com.facebook.buck.io.FileFinder.java Source code

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Here is the source code for com.facebook.buck.io.FileFinder.java

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/*
 * Copyright 2015-present Facebook, Inc.
 *
 * 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.facebook.buck.io;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableSet;

import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Optional;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * Methods for finding files.
 */
public class FileFinder {
    /**
     * Filter that checks that a file exists.
     */
    public static final Function<Path, Boolean> EXISTS = path -> Files.exists(path);

    /**
     * Filter that tests if a file is a regular file.
     */
    public static final Function<Path, Boolean> IS_REGULAR_FILE = path -> Files.isRegularFile(path);

    /**
     * Combines prefixes, base, and suffixes to create a set of file names.
     * @param prefixes set of prefixes. May be null or empty.
     * @param base base name. May be empty.
     * @param suffixes set of suffixes. May be null or empty.
     * @return a set containing all combinations of prefix, base, and suffix.
     */
    public static ImmutableSet<String> combine(@Nullable Set<String> prefixes, String base,
            @Nullable Set<String> suffixes) {

        ImmutableSet<String> suffixedSet;
        if (suffixes == null || suffixes.isEmpty()) {
            suffixedSet = ImmutableSet.of(base);
        } else {
            ImmutableSet.Builder<String> suffixedBuilder = ImmutableSet.builder();
            for (String suffix : suffixes) {
                suffixedBuilder.add(base + suffix);
            }
            suffixedSet = suffixedBuilder.build();
        }

        if (prefixes == null || prefixes.isEmpty()) {
            return suffixedSet;
        } else {
            ImmutableSet.Builder<String> builder = ImmutableSet.builder();
            for (String prefix : prefixes) {
                for (String suffix : suffixedSet) {
                    builder.add(prefix + suffix);
                }
            }
            return builder.build();
        }
    }

    /**
     * Tries to find a file with a specific name in a search path.
     * @param name file name to look for.
     * @param searchPath directories to search.
     * @return if found: the path to the file. if not found, Optional.empty().
     */
    public static Optional<Path> getOptionalFile(String name, Iterable<Path> searchPath) {
        return getOptionalFile(name, searchPath, EXISTS);
    }

    /**
     * Tries to find a file with a specific name in a search path.
     * @param name file name to look for.
     * @param searchPath directories to search.
     * @param filter additional check that discovered paths must pass to be eligible.
     * @return if found: the path to the file. if not found, Optional.empty().
     */
    public static Optional<Path> getOptionalFile(String name, Iterable<Path> searchPath,
            Function<Path, Boolean> filter) {
        return getOptionalFile(ImmutableSet.of(name), searchPath, filter);
    }

    /**
     * Tries to find a file with one of a number of possible names in a search path.
     * @param possibleNames file names to look for.
     * @param searchPath directories to search.
     * @return if found: the path to the file. if not found, Optional.empty().
     */
    public static Optional<Path> getOptionalFile(Set<String> possibleNames, Iterable<Path> searchPath) {
        return getOptionalFile(possibleNames, searchPath, EXISTS);
    }

    /**
     * Tries to find a file with one of a number of possible names in a search path.
     * @param possibleNames file names to look for.
     * @param searchPath directories to search.
     * @param filter additional check that discovered paths must pass to be eligible.
     * @return if found: the path to the file. if not found, Optional.empty().
     */
    public static Optional<Path> getOptionalFile(Set<String> possibleNames, Iterable<Path> searchPath,
            Function<Path, Boolean> filter) {

        for (Path path : searchPath) {
            for (String filename : possibleNames) {
                Path resolved = path.resolve(filename);
                if (filter.apply(resolved)) {
                    return Optional.of(resolved);
                }
            }
        }

        return Optional.empty();
    }

    /**
     * Constructor hidden; there is no reason to instantiate this class.
     */
    private FileFinder() {
    }
}