Switch.java

/*
 * Copyright (c) 2001-2004 Ant-Contrib project.  All rights reserved.
 *
 * 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 net.sf.antcontrib.logic;

import java.util.Vector;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.taskdefs.Sequential;

/***
 * Task definition for the ANT task to switch on a particular value.
 *
 * <pre>
 *
 * Usage:
 *
 *   Task declaration in the project:
 *   <code>
 *     <taskdef name="switch" classname="net.sf.antcontrib.logic.Switch" />
 *   </code>
 *
 *   Task calling syntax:
 *    <code>
 *     <switch value="value" [caseinsensitive="true|false"] >
 *       <case value="val">
 *         <property name="propname" value="propvalue" /> |
 *         <antcall target="targetname" /> |
 *         any other tasks
 *       </case>
 *      [
 *       <default>
 *         <property name="propname" value="propvalue" /> |
 *         <antcall target="targetname" /> |
 *         any other tasks
 *       </default> 
 *      ]
 *     </switch>
 *    </code>
 *
 *
 *   Attributes:
 *       value           -> The value to switch on
 *       caseinsensitive -> Should we do case insensitive comparisons?
 *                          (default is false)
 *
 *   Subitems:
 *       case     --> An individual case to consider, if the value that
 *                    is being switched on matches to value attribute of
 *                    the case, then the nested tasks will be executed.
 *       default  --> The default case for when no match is found.
 *
 * 
 * Crude Example:
 *
 *     <code>
 *     <switch value="${foo}">
 *       <case value="bar">
 *         <echo message="The value of property foo is bar" />
 *       </case>
 *       <case value="baz">
 *         <echo message="The value of property foo is baz" />
 *       </case>
 *       <default>
 *         <echo message="The value of property foo is not sensible" />
 *       </default>
 *     </switch>
 *     </code>
 *
 * </pre>
 *
 * @author <a href="mailto:mattinger@yahoo.com">Matthew Inger</a>
 * @author <a href="mailto:stefan.bodewig@freenet.de">Stefan Bodewig</a>
 */
public class Switch extends Task
{
    private String value;
    private Vector cases;
    private Sequential defaultCase;
    private boolean caseInsensitive;
    
    /***
     * Default Constructor
     */
    public Switch()
    {
        cases = new Vector();
    }

    public void execute()
        throws BuildException
    {
        if (value == null)
            throw new BuildException("Value is missing");
        if (cases.size() == 0 && defaultCase == null)
            throw new BuildException("No cases supplied");

        Sequential selectedCase = defaultCase;

        int sz = cases.size();
        for (int i=0;i<sz;i++)
        {
            Case c = (Case)(cases.elementAt(i));

            String cvalue = c.value;
            if (cvalue == null) {
                throw new BuildException("Value is required for case.");
            }
            String mvalue = value;

            if (caseInsensitive)
            {
                cvalue = cvalue.toUpperCase();
                mvalue = mvalue.toUpperCase();
            }

            if (cvalue.equals(mvalue) && c != defaultCase)
                selectedCase = c;
        }

        if (selectedCase == null) {
            throw new BuildException("No case matched the value " + value
                                     + " and no default has been specified.");
        }
        selectedCase.perform();
    }

    /***
     * Sets the value being switched on
     */
    public void setValue(String value)
    {
        this.value = value;
    }

    public void setCaseInsensitive(boolean c)
    {
        caseInsensitive = c;
    }

    public final class Case extends Sequential
    {
        private String value;

        public Case()
        {
            super();
        }
        
        public void setValue(String value)
        {
            this.value = value;
        }

        public void execute()
            throws BuildException
        {
            super.execute();
        }

        public boolean equals(Object o)
        {
            boolean res = false;
            Case c = (Case)o;
            if (c.value.equals(value))
                res = true;
            return res;                
        }
    }

    /***
     * Creates the <case> tag
     */
    public Switch.Case createCase()
        throws BuildException
    {
        Switch.Case res = new Switch.Case();
        cases.addElement(res);
        return res;
    }

    /***
     * Creates the <default> tag
     */
    public void addDefault(Sequential res)
        throws BuildException
    {
        if (defaultCase != null)
            throw new BuildException("Cannot specify multiple default cases");

        defaultCase = res;
    }

}