/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You 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 org.apache.commons.collections4.functors;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import org.apache.commons.collections4.FunctorException;

import org.apache.commons.collections4.Transformer;

/**

 * Transformer implementation that creates a new object instance by reflection.

 * <p>

 * <b>WARNING:</b> from v4.1 onwards this class will <b>not</b> be serializable anymore

 * in order to prevent potential remote code execution exploits. Please refer to

 * <a href="https://issues.apache.org/jira/browse/COLLECTIONS-580">COLLECTIONS-580</a>

 * for more details.

 * </p>

 *

 * @since 3.0

 */

public class InvokerTransformer<I, O> implements Transformer<I, O> {

    /** The method name to call */

    private final String iMethodName;

    /** The array of reflection parameter types */

    private final Class<?>[] iParamTypes;

    /** The array of reflection arguments */

    private final Object[] iArgs;

    /**

     * Gets an instance of this transformer calling a specific method with no arguments.

     *

     * @param <I>  the input type

     * @param <O>  the output type

     * @param methodName  the method name to call

     * @return an invoker transformer

     * @throws NullPointerException if methodName is null

     * @since 3.1

     */

    public static <I, O> Transformer<I, O> invokerTransformer(final String methodName) {

        if (methodName == null) {

            throw new NullPointerException("The method to invoke must not be null");

        }

        return new InvokerTransformer<>(methodName);

    }

    /**

     * Gets an instance of this transformer calling a specific method with specific values.

     *

     * @param <I>  the input type

     * @param <O>  the output type

     * @param methodName  the method name to call

     * @param paramTypes  the parameter types of the method

     * @param args  the arguments to pass to the method

     * @return an invoker transformer

     * @throws NullPointerException if methodName is null

     * @throws IllegalArgumentException if paramTypes does not match args

     */

    public static <I, O> Transformer<I, O> invokerTransformer(final String methodName, final Class<?>[] paramTypes,

                                                              final Object[] args) {

        if (methodName == null) {

            throw new NullPointerException("The method to invoke must not be null");

        }

        if (((paramTypes == null) && (args != null))

            || ((paramTypes != null) && (args == null))

            || ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) {

            throw new IllegalArgumentException("The parameter types must match the arguments");

        }

        if (paramTypes == null || paramTypes.length == 0) {

            return new InvokerTransformer<>(methodName);

        }

        return new InvokerTransformer<>(methodName, paramTypes, args);

    }

    /**

     * Constructor for no arg instance.

     *

     * @param methodName  the method to call

     */

    private InvokerTransformer(final String methodName) {

        super();

        iMethodName = methodName;

        iParamTypes = null;

        iArgs = null;

    }

    /**

     * Constructor that performs no validation.

     * Use <code>invokerTransformer</code> if you want that.

     * <p>

     * Note: from 4.0, the input parameters will be cloned

     *

     * @param methodName  the method to call

     * @param paramTypes  the constructor parameter types

     * @param args  the constructor arguments

     */

    public InvokerTransformer(final String methodName, final Class<?>[] paramTypes, final Object[] args) {

        super();

        iMethodName = methodName;

        iParamTypes = paramTypes != null ? paramTypes.clone() : null;

        iArgs = args != null ? args.clone() : null;

    }

    /**

     * Transforms the input to result by invoking a method on the input.

     *

     * @param input  the input object to transform

     * @return the transformed result, null if null input

     */

    @Override

    @SuppressWarnings("unchecked")

    public O transform(final Object input) {

        if (input == null) {

            return null;

        }

        try {

            final Class<?> cls = input.getClass();

            final Method method = cls.getMethod(iMethodName, iParamTypes);

            return (O) method.invoke(input, iArgs);

        } catch (final NoSuchMethodException ex) {

            throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" +

                                       input.getClass() + "' does not exist");

        } catch (final IllegalAccessException ex) {

            throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" +

                                       input.getClass() + "' cannot be accessed");

        } catch (final InvocationTargetException ex) {

            throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" +

                                       input.getClass() + "' threw an exception", ex);

        }

    }

}