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1   /*
2    * Copyright (C) 2012 Atlassian
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package com.atlassian.jira.rest.client.domain.input;
18  
19  import com.google.common.base.Function;
20  import com.google.common.collect.ImmutableList;
21  import com.google.common.collect.Iterables;
22  import com.google.common.collect.Lists;
23  
24  import javax.annotation.Nullable;
25  import java.util.List;
26  
27  /**
28   * This class allows to register {@link ValueTransformer} objects and then perform value transformation using
29   * registered transformers by invoking {@link ValueTransformerManager#apply(Object)}.<br/>
30   *
31   * @since v1.0
32   */
33  public class ValueTransformerManager implements Function<Object, Object> {
34  	public final List<ValueTransformer> valueTransformers = Lists.newArrayList();
35  
36  	public ValueTransformerManager() {
37  	}
38  
39  	/**
40  	 * Registers new transformer at the end of list so it will be processed after existing transformers.
41  	 *
42  	 * @param transformer Transformer to register
43  	 * @return this
44  	 */
45  	public ValueTransformerManager registerTransformer(final ValueTransformer transformer) {
46  		valueTransformers.add(transformer);
47  		return this;
48  	}
49  
50  	/**
51  	 * Registers new transformer at the beginning of list so it will be processed before existing transformers.
52  	 *
53  	 * @param transformer Transformer to register
54  	 * @return this
55  	 */
56  	@SuppressWarnings("unused")
57  	public ValueTransformerManager registerTransformerAsFirst(final ValueTransformer transformer) {
58  		valueTransformers.add(0, transformer);
59  		return this;
60  	}
61  
62  	/**
63  	 * Use registered transformers to transform given value.
64  	 *
65  	 * @param rawInput Value to transform
66  	 * @return transformed value
67  	 * @throws CannotTransformValueException when any of available transformers was able to transform given value
68  	 */
69  	public Object apply(@Nullable Object rawInput) {
70  		if (rawInput instanceof Iterable) {
71  			@SuppressWarnings("unchecked")
72  			final Iterable<Object> rawInputObjects= (Iterable<Object>) rawInput;
73  			return ImmutableList.copyOf(Iterables.transform(rawInputObjects, this));
74  		}
75  		
76  		for (ValueTransformer valueTransformer : valueTransformers) {
77  			final Object transformedValue = valueTransformer.apply(rawInput);
78  			if (!ValueTransformer.CANNOT_HANDLE.equals(transformedValue)) {
79  				return transformedValue;
80  			}
81  		}
82  
83  		throw new CannotTransformValueException("Any of available transformers was able to transform given value. Value is: "
84  				+ (rawInput == null ? "NULL" : rawInput.getClass().getName() + ": " + rawInput.toString()));
85  	}
86  }