// 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.query.change;

import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.google.gerrit.common.data.SubmitTypeRecord;
import com.google.gerrit.extensions.client.SubmitType;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gerrit.server.git.CodeReviewCommit;
import com.google.gerrit.server.git.MergeException;
import com.google.gerrit.server.git.strategy.SubmitStrategy;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.gerrit.server.project.ProjectCache;
import com.google.gerrit.server.project.ProjectState;
import com.google.gerrit.server.project.SubmitRuleEvaluator;
import com.google.gerrit.server.query.OperatorPredicate;
import com.google.gerrit.server.query.OrPredicate;
import com.google.gerrit.server.query.Predicate;
import com.google.gerrit.server.query.change.ChangeQueryBuilder.Arguments;
import com.google.gwtorm.server.OrmException;
import com.google.inject.Provider;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevFlag;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.revwalk.filter.RevFilter;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.eclipse.jgit.treewalk.filter.TreeFilter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

class ConflictsPredicate extends OrPredicate<ChangeData> {
  private final String value;

  ConflictsPredicate(Arguments args, String value, List<Change> changes)
      throws OrmException {
    super(predicates(args, value, changes));
    this.value = value;
  }

  private static List<Predicate<ChangeData>> predicates(final Arguments args,
      String value, List<Change> changes) throws OrmException {
    List<Predicate<ChangeData>> changePredicates =
        Lists.newArrayListWithCapacity(changes.size());
    final Provider<ReviewDb> db = args.db;
    for (final Change c : changes) {
      final ChangeDataCache changeDataCache = new ChangeDataCache(
          c, db, args.changeDataFactory, args.projectCache);
      List<String> files = listFiles(c, args, changeDataCache);
      List<Predicate<ChangeData>> filePredicates =
          Lists.newArrayListWithCapacity(files.size());
      for (String file : files) {
        filePredicates.add(
            new EqualsPathPredicate(ChangeQueryBuilder.FIELD_PATH, file));
      }

      List<Predicate<ChangeData>> predicatesForOneChange =
          Lists.newArrayListWithCapacity(5);
      predicatesForOneChange.add(
          not(new LegacyChangeIdPredicate(c.getId())));
      predicatesForOneChange.add(
          new ProjectPredicate(c.getProject().get()));
      predicatesForOneChange.add(
          new RefPredicate(c.getDest().get()));

      OperatorPredicate<ChangeData> isMerge = new OperatorPredicate<ChangeData>(
              ChangeQueryBuilder.FIELD_MERGE, value) {

        @Override
        public boolean match(ChangeData cd) throws OrmException {
          ObjectId id = ObjectId.fromString(
              cd.currentPatchSet().getRevision().get());
          try (Repository repo =
                args.repoManager.openRepository(cd.change().getProject());
              RevWalk rw = CodeReviewCommit.newRevWalk(repo)) {
            RevCommit commit = rw.parseCommit(id);
            return commit.getParentCount() > 1;
          } catch (IOException e) {
            throw new IllegalStateException(e);
          }
        }

        @Override
        public int getCost() {
          return 2;
        }
      };

      predicatesForOneChange.add(or(or(filePredicates), isMerge));

      predicatesForOneChange.add(new OperatorPredicate<ChangeData>(
          ChangeQueryBuilder.FIELD_CONFLICTS, value) {

        @Override
        public boolean match(ChangeData object) throws OrmException {
          Change otherChange = object.change();
          if (otherChange == null) {
            return false;
          }
          if (!otherChange.getDest().equals(c.getDest())) {
            return false;
          }
          SubmitType submitType = getSubmitType(object);
          if (submitType == null) {
            return false;
          }
          ObjectId other = ObjectId.fromString(
              object.currentPatchSet().getRevision().get());
          ConflictKey conflictsKey =
              new ConflictKey(changeDataCache.getTestAgainst(), other, submitType,
                  changeDataCache.getProjectState().isUseContentMerge());
          Boolean conflicts = args.conflictsCache.getIfPresent(conflictsKey);
          if (conflicts != null) {
            return conflicts;
          }
          try (Repository repo =
                args.repoManager.openRepository(otherChange.getProject());
              RevWalk rw = CodeReviewCommit.newRevWalk(repo)) {
            RevFlag canMergeFlag = rw.newFlag("CAN_MERGE");
            CodeReviewCommit commit =
                (CodeReviewCommit) rw.parseCommit(changeDataCache.getTestAgainst());
            SubmitStrategy strategy =
                args.submitStrategyFactory.create(submitType,
                    db.get(), repo, rw, null, canMergeFlag,
                    getAlreadyAccepted(repo, rw, commit),
                    otherChange.getDest());
            CodeReviewCommit otherCommit =
                (CodeReviewCommit) rw.parseCommit(other);
            otherCommit.add(canMergeFlag);
            conflicts = !strategy.dryRun(commit, otherCommit);
            args.conflictsCache.put(conflictsKey, conflicts);
            return conflicts;
          } catch (MergeException | NoSuchProjectException | IOException e) {
            throw new IllegalStateException(e);
          }
        }

        @Override
        public int getCost() {
          return 5;
        }

        private SubmitType getSubmitType(ChangeData cd) throws OrmException {
          SubmitTypeRecord r = new SubmitRuleEvaluator(cd).getSubmitType();
          if (r.status != SubmitTypeRecord.Status.OK) {
            return null;
          }
          return r.type;
        }

        private Set<RevCommit> getAlreadyAccepted(Repository repo, RevWalk rw,
            CodeReviewCommit tip) throws MergeException {
          Set<RevCommit> alreadyAccepted = Sets.newHashSet();

          if (tip != null) {
            alreadyAccepted.add(tip);
          }

          try {
            for (ObjectId id : changeDataCache.getAlreadyAccepted(repo)) {
              try {
                alreadyAccepted.add(rw.parseCommit(id));
              } catch (IncorrectObjectTypeException iote) {
                // Not a commit? Skip over it.
              }
            }
          } catch (IOException e) {
            throw new MergeException(
                "Failed to determine already accepted commits.", e);
          }

          return alreadyAccepted;
        }
      });
      changePredicates.add(and(predicatesForOneChange));
    }
    return changePredicates;
  }

  private static List<String> listFiles(Change c, Arguments args,
      ChangeDataCache changeDataCache) throws OrmException {
    try (Repository repo = args.repoManager.openRepository(c.getProject());
        RevWalk rw = new RevWalk(repo)) {
      RevCommit ps = rw.parseCommit(changeDataCache.getTestAgainst());
      if (ps.getParentCount() > 1) {
        String dest = c.getDest().get();
        Ref destBranch = repo.getRefDatabase().getRef(dest);
        destBranch.getObjectId();
        rw.setRevFilter(RevFilter.MERGE_BASE);
        rw.markStart(rw.parseCommit(destBranch.getObjectId()));
        rw.markStart(ps);
        RevCommit base = rw.next();
        // TODO(zivkov): handle the case with multiple merge bases

        List<String> files = new ArrayList<>();
        try (TreeWalk tw = new TreeWalk(repo)) {
          if (base != null) {
            tw.setFilter(TreeFilter.ANY_DIFF);
            tw.addTree(base.getTree());
          }
          tw.addTree(ps.getTree());
          tw.setRecursive(true);
          while (tw.next()) {
            files.add(tw.getPathString());
          }
        }
        return files;
      } else {
        return args.changeDataFactory.create(args.db.get(), c).currentFilePaths();
      }
    } catch (IOException e) {
      throw new OrmException(e);
    }
  }

  @Override
  public String toString() {
    return ChangeQueryBuilder.FIELD_CONFLICTS + ":" + value;
  }

  private static class ChangeDataCache {
    private final Change change;
    private final Provider<ReviewDb> db;
    private final ChangeData.Factory changeDataFactory;
    private final ProjectCache projectCache;

    private ObjectId testAgainst;
    private ProjectState projectState;
    private Set<ObjectId> alreadyAccepted;

    ChangeDataCache(Change change, Provider<ReviewDb> db,
        ChangeData.Factory changeDataFactory, ProjectCache projectCache) {
      this.change = change;
      this.db = db;
      this.changeDataFactory = changeDataFactory;
      this.projectCache = projectCache;
    }

    ObjectId getTestAgainst()
        throws OrmException {
      if (testAgainst == null) {
        testAgainst = ObjectId.fromString(
            changeDataFactory.create(db.get(), change)
                .currentPatchSet().getRevision().get());
      }
      return testAgainst;
    }

    ProjectState getProjectState() {
      if (projectState == null) {
        projectState = projectCache.get(change.getProject());
        if (projectState == null) {
          throw new IllegalStateException(
              new NoSuchProjectException(change.getProject()));
        }
      }
      return projectState;
    }

    Set<ObjectId> getAlreadyAccepted(Repository repo) {
      if (alreadyAccepted == null) {
        alreadyAccepted = Sets.newHashSet();
        for (Ref r : repo.getAllRefs().values()) {
          if (r.getName().startsWith(Constants.R_HEADS)
              || r.getName().startsWith(Constants.R_TAGS)) {
            if (r.getObjectId() != null) {
              alreadyAccepted.add(r.getObjectId());
            }
          }
        }
      }
      return alreadyAccepted;
    }
  }
}