// 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.notedb;

import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_LABEL;
import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_PATCH_SET;
import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_STATUS;
import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_SUBMITTED_WITH;
import static com.google.gerrit.server.notedb.ChangeNoteUtil.GERRIT_PLACEHOLDER_HOST;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Enums;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.base.Supplier;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ImmutableSetMultimap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Ordering;
import com.google.common.collect.Table;
import com.google.common.collect.Tables;
import com.google.common.primitives.Ints;
import com.google.gerrit.common.data.SubmitRecord;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.PatchSet;
import com.google.gerrit.reviewdb.client.PatchSetApproval;
import com.google.gerrit.reviewdb.client.PatchSetApproval.LabelId;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.VersionedMetaData;
import com.google.gerrit.server.util.LabelVote;
import com.google.gwtorm.server.OrmException;
import com.google.inject.Inject;
import com.google.inject.Singleton;

import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.lib.CommitBuilder;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.FooterKey;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.util.RawParseUtils;

import java.io.IOException;
import java.sql.Timestamp;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/** View of a single {@link Change} based on the log of its notes branch. */
public class ChangeNotes extends VersionedMetaData {
  private static final Ordering<PatchSetApproval> PSA_BY_TIME =
      Ordering.natural().onResultOf(
        new Function<PatchSetApproval, Timestamp>() {
          @Override
          public Timestamp apply(PatchSetApproval input) {
            return input.getGranted();
          }
        });

  @Singleton
  public static class Factory {
    private final GitRepositoryManager repoManager;

    @VisibleForTesting
    @Inject
    public Factory(GitRepositoryManager repoManager) {
      this.repoManager = repoManager;
    }

    public ChangeNotes create(Change change) {
      return new ChangeNotes(repoManager, change);
    }
  }

  private static class Parser {
    private final Change.Id changeId;
    private final ObjectId tip;
    private final RevWalk walk;
    private final Map<PatchSet.Id,
        Table<Account.Id, String, Optional<PatchSetApproval>>> approvals;
    private final Map<Account.Id, ReviewerState> reviewers;
    private final List<SubmitRecord> submitRecords;
    private Change.Status status;

    private Parser(Change.Id changeId, ObjectId tip, RevWalk walk) {
      this.changeId = changeId;
      this.tip = tip;
      this.walk = walk;
      approvals = Maps.newHashMap();
      reviewers = Maps.newLinkedHashMap();
      submitRecords = Lists.newArrayListWithExpectedSize(1);
    }

    private void parseAll() throws ConfigInvalidException, IOException {
      walk.markStart(walk.parseCommit(tip));
      for (RevCommit commit : walk) {
        parse(commit);
      }
      pruneReviewers();
    }

    private ImmutableListMultimap<PatchSet.Id, PatchSetApproval>
        buildApprovals() {
      Multimap<PatchSet.Id, PatchSetApproval> result =
          ArrayListMultimap.create(approvals.keySet().size(), 3);
      for (Table<?, ?, Optional<PatchSetApproval>> curr
          : approvals.values()) {
        for (PatchSetApproval psa : Optional.presentInstances(curr.values())) {
          result.put(psa.getPatchSetId(), psa);
        }
      }
      for (Collection<PatchSetApproval> v : result.asMap().values()) {
        Collections.sort((List<PatchSetApproval>) v, PSA_BY_TIME);
      }
      return ImmutableListMultimap.copyOf(result);
    }

    private void parse(RevCommit commit) throws ConfigInvalidException {
      if (status == null) {
        status = parseStatus(commit);
      }
      PatchSet.Id psId = parsePatchSetId(commit);
      Account.Id accountId = parseIdent(commit);

      if (submitRecords.isEmpty()) {
        // Only parse the most recent set of submit records; any older ones are
        // still there, but not currently used.
        parseSubmitRecords(commit.getFooterLines(FOOTER_SUBMITTED_WITH));
      }

      for (String line : commit.getFooterLines(FOOTER_LABEL)) {
        parseApproval(psId, accountId, commit, line);
      }

      for (ReviewerState state : ReviewerState.values()) {
        for (String line : commit.getFooterLines(state.getFooterKey())) {
          parseReviewer(state, line);
        }
      }
    }

    private Change.Status parseStatus(RevCommit commit)
        throws ConfigInvalidException {
      List<String> statusLines = commit.getFooterLines(FOOTER_STATUS);
      if (statusLines.isEmpty()) {
        return null;
      } else if (statusLines.size() > 1) {
        throw expectedOneFooter(FOOTER_STATUS, statusLines);
      }
      Optional<Change.Status> status = Enums.getIfPresent(
          Change.Status.class, statusLines.get(0).toUpperCase());
      if (!status.isPresent()) {
        throw invalidFooter(FOOTER_STATUS, statusLines.get(0));
      }
      return status.get();
    }

    private PatchSet.Id parsePatchSetId(RevCommit commit)
        throws ConfigInvalidException {
      List<String> psIdLines = commit.getFooterLines(FOOTER_PATCH_SET);
      if (psIdLines.size() != 1) {
        throw expectedOneFooter(FOOTER_PATCH_SET, psIdLines);
      }
      Integer psId = Ints.tryParse(psIdLines.get(0));
      if (psId == null) {
        throw invalidFooter(FOOTER_PATCH_SET, psIdLines.get(0));
      }
      return new PatchSet.Id(changeId, psId);
    }

    private void parseApproval(PatchSet.Id psId, Account.Id accountId,
        RevCommit commit, String line) throws ConfigInvalidException {
      Table<Account.Id, String, Optional<PatchSetApproval>> curr =
          approvals.get(psId);
      if (curr == null) {
        curr = Tables.newCustomTable(
            Maps.<Account.Id, Map<String, Optional<PatchSetApproval>>>
                newHashMapWithExpectedSize(2),
            new Supplier<Map<String, Optional<PatchSetApproval>>>() {
              @Override
              public Map<String, Optional<PatchSetApproval>> get() {
                return Maps.newLinkedHashMap();
              }
            });
        approvals.put(psId, curr);
      }

      if (line.startsWith("-")) {
        String label = line.substring(1);
        if (!curr.contains(accountId, label)) {
          curr.put(accountId, label, Optional.<PatchSetApproval> absent());
        }
      } else {
        LabelVote l;
        try {
          l = LabelVote.parseWithEquals(line);
        } catch (IllegalArgumentException e) {
          ConfigInvalidException pe =
              parseException("invalid %s: %s", FOOTER_LABEL, line);
          pe.initCause(e);
          throw pe;
        }
        if (!curr.contains(accountId, l.getLabel())) {
          curr.put(accountId, l.getLabel(), Optional.of(new PatchSetApproval(
              new PatchSetApproval.Key(
                  psId,
                  accountId,
                  new LabelId(l.getLabel())),
              l.getValue(),
              new Timestamp(commit.getCommitterIdent().getWhen().getTime()))));
        }
      }
    }

    private void parseSubmitRecords(List<String> lines)
        throws ConfigInvalidException {
      SubmitRecord rec = null;

      for (String line : lines) {
        int c = line.indexOf(": ");
        if (c < 0) {
          rec = new SubmitRecord();
          submitRecords.add(rec);
          int s = line.indexOf(' ');
          String statusStr = s >= 0 ? line.substring(0, s) : line;
          Optional<SubmitRecord.Status> status =
              Enums.getIfPresent(SubmitRecord.Status.class, statusStr);
          checkFooter(status.isPresent(), FOOTER_SUBMITTED_WITH, line);
          rec.status = status.get();
          if (s >= 0) {
            rec.errorMessage = line.substring(s);
          }
        } else {
          checkFooter(rec != null, FOOTER_SUBMITTED_WITH, line);
          SubmitRecord.Label label = new SubmitRecord.Label();
          if (rec.labels == null) {
            rec.labels = Lists.newArrayList();
          }
          rec.labels.add(label);

          Optional<SubmitRecord.Label.Status> status = Enums.getIfPresent(
              SubmitRecord.Label.Status.class, line.substring(0, c));
          checkFooter(status.isPresent(), FOOTER_SUBMITTED_WITH, line);
          label.status = status.get();
          int c2 = line.indexOf(": ", c + 2);
          if (c2 >= 0) {
            label.label = line.substring(c + 2, c2);
            PersonIdent ident =
                RawParseUtils.parsePersonIdent(line.substring(c2 + 2));
            checkFooter(ident != null, FOOTER_SUBMITTED_WITH, line);
            label.appliedBy = parseIdent(ident);
          } else {
            label.label = line.substring(c + 2);
          }
        }
      }
    }

    private Account.Id parseIdent(RevCommit commit)
        throws ConfigInvalidException {
      return parseIdent(commit.getAuthorIdent());
    }

    private Account.Id parseIdent(PersonIdent ident)
        throws ConfigInvalidException {
      String email = ident.getEmailAddress();
      int at = email.indexOf('@');
      if (at >= 0) {
        String host = email.substring(at + 1, email.length());
        Integer id = Ints.tryParse(email.substring(0, at));
        if (id != null && host.equals(GERRIT_PLACEHOLDER_HOST)) {
          return new Account.Id(id);
        }
      }
      throw parseException("invalid identity, expected <id>@%s: %s",
        GERRIT_PLACEHOLDER_HOST, email);
    }

    private void parseReviewer(ReviewerState state, String line)
        throws ConfigInvalidException {
      PersonIdent ident = RawParseUtils.parsePersonIdent(line);
      if (ident == null) {
        throw invalidFooter(state.getFooterKey(), line);
      }
      Account.Id accountId = parseIdent(ident);
      if (!reviewers.containsKey(accountId)) {
        reviewers.put(accountId, state);
      }
    }

    private void pruneReviewers() {
      Iterator<Map.Entry<Account.Id, ReviewerState>> rit =
          reviewers.entrySet().iterator();
      while (rit.hasNext()) {
        Map.Entry<Account.Id, ReviewerState> e = rit.next();
        if (e.getValue() == ReviewerState.REMOVED) {
          rit.remove();
          for (Table<Account.Id, ?, ?> curr : approvals.values()) {
            curr.rowKeySet().remove(e.getKey());
          }
        }
      }
    }

    private ConfigInvalidException parseException(String fmt, Object... args) {
      return new ConfigInvalidException("Change " + changeId + ": "
          + String.format(fmt, args));
    }

    private ConfigInvalidException expectedOneFooter(FooterKey footer,
        List<String> actual) {
      return parseException("missing or multiple %s: %s",
          footer.getName(), actual);
    }

    private ConfigInvalidException invalidFooter(FooterKey footer,
        String actual) {
      return parseException("invalid %s: %s", footer.getName(), actual);
    }

    private void checkFooter(boolean expr, FooterKey footer, String actual)
        throws ConfigInvalidException {
      if (!expr) {
        throw invalidFooter(footer, actual);
      }
    }
  }

  private final GitRepositoryManager repoManager;
  private final Change change;
  private boolean loaded;
  private ImmutableListMultimap<PatchSet.Id, PatchSetApproval> approvals;
  private ImmutableSetMultimap<ReviewerState, Account.Id> reviewers;
  private ImmutableList<SubmitRecord> submitRecords;

  @VisibleForTesting
  ChangeNotes(GitRepositoryManager repoManager, Change change) {
    this.repoManager = repoManager;
    this.change = new Change(change);
  }

  // TODO(dborowitz): Wrap fewer exceptions if/when we kill gwtorm.
  public ChangeNotes load() throws OrmException {
    if (!loaded) {
      Repository repo;
      try {
        repo = repoManager.openRepository(change.getProject());
      } catch (IOException e) {
        throw new OrmException(e);
      }
      try {
        load(repo);
        loaded = true;
      } catch (ConfigInvalidException | IOException e) {
        throw new OrmException(e);
      } finally {
        repo.close();
      }
    }
    return this;
  }

  public Change.Id getChangeId() {
    return change.getId();
  }

  public Change getChange() {
    return change;
  }

  public ImmutableListMultimap<PatchSet.Id, PatchSetApproval> getApprovals() {
    return approvals;
  }

  public ImmutableSetMultimap<ReviewerState, Account.Id> getReviewers() {
    return reviewers;
  }

  /**
   * @return submit records stored during the most recent submit; only for
   *     changes that were actually submitted.
   */
  public ImmutableList<SubmitRecord> getSubmitRecords() {
    return submitRecords;
  }

  @Override
  protected String getRefName() {
    return ChangeNoteUtil.changeRefName(change.getId());
  }

  @Override
  protected void onLoad() throws IOException, ConfigInvalidException {
    ObjectId rev = getRevision();
    if (rev == null) {
      return;
    }
    RevWalk walk = new RevWalk(reader);
    try {
      Parser parser = new Parser(change.getId(), rev, walk);
      parser.parseAll();

      if (parser.status != null) {
        change.setStatus(parser.status);
      }
      approvals = parser.buildApprovals();

      ImmutableSetMultimap.Builder<ReviewerState, Account.Id> reviewers =
          ImmutableSetMultimap.builder();
      for (Map.Entry<Account.Id, ReviewerState> e
          : parser.reviewers.entrySet()) {
        reviewers.put(e.getValue(), e.getKey());
      }
      this.reviewers = reviewers.build();
      submitRecords = ImmutableList.copyOf(parser.submitRecords);
    } finally {
      walk.release();
    }
  }

  @Override
  protected boolean onSave(CommitBuilder commit) {
    throw new UnsupportedOperationException(
        getClass().getSimpleName() + " is read-only");
  }
}