// Copyright (C) 2019 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.googlesource.gerrit.plugins.multisite.validation.dfsrefdb;

import java.io.IOException;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdRef;
import org.eclipse.jgit.lib.Ref;

public interface SharedRefDatabase {

  /** A null ref that isn't associated to any name. */
  Ref NULL_REF = nullRef(null);

  /**
   * Create a new in-memory ref name associated with an NULL object id.
   *
   * @param refName ref name
   * @return the new NULL ref object
   */
  static Ref nullRef(String refName) {
    return new Ref() {

      @Override
      public String getName() {
        return refName;
      }

      @Override
      public boolean isSymbolic() {
        return false;
      }

      @Override
      public Ref getLeaf() {
        return null;
      }

      @Override
      public Ref getTarget() {
        return null;
      }

      @Override
      public ObjectId getObjectId() {
        return ObjectId.zeroId();
      }

      @Override
      public ObjectId getPeeledObjectId() {
        return ObjectId.zeroId();
      }

      @Override
      public boolean isPeeled() {
        return false;
      }

      @Override
      public Storage getStorage() {
        return Storage.NEW;
      }
    };
  }

  /**
   * Create a new in-memory Ref name associated with an objectId.
   *
   * @param refName ref name
   * @param objectId object id
   */
  static Ref newRef(String refName, ObjectId objectId) {
    return new ObjectIdRef.Unpeeled(Ref.Storage.NETWORK, refName, objectId);
  }

  /**
   * Verify in shared db if Ref is the most recent
   *
   * @param project project name of the ref
   * @param ref to be checked against shared-ref db
   * @return true if it is; false otherwise
   * @throws SharedLockException if there was a problem locking the resource
   */
  boolean isUpToDate(String project, Ref ref) throws SharedLockException;

  /**
   * Compare a reference, and put if it matches.
   *
   * <p>Two reference match if and only if they satisfy the following:
   *
   * <ul>
   *   <li>If one reference is a symbolic ref, the other one should be a symbolic ref.
   *   <li>If both are symbolic refs, the target names should be same.
   *   <li>If both are object ID refs, the object IDs should be same.
   * </ul>
   *
   * @param project project name of the ref
   * @param currRef old value to compare to. If the reference is expected to not exist the old value
   *     has a storage of {@link org.eclipse.jgit.lib.Ref.Storage#NEW} and an ObjectId value of
   *     {@code null}.
   * @param newRefValue new reference to store.
   * @return true if the put was successful; false otherwise.
   * @throws java.io.IOException the reference cannot be put due to a system error.
   */
  boolean compareAndPut(String project, Ref currRef, ObjectId newRefValue) throws IOException;

  /**
   * Lock a reference for writing.
   *
   * @param project project name
   * @param refName ref to lock
   * @return lock object
   * @throws SharedLockException if the lock cannot be obtained
   */
  AutoCloseable lockRef(String project, String refName) throws SharedLockException;

  /**
   * Verify if the DB contains a value for the specific project and ref name
   *
   * @param project
   * @param refName
   * @return true if the ref exists on the project
   */
  boolean exists(String project, String refName);

  /**
   * Clean project path from SharedRefDatabase
   *
   * @param project project name
   * @throws IOException
   */
  void removeProject(String project) throws IOException;
}