/*
 *  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.tools.ant.dispatch;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.UnknownElement;
import org.apache.tools.ant.Task;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

/**
 * Determines and Executes the action method for the task.
 */
public class DispatchUtils {
    /**
     * Determines and Executes the action method for the task.
     * @param task the task to execute.
     * @throws BuildException on error.
     */
    public static final void execute(Object task) throws BuildException {
        String methodName = "execute";
        Dispatchable dispatchable = null;
        try {
            if (task instanceof Dispatchable) {
                dispatchable = (Dispatchable) task;
            } else if (task instanceof UnknownElement) {
                UnknownElement ue = (UnknownElement) task;
                Object realThing = ue.getRealThing();
                if (realThing != null
                    && realThing instanceof Dispatchable
                    && realThing instanceof Task) {
                    dispatchable = (Dispatchable) realThing;
                }
            }
            if (dispatchable != null) {
                String mName = null;
                try {
                    final String name = dispatchable.getActionParameterName();
                    if (name != null && name.trim().length() > 0) {
                        mName = "get" + name.trim().substring(0, 1).toUpperCase();
                        if (name.length() > 1) {
                            mName += name.substring(1);
                        }
                        final Class c = dispatchable.getClass();
                        final Method actionM = c.getMethod(mName, new Class[0]);
                        if (actionM != null) {
                            final Object o = actionM.invoke(dispatchable, (Object[]) null);
                            if (o != null) {
                                final String s = o.toString();
                                if (s != null && s.trim().length() > 0) {
                                    methodName = s.trim();
                                    Method executeM = null;
                                    executeM = dispatchable.getClass().getMethod(
                                        methodName, new Class[0]);
                                    if (executeM == null) {
                                        throw new BuildException(
                                            "No public " + methodName + "() in "
                                            + dispatchable.getClass());
                                    }
                                    executeM.invoke(dispatchable, (Object[]) null);
                                    if (task instanceof UnknownElement) {
                                        ((UnknownElement) task).setRealThing(null);
                                    }
                                } else {
                                    throw new BuildException(
                                        "Dispatchable Task attribute '" + name.trim()
                                        + "' not set or value is empty.");
                                }
                            } else {
                                    throw new BuildException(
                                        "Dispatchable Task attribute '" + name.trim()
                                        + "' not set or value is empty.");
                            }
                        }
                    } else {
                        throw new BuildException(
                            "Action Parameter Name must not be empty for Dispatchable Task.");
                    }
                } catch (NoSuchMethodException nsme) {
                    throw new BuildException("No public " + mName + "() in " + task.getClass());
                }
            } else {
                Method executeM = null;
                executeM = task.getClass().getMethod(methodName, new Class[0]);
                if (executeM == null) {
                    throw new BuildException("No public " + methodName + "() in "
                        + task.getClass());
                }
                executeM.invoke(task, (Object[]) null);
                if (task instanceof UnknownElement) {
                    ((UnknownElement) task).setRealThing(null);
                }
            }
        } catch (InvocationTargetException ie) {
            Throwable t = ie.getTargetException();
            if (t instanceof BuildException) {
                throw ((BuildException) t);
            } else {
                throw new BuildException(t);
            }
        } catch (NoSuchMethodException e) {
            throw new BuildException(e);
        } catch (IllegalAccessException e) {
            throw new BuildException(e);
        }
    }
}