the selected parameter as the hint. For example, imagine the following
 * method:
 * void foo(A firstArg, B secondArg, Closure c) {...}
 * If the c closure should be { B it -> ...}, then we can see that the parameter type
 * should be picked from the second parameter of the foo method, which is what {@link groovy.transform.stc.PickAnyArgumentHint}
 * lets you do.
 * Alternatively, the method may look like this:
 * void <T> foo(A<T> firstArg, B secondArg, Closure c) {...}
 * in which case if you want to express the fact that c should accept a <T> then you can use the
 * {@link #genericTypeIndex} value.
 * 
 * This class is extended by several hint providers that make it easier to use as annotation values.
 *
 * @author Cédric Champeau
 * @since 2.3.0
 */
public class PickAnyArgumentHint extends SingleSignatureClosureHint {
    private final int parameterIndex;
    private final int genericTypeIndex;

    /**
     * Creates the an argument picker which extracts the type of the first parameter.
     */
    public PickAnyArgumentHint() {
        this(0,-1);
    }

    /**
     * Creates a picker which will extract the parameterIndex-th parameter type, or its
     * genericTypeIndex-th generic type genericTypeIndex is >=0.
     * @param parameterIndex the index of the parameter from which to extract the type
     * @param genericTypeIndex if >=0, then returns the corresponding generic type instead of the parameter type.
     */
    public PickAnyArgumentHint(final int parameterIndex, final int genericTypeIndex) {
        this.parameterIndex = parameterIndex;
        this.genericTypeIndex = genericTypeIndex;
    }

    @Override
    public ClassNode[] getParameterTypes(final MethodNode node, final String[] options, final SourceUnit sourceUnit, final CompilationUnit unit, final ASTNode usage) {
        ClassNode type = node.getParameters()[parameterIndex].getOriginType();
        if (genericTypeIndex>=0) {
            type = pickGenericType(type, genericTypeIndex);
        }
        return new ClassNode[]{type};
    }
}