/*
    * Copyright (C) 2015, Google Inc. and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.internal.storage.file;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import java.io.BufferedReader;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.Reader;
  
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.MutableObjectId;
  import org.eclipse.jgit.lib.ObjectIdOwnerMap;
  import org.eclipse.jgit.lib.ObjectIdSet;
  
  /**
   * Lazily loads a set of ObjectIds, one per line.
   */
  public class LazyObjectIdSetFile implements ObjectIdSet {
  	private final File src;
  	private ObjectIdOwnerMap<Entry> set;
  
  	/**
  	 * Create a new lazy set from a file.
  	 *
  	 * @param src
  	 *            the source file.
  	 */
  	public LazyObjectIdSetFile(File src) {
  		this.src = src;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public boolean contains(AnyObjectId objectId) {
  		if (set == null) {
  			set = load();
  		}
  		return set.contains(objectId);
  	}
  
  	private ObjectIdOwnerMap<Entry> load() {
  		ObjectIdOwnerMap<Entry> r = new ObjectIdOwnerMap<>();
  		try (FileInputStream fin = new FileInputStream(src);
  				Reader rin = new InputStreamReader(fin, UTF_8);
  				BufferedReader br = new BufferedReader(rin)) {
  			MutableObjectId id = new MutableObjectId();
  			for (String line; (line = br.readLine()) != null;) {
  				id.fromString(line);
  				if (!r.contains(id)) {
  					r.add(new Entry(id));
  				}
  			}
  		} catch (IOException e) {
  			// Ignore IO errors accessing the lazy set.
  		}
  		return r;
  	}
  
  	static class Entry extends ObjectIdOwnerMap.Entry {
  		Entry(AnyObjectId id) {
  			super(id);
  		}
  	}
  }