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 *
 *      http://www.apache.org/licenses/LICENSE-2.0
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 *  distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.commons.collections.functors;

import java.io.Serializable;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.collections.Predicate;
import org.apache.commons.collections.Transformer;

Transformer implementation calls the transformer whose predicate returns true,
like a switch statement.
Author:
Stephen Colebourne
Since:
Commons Collections 3.0
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $/**
 * Transformer implementation calls the transformer whose predicate returns true,
 * like a switch statement.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class SwitchTransformer implements Transformer, Serializable {

    
Serial version UID /** Serial version UID */
    private static final long serialVersionUID = -6404460890903469332L;

    
The tests to consider /** The tests to consider */
    private final Predicate[] iPredicates;
    
The matching transformers to call /** The matching transformers to call */
    private final Transformer[] iTransformers;
    
The default transformer to call if no tests match /** The default transformer to call if no tests match */
    private final Transformer iDefault;

    
Factory method that performs validation and copies the parameter arrays.
Params:
predicates –  array of predicates, cloned, no nulls
transformers –  matching array of transformers, cloned, no nulls
defaultTransformer –  the transformer to use if no match, null means return null
Throws:
IllegalArgumentException – if array is null
IllegalArgumentException – if any element in the array is null
Returns:
the chained transformer/**
     * Factory method that performs validation and copies the parameter arrays.
     * 
     * @param predicates  array of predicates, cloned, no nulls
     * @param transformers  matching array of transformers, cloned, no nulls
     * @param defaultTransformer  the transformer to use if no match, null means return null
     * @return the <code>chained</code> transformer
     * @throws IllegalArgumentException if array is null
     * @throws IllegalArgumentException if any element in the array is null
     */
    public static Transformer getInstance(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer) {
        FunctorUtils.validate(predicates);
        FunctorUtils.validate(transformers);
        if (predicates.length != transformers.length) {
            throw new IllegalArgumentException("The predicate and transformer arrays must be the same size");
        }
        if (predicates.length == 0) {
            return (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer);
        }
        predicates = FunctorUtils.copy(predicates);
        transformers = FunctorUtils.copy(transformers);
        return new SwitchTransformer(predicates, transformers, defaultTransformer);
    }

    
Create a new Transformer that calls one of the transformers depending 
on the predicates. 

The Map consists of Predicate keys and Transformer values. A transformer 
is called if its matching predicate returns true. Each predicate is evaluated
until one returns true. If no predicates evaluate to true, the default
transformer is called. The default transformer is set in the map with a 
null key. The ordering is that of the iterator() method on the entryset 
collection of the map.
Params:
predicatesAndTransformers –  a map of predicates to transformers
Throws:
IllegalArgumentException – if the map is null
IllegalArgumentException – if any transformer in the map is null
ClassCastException –  if the map elements are of the wrong type
Returns:
the switch transformer/**
     * Create a new Transformer that calls one of the transformers depending 
     * on the predicates. 
     * <p>
     * The Map consists of Predicate keys and Transformer values. A transformer 
     * is called if its matching predicate returns true. Each predicate is evaluated
     * until one returns true. If no predicates evaluate to true, the default
     * transformer is called. The default transformer is set in the map with a 
     * null key. The ordering is that of the iterator() method on the entryset 
     * collection of the map.
     * 
     * @param predicatesAndTransformers  a map of predicates to transformers
     * @return the <code>switch</code> transformer
     * @throws IllegalArgumentException if the map is null
     * @throws IllegalArgumentException if any transformer in the map is null
     * @throws ClassCastException  if the map elements are of the wrong type
     */
    public static Transformer getInstance(Map predicatesAndTransformers) {
        Transformer[] transformers = null;
        Predicate[] preds = null;
        if (predicatesAndTransformers == null) {
            throw new IllegalArgumentException("The predicate and transformer map must not be null");
        }
        if (predicatesAndTransformers.size() == 0) {
            return ConstantTransformer.NULL_INSTANCE;
        }
        // convert to array like this to guarantee iterator() ordering
        Transformer defaultTransformer = (Transformer) predicatesAndTransformers.remove(null);
        int size = predicatesAndTransformers.size();
        if (size == 0) {
            return (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer);
        }
        transformers = new Transformer[size];
        preds = new Predicate[size];
        int i = 0;
        for (Iterator it = predicatesAndTransformers.entrySet().iterator(); it.hasNext();) {
            Map.Entry entry = (Map.Entry) it.next();
            preds[i] = (Predicate) entry.getKey();
            transformers[i] = (Transformer) entry.getValue();
            i++;
        }
        return new SwitchTransformer(preds, transformers, defaultTransformer);
    }
    
    
Constructor that performs no validation.
Use getInstance if you want that.
Params:
predicates –  array of predicates, not cloned, no nulls
transformers –  matching array of transformers, not cloned, no nulls
defaultTransformer –  the transformer to use if no match, null means return null/**
     * Constructor that performs no validation.
     * Use <code>getInstance</code> if you want that.
     * 
     * @param predicates  array of predicates, not cloned, no nulls
     * @param transformers  matching array of transformers, not cloned, no nulls
     * @param defaultTransformer  the transformer to use if no match, null means return null
     */
    public SwitchTransformer(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer) {
        super();
        iPredicates = predicates;
        iTransformers = transformers;
        iDefault = (defaultTransformer == null ? ConstantTransformer.NULL_INSTANCE : defaultTransformer);
    }

    
Transforms the input to result by calling the transformer whose matching
predicate returns true.
Params:
input –  the input object to transform
Returns:
the transformed result/**
     * Transforms the input to result by calling the transformer whose matching
     * predicate returns true.
     * 
     * @param input  the input object to transform
     * @return the transformed result
     */
    public Object transform(Object input) {
        for (int i = 0; i < iPredicates.length; i++) {
            if (iPredicates[i].evaluate(input) == true) {
                return iTransformers[i].transform(input);
            }
        }
        return iDefault.transform(input);
    }

    
Gets the predicates, do not modify the array.
Returns:
the predicates
Since:
Commons Collections 3.1/**
     * Gets the predicates, do not modify the array.
     * 
     * @return the predicates
     * @since Commons Collections 3.1
     */
    public Predicate[] getPredicates() {
        return iPredicates;
    }

    
Gets the transformers, do not modify the array.
Returns:
the transformers
Since:
Commons Collections 3.1/**
     * Gets the transformers, do not modify the array.
     * 
     * @return the transformers
     * @since Commons Collections 3.1
     */
    public Transformer[] getTransformers() {
        return iTransformers;
    }

    
Gets the default transformer.
Returns:
the default transformer
Since:
Commons Collections 3.1/**
     * Gets the default transformer.
     * 
     * @return the default transformer
     * @since Commons Collections 3.1
     */
    public Transformer getDefaultTransformer() {
        return iDefault;
    }

}