// Copyright (C) 2016 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 com.google.gerrit.server.Sequence.NAME_ACCOUNTS;
import static com.google.gerrit.server.Sequence.NAME_CHANGES;
import static com.google.gerrit.server.Sequence.NAME_GROUPS;

import com.google.common.collect.ImmutableList;
import com.google.gerrit.metrics.Description;
import com.google.gerrit.metrics.Description.Units;
import com.google.gerrit.metrics.Field;
import com.google.gerrit.metrics.MetricMaker;
import com.google.gerrit.metrics.Timer2;
import com.google.gerrit.server.Sequence.SequenceType;
import com.google.gerrit.server.logging.Metadata;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import com.google.inject.name.Named;

@Singleton
public class Sequences {
  public static final int FIRST_CHANGE_ID = 1;
  public static final int FIRST_GROUP_ID = 1;
  public static final int FIRST_ACCOUNT_ID = 1000000;

  private final Sequence accountSeq;
  private final Sequence changeSeq;
  private final Sequence groupSeq;
  private final Timer2<SequenceType, Boolean> nextIdLatency;

  @Inject
  public Sequences(
      MetricMaker metrics,
      @Named(NAME_ACCOUNTS) Sequence accountsSeq,
      @Named(NAME_GROUPS) Sequence groupsSeq,
      @Named(NAME_CHANGES) Sequence changesSeq) {
    this.accountSeq = accountsSeq;
    this.groupSeq = groupsSeq;
    this.changeSeq = changesSeq;

    nextIdLatency =
        metrics.newTimer(
            "sequence/next_id_latency",
            new Description("Latency of requesting IDs from repo sequences")
                .setCumulative()
                .setUnit(Units.MILLISECONDS),
            Field.ofEnum(SequenceType.class, "sequence", Metadata.Builder::noteDbSequenceType)
                .description("The sequence from which IDs were retrieved.")
                .build(),
            Field.ofBoolean("multiple", Metadata.Builder::multiple)
                .description("Whether more than one ID was retrieved.")
                .build());
  }

  public int nextAccountId() {
    try (Timer2.Context<SequenceType, Boolean> timer =
        nextIdLatency.start(Sequence.SequenceType.ACCOUNTS, false)) {
      return accountSeq.next();
    }
  }

  public int nextChangeId() {
    try (Timer2.Context<SequenceType, Boolean> timer =
        nextIdLatency.start(Sequence.SequenceType.CHANGES, false)) {
      return changeSeq.next();
    }
  }

  public ImmutableList<Integer> nextChangeIds(int count) {
    try (Timer2.Context<SequenceType, Boolean> timer =
        nextIdLatency.start(Sequence.SequenceType.CHANGES, count > 1)) {
      return changeSeq.next(count);
    }
  }

  public int nextGroupId() {
    try (Timer2.Context<SequenceType, Boolean> timer =
        nextIdLatency.start(Sequence.SequenceType.GROUPS, false)) {
      return groupSeq.next();
    }
  }

  public int currentChangeId() {
    return changeSeq.current();
  }

  public int currentAccountId() {
    return accountSeq.current();
  }

  public int currentGroupId() {
    return groupSeq.current();
  }

  public void setChangeIdValue(int value) {
    changeSeq.storeNew(value);
  }

  public void setAccountIdValue(int value) {
    accountSeq.storeNew(value);
  }

  public void setGroupIdValue(int value) {
    groupSeq.storeNew(value);
  }
}