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