/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF 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
    *
   *   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.apache.maven.surefire.booter;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.nio.channels.ClosedChannelException;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.Semaphore;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.maven.plugin.surefire.log.api.ConsoleLogger;
  import org.apache.maven.surefire.api.booter.BiProperty;
  import org.apache.maven.surefire.api.booter.Command;
  import org.apache.maven.surefire.api.booter.DumpErrorSingleton;
  import org.apache.maven.surefire.api.booter.MasterProcessChannelDecoder;
  import org.apache.maven.surefire.api.booter.MasterProcessChannelEncoder;
  import org.apache.maven.surefire.api.booter.MasterProcessCommand;
  import org.apache.maven.surefire.api.booter.Shutdown;
  import org.apache.maven.surefire.api.provider.CommandChainReader;
  import org.apache.maven.surefire.api.provider.CommandListener;
  import org.apache.maven.surefire.api.testset.TestSetFailedException;
  
  import static java.lang.StrictMath.max;
  import static java.lang.Thread.State.NEW;
  import static java.lang.Thread.State.RUNNABLE;
  import static java.lang.Thread.State.TERMINATED;
  import static java.util.Objects.requireNonNull;
  import static org.apache.maven.surefire.api.booter.Command.toShutdown;
  import static org.apache.maven.surefire.api.booter.MasterProcessCommand.BYE_ACK;
  import static org.apache.maven.surefire.api.booter.MasterProcessCommand.NOOP;
  import static org.apache.maven.surefire.api.booter.MasterProcessCommand.SHUTDOWN;
  import static org.apache.maven.surefire.api.booter.MasterProcessCommand.SKIP_SINCE_NEXT_TEST;
  import static org.apache.maven.surefire.api.util.internal.DaemonThreadFactory.newDaemonThread;
  import static org.apache.maven.surefire.shared.utils.StringUtils.isBlank;
  import static org.apache.maven.surefire.shared.utils.StringUtils.isNotBlank;
  
  /**
   * Reader of commands coming from plugin(master) process.
   *
   * @author <a href="mailto:tibordigana@apache.org">Tibor Digana (tibor17)</a>
   * @since 2.19
   */
  public final class CommandReader implements CommandChainReader {
      private static final String LAST_TEST_SYMBOL = "";
  
      private final Queue<BiProperty<MasterProcessCommand, CommandListener>> listeners = new ConcurrentLinkedQueue<>();
  
      private final Thread commandThread = newDaemonThread(new CommandRunnable(), "surefire-forkedjvm-command-thread");
  
      private final AtomicReference<Thread.State> state = new AtomicReference<>(NEW);
  
      private final CountDownLatch startMonitor = new CountDownLatch(1);
  
      private final Semaphore nextCommandNotifier = new Semaphore(0);
  
      private final CopyOnWriteArrayList<String> testClasses = new CopyOnWriteArrayList<>();
  
      private final MasterProcessChannelDecoder decoder;
  
      private final Shutdown shutdown;
  
      private final ConsoleLogger logger;
  
      private int iteratedCount;
  
      public CommandReader(MasterProcessChannelDecoder decoder, Shutdown shutdown, ConsoleLogger logger) {
          this.decoder = requireNonNull(decoder, "null decoder");
          this.shutdown = requireNonNull(shutdown, "null Shutdown config");
          this.logger = requireNonNull(logger, "null logger");
          state.set(RUNNABLE);
          commandThread.start();
      }
  
      @Override
      public boolean awaitStarted() throws TestSetFailedException {
          if (state.get() == RUNNABLE) {
             try {
                 startMonitor.await();
                 return true;
             } catch (InterruptedException e) {
                 DumpErrorSingleton.getSingleton().dumpException(e);
                 throw new TestSetFailedException(e.getLocalizedMessage());
             }
         } else {
             return false;
         }
     }
 
     @Override
     public void addSkipNextTestsListener(CommandListener listener) {
         addListener(SKIP_SINCE_NEXT_TEST, listener);
     }
 
     @Override
     public void addShutdownListener(CommandListener listener) {
         addListener(SHUTDOWN, listener);
     }
 
     public void addNoopListener(CommandListener listener) {
         addListener(NOOP, listener);
     }
 
     public void addByeAckListener(CommandListener listener) {
         addListener(BYE_ACK, listener);
     }
 
     private void addListener(MasterProcessCommand cmd, CommandListener listener) {
         listeners.add(new BiProperty<>(cmd, listener));
     }
 
     /**
      * @return test classes which have been retrieved by
      * {@link CommandReader#getIterableClasses(MasterProcessChannelEncoder)}.
      */
     Iterator<String> iterated() {
         return testClasses.subList(0, iteratedCount).iterator();
     }
 
     /**
      * The iterator can be used only in one Thread.
      * Two simultaneous instances are not allowed for sake of only one {@link #nextCommandNotifier}.
      *
      * @param eventChannel original stream in current JVM process
      * @return Iterator with test classes lazily loaded as commands from the main process
      */
     Iterable<String> getIterableClasses(MasterProcessChannelEncoder eventChannel) {
         return new ClassesIterable(eventChannel);
     }
 
     public void stop() {
         if (!isStopped()) {
             state.set(TERMINATED);
             makeQueueFull();
             listeners.clear();
             commandThread.interrupt();
         }
     }
 
     private boolean isStopped() {
         return state.get() == TERMINATED;
     }
 
     /**
      * @return {@code true} if {@link #LAST_TEST_SYMBOL} found at the last index in {@link #testClasses}.
      */
     private boolean isQueueFull() {
         // The problem with COWAL is that such collection doe not have operation getLast, however it has get(int)
         // and we need both atomic.
         //
         // Both lines can be Java Concurrent, but the last operation is atomic with optimized search.
         // Searching index of LAST_TEST_SYMBOL in the only last few (concurrently) inserted strings.
         // The insert operation is concurrent with this method.
         // Prerequisite: The strings are added but never removed and the method insertToQueue() does not
         // allow adding a string after LAST_TEST_SYMBOL.
         int searchFrom = max(0, testClasses.size() - 1);
         return testClasses.indexOf(LAST_TEST_SYMBOL, searchFrom) != -1;
     }
 
     private void makeQueueFull() {
         testClasses.addIfAbsent(LAST_TEST_SYMBOL);
     }
 
     private boolean insertToQueue(String test) {
         return isNotBlank(test) && !isQueueFull() && testClasses.add(test);
     }
 
     private final class ClassesIterable implements Iterable<String> {
         private final MasterProcessChannelEncoder eventChannel;
 
         ClassesIterable(MasterProcessChannelEncoder eventChannel) {
             this.eventChannel = eventChannel;
         }
 
         @Override
         public Iterator<String> iterator() {
             return new ClassesIterator(eventChannel);
         }
     }
 
     private final class ClassesIterator implements Iterator<String> {
         private final MasterProcessChannelEncoder eventChannel;
 
         private String clazz;
 
         private int nextQueueIndex;
 
         private ClassesIterator(MasterProcessChannelEncoder eventChannel) {
             this.eventChannel = eventChannel;
         }
 
         @Override
         public boolean hasNext() {
             popUnread();
             return isNotBlank(clazz);
         }
 
         @Override
         public String next() {
             popUnread();
             try {
                 if (isBlank(clazz)) {
                     throw new NoSuchElementException(CommandReader.this.isStopped() ? "stream was stopped" : "");
                 } else {
                     return clazz;
                 }
             } finally {
                 clazz = null;
             }
         }
 
         @Override
         public void remove() {
             throw new UnsupportedOperationException();
         }
 
         private void popUnread() {
             if (shouldFinish()) {
                 clazz = null;
                 return;
             }
 
             if (isBlank(clazz)) {
                 requestNextTest();
                 CommandReader.this.awaitNextTest();
                 if (shouldFinish()) {
                     clazz = null;
                     return;
                 }
                 clazz = CommandReader.this.testClasses.get(nextQueueIndex++);
                 CommandReader.this.iteratedCount = nextQueueIndex;
             }
 
             if (CommandReader.this.isStopped()) {
                 clazz = null;
             }
         }
 
         private void requestNextTest() {
             eventChannel.acquireNextTest();
         }
 
         private boolean shouldFinish() {
             boolean wasLastTestRead = isEndSymbolAt(nextQueueIndex);
             return CommandReader.this.isStopped() || wasLastTestRead;
         }
 
         private boolean isEndSymbolAt(int index) {
             return CommandReader.this.isQueueFull() && 1 + index == CommandReader.this.testClasses.size();
         }
     }
 
     private void awaitNextTest() {
         nextCommandNotifier.acquireUninterruptibly();
     }
 
     private void wakeupIterator() {
         nextCommandNotifier.release();
     }
 
     private final class CommandRunnable implements Runnable {
         @Override
         public void run() {
             CommandReader.this.startMonitor.countDown();
             boolean isTestSetFinished = false;
             try (MasterProcessChannelDecoder commandReader = CommandReader.this.decoder) {
                 while (CommandReader.this.state.get() == RUNNABLE) {
                     Command command = commandReader.decode();
                     switch (command.getCommandType()) {
                         case RUN_CLASS:
                             String test = command.getData();
                             boolean inserted = CommandReader.this.insertToQueue(test);
                             if (inserted) {
                                 CommandReader.this.wakeupIterator();
                                 callListeners(command);
                             }
                             break;
                         case TEST_SET_FINISHED:
                             CommandReader.this.makeQueueFull();
                             isTestSetFinished = true;
                             CommandReader.this.wakeupIterator();
                             callListeners(command);
                             break;
                         case SHUTDOWN:
                             CommandReader.this.makeQueueFull();
                             CommandReader.this.wakeupIterator();
                             callListeners(command);
                             break;
                         case BYE_ACK:
                             callListeners(command);
                             // After SHUTDOWN no more commands can come.
                             // Hence, do NOT go back to blocking in I/O.
                             CommandReader.this.state.set(TERMINATED);
                             break;
                         default:
                             callListeners(command);
                             break;
                     }
                 }
             } catch (EOFException | ClosedChannelException e) {
                 CommandReader.this.state.set(TERMINATED);
                 if (!isTestSetFinished) {
                     String msg = "TestSet has not finished before stream error has appeared >> "
                             + "initializing exit by non-null configuration: "
                             + CommandReader.this.shutdown;
                     DumpErrorSingleton.getSingleton().dumpStreamException(e, msg);
 
                     exitByConfiguration();
                     // does not go to finally for non-default config: Shutdown.EXIT or Shutdown.KILL
                 }
             } catch (IOException e) {
                 CommandReader.this.state.set(TERMINATED);
                 // If #stop() method is called, reader thread is interrupted
                 // and exception is InterruptedIOException or its cause is InterruptedException.
                 if (!(e instanceof InterruptedIOException || e.getCause() instanceof InterruptedException)) {
                     String msg = "[SUREFIRE] std/in stream corrupted";
                     DumpErrorSingleton.getSingleton().dumpStreamException(e, msg);
                     CommandReader.this.logger.error(msg, e);
                 }
             } finally {
                 // ensure fail-safe iterator as well as safe to finish in for-each loop using ClassesIterator
                 if (!isTestSetFinished) {
                     CommandReader.this.makeQueueFull();
                 }
                 CommandReader.this.wakeupIterator();
             }
         }
 
         private void callListeners(Command cmd) {
             MasterProcessCommand expectedCommandType = cmd.getCommandType();
             for (BiProperty<MasterProcessCommand, CommandListener> listenerWrapper : CommandReader.this.listeners) {
                 MasterProcessCommand commandType = listenerWrapper.getP1();
                 CommandListener listener = listenerWrapper.getP2();
                 if (commandType == null || commandType == expectedCommandType) {
                     listener.update(cmd);
                 }
             }
         }
 
         private void exitByConfiguration() {
             Shutdown shutdown = CommandReader.this.shutdown; // won't read inconsistent changes through the stack
             if (shutdown != null) {
                 CommandReader.this.makeQueueFull();
                 CommandReader.this.wakeupIterator();
                 callListeners(toShutdown(shutdown));
             }
         }
     }
 }