/*
    * junixsocket
    *
    * Copyright 2009-2024 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;
  
  import java.io.Closeable;
  import java.io.File;
  import java.io.FileDescriptor;
  import java.io.IOException;
  import java.net.InetAddress;
  import java.net.ServerSocket;
  import java.net.SocketAddress;
  import java.net.SocketException;
  import java.net.SocketOption;
  import java.net.SocketOptions;
  import java.nio.channels.IllegalBlockingModeException;
  import java.util.Objects;
  import java.util.Set;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.eclipse.jdt.annotation.NonNull;
  import org.eclipse.jdt.annotation.Nullable;
  
  import com.kohlschutter.annotations.compiletime.SuppressFBWarnings;
  
  /**
   * The server part of a junixsocket socket.
   *
   * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
   * @author Christian Kohlschütter
   */
  @SuppressWarnings({"PMD.CyclomaticComplexity", "PMD.CouplingBetweenObjects"})
  public abstract class AFServerSocket<A extends AFSocketAddress> extends ServerSocket implements
      AFSomeSocketThing {
    private final AFSocketImpl<A> implementation;
    private @Nullable A boundEndpoint;
    private final Closeables closeables = new Closeables();
    private final AtomicBoolean created = new AtomicBoolean(false);
    private final AtomicBoolean deleteOnClose = new AtomicBoolean(true);
  
    @SuppressWarnings("this-escape")
    private final AFServerSocketChannel<A> channel = newChannel();
    private @Nullable SocketAddressFilter bindFilter;
  
    private final AtomicBoolean closed = new AtomicBoolean(false);
  
    /**
     * The constructor of the concrete subclass.
     *
     * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
     */
    public interface Constructor<A extends AFSocketAddress> {
      /**
       * Creates a new {@link AFServerSocket} instance.
       *
       * @param fd The file descriptor.
       * @return The new instance.
       * @throws IOException on error.
       */
      @NonNull
      AFServerSocket<A> newInstance(FileDescriptor fd) throws IOException;
    }
  
    /**
     * Constructs a new, unconnected instance.
     *
     * @throws IOException if the operation fails.
     */
    @SuppressFBWarnings("CT_CONSTRUCTOR_THROW")
    protected AFServerSocket() throws IOException {
      this(null);
    }
  
    /**
     * Constructs a new instance, optionally associated with the given file descriptor.
     *
     * @param fdObj The file descriptor, or {@code null}.
     * @throws IOException if the operation fails.
     */
    @SuppressWarnings({"this-escape", "PMD.ConstructorCallsOverridableMethod"})
    @SuppressFBWarnings("CT_CONSTRUCTOR_THROW")
    protected AFServerSocket(FileDescriptor fdObj) throws IOException {
      super();
  
      this.implementation = newImpl(fdObj);
     NativeUnixSocket.initServerImpl(this, implementation);
 
     getAFImpl().setOption(SocketOptions.SO_REUSEADDR, true);
   }
 
   /**
    * Creates a new AFServerSocketChannel for this socket.
    *
    * @return The new instance.
    */
   protected abstract AFServerSocketChannel<A> newChannel();
 
   /**
    * Creates a new AFSocketImpl.
    *
    * @param fdObj The file descriptor.
    * @return The new instance.
    * @throws IOException on error.
    */
   protected abstract AFSocketImpl<A> newImpl(FileDescriptor fdObj) throws IOException;
 
   /**
    * Creates a new AFServerSocket instance, using the given subclass constructor.
    *
    * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
    * @param instanceSupplier The subclass constructor.
    * @return The new instance.
    * @throws IOException on error.
    */
   protected static <A extends AFSocketAddress> AFServerSocket<A> newInstance(
       Constructor<A> instanceSupplier) throws IOException {
     return instanceSupplier.newInstance(null);
   }
 
   /**
    * Creates a new AFServerSocket instance, using the given subclass constructor.
    *
    * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
    * @param instanceSupplier The subclass constructor.
    * @param fdObj The file descriptor.
    * @param localPort The local port.
    * @param remotePort The remote port.
    * @return The new instance.
    * @throws IOException on error.
    */
   protected static <A extends AFSocketAddress> AFServerSocket<A> newInstance(
       Constructor<A> instanceSupplier, FileDescriptor fdObj, int localPort, int remotePort)
       throws IOException {
     if (fdObj == null) {
       return instanceSupplier.newInstance(null);
     }
 
     int status = NativeUnixSocket.socketStatus(fdObj);
     if (!fdObj.valid() || status == NativeUnixSocket.SOCKETSTATUS_INVALID) {
       throw new SocketException("Not a valid socket");
     }
     AFServerSocket<A> socket = instanceSupplier.newInstance(fdObj);
     socket.getAFImpl().updatePorts(localPort, remotePort);
 
     switch (status) {
       case NativeUnixSocket.SOCKETSTATUS_CONNECTED:
         throw new SocketException("Not a ServerSocket");
       case NativeUnixSocket.SOCKETSTATUS_BOUND:
         socket.bind(AFSocketAddress.INTERNAL_DUMMY_BIND);
 
         socket.setBoundEndpoint(AFSocketAddress.getSocketAddress(fdObj, false, localPort, socket
             .addressFamily()));
         break;
       case NativeUnixSocket.SOCKETSTATUS_UNKNOWN:
         break;
       default:
         throw new IllegalStateException("Invalid socketStatus response: " + status);
     }
 
     socket.getAFImpl().setSocketAddress(socket.getLocalSocketAddress());
     return socket;
   }
 
   /**
    * Returns a new {@link ServerSocket} that is bound to the given {@link AFSocketAddress}.
    *
    * @param instanceSupplier The constructor of the concrete subclass.
    * @param addr The socket file to bind to.
    * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
    * @return The new, bound {@link AFServerSocket}.
    * @throws IOException if the operation fails.
    */
   protected static <A extends AFSocketAddress> AFServerSocket<A> bindOn(
       Constructor<A> instanceSupplier, final AFSocketAddress addr) throws IOException {
     AFServerSocket<A> socket = instanceSupplier.newInstance(null);
     socket.bind(addr);
     return socket;
   }
 
   /**
    * Returns a new {@link ServerSocket} that is bound to the given {@link AFSocketAddress}.
    *
    * @param instanceSupplier The constructor of the concrete subclass.
    * @param addr The socket file to bind to.
    * @param deleteOnClose If {@code true}, the socket file (if the address points to a file) will be
    *          deleted upon {@link #close}.
    * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
    * @return The new, bound {@link AFServerSocket}.
    * @throws IOException if the operation fails.
    */
   protected static <A extends AFSocketAddress> AFServerSocket<A> bindOn(
       Constructor<A> instanceSupplier, final A addr, boolean deleteOnClose) throws IOException {
     AFServerSocket<A> socket = instanceSupplier.newInstance(null);
     socket.bind(addr);
     socket.setDeleteOnClose(deleteOnClose);
     return socket;
   }
 
   /**
    * Returns a new, <em>unbound</em> {@link ServerSocket} that will always bind to the given
    * address, regardless of any socket address used in a call to <code>bind</code>.
    *
    * @param instanceSupplier The constructor of the concrete subclass.
    * @param forceAddr The address to use.
    * @param <A> The concrete {@link AFSocketAddress} that is supported by this type.
    * @return The new, yet unbound {@link AFServerSocket}.
    * @throws IOException if an exception occurs.
    */
   protected static <A extends AFSocketAddress> AFServerSocket<A> forceBindOn(
       Constructor<A> instanceSupplier, final A forceAddr) throws IOException {
     AFServerSocket<A> socket = instanceSupplier.newInstance(null);
     return socket.forceBindAddress(forceAddr);
   }
 
   /**
    * Forces the address to be used for any subsequent call to {@link #bind(SocketAddress)} to be the
    * given one, regardless of what'll be passed to {@link #bind(SocketAddress, int)}, but doesn't
    * bind yet.
    *
    * @param endpoint The forced endpoint address.
    * @return This {@link AFServerSocket}.
    */
   public final AFServerSocket<A> forceBindAddress(SocketAddress endpoint) {
     return bindHook((SocketAddress orig) -> {
       return orig == null ? null : endpoint;
     });
   }
 
   @Override
   public final void bind(SocketAddress endpoint) throws IOException {
     bind(endpoint, 50);
   }
 
   @SuppressWarnings("unchecked")
   @Override
   public final void bind(SocketAddress endpoint, int backlog) throws IOException {
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
 
     boolean bindErrorOk;
     if (bindFilter != null) {
       endpoint = bindFilter.apply(endpoint);
       bindErrorOk = endpoint != null && isBound();
     } else {
       bindErrorOk = false;
     }
 
     endpoint = AFSocketAddress.mapOrFail(endpoint);
 
     A endpointCast;
     try {
       endpointCast = (A) endpoint;
     } catch (ClassCastException e) {
       throw new IllegalArgumentException("Can only bind to specific endpoints", e);
     }
 
     try {
       getAFImpl().bind(endpoint, getReuseAddress() ? NativeUnixSocket.BIND_OPT_REUSE : 0);
     } catch (SocketException e) {
       if (bindErrorOk) {
         // force-binding an address could mean double-binding the same address, that's OK.
         return;
       } else {
         throw e;
       }
     }
     setBoundEndpoint(getAFImpl().getLocalSocketAddress());
     if (boundEndpoint0() == null) {
       setBoundEndpoint(endpointCast);
     }
 
     if (endpoint == AFSocketAddress.INTERNAL_DUMMY_BIND) { // NOPMD
       return;
     }
 
     implementation.listen(backlog);
   }
 
   @Override
   public final boolean isBound() {
     return boundEndpoint0() != null && implementation.getFD().valid();
   }
 
   @Override
   public final boolean isClosed() {
     return super.isClosed() || (isBound() && !implementation.getFD().valid()) || implementation
         .isClosed();
   }
 
   @Override
   public AFSocket<A> accept() throws IOException {
     return accept1(true);
   }
 
   AFSocket<A> accept1(boolean throwOnFail) throws IOException {
     AFSocket<A> as = newSocketInstance();
 
     boolean success = implementation.accept0(as.getAFImpl(false));
     if (isClosed()) {
       // We may have connected to the socket to unblock it
       throw new BrokenPipeSocketException("Socket is closed");
     }
 
     if (!success) {
       if (throwOnFail) {
         if (getChannel().isBlocking()) {
           // unexpected
           return null;
         } else {
           // non-blocking socket, nothing to accept
           throw new IllegalBlockingModeException();
         }
       } else {
         return null;
       }
     }
 
     as.getAFImpl(true); // trigger create
     as.connect(AFSocketAddress.INTERNAL_DUMMY_CONNECT);
     as.getAFImpl().updatePorts(getAFImpl().getLocalPort1(), getAFImpl().getRemotePort());
 
     return as;
   }
 
   /**
    * Returns a new {@link AFSocket} instance.
    *
    * @return The new instance.
    * @throws IOException on error.
    */
   protected abstract AFSocket<A> newSocketInstance() throws IOException;
 
   @Override
   public String toString() {
     return getClass().getSimpleName() + "[" + (isBound() ? boundEndpoint0() : "unbound") + "]";
   }
 
   @Override
   public void close() throws IOException {
     if (!closed.compareAndSet(false, true)) {
       return;
     }
     if (isClosed()) {
       return;
     }
 
     boolean localSocketAddressValid = isLocalSocketAddressValid();
 
     AFSocketAddress endpoint = boundEndpoint;
 
     IOException superException = null;
     try {
       super.close();
     } catch (IOException e) {
       superException = e;
     }
     if (implementation != null) {
       try {
         implementation.close();
       } catch (IOException e) {
         if (superException == null) {
           superException = e;
         } else {
           superException.addSuppressed(e);
         }
       }
     }
 
     IOException ex = null;
     try {
       closeables.close(superException);
     } finally {
       if (endpoint != null && endpoint.hasFilename() && localSocketAddressValid
           && isDeleteOnClose()) {
         File f = endpoint.getFile();
         if (!f.delete() && f.exists()) {
           ex = new IOException("Could not delete socket file after close: " + f);
         }
       }
     }
     if (ex != null) {
       throw ex;
     }
   }
 
   /**
    * Registers a {@link Closeable} that should be closed when this socket is closed.
    *
    * @param closeable The closeable.
    */
   public final void addCloseable(Closeable closeable) {
     closeables.add(closeable);
   }
 
   /**
    * Unregisters a previously registered {@link Closeable}.
    *
    * @param closeable The closeable.
    */
   public final void removeCloseable(Closeable closeable) {
     closeables.remove(closeable);
   }
 
   /**
    * Checks whether everything is setup to support junixsocket sockets.
    *
    * @return {@code true} if supported.
    */
   public static boolean isSupported() {
     return NativeUnixSocket.isLoaded();
   }
 
   @Override
   @SuppressFBWarnings("EI_EXPOSE_REP")
   public final @Nullable A getLocalSocketAddress() {
     @Nullable
     A ep = boundEndpoint0();
     if (ep == null) {
       ep = getAFImpl().getLocalSocketAddress();
       setBoundEndpoint(ep);
     }
     return ep;
   }
 
   private synchronized @Nullable A boundEndpoint0() {
     return boundEndpoint;
   }
 
   /**
    * Checks if the local socket address returned by {@link #getLocalSocketAddress()} is still valid.
    *
    * The address is no longer valid if the server socket has been closed, {@code null}, or another
    * server socket has been bound on that address.
    *
    * @return {@code true} iff still valid.
    */
   public boolean isLocalSocketAddressValid() {
     if (isClosed()) {
       return false;
     }
     @Nullable
     A addr = getLocalSocketAddress();
     if (addr == null) {
       return false;
     }
     return addr.equals(getAFImpl().getLocalSocketAddress());
   }
 
   final synchronized void setBoundEndpoint(@Nullable A addr) {
     this.boundEndpoint = addr;
     int port;
     if (addr == null) {
       port = -1;
     } else {
       port = addr.getPort();
     }
     getAFImpl().updatePorts(port, -1);
   }
 
   @Override
   public final int getLocalPort() {
     if (boundEndpoint0() == null) {
       setBoundEndpoint(getAFImpl().getLocalSocketAddress());
     }
     if (boundEndpoint0() == null) {
       return -1;
     } else {
       return getAFImpl().getLocalPort1();
     }
   }
 
   /**
    * Checks if this {@link AFServerSocket}'s file should be removed upon {@link #close()}.
    *
    * Deletion is not guaranteed, especially when not supported (e.g., addresses in the abstract
    * namespace).
    *
    * @return {@code true} if an attempt is made to delete the socket file upon {@link #close()}.
    */
   public final boolean isDeleteOnClose() {
     return deleteOnClose.get();
   }
 
   /**
    * Enables/disables deleting this {@link AFServerSocket}'s file (or other resource type) upon
    * {@link #close()}.
    *
    * Deletion is not guaranteed, especially when not supported (e.g., addresses in the abstract
    * namespace).
    *
    * @param b Enabled if {@code true}.
    */
   public final void setDeleteOnClose(boolean b) {
     deleteOnClose.set(b);
   }
 
   final AFSocketImpl<A> getAFImpl() {
     if (created.compareAndSet(false, true)) {
       try {
         getAFImpl().create(true);
         getSoTimeout(); // trigger create via java.net.Socket
       } catch (IOException e) {
         // ignore
       }
     }
     return implementation;
   }
 
   @SuppressFBWarnings("EI_EXPOSE_REP")
   @Override
   public AFServerSocketChannel<A> getChannel() {
     return channel;
   }
 
   @Override
   public final FileDescriptor getFileDescriptor() throws IOException {
     return implementation.getFileDescriptor();
   }
 
   /**
    * Returns the address family supported by this implementation.
    *
    * @return The family.
    */
   protected final AFAddressFamily<A> addressFamily() {
     return getAFImpl().getAddressFamily();
   }
 
   /**
    * Sets the hook for any subsequent call to {@link #bind(SocketAddress)} and
    * {@link #bind(SocketAddress, int)} to be the given function.
    *
    * The function can monitor calls or even alter the endpoint address.
    *
    * @param hook The function that gets called for each {@code bind} call.
    * @return This instance.
    */
   public final AFServerSocket<A> bindHook(SocketAddressFilter hook) {
     this.bindFilter = hook;
     return this;
   }
 
   @Override
   public InetAddress getInetAddress() {
     if (!isBound()) {
       return null;
     } else {
       return getAFImpl().getInetAddress();
     }
   }
 
   @Override
   public synchronized void setReceiveBufferSize(int size) throws SocketException {
     if (size <= 0) {
       throw new IllegalArgumentException("receive buffer size must be a positive number");
     }
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     getAFImpl().setOption(SocketOptions.SO_RCVBUF, size);
   }
 
   @Override
   public synchronized int getReceiveBufferSize() throws SocketException {
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     int result = 0;
     Object o = getAFImpl().getOption(SocketOptions.SO_RCVBUF);
     if (o instanceof Number) {
       result = ((Number) o).intValue();
     }
     return result;
   }
 
   @Override
   @SuppressWarnings("UnsynchronizedOverridesSynchronized" /* errorprone */)
   public void setSoTimeout(int timeout) throws SocketException {
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     if (timeout < 0) {
       throw new IllegalArgumentException("timeout < 0");
     }
     getAFImpl().setOption(SocketOptions.SO_TIMEOUT, timeout);
   }
 
   @Override
   @SuppressWarnings("UnsynchronizedOverridesSynchronized" /* errorprone */)
   public int getSoTimeout() throws IOException {
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     Object o = getAFImpl().getOption(SocketOptions.SO_TIMEOUT);
     /* extra type safety */
     if (o instanceof Number) {
       return ((Number) o).intValue();
     } else {
       return 0;
     }
   }
 
   @Override
   public void setReuseAddress(boolean on) throws SocketException {
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     getAFImpl().setOption(SocketOptions.SO_REUSEADDR, on);
   }
 
   @Override
   public boolean getReuseAddress() throws SocketException {
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     return ((Boolean) (getAFImpl().getOption(SocketOptions.SO_REUSEADDR)));
   }
 
   @Override
   public void setPerformancePreferences(int connectionTime, int latency, int bandwidth) {
   }
 
   @SuppressWarnings({"all", "MissingOverride" /* errorprone */})
   public <T> T getOption(SocketOption<T> name) throws IOException {
     Objects.requireNonNull(name);
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     return getAFImpl().getOption(name);
   }
 
   @SuppressWarnings({"all", "MissingOverride" /* errorprone */})
   public <T> ServerSocket setOption(SocketOption<T> name, T value) throws IOException {
     Objects.requireNonNull(name);
     if (isClosed()) {
       throw new SocketException("Socket is closed");
     }
     getAFImpl().setOption(name, value);
     return this;
   }
 
   @SuppressWarnings("all")
   public Set<SocketOption<?>> supportedOptions() {
     return getAFImpl().supportedOptions();
   }
 
   @Override
   public void setShutdownOnClose(boolean enabled) {
     getAFImpl().getCore().setShutdownOnClose(enabled);
   }
 
   // NOTE: We shall re-implement all methods defined in ServerSocket that internally call getImpl()
   // and call getAFImpl() here. This is not strictly necessary for environments where we can
   // override "impl"; however it's the right thing to do.
 }