// Copyright (C) 2009 The Android Open Source Project
//
// 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.google.gerrit.server;

import static java.util.Comparator.comparingInt;

import com.google.common.collect.Maps;
import com.google.common.collect.Ordering;
import com.google.common.io.BaseEncoding;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.inject.Singleton;
import java.io.IOException;
import java.security.SecureRandom;
import java.util.Map;
import java.util.Random;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;

@Singleton
public class ChangeUtil {
  private static final Random UUID_RANDOM = new SecureRandom();
  private static final BaseEncoding UUID_ENCODING = BaseEncoding.base16().lowerCase();

  private static final int SUBJECT_MAX_LENGTH = 80;
  private static final String SUBJECT_CROP_APPENDIX = "...";
  private static final int SUBJECT_CROP_RANGE = 10;

  public static final Ordering<PatchSet> PS_ID_ORDER =
      Ordering.from(comparingInt(PatchSet::getPatchSetId));

  /** @return a new unique identifier for change message entities. */
  public static String messageUuid() {
    byte[] buf = new byte[8];
    UUID_RANDOM.nextBytes(buf);
    return UUID_ENCODING.encode(buf, 0, 4) + '_' + UUID_ENCODING.encode(buf, 4, 4);
  }

  /**
   * Get the next patch set ID from a previously-read map of all refs.
   *
   * @param allRefs map of full ref name to ref, in the same format returned by {@link
   *     org.eclipse.jgit.lib.RefDatabase#getRefs(String)} when passing {@code ""}.
   * @param id previous patch set ID.
   * @return next unused patch set ID for the same change, skipping any IDs whose corresponding ref
   *     names appear in the {@code allRefs} map.
   */
  public static PatchSet.Id nextPatchSetIdFromAllRefsMap(Map<String, Ref> allRefs, PatchSet.Id id) {
    PatchSet.Id next = nextPatchSetId(id);
    while (allRefs.containsKey(next.toRefName())) {
      next = nextPatchSetId(next);
    }
    return next;
  }

  /**
   * Get the next patch set ID from a previously-read map of refs below the change prefix.
   *
   * @param changeRefs map of ref suffix to SHA-1, where the keys are ref names with the {@code
   *     refs/changes/CD/ABCD/} prefix stripped. All refs should be under {@code id}'s change ref
   *     prefix. The keys match the format returned by {@link
   *     org.eclipse.jgit.lib.RefDatabase#getRefs(String)} when passing the appropriate {@code
   *     refs/changes/CD/ABCD}.
   * @param id previous patch set ID.
   * @return next unused patch set ID for the same change, skipping any IDs whose corresponding ref
   *     names appear in the {@code changeRefs} map.
   */
  public static PatchSet.Id nextPatchSetIdFromChangeRefsMap(
      Map<String, ObjectId> changeRefs, PatchSet.Id id) {
    int prefixLen = id.getParentKey().toRefPrefix().length();
    PatchSet.Id next = nextPatchSetId(id);
    while (changeRefs.containsKey(next.toRefName().substring(prefixLen))) {
      next = nextPatchSetId(next);
    }
    return next;
  }

  /**
   * Get the next patch set ID just looking at a single previous patch set ID.
   *
   * <p>This patch set ID may or may not be available in the database; callers that want a
   * previously-unused ID should use {@link #nextPatchSetIdFromAllRefsMap} or {@link
   * #nextPatchSetIdFromChangeRefsMap}.
   *
   * @param id previous patch set ID.
   * @return next patch set ID for the same change, incrementing by 1.
   */
  public static PatchSet.Id nextPatchSetId(PatchSet.Id id) {
    return new PatchSet.Id(id.getParentKey(), id.get() + 1);
  }

  /**
   * Get the next patch set ID from scanning refs in the repo.
   *
   * @param git repository to scan for patch set refs.
   * @param id previous patch set ID.
   * @return next unused patch set ID for the same change, skipping any IDs whose corresponding ref
   *     names appear in the repository.
   */
  public static PatchSet.Id nextPatchSetId(Repository git, PatchSet.Id id) throws IOException {
    return nextPatchSetIdFromChangeRefsMap(
        Maps.transformValues(
            git.getRefDatabase().getRefs(id.getParentKey().toRefPrefix()), Ref::getObjectId),
        id);
  }

  public static String cropSubject(String subject) {
    if (subject.length() > SUBJECT_MAX_LENGTH) {
      int maxLength = SUBJECT_MAX_LENGTH - SUBJECT_CROP_APPENDIX.length();
      for (int cropPosition = maxLength;
          cropPosition > maxLength - SUBJECT_CROP_RANGE;
          cropPosition--) {
        if (Character.isWhitespace(subject.charAt(cropPosition - 1))) {
          return subject.substring(0, cropPosition) + SUBJECT_CROP_APPENDIX;
        }
      }
      return subject.substring(0, maxLength) + SUBJECT_CROP_APPENDIX;
    }
    return subject;
  }

  public static String status(Change c) {
    return c != null ? c.getStatus().name().toLowerCase() : "deleted";
  }

  private ChangeUtil() {}
}