/*
    * Copyright (C) 2015, 2021 Dariusz Luksza <dariusz@luksza.org> 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.lfs.lib;
  
  import java.io.IOException;
  
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.lfs.LfsPointer;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectLoader;
  import org.eclipse.jgit.lib.ObjectStream;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.treewalk.filter.TreeFilter;
  
  /**
   * Detects Large File pointers, as described in [1] in Git repository.
   *
   * [1] https://github.com/github/git-lfs/blob/master/docs/spec.md
   *
   * @since 4.7
   */
  public class LfsPointerFilter extends TreeFilter {
  
  	private LfsPointer pointer;
  
  	/**
  	 * Get the field <code>pointer</code>.
  	 *
  	 * @return {@link org.eclipse.jgit.lfs.LfsPointer} or {@code null}
  	 */
  	public LfsPointer getPointer() {
  		return pointer;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public boolean include(TreeWalk walk) throws MissingObjectException,
  			IncorrectObjectTypeException, IOException {
  		pointer = null;
  		if (walk.isSubtree()) {
  			return walk.isRecursive();
  		}
  		ObjectId objectId = walk.getObjectId(0);
  		ObjectLoader object = walk.getObjectReader().open(objectId);
  		if (object.getSize() > 1024) {
  			return false;
  		}
  
  		try (ObjectStream stream = object.openStream()) {
  			pointer = LfsPointer.parseLfsPointer(stream);
  			return pointer != null;
  		} catch (RuntimeException e) {
  			return false;
  		}
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public boolean shouldBeRecursive() {
  		return false;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public TreeFilter clone() {
  		return new LfsPointerFilter();
  	}
  }