// 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.notedb;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

import com.google.auto.value.AutoValue;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ListMultimap;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.common.data.SubmitRecord;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.Branch;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.ChangeMessage;
import com.google.gerrit.reviewdb.client.Comment;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.PatchSetApproval;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.reviewdb.client.RevId;
import com.google.gerrit.server.ReviewerSet;
import com.google.gerrit.server.ReviewerStatusUpdate;
import com.google.gerrit.server.notedb.NoteDbChangeState.PrimaryStorage;

import org.eclipse.jgit.lib.ObjectId;

import java.io.IOException;
import java.sql.Timestamp;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Immutable state associated with a change meta ref at a given commit.
 * <p>
 * One instance is the output of a single {@link ChangeNotesParser}, and
 * contains types required to support public methods on {@link ChangeNotes}. It
 * is intended to be cached in-process.
 * <p>
 * Note that {@link ChangeNotes} contains more than just a single {@code
 * ChangeNoteState}, such as per-draft information, so that class is not cached
 * directly.
 */
@AutoValue
public abstract class ChangeNotesState {
  static ChangeNotesState empty(Change change) {
    return new AutoValue_ChangeNotesState(
        null,
        change.getId(),
        null,
        ImmutableSet.of(),
        ImmutableSet.of(),
        ImmutableList.of(),
        ImmutableList.of(),
        ReviewerSet.empty(),
        ImmutableList.of(),
        ImmutableList.of(),
        ImmutableList.of(),
        ImmutableList.of(),
        ImmutableListMultimap.of(),
        ImmutableListMultimap.of());
  }

  static ChangeNotesState create(
      @Nullable ObjectId metaId,
      Change.Id changeId,
      Change.Key changeKey,
      Timestamp createdOn,
      Timestamp lastUpdatedOn,
      Account.Id owner,
      String branch,
      @Nullable PatchSet.Id currentPatchSetId,
      String subject,
      @Nullable String topic,
      @Nullable String originalSubject,
      @Nullable String submissionId,
      @Nullable Account.Id assignee,
      @Nullable Change.Status status,
      @Nullable Set<Account.Id> pastAssignees,
      @Nullable Set<String> hashtags,
      Map<PatchSet.Id, PatchSet> patchSets,
      ListMultimap<PatchSet.Id, PatchSetApproval> approvals,
      ReviewerSet reviewers,
      List<Account.Id> allPastReviewers,
      List<ReviewerStatusUpdate> reviewerUpdates,
      List<SubmitRecord> submitRecords,
      List<ChangeMessage> allChangeMessages,
      ListMultimap<PatchSet.Id, ChangeMessage> changeMessagesByPatchSet,
      ListMultimap<RevId, Comment> publishedComments) {
    if (hashtags == null) {
      hashtags = ImmutableSet.of();
    }
    return new AutoValue_ChangeNotesState(
        metaId,
        changeId,
        new AutoValue_ChangeNotesState_ChangeColumns(
            changeKey,
            createdOn,
            lastUpdatedOn,
            owner,
            branch,
            currentPatchSetId,
            subject,
            topic,
            originalSubject,
            submissionId,
            assignee,
            status),
        ImmutableSet.copyOf(pastAssignees),
        ImmutableSet.copyOf(hashtags),
        ImmutableList.copyOf(patchSets.entrySet()),
        ImmutableList.copyOf(approvals.entries()),
        reviewers,
        ImmutableList.copyOf(allPastReviewers),
        ImmutableList.copyOf(reviewerUpdates),
        ImmutableList.copyOf(submitRecords),
        ImmutableList.copyOf(allChangeMessages),
        ImmutableListMultimap.copyOf(changeMessagesByPatchSet),
        ImmutableListMultimap.copyOf(publishedComments));
  }


  /**
   * Subset of Change columns that can be represented in NoteDb.
   * <p>
   * Notable exceptions include rowVersion and noteDbState, which are only make
   * sense when read from NoteDb, so they cannot be cached.
   * <p>
   * Fields are in listed column order.
   */
  @AutoValue
  abstract static class ChangeColumns {
    abstract Change.Key changeKey();
    abstract Timestamp createdOn();
    abstract Timestamp lastUpdatedOn();
    abstract Account.Id owner();

    // Project not included, as it's not stored anywhere in the meta ref.
    abstract String branch();

    @Nullable abstract PatchSet.Id currentPatchSetId();
    abstract String subject();
    @Nullable abstract String topic();
    @Nullable abstract String originalSubject();
    @Nullable abstract String submissionId();
    @Nullable abstract Account.Id assignee();
    // TODO(dborowitz): Use a sensible default other than null
    @Nullable abstract Change.Status status();
  }

  // Only null if NoteDb is disabled.
  @Nullable abstract ObjectId metaId();

  abstract Change.Id changeId();

  // Only null if NoteDb is disabled.
  @Nullable abstract ChangeColumns columns();

  // Other related to this Change.
  abstract ImmutableSet<Account.Id> pastAssignees();
  abstract ImmutableSet<String> hashtags();
  abstract ImmutableList<Map.Entry<PatchSet.Id, PatchSet>> patchSets();
  abstract ImmutableList<Map.Entry<PatchSet.Id, PatchSetApproval>> approvals();

  abstract ReviewerSet reviewers();
  abstract ImmutableList<Account.Id> allPastReviewers();
  abstract ImmutableList<ReviewerStatusUpdate> reviewerUpdates();

  abstract ImmutableList<SubmitRecord> submitRecords();
  abstract ImmutableList<ChangeMessage> allChangeMessages();
  abstract ImmutableListMultimap<PatchSet.Id, ChangeMessage>
      changeMessagesByPatchSet();
  abstract ImmutableListMultimap<RevId, Comment> publishedComments();

  Change newChange(Project.NameKey project) {
    ChangeColumns c = checkNotNull(columns(), "columns are required");
    Change change = new Change(
        c.changeKey(),
        changeId(),
        c.owner(),
        new Branch.NameKey(project, c.branch()),
        c.createdOn());
    copyNonConstructorColumnsTo(change);
    change.setNoteDbState(NoteDbChangeState.NOTE_DB_PRIMARY_STATE);
    return change;
  }

  void copyColumnsTo(Change change) throws IOException {
    ChangeColumns c = columns();
    checkState(c != null && metaId() != null,
        "missing columns or metaId in ChangeNotesState; is NoteDb enabled? %s",
        this);
    checkMetaId(change);
    change.setKey(c.changeKey());
    change.setOwner(c.owner());
    change.setDest(new Branch.NameKey(change.getProject(), c.branch()));
    change.setCreatedOn(c.createdOn());
    copyNonConstructorColumnsTo(change);
  }

  private void checkMetaId(Change change) throws IOException {
    NoteDbChangeState state = NoteDbChangeState.parse(change);
    if (state == null) {
      return; // Can happen during small NoteDb tests.
    } else if (state.getPrimaryStorage() == PrimaryStorage.NOTE_DB) {
      return;
    }
    checkState(state.getRefState().isPresent(), "expected RefState: %s", state);
    ObjectId idFromState = state.getRefState().get().changeMetaId();
    if (!idFromState.equals(metaId())) {
      throw new IOException(
          "cannot copy ChangeNotesState into Change " + changeId()
          + "; this ChangeNotesState was created from " + metaId()
          + ", but change requires state " + idFromState);
    }
  }

  private void copyNonConstructorColumnsTo(Change change) {
    ChangeColumns c = checkNotNull(columns(), "columns are required");
    if (c.status() != null) {
      change.setStatus(c.status());
    }
    change.setTopic(Strings.emptyToNull(c.topic()));
    change.setLastUpdatedOn(c.lastUpdatedOn());
    change.setSubmissionId(c.submissionId());
    change.setAssignee(c.assignee());

    if (!patchSets().isEmpty()) {
      change.setCurrentPatchSet(
          c.currentPatchSetId(), c.subject(), c.originalSubject());
    } else {
      // TODO(dborowitz): This should be an error, but for now it's required for
      // some tests to pass.
      change.clearCurrentPatchSet();
    }
  }
}