// 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;

import static java.util.Objects.requireNonNull;

import com.google.auto.value.AutoValue;
import com.google.common.base.MoreObjects;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.gerrit.server.util.time.TimeUtil;

public class AuditEvent {

  public static final String UNKNOWN_SESSION_ID = "000000000000000000000000000";
  protected static final ImmutableListMultimap<String, ?> EMPTY_PARAMS = ImmutableListMultimap.of();

  public final String sessionId;
  public final CurrentUser who;
  public final long when;
  public final String what;
  public final ListMultimap<String, ?> params;
  public final Object result;
  public final long timeAtStart;
  public final long elapsed;
  public final UUID uuid;

  @AutoValue
  public abstract static class UUID {
    private static UUID create() {
      return new AutoValue_AuditEvent_UUID(
          String.format("audit:%s", java.util.UUID.randomUUID().toString()));
    }

    public abstract String uuid();
  }

  /**
   * Creates a new audit event with results
   *
   * @param sessionId session id the event belongs to
   * @param who principal that has generated the event
   * @param what object of the event
   * @param when time-stamp of when the event started
   * @param params parameters of the event
   * @param result result of the event
   */
  public AuditEvent(
      String sessionId,
      CurrentUser who,
      String what,
      long when,
      ListMultimap<String, ?> params,
      Object result) {
    requireNonNull(what, "what is a mandatory not null param !");

    this.sessionId = MoreObjects.firstNonNull(sessionId, UNKNOWN_SESSION_ID);
    this.who = who;
    this.what = what;
    this.when = when;
    this.timeAtStart = this.when;
    this.params = MoreObjects.firstNonNull(params, EMPTY_PARAMS);
    this.uuid = UUID.create();
    this.result = result;
    this.elapsed = TimeUtil.nowMs() - timeAtStart;
  }

  @Override
  public int hashCode() {
    return uuid.hashCode();
  }

  // This is a value class that allows adding attributes by subclassing.
  // Doing this is discouraged and using composition rather than inheritance to add fields to value
  // types is preferred. However this class is part of the plugin API (used in the AuditListener
  // extension point), hence we cannot change it without breaking plugins. Hence suppress the
  // EqualsGetClass warning here.
  @SuppressWarnings("EqualsGetClass")
  @Override
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }

    AuditEvent other = (AuditEvent) obj;
    return this.uuid.equals(other.uuid);
  }

  @Override
  public String toString() {
    return String.format(
        "AuditEvent UUID:%s, SID:%s, TS:%d, who:%s, what:%s",
        uuid.uuid(), sessionId, when, who, what);
  }
}