// Copyright (C) 2016 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.googlesource.gerrit.plugins.uploadvalidator;

import static com.googlesource.gerrit.plugins.uploadvalidator.PatternCacheModule.CACHE_NAME;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Joiner;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableMap;
import com.google.gerrit.extensions.annotations.Exports;
import com.google.gerrit.extensions.annotations.PluginName;
import com.google.gerrit.extensions.api.projects.ProjectConfigEntryType;
import com.google.gerrit.extensions.registration.DynamicSet;
import com.google.gerrit.server.config.PluginConfig;
import com.google.gerrit.server.config.PluginConfigFactory;
import com.google.gerrit.server.config.ProjectConfigEntry;
import com.google.gerrit.server.events.CommitReceivedEvent;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.git.validators.CommitValidationException;
import com.google.gerrit.server.git.validators.CommitValidationListener;
import com.google.gerrit.server.git.validators.CommitValidationMessage;
import com.google.gerrit.server.project.NoSuchProjectException;
import com.google.inject.AbstractModule;
import com.google.inject.Inject;
import com.google.inject.name.Named;

import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectLoader;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class BlockedKeywordValidator implements CommitValidationListener {
  private static final String KEY_CHECK_BLOCKED_KEYWORD = "blockedKeyword";
  private static final String KEY_CHECK_BLOCKED_KEYWORD_PATTERN =
      KEY_CHECK_BLOCKED_KEYWORD + "Pattern";

  public static AbstractModule module() {
    return new AbstractModule() {
      @Override
      protected void configure() {
        DynamicSet.bind(binder(), CommitValidationListener.class)
            .to(BlockedKeywordValidator.class);
        bind(ProjectConfigEntry.class)
            .annotatedWith(Exports.named(KEY_CHECK_BLOCKED_KEYWORD_PATTERN))
            .toInstance(new ProjectConfigEntry("Blocked Keyword Pattern", null,
                ProjectConfigEntryType.ARRAY, null, false,
                "Pushes of commits that contain files with blocked keywords "
                    + "will be rejected."));
      }
    };
  }

  private final String pluginName;
  private final PluginConfigFactory cfgFactory;
  private final GitRepositoryManager repoManager;
  private final LoadingCache<String, Pattern> patternCache;
  private final ContentTypeUtil contentTypeUtil;
  private final ValidatorConfig validatorConfig;

  @Inject
  BlockedKeywordValidator(@PluginName String pluginName,
      ContentTypeUtil contentTypeUtil,
      @Named(CACHE_NAME) LoadingCache<String, Pattern> patternCache,
      PluginConfigFactory cfgFactory,
      GitRepositoryManager repoManager,
      ValidatorConfig validatorConfig) {
    this.pluginName = pluginName;
    this.patternCache = patternCache;
    this.cfgFactory = cfgFactory;
    this.repoManager = repoManager;
    this.contentTypeUtil = contentTypeUtil;
    this.validatorConfig = validatorConfig;
  }

  static boolean isActive(PluginConfig cfg) {
    return cfg.getStringList(KEY_CHECK_BLOCKED_KEYWORD_PATTERN).length > 0;
  }

  @Override
  public List<CommitValidationMessage> onCommitReceived(
      CommitReceivedEvent receiveEvent) throws CommitValidationException {
    try {
      PluginConfig cfg = cfgFactory
          .getFromProjectConfigWithInheritance(
              receiveEvent.project.getNameKey(), pluginName);
      if (isActive(cfg)
          && validatorConfig.isEnabledForRef(receiveEvent.user,
              receiveEvent.getProjectNameKey(), receiveEvent.getRefName(),
              KEY_CHECK_BLOCKED_KEYWORD)) {
        ImmutableMap<String, Pattern> blockedKeywordPatterns =
            patternCache.getAll(Arrays
                .asList(cfg.getStringList(KEY_CHECK_BLOCKED_KEYWORD_PATTERN)));
        try (Repository repo =
            repoManager.openRepository(receiveEvent.project.getNameKey())) {
          List<CommitValidationMessage> messages =
              performValidation(repo, receiveEvent.commit,
                  blockedKeywordPatterns.values(), cfg);
          if (!messages.isEmpty()) {
            throw new CommitValidationException(
                "includes files containing blocked keywords", messages);
          }
        }
      }
    } catch (NoSuchProjectException | IOException | ExecutionException e) {
      throw new CommitValidationException("failed to check on blocked keywords",
          e);
    }
    return Collections.emptyList();
  }

  @VisibleForTesting
  List<CommitValidationMessage> performValidation(Repository repo, RevCommit c,
      ImmutableCollection<Pattern> blockedKeywordPartterns, PluginConfig cfg)
          throws IOException, ExecutionException {
    List<CommitValidationMessage> messages = new LinkedList<>();
    Map<String, ObjectId> content = CommitUtils.getChangedContent(repo, c);
    for (String path : content.keySet()) {
      ObjectLoader ol = repo.open(content.get(path));
      if (contentTypeUtil.isBinary(ol, path, cfg)) {
        continue;
      }
      checkFileForBlockedKeywords(blockedKeywordPartterns, messages, path, ol);
    }
    return messages;
  }

  private static void checkFileForBlockedKeywords(
      ImmutableCollection<Pattern> blockedKeywordPartterns,
      List<CommitValidationMessage> messages, String path, ObjectLoader ol)
          throws IOException {
    try (BufferedReader br = new BufferedReader(
        new InputStreamReader(ol.openStream(), StandardCharsets.UTF_8))) {
      int line = 0;
      for (String l = br.readLine(); l != null; l = br.readLine()) {
        line++;
        checkLineForBlockedKeywords(blockedKeywordPartterns, messages, path,
            line, l);
      }
    }
  }

  private static void checkLineForBlockedKeywords(
      ImmutableCollection<Pattern> blockedKeywordPartterns,
      List<CommitValidationMessage> messages, String path, int lineNumber,
      String line) {
    List<String> found = new ArrayList<>();
    for (Pattern p : blockedKeywordPartterns) {
      Matcher matcher = p.matcher(line);
      while (matcher.find()) {
        found.add(matcher.group());
      }
    }
    if (!found.isEmpty()) {
      messages.add(new CommitValidationMessage(MessageFormat.format(
          "blocked keyword(s) found in file: {0} (Line: {1}) (found: {2})",
          path, lineNumber, Joiner.on(", ").join(found)), true));
    }
  }
}