/*
    * 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.junitcore.pc;
  
  import java.util.Collection;
  import java.util.Set;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.CopyOnWriteArraySet;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.RejectedExecutionHandler;
  import java.util.concurrent.ThreadPoolExecutor;
  
  import org.apache.maven.plugin.surefire.log.api.ConsoleLogger;
  import org.junit.runner.Description;
  import org.junit.runners.model.RunnerScheduler;
  
  /**
   * Schedules tests, controls thread resources, awaiting tests and other schedulers finished, and
   * a master scheduler can shutdown slaves.
   * <br>
   * The scheduler objects should be first created (and wired) and set in runners
   * {@link org.junit.runners.ParentRunner#setScheduler(org.junit.runners.model.RunnerScheduler)}.
   * <br>
   * A new instance of scheduling strategy should be passed to the constructor of this scheduler.
   *
   * @author Tibor Digana (tibor17)
   * @since 2.16
   */
  public class Scheduler implements RunnerScheduler {
      private final Balancer balancer;
  
      private final SchedulingStrategy strategy;
  
      private final Set<Controller> slaves = new CopyOnWriteArraySet<>();
  
      private final Description description;
  
      private final ConsoleLogger logger;
  
      private volatile boolean shutdown = false;
  
      private volatile boolean started = false;
  
      private volatile boolean finished = false;
  
      private volatile Controller masterController;
  
      /**
       * Use e.g. parallel classes have own non-shared thread pool, and methods another pool.
       * <br>
       * You can use it with one infinite thread pool shared in strategies across all
       * suites, class runners, etc.
       *
       * @param logger          console logger
       * @param description     JUnit description of class
       * @param strategy        scheduling strategy
       */
      public Scheduler(ConsoleLogger logger, Description description, SchedulingStrategy strategy) {
          this(logger, description, strategy, -1);
      }
  
      /**
       * Should be used if schedulers in parallel children and parent use one instance of bounded thread pool.
       * <br>
       * Set this scheduler in a e.g. one suite of classes, then every individual class runner should reference
       * {@link #Scheduler(ConsoleLogger, org.junit.runner.Description, Scheduler, SchedulingStrategy)}
       * or {@link #Scheduler(ConsoleLogger, org.junit.runner.Description, Scheduler, SchedulingStrategy, int)}.
       *
       * @param logger current logger implementation
       * @param description description of current runner
       * @param strategy    scheduling strategy with a shared thread pool
       * @param concurrency determines maximum concurrent children scheduled a time via {@link #schedule(Runnable)}
       * @throws NullPointerException if null <code>strategy</code>
       */
      public Scheduler(ConsoleLogger logger, Description description, SchedulingStrategy strategy, int concurrency) {
          this(logger, description, strategy, BalancerFactory.createBalancer(concurrency));
      }
  
      /**
       * New instances should be used by schedulers with limited concurrency by <code>balancer</code>
       * against other groups of schedulers. The schedulers share one pool.
       * <br>
       * Unlike in {@link #Scheduler(ConsoleLogger, org.junit.runner.Description, SchedulingStrategy, int)} which was
      * limiting the <code>concurrency</code> of children of a runner where this scheduler was set, {@code this}
      * <code>balancer</code> is limiting the concurrency of all children in runners having schedulers created by this
      * constructor.
      *
      * @param logger current logger implementation
      * @param description description of current runner
      * @param strategy    scheduling strategy which may share threads with other strategy
      * @param balancer    determines maximum concurrent children scheduled a time via {@link #schedule(Runnable)}
      * @throws NullPointerException if null <code>strategy</code> or <code>balancer</code>
      */
     public Scheduler(ConsoleLogger logger, Description description, SchedulingStrategy strategy, Balancer balancer) {
         strategy.setDefaultShutdownHandler(newShutdownHandler());
         this.logger = logger;
         this.description = description;
         this.strategy = strategy;
         this.balancer = balancer;
         masterController = null;
     }
 
     /**
      * Can be used by e.g. a runner having parallel classes in use case with parallel
      * suites, classes and methods sharing the same thread pool.
      *
      * @param logger current logger implementation
      * @param description     description of current runner
      * @param masterScheduler scheduler sharing own threads with this slave
      * @param strategy        scheduling strategy for this scheduler
      * @param balancer        determines maximum concurrent children scheduled a time via {@link #schedule(Runnable)}
      * @throws NullPointerException if null <code>masterScheduler</code>, <code>strategy</code> or <code>balancer</code>
      */
     public Scheduler(
             ConsoleLogger logger,
             Description description,
             Scheduler masterScheduler,
             SchedulingStrategy strategy,
             Balancer balancer) {
         this(logger, description, strategy, balancer);
         strategy.setDefaultShutdownHandler(newShutdownHandler());
         masterScheduler.register(this);
     }
 
     /**
      * @param logger          console logger
      * @param description     JUnit description of class
      * @param masterScheduler a reference to
      * {@link #Scheduler(ConsoleLogger, org.junit.runner.Description, SchedulingStrategy, int)}
      *                        or {@link #Scheduler(ConsoleLogger, org.junit.runner.Description, SchedulingStrategy)}
      * @param strategy        scheduling strategy
      * @param concurrency     determines maximum concurrent children scheduled a time via {@link #schedule(Runnable)}
      *
      * @see #Scheduler(ConsoleLogger, org.junit.runner.Description, SchedulingStrategy)
      * @see #Scheduler(ConsoleLogger, org.junit.runner.Description, SchedulingStrategy, int)
      */
     public Scheduler(
             ConsoleLogger logger,
             Description description,
             Scheduler masterScheduler,
             SchedulingStrategy strategy,
             int concurrency) {
         this(logger, description, strategy, concurrency);
         strategy.setDefaultShutdownHandler(newShutdownHandler());
         masterScheduler.register(this);
     }
 
     /**
      * Should be used with individual pools on suites, classes and methods, see
      * {@link org.apache.maven.surefire.junitcore.pc.ParallelComputerBuilder#useSeparatePools()}.
      * <br>
      * Cached thread pool is infinite and can be always shared.
      *
      * @param logger          console logger
      * @param description     JUnit description of class
      * @param masterScheduler parent scheduler
      * @param strategy        scheduling strategy
      */
     public Scheduler(
             ConsoleLogger logger, Description description, Scheduler masterScheduler, SchedulingStrategy strategy) {
         this(logger, description, masterScheduler, strategy, 0);
     }
 
     private void setController(Controller masterController) {
         if (masterController == null) {
             throw new NullPointerException("null ExecutionController");
         }
         this.masterController = masterController;
     }
 
     /**
      * @param slave a slave scheduler to register
      * @return {@code true} if successfully registered the <code>slave</code>.
      */
     private boolean register(Scheduler slave) {
         boolean canRegister = slave != null && slave != this;
         if (canRegister) {
             Controller controller = new Controller(slave);
             canRegister = !slaves.contains(controller);
             if (canRegister) {
                 slaves.add(controller);
                 slave.setController(controller);
             }
         }
         return canRegister;
     }
 
     /**
      * @return {@code true} if new tasks can be scheduled.
      */
     private boolean canSchedule() {
         return !shutdown && (masterController == null || masterController.canSchedule());
     }
 
     protected void logQuietly(Throwable t) {
         logger.error(t);
     }
 
     protected void logQuietly(String msg) {
         logger.warning(msg);
     }
 
     /**
      * Attempts to stop all actively executing tasks and immediately returns a collection
      * of descriptions of those tasks which have started prior to this call.
      * <br>
      * This scheduler and other registered schedulers will stop, see {@link #register(Scheduler)}.
      * If <code>shutdownNow</code> is set, waiting methods will be interrupted via {@link Thread#interrupt}.
      *
      * @param stopNow if {@code true} interrupts waiting test methods
      * @return collection of descriptions started before shutting down
      */
     protected ShutdownResult describeStopped(boolean stopNow) {
         Collection<Description> executedTests = new ConcurrentLinkedQueue<>();
         Collection<Description> incompleteTests = new ConcurrentLinkedQueue<>();
         stop(executedTests, incompleteTests, false, stopNow);
         return new ShutdownResult(executedTests, incompleteTests);
     }
 
     /**
      * Stop/Shutdown/Interrupt scheduler and its children (if any).
      *
      * @param executedTests       Started tests which have finished normally or abruptly till called this method.
      * @param incompleteTests     Started tests which have finished incomplete due to shutdown.
      * @param tryCancelFutures    Useful to set to {@code false} if a timeout is specified in plugin config.
      *                            When the runner of
      *                            {@link ParallelComputer#getSuite(org.junit.runners.model.RunnerBuilder, Class[])}
      *                            is finished in
      *                            {@link org.junit.runners.Suite#run(org.junit.runner.notification.RunNotifier)}
      *                            all the thread-pools created by {@link ParallelComputerBuilder.PC} are already dead.
      *                            See the unit test {@code ParallelComputerBuilder#timeoutAndForcedShutdown()}.
      * @param stopNow             Interrupting tests by {@link java.util.concurrent.ExecutorService#shutdownNow()} or
      *                            {@link java.util.concurrent.Future#cancel(boolean) Future#cancel(true)} or
      *                            {@link Thread#interrupt()}.
      */
     private void stop(
             Collection<Description> executedTests,
             Collection<Description> incompleteTests,
             boolean tryCancelFutures,
             boolean stopNow) {
         shutdown = true;
         try {
             if (started && !ParallelComputerUtil.isUnusedDescription(description)) {
                 if (executedTests != null) {
                     executedTests.add(description);
                 }
 
                 if (incompleteTests != null && !finished) {
                     incompleteTests.add(description);
                 }
             }
 
             for (Controller slave : slaves) {
                 slave.stop(executedTests, incompleteTests, tryCancelFutures, stopNow);
             }
         } finally {
             try {
                 balancer.releaseAllPermits();
             } finally {
                 if (stopNow) {
                     strategy.stopNow();
                 } else if (tryCancelFutures) {
                     strategy.stop();
                 } else {
                     strategy.disable();
                 }
             }
         }
     }
 
     protected boolean shutdownThreadPoolsAwaitingKilled() {
         if (masterController == null) {
             stop(null, null, true, false);
             boolean isNotInterrupted = true;
             if (strategy != null) {
                 isNotInterrupted = strategy.destroy();
             }
             for (Controller slave : slaves) {
                 isNotInterrupted &= slave.destroy();
             }
             return isNotInterrupted;
         } else {
             throw new UnsupportedOperationException("cannot call this method if this is not a master scheduler");
         }
     }
 
     protected void beforeExecute() {}
 
     protected void afterExecute() {}
 
     @Override
     public void schedule(Runnable childStatement) {
         if (childStatement == null) {
             logQuietly("cannot schedule null");
         } else if (canSchedule() && strategy.canSchedule()) {
             try {
                 boolean isNotInterrupted = balancer.acquirePermit();
                 if (isNotInterrupted && !shutdown) {
                     Runnable task = wrapTask(childStatement);
                     strategy.schedule(task);
                     started = true;
                 }
             } catch (RejectedExecutionException e) {
                 stop(null, null, true, false);
             } catch (Throwable t) {
                 balancer.releasePermit();
                 logQuietly(t);
             }
         }
     }
 
     @Override
     public void finished() {
         try {
             strategy.finished();
         } catch (InterruptedException e) {
             logQuietly(e);
         } finally {
             finished = true;
         }
     }
 
     private Runnable wrapTask(final Runnable task) {
         return new Runnable() {
             @Override
             public void run() {
                 try {
                     beforeExecute();
                     task.run();
                 } finally {
                     try {
                         afterExecute();
                     } finally {
                         balancer.releasePermit();
                     }
                 }
             }
         };
     }
 
     protected ShutdownHandler newShutdownHandler() {
         return new ShutdownHandler();
     }
 
     /**
      * If this is a master scheduler, the slaves can stop scheduling by the master through the controller.
      */
     private final class Controller {
         private final Scheduler slave;
 
         private Controller(Scheduler slave) {
             this.slave = slave;
         }
 
         /**
          * @return {@code true} if new children can be scheduled.
          */
         boolean canSchedule() {
             return Scheduler.this.canSchedule();
         }
 
         void stop(
                 Collection<Description> executedTests,
                 Collection<Description> incompleteTests,
                 boolean tryCancelFutures,
                 boolean shutdownNow) {
             slave.stop(executedTests, incompleteTests, tryCancelFutures, shutdownNow);
         }
 
         /**
          * @see org.apache.maven.surefire.junitcore.pc.Destroyable#destroy()
          */
         boolean destroy() {
             return slave.strategy.destroy();
         }
 
         @Override
         public int hashCode() {
             return slave.hashCode();
         }
 
         @Override
         public boolean equals(Object o) {
             return o == this || (o instanceof Controller) && slave.equals(((Controller) o).slave);
         }
     }
 
     /**
      * There is a way to shutdown the hierarchy of schedulers. You can do it in master scheduler via
      * {@link #shutdownThreadPoolsAwaitingKilled()} which kills the current master and children recursively.
      * If alternatively a shared {@link java.util.concurrent.ExecutorService} used by the master and children
      * schedulers is shutdown from outside, then the {@link ShutdownHandler} is a hook calling current
      * {@link #describeStopped(boolean)}. The method {@link #describeStopped(boolean)} is again shutting down children
      * schedulers recursively as well.
      */
     public class ShutdownHandler implements RejectedExecutionHandler {
         private volatile RejectedExecutionHandler poolHandler;
 
         protected ShutdownHandler() {
             poolHandler = null;
         }
 
         public void setRejectedExecutionHandler(RejectedExecutionHandler poolHandler) {
             this.poolHandler = poolHandler;
         }
 
         @Override
         public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
             if (executor.isShutdown()) {
                 Scheduler.this.stop(null, null, true, false);
             }
             final RejectedExecutionHandler poolHandler = this.poolHandler;
             if (poolHandler != null) {
                 poolHandler.rejectedExecution(r, executor);
             }
         }
     }
 }