// Copyright (C) 2013 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.git;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.auto.value.AutoValue;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.gerrit.common.data.LabelType;
import com.google.gerrit.common.data.LabelTypes;
import com.google.gerrit.common.data.LabelValue;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.PatchSetApproval;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.notedb.ChangeNotes;
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.gwtorm.server.OrmException;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.Singleton;
import java.io.IOException;
import java.util.Collection;
import java.util.List;

/**
 * Normalizes votes on labels according to project config and permissions.
 *
 * <p>Votes are recorded in the database for a user based on the state of the project at that time:
 * what labels are defined for the project, and what the user is allowed to vote on. Both of those
 * can change between the time a vote is originally made and a later point, for example when a
 * change is submitted. This class normalizes old votes against current project configuration.
 */
@Singleton
public class LabelNormalizer {
  @AutoValue
  public abstract static class Result {
    @VisibleForTesting
    static Result create(
        List<PatchSetApproval> unchanged,
        List<PatchSetApproval> updated,
        List<PatchSetApproval> deleted) {
      return new AutoValue_LabelNormalizer_Result(
          ImmutableList.copyOf(unchanged),
          ImmutableList.copyOf(updated),
          ImmutableList.copyOf(deleted));
    }

    public abstract ImmutableList<PatchSetApproval> unchanged();

    public abstract ImmutableList<PatchSetApproval> updated();

    public abstract ImmutableList<PatchSetApproval> deleted();

    public Iterable<PatchSetApproval> getNormalized() {
      return Iterables.concat(unchanged(), updated());
    }
  }

  private final Provider<ReviewDb> db;
  private final IdentifiedUser.GenericFactory userFactory;
  private final PermissionBackend permissionBackend;
  private final ProjectCache projectCache;

  @Inject
  LabelNormalizer(
      Provider<ReviewDb> db,
      IdentifiedUser.GenericFactory userFactory,
      PermissionBackend permissionBackend,
      ProjectCache projectCache) {
    this.db = db;
    this.userFactory = userFactory;
    this.permissionBackend = permissionBackend;
    this.projectCache = projectCache;
  }

  /**
   * @param notes change containing the given approvals.
   * @param approvals list of approvals.
   * @return copies of approvals normalized to the defined ranges for the label type and permissions
   *     for the user. Approvals for unknown labels are not included in the output, nor are
   *     approvals where the user has no permissions for that label.
   * @throws OrmException
   */
  public Result normalize(ChangeNotes notes, Collection<PatchSetApproval> approvals)
      throws OrmException, PermissionBackendException, IOException {
    IdentifiedUser user = userFactory.create(notes.getChange().getOwner());
    return normalize(notes, user, approvals);
  }

  /**
   * @param notes change notes containing the given approvals.
   * @param user current user.
   * @param approvals list of approvals.
   * @return copies of approvals normalized to the defined ranges for the label type and permissions
   *     for the user. Approvals for unknown labels are not included in the output, nor are
   *     approvals where the user has no permissions for that label.
   */
  public Result normalize(
      ChangeNotes notes, CurrentUser user, Collection<PatchSetApproval> approvals)
      throws PermissionBackendException, IOException {
    List<PatchSetApproval> unchanged = Lists.newArrayListWithCapacity(approvals.size());
    List<PatchSetApproval> updated = Lists.newArrayListWithCapacity(approvals.size());
    List<PatchSetApproval> deleted = Lists.newArrayListWithCapacity(approvals.size());
    LabelTypes labelTypes =
        projectCache.checkedGet(notes.getProjectName()).getLabelTypes(notes, user);
    for (PatchSetApproval psa : approvals) {
      Change.Id changeId = psa.getKey().getParentKey().getParentKey();
      checkArgument(
          changeId.equals(notes.getChangeId()),
          "Approval %s does not match change %s",
          psa.getKey(),
          notes.getChange().getKey());
      if (psa.isLegacySubmit()) {
        unchanged.add(psa);
        continue;
      }
      LabelType label = labelTypes.byLabel(psa.getLabelId());
      if (label == null) {
        deleted.add(psa);
        continue;
      }
      PatchSetApproval copy = copy(psa);
      applyTypeFloor(label, copy);
      if (!applyRightFloor(notes, label, copy)) {
        deleted.add(psa);
      } else if (copy.getValue() != psa.getValue()) {
        updated.add(copy);
      } else {
        unchanged.add(psa);
      }
    }
    return Result.create(unchanged, updated, deleted);
  }

  private PatchSetApproval copy(PatchSetApproval src) {
    return new PatchSetApproval(src.getPatchSetId(), src);
  }

  private boolean applyRightFloor(ChangeNotes notes, LabelType lt, PatchSetApproval a)
      throws PermissionBackendException {
    PermissionBackend.ForChange forChange =
        permissionBackend.user(userFactory.create(a.getAccountId())).database(db).change(notes);
    // Check if the user is allowed to vote on the label at all
    try {
      forChange.check(new LabelPermission(lt.getName()));
    } catch (AuthException e) {
      return false;
    }
    // Squash vote to nearest allowed value
    try {
      forChange.check(new LabelPermission.WithValue(lt.getName(), a.getValue()));
      return true;
    } catch (AuthException e) {
      a.setValue(forChange.squashThenCheck(lt, a.getValue()));
      return true;
    }
  }

  private void applyTypeFloor(LabelType lt, PatchSetApproval a) {
    LabelValue atMin = lt.getMin();
    if (atMin != null && a.getValue() < atMin.getValue()) {
      a.setValue(atMin.getValue());
    }
    LabelValue atMax = lt.getMax();
    if (atMax != null && a.getValue() > atMax.getValue()) {
      a.setValue(atMax.getValue());
    }
  }
}