001    /*
002     * Copyright 2010-2015 JetBrains s.r.o.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package org.jetbrains.kotlin.js.translate.context.generator;
018    
019    import com.google.common.collect.Lists;
020    import com.google.common.collect.Maps;
021    import org.jetbrains.annotations.NotNull;
022    import org.jetbrains.annotations.Nullable;
023    import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
024    
025    import java.util.List;
026    import java.util.Map;
027    
028    public class Generator<V> {
029        @NotNull
030        private final Map<DeclarationDescriptor, V> values = Maps.newHashMap();
031        @NotNull
032        private final List<Rule<V>> rules = Lists.newArrayList();
033    
034        protected final void addRule(@NotNull Rule<V> rule) {
035            rules.add(rule);
036        }
037    
038        @Nullable
039        public V get(@NotNull DeclarationDescriptor descriptor) {
040            V result = values.get(descriptor);
041            if (result != null) {
042                return result;
043            }
044            result = generate(descriptor);
045            values.put(descriptor, result);
046            return result;
047        }
048    
049        @Nullable
050        private V generate(@NotNull DeclarationDescriptor descriptor) {
051            for (Rule<V> rule : rules) {
052                V result = rule.apply(descriptor);
053                if (result != null) {
054                    return result;
055                }
056            }
057            return null;
058        }
059    }