// Copyright (C) 2018 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.restapi.project;

import static com.google.gerrit.entities.RefNames.REFS_HEADS;

import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import com.google.gerrit.entities.Account;
import com.google.gerrit.entities.BranchNameKey;
import com.google.gerrit.extensions.api.config.AccessCheckInfo;
import com.google.gerrit.extensions.api.config.AccessCheckInput;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.extensions.restapi.BadRequestException;
import com.google.gerrit.extensions.restapi.Response;
import com.google.gerrit.extensions.restapi.RestApiException;
import com.google.gerrit.extensions.restapi.RestReadView;
import com.google.gerrit.server.account.AccountResolver;
import com.google.gerrit.server.git.GitRepositoryManager;
import com.google.gerrit.server.logging.TraceContext;
import com.google.gerrit.server.permissions.DefaultPermissionMappings;
import com.google.gerrit.server.permissions.GlobalPermission;
import com.google.gerrit.server.permissions.PermissionBackend;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.permissions.ProjectPermission;
import com.google.gerrit.server.permissions.RefPermission;
import com.google.gerrit.server.project.ProjectResource;
import com.google.inject.Inject;
import java.io.IOException;
import java.util.Optional;
import javax.servlet.http.HttpServletResponse;
import org.eclipse.jgit.errors.ConfigInvalidException;
import org.eclipse.jgit.lib.Repository;
import org.kohsuke.args4j.Option;

public class CheckAccess implements RestReadView<ProjectResource> {
  private final AccountResolver accountResolver;
  private final PermissionBackend permissionBackend;
  private final GitRepositoryManager gitRepositoryManager;

  @Inject
  CheckAccess(
      AccountResolver resolver,
      PermissionBackend permissionBackend,
      GitRepositoryManager gitRepositoryManager) {
    this.accountResolver = resolver;
    this.permissionBackend = permissionBackend;
    this.gitRepositoryManager = gitRepositoryManager;
  }

  @Option(name = "--ref", usage = "ref name to check permission for")
  String refName;

  @Option(name = "--account", usage = "account to check acccess for")
  String account;

  @Option(name = "--perm", usage = "permission to check; default: read of any ref.")
  String permission;

  public Response<AccessCheckInfo> apply(ProjectResource rsrc, AccessCheckInput input)
      throws PermissionBackendException, RestApiException, IOException, ConfigInvalidException {
    permissionBackend.user(rsrc.getUser()).check(GlobalPermission.VIEW_ACCESS);

    rsrc.getProjectState().checkStatePermitsRead();

    if (input == null) {
      throw new BadRequestException("input is required");
    }
    if (Strings.isNullOrEmpty(input.account)) {
      throw new BadRequestException("input requires 'account'");
    }

    try (TraceContext traceContext = TraceContext.open()) {
      traceContext.enableAclLogging();

      Account.Id match = accountResolver.resolve(input.account).asUnique().account().id();

      try {
        permissionBackend
            .absentUser(match)
            .project(rsrc.getNameKey())
            .check(ProjectPermission.ACCESS);
      } catch (AuthException e) {
        return Response.ok(
            createInfo(
                HttpServletResponse.SC_FORBIDDEN,
                String.format("user %s cannot see project %s", match, rsrc.getName())));
      }

      RefPermission refPerm;
      if (!Strings.isNullOrEmpty(input.permission)) {
        if (Strings.isNullOrEmpty(input.ref)) {
          throw new BadRequestException("must set 'ref' when specifying 'permission'");
        }
        Optional<RefPermission> rp = DefaultPermissionMappings.refPermission(input.permission);
        if (!rp.isPresent()) {
          throw new BadRequestException(
              String.format("'%s' is not recognized as ref permission", input.permission));
        }

        refPerm = rp.get();
      } else {
        refPerm = RefPermission.READ;
      }

      String message = null;
      if (!Strings.isNullOrEmpty(input.ref)) {
        try {
          permissionBackend
              .absentUser(match)
              .ref(BranchNameKey.create(rsrc.getNameKey(), input.ref))
              .check(refPerm);
        } catch (AuthException e) {
          return Response.ok(
              createInfo(
                  HttpServletResponse.SC_FORBIDDEN,
                  String.format(
                      "user %s lacks permission %s for %s in project %s",
                      match, input.permission, input.ref, rsrc.getName())));
        }
      } else {
        // We say access is okay if there are no refs, but this warrants a warning,
        // as access denied looks the same as no branches to the user.
        try (Repository repo = gitRepositoryManager.openRepository(rsrc.getNameKey())) {
          if (repo.getRefDatabase().getRefsByPrefix(REFS_HEADS).isEmpty()) {
            message = "access is OK, but repository has no branches under refs/heads/";
          }
        }
      }
      return Response.ok(createInfo(HttpServletResponse.SC_OK, message));
    }
  }

  private AccessCheckInfo createInfo(int statusCode, String message) {
    AccessCheckInfo info = new AccessCheckInfo();
    info.status = statusCode;
    info.message = message;
    info.debugLogs = TraceContext.getAclLogRecords();
    if (info.debugLogs.isEmpty()) {
      info.debugLogs =
          ImmutableList.of("Found no rules that apply, so defaulting to no permission");
    }
    return info;
  }

  @Override
  public Response<AccessCheckInfo> apply(ProjectResource rsrc)
      throws PermissionBackendException, RestApiException, IOException, ConfigInvalidException {

    AccessCheckInput input = new AccessCheckInput();
    input.ref = refName;
    input.account = account;
    input.permission = permission;

    return apply(rsrc, input);
  }
}