/*
    * junixsocket
    *
    * Copyright 2009-2026 Christian Kohlschütter
    *
    * 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 org.newsclub.net.unix.vsock;
  
  import java.io.File;
  import java.io.IOException;
  
  import org.newsclub.net.unix.AFServerSocket;
  import org.newsclub.net.unix.AFServerSocketConnector;
  import org.newsclub.net.unix.AFSocketAddress;
  import org.newsclub.net.unix.AFUNIXSocketAddress;
  import org.newsclub.net.unix.AFVSOCKSocketAddress;
  import org.newsclub.net.unix.AddressUnavailableSocketException;
  
  import com.kohlschutter.annotations.compiletime.SuppressFBWarnings;
  
  /**
   * Provides access to AF_VSOCK connections that aren't directly accessible but exposed via a
   * proxying/multiplexing Unix domain socket.
   *
   * @author Christian Kohlschütter
   * @see #openFirecrackerStyleConnector(File, int)
   * @see #openDirectConnector()
   */
  @SuppressFBWarnings("PATH_TRAVERSAL_IN")
  public final class AFVSOCKProxyServerSocketConnector implements
      AFServerSocketConnector<AFVSOCKSocketAddress, AFSocketAddress> {
    private static final AFServerSocketConnector<AFVSOCKSocketAddress, AFSocketAddress> DIRECT_CONNECTOR =
        new AFServerSocketConnector<AFVSOCKSocketAddress, AFSocketAddress>() {
  
          @Override
          public AFServerSocket<? extends AFSocketAddress> bind(AFVSOCKSocketAddress addr)
              throws IOException {
            return addr.newForceBoundServerSocket();
          }
        };
  
    private final String listenAddressPrefix;
    private final int allowedCID;
  
    private AFVSOCKProxyServerSocketConnector(String listenAddressPrefix, int allowedCID) {
      this.listenAddressPrefix = listenAddressPrefix;
      this.allowedCID = allowedCID;
    }
  
    /**
     * Returns an instance that is configured to support
     * [Firecracker-style](https://github.com/firecracker-microvm/firecracker/blob/main/docs/vsock.md)
     * Unix domain sockets.
     *
     * @param listenAddressPrefix The prefix of any listening socket. The actual socket will have
     *          <code>_<em>vsockPort</em></code> appended to it (with {@code vsockPort} being replaced
     *          by the corresponding port number).
     * @param allowedCID The permitted CID, or {@link AFVSOCKSocketAddress#VMADDR_CID_ANY} for "any".
     * @return The instance.
     */
    public static AFServerSocketConnector<AFVSOCKSocketAddress, AFSocketAddress> openFirecrackerStyleConnector(
        File listenAddressPrefix, int allowedCID) {
      return new AFVSOCKProxyServerSocketConnector(listenAddressPrefix.getAbsolutePath(), allowedCID);
    }
  
    /**
     * Returns an instance that is configured to connect directly to the given address.
     *
     * @return The direct instance.
     */
    public static AFServerSocketConnector<AFVSOCKSocketAddress, AFSocketAddress> openDirectConnector() {
      return DIRECT_CONNECTOR;
    }
  
    @Override
    public AFServerSocket<?> bind(AFVSOCKSocketAddress addr) throws IOException {
      int cid = addr.getVSOCKCID();
      if (cid != allowedCID && cid != AFVSOCKSocketAddress.VMADDR_CID_ANY
          && allowedCID != AFVSOCKSocketAddress.VMADDR_CID_ANY) {
        throw new AddressUnavailableSocketException("Factory does not cover CID " + cid);
      }
  
      return AFUNIXSocketAddress.of(new File(listenAddressPrefix + "_" + addr.getVSOCKPort()))
          .newForceBoundServerSocket();
    }
  }