001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.util.graph.version;
020
021import java.util.Iterator;
022
023import org.eclipse.aether.collection.DependencyCollectionContext;
024import org.eclipse.aether.collection.VersionFilter;
025import org.eclipse.aether.version.Version;
026
027/**
028 * A version filter that excludes any version except the lowest one.
029 *
030 * @since 2.0.0
031 */
032public final class LowestVersionFilter implements VersionFilter {
033    private final int count;
034
035    /**
036     * Creates a new instance of this version filter.
037     */
038    public LowestVersionFilter() {
039        this.count = 1;
040    }
041
042    /**
043     * Creates a new instance of this version filter.
044     */
045    public LowestVersionFilter(int count) {
046        if (count < 1) {
047            throw new IllegalArgumentException("Count should be greater or equal to 1");
048        }
049        this.count = count;
050    }
051
052    @Override
053    public void filterVersions(VersionFilterContext context) {
054        if (context.getCount() <= count) {
055            return;
056        }
057        // iterator comes in ascending order, basically we "step over" (leave) first few
058        int stepOver = count;
059        Iterator<Version> it = context.iterator();
060        while (it.hasNext()) {
061            it.next();
062            stepOver--;
063            if (stepOver < 0) {
064                it.remove();
065            }
066        }
067    }
068
069    @Override
070    public VersionFilter deriveChildFilter(DependencyCollectionContext context) {
071        return this;
072    }
073
074    @Override
075    public boolean equals(Object obj) {
076        if (this == obj) {
077            return true;
078        } else if (null == obj || !getClass().equals(obj.getClass())) {
079            return false;
080        }
081        return true;
082    }
083
084    @Override
085    public int hashCode() {
086        return getClass().hashCode();
087    }
088}