1/*
2 * Copyright (C) 2009 The Guava Authors
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
17package com.google.common.collect;
18
19import static com.google.common.base.Preconditions.checkNotNull;
20
21import com.google.common.primitives.Primitives;
22
23import java.io.Serializable;
24import java.util.Map;
25
26import javax.annotation.Nullable;
27
28/**
29 * A class-to-instance map backed by an {@link ImmutableMap}. See also {@link
30 * MutableClassToInstanceMap}.
31 *
32 * @author Kevin Bourrillion
33 * @since 2.0 (imported from Google Collections Library)
34 */
35public final class ImmutableClassToInstanceMap<B>
36    extends ForwardingMap<Class<? extends B>, B>
37    implements ClassToInstanceMap<B>, Serializable {
38
39  /**
40   * Returns a new builder. The generated builder is equivalent to the builder
41   * created by the {@link Builder} constructor.
42   */
43  public static <B> Builder<B> builder() {
44    return new Builder<B>();
45  }
46
47  /**
48   * A builder for creating immutable class-to-instance maps. Example:
49   * <pre>   {@code
50   *
51   *   static final ImmutableClassToInstanceMap<Handler> HANDLERS =
52   *       new ImmutableClassToInstanceMap.Builder<Handler>()
53   *           .put(FooHandler.class, new FooHandler())
54   *           .put(BarHandler.class, new SubBarHandler())
55   *           .put(Handler.class, new QuuxHandler())
56   *           .build();}</pre>
57   *
58   * <p>After invoking {@link #build()} it is still possible to add more entries
59   * and build again. Thus each map generated by this builder will be a superset
60   * of any map generated before it.
61   *
62   * @since 2.0 (imported from Google Collections Library)
63   */
64  public static final class Builder<B> {
65    private final ImmutableMap.Builder<Class<? extends B>, B> mapBuilder
66        = ImmutableMap.builder();
67
68    /**
69     * Associates {@code key} with {@code value} in the built map. Duplicate
70     * keys are not allowed, and will cause {@link #build} to fail.
71     */
72    public <T extends B> Builder<B> put(Class<T> key, T value) {
73      mapBuilder.put(key, value);
74      return this;
75    }
76
77    /**
78     * Associates all of {@code map's} keys and values in the built map.
79     * Duplicate keys are not allowed, and will cause {@link #build} to fail.
80     *
81     * @throws NullPointerException if any key or value in {@code map} is null
82     * @throws ClassCastException if any value is not an instance of the type
83     *     specified by its key
84     */
85    public <T extends B> Builder<B> putAll(
86        Map<? extends Class<? extends T>, ? extends T> map) {
87      for (Entry<? extends Class<? extends T>, ? extends T> entry
88          : map.entrySet()) {
89        Class<? extends T> type = entry.getKey();
90        T value = entry.getValue();
91        mapBuilder.put(type, cast(type, value));
92      }
93      return this;
94    }
95
96    private static <B, T extends B> T cast(Class<T> type, B value) {
97      return Primitives.wrap(type).cast(value);
98    }
99
100    /**
101     * Returns a new immutable class-to-instance map containing the entries
102     * provided to this builder.
103     *
104     * @throws IllegalArgumentException if duplicate keys were added
105     */
106    public ImmutableClassToInstanceMap<B> build() {
107      return new ImmutableClassToInstanceMap<B>(mapBuilder.build());
108    }
109  }
110
111  /**
112   * Returns an immutable map containing the same entries as {@code map}. If
113   * {@code map} somehow contains entries with duplicate keys (for example, if
114   * it is a {@code SortedMap} whose comparator is not <i>consistent with
115   * equals</i>), the results of this method are undefined.
116   *
117   * <p><b>Note:</b> Despite what the method name suggests, if {@code map} is
118   * an {@code ImmutableClassToInstanceMap}, no copy will actually be performed.
119   *
120   * @throws NullPointerException if any key or value in {@code map} is null
121   * @throws ClassCastException if any value is not an instance of the type
122   *     specified by its key
123   */
124  public static <B, S extends B> ImmutableClassToInstanceMap<B> copyOf(
125      Map<? extends Class<? extends S>, ? extends S> map) {
126    if (map instanceof ImmutableClassToInstanceMap) {
127      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
128      // Eclipse won't compile if we cast to the parameterized type.
129      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap) map;
130      return cast;
131    }
132    return new Builder<B>().putAll(map).build();
133  }
134
135  private final ImmutableMap<Class<? extends B>, B> delegate;
136
137  private ImmutableClassToInstanceMap(
138      ImmutableMap<Class<? extends B>, B> delegate) {
139    this.delegate = delegate;
140  }
141
142  @Override protected Map<Class<? extends B>, B> delegate() {
143    return delegate;
144  }
145
146  @Override
147  @SuppressWarnings("unchecked") // value could not get in if not a T
148  @Nullable
149  public <T extends B> T getInstance(Class<T> type) {
150    return (T) delegate.get(checkNotNull(type));
151  }
152
153  /**
154   * Guaranteed to throw an exception and leave the map unmodified.
155   *
156   * @throws UnsupportedOperationException always
157   * @deprecated Unsupported operation.
158   */
159  @Deprecated
160  @Override
161  public <T extends B> T putInstance(Class<T> type, T value) {
162    throw new UnsupportedOperationException();
163  }
164}
165