// Copyright (C) 2014 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 java.util.Objects.requireNonNull;

import com.google.common.collect.HashBasedTable;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Table;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.common.data.LabelType;
import com.google.gerrit.exceptions.StorageException;
import com.google.gerrit.extensions.client.ChangeKind;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.PatchSetApproval;
import com.google.gerrit.server.change.ChangeKindCache;
import com.google.gerrit.server.change.LabelNormalizer;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.server.project.ProjectCache;
import com.google.gerrit.server.project.ProjectState;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.TreeMap;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.revwalk.RevWalk;

/**
 * Copies approvals between patch sets.
 *
 * <p>The result of a copy may either be stored, as when stamping approvals in the database at
 * submit time, or refreshed on demand, as when reading approvals from the NoteDb.
 */
@Singleton
public class ApprovalCopier {
  private final ProjectCache projectCache;
  private final ChangeKindCache changeKindCache;
  private final LabelNormalizer labelNormalizer;
  private final ChangeData.Factory changeDataFactory;
  private final PatchSetUtil psUtil;

  @Inject
  ApprovalCopier(
      ProjectCache projectCache,
      ChangeKindCache changeKindCache,
      LabelNormalizer labelNormalizer,
      ChangeData.Factory changeDataFactory,
      PatchSetUtil psUtil) {
    this.projectCache = projectCache;
    this.changeKindCache = changeKindCache;
    this.labelNormalizer = labelNormalizer;
    this.changeDataFactory = changeDataFactory;
    this.psUtil = psUtil;
  }

  Iterable<PatchSetApproval> getForPatchSet(
      ChangeNotes notes, PatchSet.Id psId, @Nullable RevWalk rw, @Nullable Config repoConfig) {
    return getForPatchSet(notes, psId, rw, repoConfig, Collections.emptyList());
  }

  Iterable<PatchSetApproval> getForPatchSet(
      ChangeNotes notes,
      PatchSet.Id psId,
      @Nullable RevWalk rw,
      @Nullable Config repoConfig,
      Iterable<PatchSetApproval> dontCopy) {
    PatchSet ps = psUtil.get(notes, psId);
    if (ps == null) {
      return Collections.emptyList();
    }
    return getForPatchSet(notes, ps, rw, repoConfig, dontCopy);
  }

  private Iterable<PatchSetApproval> getForPatchSet(
      ChangeNotes notes,
      PatchSet ps,
      @Nullable RevWalk rw,
      @Nullable Config repoConfig,
      Iterable<PatchSetApproval> dontCopy) {
    requireNonNull(ps, "ps should not be null");
    ChangeData cd = changeDataFactory.create(notes);
    try {
      ProjectState project = projectCache.checkedGet(cd.change().getDest().getParentKey());
      ListMultimap<PatchSet.Id, PatchSetApproval> all = cd.approvals();
      requireNonNull(all, "all should not be null");

      Table<String, Account.Id, PatchSetApproval> wontCopy = HashBasedTable.create();
      for (PatchSetApproval psa : dontCopy) {
        wontCopy.put(psa.getLabel(), psa.getAccountId(), psa);
      }

      Table<String, Account.Id, PatchSetApproval> byUser = HashBasedTable.create();
      for (PatchSetApproval psa : all.get(ps.getId())) {
        if (!wontCopy.contains(psa.getLabel(), psa.getAccountId())) {
          byUser.put(psa.getLabel(), psa.getAccountId(), psa);
        }
      }

      TreeMap<Integer, PatchSet> patchSets = getPatchSets(cd);

      // Walk patch sets strictly less than current in descending order.
      Collection<PatchSet> allPrior =
          patchSets.descendingMap().tailMap(ps.getId().get(), false).values();
      for (PatchSet priorPs : allPrior) {
        List<PatchSetApproval> priorApprovals = all.get(priorPs.getId());
        if (priorApprovals.isEmpty()) {
          continue;
        }

        ChangeKind kind =
            changeKindCache.getChangeKind(
                project.getNameKey(),
                rw,
                repoConfig,
                ObjectId.fromString(priorPs.getRevision().get()),
                ObjectId.fromString(ps.getRevision().get()));

        for (PatchSetApproval psa : priorApprovals) {
          if (wontCopy.contains(psa.getLabel(), psa.getAccountId())) {
            continue;
          }
          if (byUser.contains(psa.getLabel(), psa.getAccountId())) {
            continue;
          }
          if (!canCopy(project, psa, ps.getId(), kind)) {
            wontCopy.put(psa.getLabel(), psa.getAccountId(), psa);
            continue;
          }
          byUser.put(psa.getLabel(), psa.getAccountId(), copy(psa, ps.getId()));
        }
      }
      return labelNormalizer.normalize(notes, byUser.values()).getNormalized();
    } catch (IOException e) {
      throw new StorageException(e);
    }
  }

  private static TreeMap<Integer, PatchSet> getPatchSets(ChangeData cd) {
    Collection<PatchSet> patchSets = cd.patchSets();
    TreeMap<Integer, PatchSet> result = new TreeMap<>();
    for (PatchSet ps : patchSets) {
      result.put(ps.getId().get(), ps);
    }
    return result;
  }

  private static boolean canCopy(
      ProjectState project, PatchSetApproval psa, PatchSet.Id psId, ChangeKind kind) {
    int n = psa.getKey().getParentKey().get();
    checkArgument(n != psId.get());
    LabelType type = project.getLabelTypes().byLabel(psa.getLabelId());
    if (type == null) {
      return false;
    } else if ((type.isCopyMinScore() && type.isMaxNegative(psa))
        || (type.isCopyMaxScore() && type.isMaxPositive(psa))) {
      return true;
    }
    switch (kind) {
      case MERGE_FIRST_PARENT_UPDATE:
        return type.isCopyAllScoresOnMergeFirstParentUpdate();
      case NO_CODE_CHANGE:
        return type.isCopyAllScoresIfNoCodeChange();
      case TRIVIAL_REBASE:
        return type.isCopyAllScoresOnTrivialRebase();
      case NO_CHANGE:
        return type.isCopyAllScoresIfNoChange()
            || type.isCopyAllScoresOnTrivialRebase()
            || type.isCopyAllScoresOnMergeFirstParentUpdate()
            || type.isCopyAllScoresIfNoCodeChange();
      case REWORK:
      default:
        return false;
    }
  }

  private static PatchSetApproval copy(PatchSetApproval src, PatchSet.Id psId) {
    if (src.getKey().getParentKey().equals(psId)) {
      return src;
    }
    return new PatchSetApproval(psId, src);
  }
}