/*
    * Copyright 2013 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty5.channel.epoll;
  
  import io.netty5.channel.DefaultFileRegion;
  import io.netty5.channel.unix.FileDescriptor;
  import io.netty5.channel.unix.PeerCredentials;
  import io.netty5.channel.unix.Socket;
  import io.netty5.channel.unix.Unix;
  import io.netty5.util.internal.ClassInitializerUtil;
  import io.netty5.util.internal.NativeLibraryLoader;
  import io.netty5.util.internal.PlatformDependent;
  import io.netty5.util.internal.ThrowableUtil;
  import io.netty5.util.internal.logging.InternalLogger;
  import io.netty5.util.internal.logging.InternalLoggerFactory;
  
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.nio.channels.Selector;
  
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.epollerr;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.epollet;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.epollin;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.epollout;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.epollrdhup;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.isSupportingRecvmmsg;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.isSupportingSendmmsg;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.kernelVersion;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.tcpFastopenMode;
  import static io.netty5.channel.epoll.NativeStaticallyReferencedJniMethods.tcpMd5SigMaxKeyLen;
  import static io.netty5.channel.unix.Errors.ioResult;
  import static io.netty5.channel.unix.Errors.newIOException;
  
  /**
   * Native helper methods
   * <p><strong>Internal usage only!</strong>
   * <p>Static members which call JNI methods must be defined in {@link NativeStaticallyReferencedJniMethods}.
   */
  public final class Native {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(Native.class);
  
      static {
          Selector selector = null;
          try {
              // We call Selector.open() as this will under the hood cause IOUtil to be loaded.
              // This is a workaround for a possible classloader deadlock that could happen otherwise:
              //
              // See https://github.com/netty/netty/issues/10187
              selector = Selector.open();
          } catch (IOException ignore) {
              // Just ignore
          }
  
          // Preload all classes that will be used in the OnLoad(...) function of JNI to eliminate the possiblity of a
          // class-loader deadlock. This is a workaround for https://github.com/netty/netty/issues/11209.
  
          // This needs to match all the classes that are loaded via NETTY_JNI_UTIL_LOAD_CLASS or looked up via
          // NETTY_JNI_UTIL_FIND_CLASS.
          ClassInitializerUtil.tryLoadClasses(Native.class,
                  // netty_epoll_linuxsocket
                  PeerCredentials.class, DefaultFileRegion.class, FileChannel.class, java.io.FileDescriptor.class,
                  // netty_epoll_native
                  NativeDatagramPacketArray.NativeDatagramPacket.class
          );
  
          try {
              // First, try calling a side-effect free JNI method to see if the library was already
              // loaded by the application.
              offsetofEpollData();
          } catch (UnsatisfiedLinkError ignore) {
              // The library was not previously loaded, load it now.
              loadNativeLibrary();
          } finally {
              try {
                  if (selector != null) {
                      selector.close();
                  }
              } catch (IOException ignore) {
                  // Just ignore
              }
          }
          Unix.registerInternal(Native::registerUnix);
      }
  
      private static native int registerUnix();
  
     // EventLoop operations and constants
     public static final int EPOLLIN = epollin();
     public static final int EPOLLOUT = epollout();
     public static final int EPOLLRDHUP = epollrdhup();
     public static final int EPOLLET = epollet();
     public static final int EPOLLERR = epollerr();
 
     public static final boolean IS_SUPPORTING_SENDMMSG = isSupportingSendmmsg();
     static final boolean IS_SUPPORTING_RECVMMSG = isSupportingRecvmmsg();
     static final boolean IS_SUPPORTING_UDP_SEGMENT = isSupportingUdpSegment();
     private static final int TFO_ENABLED_CLIENT_MASK = 0x1;
     private static final int TFO_ENABLED_SERVER_MASK = 0x2;
     private static final int TCP_FASTOPEN_MODE = tcpFastopenMode();
     /**
      * <a href ="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">tcp_fastopen</a> client mode enabled
      * state.
      */
     static final boolean IS_SUPPORTING_TCP_FASTOPEN_CLIENT =
             (TCP_FASTOPEN_MODE & TFO_ENABLED_CLIENT_MASK) == TFO_ENABLED_CLIENT_MASK;
     /**
      * <a href ="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">tcp_fastopen</a> server mode enabled
      * state.
      */
     static final boolean IS_SUPPORTING_TCP_FASTOPEN_SERVER =
             (TCP_FASTOPEN_MODE & TFO_ENABLED_SERVER_MASK) == TFO_ENABLED_SERVER_MASK;
     /**
      * @deprecated Use {@link Epoll#isTcpFastOpenClientSideAvailable()}
      * or {@link Epoll#isTcpFastOpenServerSideAvailable()}.
      */
     @Deprecated
     public static final boolean IS_SUPPORTING_TCP_FASTOPEN = IS_SUPPORTING_TCP_FASTOPEN_CLIENT ||
             IS_SUPPORTING_TCP_FASTOPEN_SERVER;
     public static final int TCP_MD5SIG_MAXKEYLEN = tcpMd5SigMaxKeyLen();
     public static final String KERNEL_VERSION = kernelVersion();
 
     public static FileDescriptor newEventFd() {
         return new FileDescriptor(eventFd());
     }
 
     public static FileDescriptor newTimerFd() {
         return new FileDescriptor(timerFd());
     }
 
     private static native boolean isSupportingUdpSegment();
     private static native int eventFd();
     private static native int timerFd();
     public static native void eventFdWrite(int fd, long value);
 
     public static FileDescriptor newEpollCreate() {
         return new FileDescriptor(epollCreate());
     }
 
     private static native int epollCreate();
 
     static int epollWait(FileDescriptor epollFd, EpollEventArray events, boolean immediatePoll) throws IOException {
         return epollWait(epollFd, events, immediatePoll ? 0 : -1);
     }
 
     /**
      * This uses epoll's own timeout and does not reset/re-arm any timerfd
      */
     static int epollWait(FileDescriptor epollFd, EpollEventArray events, int timeoutMillis) throws IOException {
         int ready = epollWait(epollFd.intValue(), events.memoryAddress(), events.length(), timeoutMillis);
         if (ready < 0) {
             throw newIOException("epoll_wait", ready);
         }
         return ready;
     }
 
     static long epollWait(FileDescriptor epollFd, EpollEventArray events, FileDescriptor timerFd,
                           int timeoutSec, int timeoutNs, long millisThreshold) throws IOException {
         if (timeoutSec == 0 && timeoutNs == 0) {
             // Zero timeout => poll (aka return immediately)
             // We shift this to be consistent with what is done in epollWait0(...)
             return ((long) epollWait(epollFd, events, 0)) << 32;
         }
         if (timeoutSec == Integer.MAX_VALUE) {
             // Max timeout => wait indefinitely: disarm timerfd first
             timeoutSec = 0;
             timeoutNs = 0;
         }
         long result = epollWait0(epollFd.intValue(), events.memoryAddress(), events.length(), timerFd.intValue(),
                 timeoutSec, timeoutNs, millisThreshold);
         int ready = epollReady(result);
         if (ready < 0) {
             throw newIOException("epoll_wait", ready);
         }
         return result;
     }
 
     // IMPORTANT: This needs to be consistent with what is used in netty5_epoll_native.c
     static int epollReady(long result) {
         return (int) (result >> 32);
     }
 
     // IMPORTANT: This needs to be consistent with what is used in netty5_epoll_native.c
     static boolean epollTimerWasUsed(long result) {
         return (result & 0xff) != 0;
     }
 
     /**
      * Non-blocking variant of
      * {@link #epollWait(FileDescriptor, EpollEventArray, FileDescriptor, int, int, long)}
      * that will also hint to processor we are in a busy-wait loop.
      */
     public static int epollBusyWait(FileDescriptor epollFd, EpollEventArray events) throws IOException {
         int ready = epollBusyWait0(epollFd.intValue(), events.memoryAddress(), events.length());
         if (ready < 0) {
             throw newIOException("epoll_wait", ready);
         }
         return ready;
     }
 
     private static native long epollWait0(int efd, long address, int len, int timerFd,
                                          int timeoutSec, int timeoutNs, long millisThreshold);
     private static native int epollWait(int efd, long address, int len, int timeout);
     private static native int epollBusyWait0(int efd, long address, int len);
 
     public static void epollCtlAdd(int efd, final int fd, final int flags) throws IOException {
         int res = epollCtlAdd0(efd, fd, flags);
         if (res < 0) {
             throw newIOException("epoll_ctl", res);
         }
     }
     private static native int epollCtlAdd0(int efd, int fd, int flags);
 
     public static void epollCtlMod(int efd, final int fd, final int flags) throws IOException {
         int res = epollCtlMod0(efd, fd, flags);
         if (res < 0) {
             throw newIOException("epoll_ctl", res);
         }
     }
     private static native int epollCtlMod0(int efd, int fd, int flags);
 
     public static void epollCtlDel(int efd, final int fd) throws IOException {
         int res = epollCtlDel0(efd, fd);
         if (res < 0) {
             throw newIOException("epoll_ctl", res);
         }
     }
     private static native int epollCtlDel0(int efd, int fd);
 
     @Deprecated
     public static int sendmmsg(int fd, NativeDatagramPacketArray.NativeDatagramPacket[] msgs,
                                int offset, int len) throws IOException {
         return sendmmsg(fd, Socket.isIPv6Preferred(), msgs, offset, len);
     }
 
     static int sendmmsg(int fd, boolean ipv6, NativeDatagramPacketArray.NativeDatagramPacket[] msgs,
                                int offset, int len) throws IOException {
         int res = sendmmsg0(fd, ipv6, msgs, offset, len);
         if (res >= 0) {
             return res;
         }
         return ioResult("sendmmsg", res);
     }
 
     private static native int sendmmsg0(
             int fd, boolean ipv6, NativeDatagramPacketArray.NativeDatagramPacket[] msgs, int offset, int len);
 
     static int recvmmsg(int fd, boolean ipv6, NativeDatagramPacketArray.NativeDatagramPacket[] msgs,
                         int offset, int len) throws IOException {
         int res = recvmmsg0(fd, ipv6, msgs, offset, len);
         if (res >= 0) {
             return res;
         }
         return ioResult("recvmmsg", res);
     }
 
     private static native int recvmmsg0(
             int fd, boolean ipv6, NativeDatagramPacketArray.NativeDatagramPacket[] msgs, int offset, int len);
 
     static int recvmsg(int fd, boolean ipv6, NativeDatagramPacketArray.NativeDatagramPacket packet) throws IOException {
         int res = recvmsg0(fd, ipv6, packet);
         if (res >= 0) {
             return res;
         }
         return ioResult("recvmsg", res);
     }
 
     private static native int recvmsg0(
             int fd, boolean ipv6, NativeDatagramPacketArray.NativeDatagramPacket msg);
 
     // epoll_event related
     public static native int sizeofEpollEvent();
     public static native int offsetofEpollData();
 
     private static void loadNativeLibrary() {
         String name = PlatformDependent.normalizedOs();
         if (!"linux".equals(name)) {
             throw new IllegalStateException("Only supported on Linux");
         }
         String staticLibName = "netty5_transport_native_epoll";
         String sharedLibName = staticLibName + '_' + PlatformDependent.normalizedArch();
         ClassLoader cl = PlatformDependent.getClassLoader(Native.class);
         try {
             NativeLibraryLoader.load(sharedLibName, cl);
         } catch (UnsatisfiedLinkError e1) {
             try {
                 NativeLibraryLoader.load(staticLibName, cl);
                 logger.debug("Failed to load {}", sharedLibName, e1);
             } catch (UnsatisfiedLinkError e2) {
                 ThrowableUtil.addSuppressed(e1, e2);
                 throw e1;
             }
         }
     }
 
     private Native() {
         // utility
     }
 }