// Copyright (C) 2012 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.change;

import com.google.common.base.Strings;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.extensions.restapi.BadRequestException;
import com.google.gerrit.extensions.restapi.DefaultInput;
import com.google.gerrit.extensions.restapi.Response;
import com.google.gerrit.extensions.restapi.ResourceConflictException;
import com.google.gerrit.extensions.restapi.RestModifyView;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.ChangeMessage;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.ChangeUtil;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.change.PutTopic.Input;
import com.google.gerrit.server.project.ChangeControl;
import com.google.gwtorm.server.AtomicUpdate;
import com.google.inject.Inject;
import com.google.inject.Provider;

import java.util.Collections;

class PutTopic implements RestModifyView<ChangeResource, Input> {
  private final Provider<ReviewDb> dbProvider;

  static class Input {
    @DefaultInput
    String topic;
    String message;
  }

  @Inject
  PutTopic(Provider<ReviewDb> dbProvider) {
    this.dbProvider = dbProvider;
  }

  @Override
  public Object apply(ChangeResource req, Input input)
      throws BadRequestException, AuthException,
      ResourceConflictException, Exception {
    if (input == null) {
      input = new Input();
    }

    ChangeControl control = req.getControl();
    Change change = req.getChange();
    if (!control.canEditTopicName()) {
      throw new AuthException("changing topic not permitted");
    }

    ReviewDb db = dbProvider.get();
    final String newTopicName = Strings.nullToEmpty(input.topic);
    String oldTopicName = Strings.nullToEmpty(change.getTopic());
    if (!oldTopicName.equals(newTopicName)) {
      String summary;
      if (oldTopicName.isEmpty()) {
        summary = "Topic set to \"" + newTopicName + "\".";
      } else if (newTopicName.isEmpty()) {
        summary = "Topic \"" + oldTopicName + "\" removed.";
      } else {
        summary = String.format(
            "Topic updated from \"%s\" to \"%s\".",
            oldTopicName, newTopicName);
      }

      ChangeMessage cmsg = new ChangeMessage(
          new ChangeMessage.Key(change.getId(), ChangeUtil.messageUUID(db)),
          ((IdentifiedUser) control.getCurrentUser()).getAccountId(),
          change.currentPatchSetId());
      StringBuilder msgBuf = new StringBuilder(summary);
      if (!Strings.isNullOrEmpty(input.message)) {
        msgBuf.append("\n\n");
        msgBuf.append(input.message);
      }
      cmsg.setMessage(msgBuf.toString());

      db.changes().atomicUpdate(change.getId(),
        new AtomicUpdate<Change>() {
          @Override
          public Change update(Change change) {
            change.setTopic(Strings.emptyToNull(newTopicName));
            return change;
          }
        });
      db.changeMessages().insert(Collections.singleton(cmsg));
    }
    return Strings.isNullOrEmpty(newTopicName)
        ? Response.none()
        : newTopicName;
  }
}