fabric-loom/src/main/java/net/fabricmc/loom/util/StaticPathWatcher.java

/*
 * This file is part of fabric-loom, licensed under the MIT License (MIT).
 *
 * Copyright (c) 2016, 2017, 2018 FabricMC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package net.fabricmc.loom.util;

import net.fabricmc.mappings.Mappings;
import org.gradle.api.logging.Logging;

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.SoftReference;
import java.nio.file.*;
import java.util.HashMap;
import java.util.Map;

public final class StaticPathWatcher {
    public static final StaticPathWatcher INSTANCE = new StaticPathWatcher();

    private final Map<Path, Boolean> changeCache = new HashMap<>();
    private final WatchService service;
    private final Map<Path, WatchKey> pathsObserved = new HashMap<>();

    private StaticPathWatcher() {
        try {
            service = FileSystems.getDefault().newWatchService();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    public boolean hasFileChanged(Path filePath) {
    	if(!Files.exists(filePath)){
    		return true;
	    }
        WatchKey key;
        while ((key = service.poll()) != null) {
            for (WatchEvent<?> event : key.pollEvents()) {
                Object ctx = event.context();
                if (ctx instanceof Path) {
                    changeCache.put(((Path) ctx).toAbsolutePath(), true);
                }
            }
        }

        filePath = filePath.toAbsolutePath();
        Path parentPath = filePath.getParent();
        if (changeCache.containsKey(filePath)) {
            return true;
        } else {
            if (!pathsObserved.containsKey(parentPath)) {
                try {
                    pathsObserved.put(parentPath, parentPath.register(
                            service, StandardWatchEventKinds.ENTRY_MODIFY, StandardWatchEventKinds.ENTRY_DELETE
                    ));

                    return true;
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            } else {
                return false;
            }
        }
    }
}