com.google.devtools.depan.model.RelationSets.java Source code

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Here is the source code for com.google.devtools.depan.model.RelationSets.java

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/*
 * Copyright 2015 The Depan Project Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.devtools.depan.model;

import com.google.devtools.depan.graph.api.Relation;
import com.google.devtools.depan.graph.api.RelationSet;

import com.google.common.collect.Sets;

import java.util.Arrays;
import java.util.Collection;
import java.util.Set;

/**
 * Utility object and methods for {@link RelationSet}s.
 * 
 * Several common relation set definitions and factories are provided.
 * 
 * @author <a href="mailto:leeca@pnambic.com">Lee Carver</a>
 */
public class RelationSets {

    private RelationSets() {
        // Prevent instantiation.
    }

    public static Collection<Relation> filterRelations(RelationSet filter, Collection<Relation> source) {

        Set<Relation> result = Sets.newHashSet();
        for (Relation relation : source) {
            if (filter.contains(relation)) {
                result.add(relation);
            }
        }
        return result;
    }

    /////////////////////////////////////
    // ALL Relation Set

    // Only need one instance
    public static final RelationSet ALL = new RelationSet() {
        @Override
        public boolean contains(Relation relation) {
            return true;
        }
    };

    /////////////////////////////////////
    // EMPTY Relation Set

    // Only need one instance
    public static RelationSet EMPTY = new RelationSet() {
        @Override
        public boolean contains(Relation relation) {
            return false;
        }
    };

    /////////////////////////////////////
    // Relation sets for a single relation

    public static RelationSet createSingle(Relation relation) {
        return new Single(relation);
    }

    public static class Single implements RelationSet {

        private final Relation single;

        public Single(Relation single) {
            this.single = single;
        }

        @Override
        public boolean contains(Relation relation) {
            return (single == relation);
        }

        /**
         * Provide the one relation in this relation-set.
         * Intended primarily for serialization.
         */
        public Relation getRelation() {
            return single;
        }
    }

    /////////////////////////////////////
    // Array implemented relation sets
    // Common for plugin definitions.

    public static RelationSet createArray(Relation[] relations) {
        return new Array(relations);
    }

    public static class Array implements RelationSet {

        private final Relation[] relations;

        public Array(Relation[] relations) {
            this.relations = relations;
        }

        @Override
        public boolean contains(Relation relation) {
            return Arrays.asList(relations).contains(relation);
        }

        /**
         * Provide a snapshot of the array of relations.
         * Intended primarily for serialization.
         */
        public Relation[] getRelations() {
            return Arrays.copyOf(relations, relations.length);
        }
    };

    /////////////////////////////////////
    // Collection base relation sets.
    // Use Set for Collection type for performance.

    public static RelationSet createSimple(Collection<Relation> relationSet) {
        return new Simple(relationSet);
    }

    public static class Simple implements RelationSet {
        // XStream can handle a set, but not a more generic collection
        private final Set<Relation> relationSet;

        public Simple(Collection<Relation> relations) {
            this(Sets.newHashSet(relations));
        }

        public Simple(Set<Relation> relationSet) {
            this.relationSet = relationSet;
        }

        @Override
        public boolean contains(Relation relation) {
            return relationSet.contains(relation);
        }

        /**
         * Provide a snapshot of the set of relations.
         * Intended primarily for serialization.
         */
        public Set<Relation> getRelations() {
            return Sets.newHashSet(relationSet);
        }
    }
}