gradle-master/subprojects/execution/src/main/java/org/gradle/internal/execution/history/changes/IgnoredPathCompareStrategy.java
/*
 * Copyright 2018 the original author or 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 org.gradle.internal.execution.history.changes;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.MultimapBuilder;
import org.gradle.internal.fingerprint.FileCollectionFingerprint;
import org.gradle.internal.fingerprint.FileSystemLocationFingerprint;
import org.gradle.internal.fingerprint.impl.IgnoredPathFingerprintingStrategy;
import org.gradle.internal.hash.HashCode;

import java.util.Comparator;
import java.util.List;
import java.util.Map;

/**
 * Compares {@link FileCollectionFingerprint}s ignoring the path.
 */
public class IgnoredPathCompareStrategy extends AbstractFingerprintCompareStrategy {
    public static final FingerprintCompareStrategy INSTANCE = new IgnoredPathCompareStrategy();

    private static final Comparator<Map.Entry<HashCode, FilePathWithType>> ENTRY_COMPARATOR = Map.Entry.comparingByKey();

    private IgnoredPathCompareStrategy() {
        super(IgnoredPathCompareStrategy::visitChangesSince);
    }

    /**
     * Determines changes by:
     *
     * <ul>
     *     <li>Determining which content fingerprints are only in the previous or current fingerprint collection.</li>
     *     <li>Those only in the previous fingerprint collection are reported as removed.</li>
     * </ul>
     */
    private static boolean visitChangesSince(
        Map<String, FileSystemLocationFingerprint> previous,
        Map<String, FileSystemLocationFingerprint> current,
        String propertyTitle,
        ChangeVisitor visitor
    ) {
        ListMultimap<HashCode, FilePathWithType> unaccountedForPreviousFiles = MultimapBuilder.hashKeys(previous.size()).linkedListValues().build();
        for (Map.Entry<String, FileSystemLocationFingerprint> entry : previous.entrySet()) {
            String absolutePath = entry.getKey();
            FileSystemLocationFingerprint previousFingerprint = entry.getValue();
            unaccountedForPreviousFiles.put(previousFingerprint.getNormalizedContentHash(), new FilePathWithType(absolutePath, previousFingerprint.getType()));
        }

        for (Map.Entry<String, FileSystemLocationFingerprint> entry : current.entrySet()) {
            String currentAbsolutePath = entry.getKey();
            FileSystemLocationFingerprint currentFingerprint = entry.getValue();
            HashCode normalizedContentHash = currentFingerprint.getNormalizedContentHash();
            List<FilePathWithType> previousFilesForContent = unaccountedForPreviousFiles.get(normalizedContentHash);
            if (previousFilesForContent.isEmpty()) {
                DefaultFileChange added = DefaultFileChange.added(currentAbsolutePath, propertyTitle, currentFingerprint.getType(), IgnoredPathFingerprintingStrategy.IGNORED_PATH);
                if (!visitor.visitChange(added)) {
                    return false;
                }
            } else {
                previousFilesForContent.remove(0);
            }
        }

        List<Map.Entry<HashCode, FilePathWithType>> unaccountedForPreviousEntries = ImmutableList.sortedCopyOf(ENTRY_COMPARATOR, unaccountedForPreviousFiles.entries());
        for (Map.Entry<HashCode, FilePathWithType> unaccountedForPreviousEntry : unaccountedForPreviousEntries) {
            FilePathWithType removedFile = unaccountedForPreviousEntry.getValue();
            DefaultFileChange removed = DefaultFileChange.removed(removedFile.getAbsolutePath(), propertyTitle, removedFile.getFileType(), IgnoredPathFingerprintingStrategy.IGNORED_PATH);
            if (!visitor.visitChange(removed)) {
                return false;
            }
        }
        return true;
    }

}
