/*
    * 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.netty.channel;
  
  import io.netty.util.internal.EmptyArrays;
  import io.netty.util.internal.MacAddressUtil;
  import io.netty.util.internal.PlatformDependent;
  import io.netty.util.internal.SystemPropertyUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.lang.reflect.Method;
  import java.util.Arrays;
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import static io.netty.util.internal.MacAddressUtil.defaultMachineId;
  import static io.netty.util.internal.MacAddressUtil.parseMAC;
  
  /**
   * The default {@link ChannelId} implementation.
   */
  public final class DefaultChannelId implements ChannelId {
  
      private static final long serialVersionUID = 809640043754842613L;
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(DefaultChannelId.class);
      private static final byte[] MACHINE_ID;
      private static final int PROCESS_ID_LEN = 4;
      private static final int PROCESS_ID;
      private static final int SEQUENCE_LEN = 4;
      private static final int TIMESTAMP_LEN = 8;
      private static final int RANDOM_LEN = 4;
  
      private static final AtomicInteger nextSequence = new AtomicInteger();
  
      private static final char[] HEX_CHARS = "0123456789abcdef".toCharArray();
  
      /**
       * Returns a new {@link DefaultChannelId} instance.
       */
      public static DefaultChannelId newInstance() {
          return new DefaultChannelId(MACHINE_ID,
                                      PROCESS_ID,
                                      nextSequence.getAndIncrement(),
                                      Long.reverse(System.nanoTime()) ^ System.currentTimeMillis(),
                                      ThreadLocalRandom.current().nextInt());
      }
  
      static {
          int processId = -1;
          String customProcessId = SystemPropertyUtil.get("io.netty.processId");
          if (customProcessId != null) {
              try {
                  processId = Integer.parseInt(customProcessId);
              } catch (NumberFormatException e) {
                  // Malformed input.
              }
  
              if (processId < 0) {
                  processId = -1;
                  logger.warn("-Dio.netty.processId: {} (malformed)", customProcessId);
              } else if (logger.isDebugEnabled()) {
                  logger.debug("-Dio.netty.processId: {} (user-set)", processId);
              }
          }
  
          if (processId < 0) {
              processId = defaultProcessId();
              if (logger.isDebugEnabled()) {
                  logger.debug("-Dio.netty.processId: {} (auto-detected)", processId);
              }
          }
  
          PROCESS_ID = processId;
  
          byte[] machineId = null;
          String customMachineId = SystemPropertyUtil.get("io.netty.machineId");
          if (customMachineId != null) {
              try {
                  machineId = parseMAC(customMachineId);
              } catch (Exception e) {
                  logger.warn("-Dio.netty.machineId: {} (malformed)", customMachineId, e);
              }
              if (machineId != null) {
                 logger.debug("-Dio.netty.machineId: {} (user-set)", customMachineId);
             }
         }
 
         if (machineId == null) {
             machineId = defaultMachineId();
             if (logger.isDebugEnabled()) {
                 logger.debug("-Dio.netty.machineId: {} (auto-detected)", MacAddressUtil.formatAddress(machineId));
             }
         }
 
         MACHINE_ID = machineId;
     }
 
     static int processHandlePid(ClassLoader loader) {
         // pid is positive on unix, non{-1,0} on windows
         int nilValue = -1;
         if (PlatformDependent.javaVersion() >= 9) {
             Long pid;
             try {
                 Class<?> processHandleImplType = Class.forName("java.lang.ProcessHandle", true, loader);
                 Method processHandleCurrent = processHandleImplType.getMethod("current");
                 Object processHandleInstance = processHandleCurrent.invoke(null);
                 Method processHandlePid = processHandleImplType.getMethod("pid");
                 pid = (Long) processHandlePid.invoke(processHandleInstance);
             } catch (Exception e) {
                 logger.debug("Could not invoke ProcessHandle.current().pid();", e);
                 return nilValue;
             }
             if (pid > Integer.MAX_VALUE || pid < Integer.MIN_VALUE) {
                 throw new IllegalStateException("Current process ID exceeds int range: " + pid);
             }
             return pid.intValue();
         }
         return nilValue;
     }
 
     static int jmxPid(ClassLoader loader) {
         String value;
         try {
             // Invoke java.lang.management.ManagementFactory.getRuntimeMXBean().getName()
             Class<?> mgmtFactoryType = Class.forName("java.lang.management.ManagementFactory", true, loader);
             Class<?> runtimeMxBeanType = Class.forName("java.lang.management.RuntimeMXBean", true, loader);
 
             Method getRuntimeMXBean = mgmtFactoryType.getMethod("getRuntimeMXBean", EmptyArrays.EMPTY_CLASSES);
             Object bean = getRuntimeMXBean.invoke(null, EmptyArrays.EMPTY_OBJECTS);
             Method getName = runtimeMxBeanType.getMethod("getName", EmptyArrays.EMPTY_CLASSES);
             value = (String) getName.invoke(bean, EmptyArrays.EMPTY_OBJECTS);
         } catch (Throwable t) {
             logger.debug("Could not invoke ManagementFactory.getRuntimeMXBean().getName(); Android?", t);
             try {
                 // Invoke android.os.Process.myPid()
                 Class<?> processType = Class.forName("android.os.Process", true, loader);
                 Method myPid = processType.getMethod("myPid", EmptyArrays.EMPTY_CLASSES);
                 value = myPid.invoke(null, EmptyArrays.EMPTY_OBJECTS).toString();
             } catch (Throwable t2) {
                 logger.debug("Could not invoke Process.myPid(); not Android?", t2);
                 value = "";
             }
         }
 
         int atIndex = value.indexOf('@');
         if (atIndex >= 0) {
             value = value.substring(0, atIndex);
         }
 
         int pid;
         try {
             pid = Integer.parseInt(value);
         } catch (NumberFormatException e) {
             // value did not contain an integer.
             pid = -1;
         }
 
         if (pid < 0) {
             pid = ThreadLocalRandom.current().nextInt();
             logger.warn("Failed to find the current process ID from '{}'; using a random value: {}",  value, pid);
         }
 
         return pid;
     }
 
     static int defaultProcessId() {
         ClassLoader loader = PlatformDependent.getClassLoader(DefaultChannelId.class);
         int processId = processHandlePid(loader);
         if (processId != -1) {
             return processId;
         }
         return jmxPid(loader);
     }
 
     private final byte[] machineId;
     private final int processId;
     private final int sequence;
     private final long timestamp;
     private final int random;
     private final int hashCode;
 
     private transient String shortValue;
     private transient String longValue;
 
     /**
      * Visible for testing
      */
     DefaultChannelId(final byte[] machineId, final int processId, final int sequence,
                      final long timestamp, final int random) {
         this.machineId = machineId;
         this.processId = processId;
         this.sequence = sequence;
         this.timestamp = timestamp;
         this.random = random;
         hashCode = computeHashCode();
     }
 
     private int computeHashCode() {
         int h = Arrays.hashCode(machineId);
         h = 31 * h + processId;
         h = 31 * h + sequence;
         h = 31 * h + Long.hashCode(timestamp);
         h = 31 * h + random;
         return h;
     }
 
     @Override
     public String asShortText() {
         String shortValue = this.shortValue;
         if (shortValue == null) {
             final StringBuilder buf = new StringBuilder(RANDOM_LEN * 2);
             appendHexInt(buf, random);
             this.shortValue = shortValue = buf.toString();
         }
         return shortValue;
     }
 
     @Override
     public String asLongText() {
         String longValue = this.longValue;
         if (longValue == null) {
             this.longValue = longValue = newLongValue();
         }
         return longValue;
     }
 
     private String newLongValue() {
         final int machineIdLen = machineId.length;
         final StringBuilder buf = new StringBuilder(
                 2 * (machineIdLen + PROCESS_ID_LEN + SEQUENCE_LEN + TIMESTAMP_LEN + RANDOM_LEN) + 4);
         appendHexBytes(buf, machineId);
         buf.append('-');
         appendHexInt(buf, processId);
         buf.append('-');
         appendHexInt(buf, sequence);
         buf.append('-');
         appendHexLong(buf, timestamp);
         buf.append('-');
         appendHexInt(buf, random);
         return buf.toString();
     }
 
     private static void appendHexBytes(StringBuilder buf, byte[] bytes) {
         for (byte b : bytes) {
             buf.append(HEX_CHARS[(b & 0xFF) >>> 4]);
             buf.append(HEX_CHARS[b & 0xF]);
         }
     }
 
     private static void appendHexInt(StringBuilder buf, int value) {
         for (int i = 28; i >= 0; i -= 4) {
             buf.append(HEX_CHARS[(value >>> i) & 0xF]);
         }
     }
 
     private static void appendHexLong(StringBuilder buf, long value) {
         for (int i = 60; i >= 0; i -= 4) {
             buf.append(HEX_CHARS[(int) ((value >>> i) & 0xF)]);
         }
     }
 
     @Override
     public int hashCode() {
         return hashCode;
     }
 
     @Override
     public int compareTo(final ChannelId o) {
         if (this == o) {
             // short circuit
             return 0;
         }
         if (o instanceof DefaultChannelId) {
             final DefaultChannelId other = (DefaultChannelId) o;
             int cmp = compareBytes(machineId, other.machineId);
             if (cmp != 0) {
                 return cmp;
             }
             cmp = Integer.compareUnsigned(processId, other.processId);
             if (cmp != 0) {
                 return cmp;
             }
             cmp = Integer.compareUnsigned(sequence, other.sequence);
             if (cmp != 0) {
                 return cmp;
             }
             cmp = Long.compareUnsigned(timestamp, other.timestamp);
             if (cmp != 0) {
                 return cmp;
             }
             return Integer.compareUnsigned(random, other.random);
         }
 
         return asLongText().compareTo(o.asLongText());
     }
 
     private static int compareBytes(byte[] a, byte[] b) {
         int len1 = a.length;
         int len2 = b.length;
         int len = Math.min(len1, len2);
         for (int k = 0; k < len; k++) {
             int cmp = (a[k] & 0xFF) - (b[k] & 0xFF);
             if (cmp != 0) {
                 return cmp;
             }
         }
         return len1 - len2;
     }
 
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {
             return true;
         }
         if (!(obj instanceof DefaultChannelId)) {
             return false;
         }
         DefaultChannelId other = (DefaultChannelId) obj;
         return hashCode == other.hashCode
                 && random == other.random
                 && processId == other.processId
                 && sequence == other.sequence
                 && timestamp == other.timestamp
                 && Arrays.equals(machineId, other.machineId);
     }
 
     @Override
     public String toString() {
         return asShortText();
     }
 }