/*
    * Copyright 2024 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.netty.channel.uring;
  
  import io.netty.channel.ChannelOption;
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.SystemPropertyUtil;
  
  public final class IoUring {
  
      private static final Throwable UNAVAILABILITY_CAUSE;
      private static final boolean IORING_CQE_F_SOCK_NONEMPTY_SUPPORTED;
      static {
          Throwable cause = null;
          boolean supported = false;
          try {
              if (SystemPropertyUtil.getBoolean("io.netty.transport.noNative", false)) {
                  cause = new UnsupportedOperationException(
                          "Native transport was explicit disabled with -Dio.netty.transport.noNative=true");
              } else {
                  String kernelVersion = Native.kernelVersion();
                  Native.checkKernelVersion(kernelVersion);
                  Throwable unsafeCause = PlatformDependent.getUnsafeUnavailabilityCause();
                  if (unsafeCause == null) {
                      RingBuffer ringBuffer = null;
                      try {
                          ringBuffer = Native.createRingBuffer();
                          Native.checkAllIOSupported(ringBuffer.fd());
                          supported = Native.isIOUringCqeFSockNonEmptySupported(ringBuffer.fd());
                      } finally {
                          if (ringBuffer != null) {
                              try {
                                  ringBuffer.close();
                              } catch (Exception ignore) {
                                  // ignore
                              }
                          }
                      }
                  } else {
                      cause = new UnsupportedOperationException("Unsafe is not supported", unsafeCause);
                  }
              }
          } catch (Throwable t) {
              cause = t;
          }
          UNAVAILABILITY_CAUSE = cause;
          IORING_CQE_F_SOCK_NONEMPTY_SUPPORTED = supported;
      }
  
      public static boolean isAvailable() {
          return UNAVAILABILITY_CAUSE == null;
      }
  
      /**
       * Returns {@code true} if the io_uring native transport is both {@linkplain #isAvailable() available} and supports
       * {@linkplain ChannelOption#TCP_FASTOPEN_CONNECT client-side TCP FastOpen}.
       *
       * @return {@code true} if it's possible to use client-side TCP FastOpen via io_uring, otherwise {@code false}.
       */
      public static boolean isTcpFastOpenClientSideAvailable() {
          return isAvailable() && Native.IS_SUPPORTING_TCP_FASTOPEN_CLIENT;
      }
  
      /**
       * Returns {@code true} if the io_uring native transport is both {@linkplain #isAvailable() available} and supports
       * {@linkplain ChannelOption#TCP_FASTOPEN server-side TCP FastOpen}.
       *
       * @return {@code true} if it's possible to use server-side TCP FastOpen via io_uring, otherwise {@code false}.
       */
      public static boolean isTcpFastOpenServerSideAvailable() {
          return isAvailable() && Native.IS_SUPPORTING_TCP_FASTOPEN_SERVER;
      }
  
      static boolean isIOUringCqeFSockNonEmptySupported() {
          return IORING_CQE_F_SOCK_NONEMPTY_SUPPORTED;
      }
  
      public static void ensureAvailability() {
          if (UNAVAILABILITY_CAUSE != null) {
              throw (Error) new UnsatisfiedLinkError(
                      "failed to load the required native library").initCause(UNAVAILABILITY_CAUSE);
          }
      }
  
      public static Throwable unavailabilityCause() {
          return UNAVAILABILITY_CAUSE;
     }
 
     private IoUring() {
     }
 }