// 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;

import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.googlesource.gerrit.plugins.multisite.SharedRefDatabaseWrapper;
import com.googlesource.gerrit.plugins.multisite.validation.dfsrefdb.SharedLockException;
import com.googlesource.gerrit.plugins.multisite.validation.dfsrefdb.SharedRefDatabase;
import com.googlesource.gerrit.plugins.replication.ReplicationPushFilter;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
import org.eclipse.jgit.transport.RemoteRefUpdate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Singleton
public class MultisiteReplicationPushFilter implements ReplicationPushFilter {
  private static final String REF_META_SUFFIX = "/meta";
  static final String REPLICATION_LOG_NAME = "replication_log";
  static final Logger repLog = LoggerFactory.getLogger(REPLICATION_LOG_NAME);

  private final SharedRefDatabaseWrapper sharedRefDb;

  @Inject
  public MultisiteReplicationPushFilter(SharedRefDatabaseWrapper sharedRefDb) {
    this.sharedRefDb = sharedRefDb;
  }

  @Override
  public List<RemoteRefUpdate> filter(String projectName, List<RemoteRefUpdate> remoteUpdatesList) {
    Set<String> outdatedChanges = new HashSet<>();

    List<RemoteRefUpdate> filteredRefUpdates =
        remoteUpdatesList.stream()
            .filter(
                refUpdate -> {
                  String ref = refUpdate.getSrcRef();
                  try {
                    if (sharedRefDb.isUpToDate(
                        projectName, SharedRefDatabase.newRef(ref, refUpdate.getNewObjectId()))) {
                      return true;
                    }
                    repLog.warn(
                        "{} is not up-to-date with the shared-refdb and thus will NOT BE replicated",
                        refUpdate);
                  } catch (SharedLockException e) {
                    repLog.warn(
                        "{} is locked on shared-refdb and thus will NOT BE replicated", refUpdate);
                  }
                  if (ref.endsWith(REF_META_SUFFIX)) {
                    outdatedChanges.add(getRootChangeRefPrefix(ref));
                  }
                  return false;
                })
            .collect(Collectors.toList());

    return filteredRefUpdates.stream()
        .filter(
            refUpdate -> {
              if (outdatedChanges.contains(changePrefix(refUpdate.getSrcRef()))) {
                repLog.warn(
                    "{} belongs to an outdated /meta ref and thus will NOT BE replicated",
                    refUpdate);
                return false;
              }
              return true;
            })
        .collect(Collectors.toList());
  }

  private String changePrefix(String changeRef) {
    if (changeRef == null || !changeRef.startsWith("refs/changes")) {
      return changeRef;
    }
    if (changeRef.endsWith(REF_META_SUFFIX)) {
      return getRootChangeRefPrefix(changeRef);
    }

    // changeRef has the form '/refs/changes/NN/NNNN/P'
    return changeRef.substring(0, changeRef.lastIndexOf('/'));
  }

  private String getRootChangeRefPrefix(String changeMetaRef) {
    if (changeMetaRef.endsWith(REF_META_SUFFIX)) {
      return changeMetaRef.substring(0, changeMetaRef.length() - REF_META_SUFFIX.length());
    }

    return changeMetaRef;
  }
}