// Copyright (C) 2009 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.common.base.Preconditions.checkArgument;
import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
import static java.util.Comparator.comparing;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.Iterables;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;
import com.google.common.collect.Sets;
import com.google.common.primitives.Shorts;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.common.data.LabelType;
import com.google.gerrit.common.data.LabelTypes;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.extensions.restapi.BadRequestException;
import com.google.gerrit.extensions.restapi.RestApiException;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.LabelId;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.PatchSetApproval;
import com.google.gerrit.reviewdb.client.PatchSetInfo;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.server.notedb.ChangeUpdate;
import com.google.gerrit.server.notedb.NotesMigration;
import com.google.gerrit.server.notedb.ReviewerStateInternal;
import com.google.gerrit.server.permissions.ChangePermission;
import com.google.gerrit.server.permissions.LabelPermission;
import com.google.gerrit.server.permissions.PermissionBackend;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.project.ProjectCache;
import com.google.gerrit.server.util.LabelVote;
import com.google.gwtorm.server.OrmException;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.revwalk.RevWalk;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utility functions to manipulate patchset approvals.
 *
 * <p>Approvals are overloaded, they represent both approvals and reviewers which should be CCed on
 * a change. To ensure that reviewers are not lost there must always be an approval on each patchset
 * for each reviewer, even if the reviewer hasn't actually given a score to the change. To mark the
 * "no score" case, a dummy approval, which may live in any of the available categories, with a
 * score of 0 is used.
 *
 * <p>The methods in this class only modify the gwtorm database.
 */
@Singleton
public class ApprovalsUtil {
  private static final Logger log = LoggerFactory.getLogger(ApprovalsUtil.class);

  private static final Ordering<PatchSetApproval> SORT_APPROVALS =
      Ordering.from(comparing(PatchSetApproval::getGranted));

  public static List<PatchSetApproval> sortApprovals(Iterable<PatchSetApproval> approvals) {
    return SORT_APPROVALS.sortedCopy(approvals);
  }

  public static PatchSetApproval newApproval(
      PatchSet.Id psId, CurrentUser user, LabelId labelId, int value, Date when) {
    PatchSetApproval psa =
        new PatchSetApproval(
            new PatchSetApproval.Key(psId, user.getAccountId(), labelId),
            Shorts.checkedCast(value),
            when);
    user.updateRealAccountId(psa::setRealAccountId);
    return psa;
  }

  private static Iterable<PatchSetApproval> filterApprovals(
      Iterable<PatchSetApproval> psas, Account.Id accountId) {
    return Iterables.filter(psas, a -> Objects.equals(a.getAccountId(), accountId));
  }

  private final NotesMigration migration;
  private final ApprovalCopier copier;
  private final PermissionBackend permissionBackend;
  private final ProjectCache projectCache;

  @VisibleForTesting
  @Inject
  public ApprovalsUtil(
      NotesMigration migration,
      ApprovalCopier copier,
      PermissionBackend permissionBackend,
      ProjectCache projectCache) {
    this.migration = migration;
    this.copier = copier;
    this.permissionBackend = permissionBackend;
    this.projectCache = projectCache;
  }

  /**
   * Get all reviewers for a change.
   *
   * @param db review database.
   * @param notes change notes.
   * @return reviewers for the change.
   * @throws OrmException if reviewers for the change could not be read.
   */
  public ReviewerSet getReviewers(ReviewDb db, ChangeNotes notes) throws OrmException {
    if (!migration.readChanges()) {
      return ReviewerSet.fromApprovals(db.patchSetApprovals().byChange(notes.getChangeId()));
    }
    return notes.load().getReviewers();
  }

  /**
   * Get all reviewers and CCed accounts for a change.
   *
   * @param allApprovals all approvals to consider; must all belong to the same change.
   * @return reviewers for the change.
   * @throws OrmException if reviewers for the change could not be read.
   */
  public ReviewerSet getReviewers(ChangeNotes notes, Iterable<PatchSetApproval> allApprovals)
      throws OrmException {
    if (!migration.readChanges()) {
      return ReviewerSet.fromApprovals(allApprovals);
    }
    return notes.load().getReviewers();
  }

  /**
   * Get updates to reviewer set. Always returns empty list for ReviewDb.
   *
   * @param notes change notes.
   * @return reviewer updates for the change.
   * @throws OrmException if reviewer updates for the change could not be read.
   */
  public List<ReviewerStatusUpdate> getReviewerUpdates(ChangeNotes notes) throws OrmException {
    if (!migration.readChanges()) {
      return ImmutableList.of();
    }
    return notes.load().getReviewerUpdates();
  }

  public List<PatchSetApproval> addReviewers(
      ReviewDb db,
      ChangeUpdate update,
      LabelTypes labelTypes,
      Change change,
      PatchSet ps,
      PatchSetInfo info,
      Iterable<Account.Id> wantReviewers,
      Collection<Account.Id> existingReviewers)
      throws OrmException {
    return addReviewers(
        db,
        update,
        labelTypes,
        change,
        ps.getId(),
        info.getAuthor().getAccount(),
        info.getCommitter().getAccount(),
        wantReviewers,
        existingReviewers);
  }

  public List<PatchSetApproval> addReviewers(
      ReviewDb db,
      ChangeNotes notes,
      ChangeUpdate update,
      LabelTypes labelTypes,
      Change change,
      Iterable<Account.Id> wantReviewers)
      throws OrmException {
    PatchSet.Id psId = change.currentPatchSetId();
    Collection<Account.Id> existingReviewers;
    if (migration.readChanges()) {
      // If using NoteDB, we only want reviewers in the REVIEWER state.
      existingReviewers = notes.load().getReviewers().byState(REVIEWER);
    } else {
      // Prior to NoteDB, we gather all reviewers regardless of state.
      existingReviewers = getReviewers(db, notes).all();
    }
    // Existing reviewers should include pending additions in the REVIEWER
    // state, taken from ChangeUpdate.
    existingReviewers = Lists.newArrayList(existingReviewers);
    for (Map.Entry<Account.Id, ReviewerStateInternal> entry : update.getReviewers().entrySet()) {
      if (entry.getValue() == REVIEWER) {
        existingReviewers.add(entry.getKey());
      }
    }
    return addReviewers(
        db, update, labelTypes, change, psId, null, null, wantReviewers, existingReviewers);
  }

  private List<PatchSetApproval> addReviewers(
      ReviewDb db,
      ChangeUpdate update,
      LabelTypes labelTypes,
      Change change,
      PatchSet.Id psId,
      Account.Id authorId,
      Account.Id committerId,
      Iterable<Account.Id> wantReviewers,
      Collection<Account.Id> existingReviewers)
      throws OrmException {
    List<LabelType> allTypes = labelTypes.getLabelTypes();
    if (allTypes.isEmpty()) {
      return ImmutableList.of();
    }

    Set<Account.Id> need = Sets.newLinkedHashSet(wantReviewers);
    if (authorId != null && canSee(db, update.getNotes(), authorId)) {
      need.add(authorId);
    }

    if (committerId != null && canSee(db, update.getNotes(), committerId)) {
      need.add(committerId);
    }
    need.remove(change.getOwner());
    need.removeAll(existingReviewers);
    if (need.isEmpty()) {
      return ImmutableList.of();
    }

    List<PatchSetApproval> cells = Lists.newArrayListWithCapacity(need.size());
    LabelId labelId = Iterables.getLast(allTypes).getLabelId();
    for (Account.Id account : need) {
      cells.add(
          new PatchSetApproval(
              new PatchSetApproval.Key(psId, account, labelId), (short) 0, update.getWhen()));
      update.putReviewer(account, REVIEWER);
    }
    db.patchSetApprovals().upsert(cells);
    return Collections.unmodifiableList(cells);
  }

  private boolean canSee(ReviewDb db, ChangeNotes notes, Account.Id accountId) {
    try {
      return projectCache.checkedGet(notes.getProjectName()).statePermitsRead()
          && permissionBackend
              .absentUser(accountId)
              .change(notes)
              .database(db)
              .test(ChangePermission.READ);
    } catch (IOException | PermissionBackendException e) {
      log.warn(
          String.format(
              "Failed to check if account %d can see change %d",
              accountId.get(), notes.getChangeId().get()),
          e);
      return false;
    }
  }

  /**
   * Adds accounts to a change as reviewers in the CC state.
   *
   * @param notes change notes.
   * @param update change update.
   * @param wantCCs accounts to CC.
   * @return whether a change was made.
   * @throws OrmException
   */
  public Collection<Account.Id> addCcs(
      ChangeNotes notes, ChangeUpdate update, Collection<Account.Id> wantCCs) throws OrmException {
    return addCcs(update, wantCCs, notes.load().getReviewers());
  }

  private Collection<Account.Id> addCcs(
      ChangeUpdate update, Collection<Account.Id> wantCCs, ReviewerSet existingReviewers) {
    Set<Account.Id> need = new LinkedHashSet<>(wantCCs);
    need.removeAll(existingReviewers.all());
    need.removeAll(update.getReviewers().keySet());
    for (Account.Id account : need) {
      update.putReviewer(account, CC);
    }
    return need;
  }

  /**
   * Adds approvals to ChangeUpdate for a new patch set, and writes to ReviewDb.
   *
   * @param db review database.
   * @param update change update.
   * @param labelTypes label types for the containing project.
   * @param ps patch set being approved.
   * @param user user adding approvals.
   * @param approvals approvals to add.
   * @throws RestApiException
   * @throws OrmException
   */
  public Iterable<PatchSetApproval> addApprovalsForNewPatchSet(
      ReviewDb db,
      ChangeUpdate update,
      LabelTypes labelTypes,
      PatchSet ps,
      CurrentUser user,
      Map<String, Short> approvals)
      throws RestApiException, OrmException, PermissionBackendException {
    Account.Id accountId = user.getAccountId();
    checkArgument(
        accountId.equals(ps.getUploader()),
        "expected user %s to match patch set uploader %s",
        accountId,
        ps.getUploader());
    if (approvals.isEmpty()) {
      return ImmutableList.of();
    }
    checkApprovals(approvals, permissionBackend.user(user).database(db).change(update.getNotes()));
    List<PatchSetApproval> cells = new ArrayList<>(approvals.size());
    Date ts = update.getWhen();
    for (Map.Entry<String, Short> vote : approvals.entrySet()) {
      LabelType lt = labelTypes.byLabel(vote.getKey());
      cells.add(newApproval(ps.getId(), user, lt.getLabelId(), vote.getValue(), ts));
    }
    for (PatchSetApproval psa : cells) {
      update.putApproval(psa.getLabel(), psa.getValue());
    }
    db.patchSetApprovals().insert(cells);
    return cells;
  }

  public static void checkLabel(LabelTypes labelTypes, String name, Short value)
      throws BadRequestException {
    LabelType label = labelTypes.byLabel(name);
    if (label == null) {
      throw new BadRequestException(String.format("label \"%s\" is not a configured label", name));
    }
    if (label.getValue(value) == null) {
      throw new BadRequestException(
          String.format("label \"%s\": %d is not a valid value", name, value));
    }
  }

  private static void checkApprovals(
      Map<String, Short> approvals, PermissionBackend.ForChange forChange)
      throws AuthException, PermissionBackendException {
    for (Map.Entry<String, Short> vote : approvals.entrySet()) {
      String name = vote.getKey();
      Short value = vote.getValue();
      try {
        forChange.check(new LabelPermission.WithValue(name, value));
      } catch (AuthException e) {
        throw new AuthException(
            String.format("applying label \"%s\": %d is restricted", name, value));
      }
    }
  }

  public ListMultimap<PatchSet.Id, PatchSetApproval> byChange(ReviewDb db, ChangeNotes notes)
      throws OrmException {
    if (!migration.readChanges()) {
      ImmutableListMultimap.Builder<PatchSet.Id, PatchSetApproval> result =
          ImmutableListMultimap.builder();
      for (PatchSetApproval psa : db.patchSetApprovals().byChange(notes.getChangeId())) {
        result.put(psa.getPatchSetId(), psa);
      }
      return result.build();
    }
    return notes.load().getApprovals();
  }

  public Iterable<PatchSetApproval> byPatchSet(
      ReviewDb db,
      ChangeNotes notes,
      CurrentUser user,
      PatchSet.Id psId,
      @Nullable RevWalk rw,
      @Nullable Config repoConfig)
      throws OrmException {
    if (!migration.readChanges()) {
      return sortApprovals(db.patchSetApprovals().byPatchSet(psId));
    }
    return copier.getForPatchSet(db, notes, user, psId, rw, repoConfig);
  }

  public Iterable<PatchSetApproval> byPatchSetUser(
      ReviewDb db,
      ChangeNotes notes,
      CurrentUser user,
      PatchSet.Id psId,
      Account.Id accountId,
      @Nullable RevWalk rw,
      @Nullable Config repoConfig)
      throws OrmException {
    if (!migration.readChanges()) {
      return sortApprovals(db.patchSetApprovals().byPatchSetUser(psId, accountId));
    }
    return filterApprovals(byPatchSet(db, notes, user, psId, rw, repoConfig), accountId);
  }

  public PatchSetApproval getSubmitter(ReviewDb db, ChangeNotes notes, PatchSet.Id c) {
    if (c == null) {
      return null;
    }
    try {
      // Submit approval is never copied, so bypass expensive byPatchSet call.
      return getSubmitter(c, byChange(db, notes).get(c));
    } catch (OrmException e) {
      return null;
    }
  }

  public static PatchSetApproval getSubmitter(PatchSet.Id c, Iterable<PatchSetApproval> approvals) {
    if (c == null) {
      return null;
    }
    PatchSetApproval submitter = null;
    for (PatchSetApproval a : approvals) {
      if (a.getPatchSetId().equals(c) && a.getValue() > 0 && a.isLegacySubmit()) {
        if (submitter == null || a.getGranted().compareTo(submitter.getGranted()) > 0) {
          submitter = a;
        }
      }
    }
    return submitter;
  }

  public static String renderMessageWithApprovals(
      int patchSetId, Map<String, Short> n, Map<String, PatchSetApproval> c) {
    StringBuilder msgs = new StringBuilder("Uploaded patch set " + patchSetId);
    if (!n.isEmpty()) {
      boolean first = true;
      for (Map.Entry<String, Short> e : n.entrySet()) {
        if (c.containsKey(e.getKey()) && c.get(e.getKey()).getValue() == e.getValue()) {
          continue;
        }
        if (first) {
          msgs.append(":");
          first = false;
        }
        msgs.append(" ").append(LabelVote.create(e.getKey(), e.getValue()).format());
      }
    }
    return msgs.toString();
  }
}