/*
 * 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.TreeSet;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;

import org.apache.maven.surefire.api.testset.TestSetFailedException;
import org.apache.maven.surefire.api.util.internal.DaemonThreadFactory;
import org.junit.runner.Computer;
import org.junit.runner.Description;

import static java.util.concurrent.TimeUnit.NANOSECONDS;

/**
 * ParallelComputer extends JUnit {@link Computer} and has a shutdown functionality.
 *
 * @author Tibor Digana (tibor17)
 * @see ParallelComputerBuilder
 * @since 2.16
 */
public abstract class ParallelComputer extends Computer {
    private static final ThreadFactory DAEMON_THREAD_FACTORY = DaemonThreadFactory.newDaemonThreadFactory();

    private static final double NANOS_IN_A_SECOND = 1E9;

    private final ShutdownStatus shutdownStatus = new ShutdownStatus();

    private final ShutdownStatus forcedShutdownStatus = new ShutdownStatus();

    private final long timeoutNanos;

    private final long timeoutForcedNanos;

    private ScheduledExecutorService shutdownScheduler;

    public ParallelComputer(double timeoutInSeconds, double timeoutForcedInSeconds) {
        this.timeoutNanos = secondsToNanos(timeoutInSeconds);
        this.timeoutForcedNanos = secondsToNanos(timeoutForcedInSeconds);
    }

    protected abstract ShutdownResult describeStopped(boolean shutdownNow);

    protected abstract boolean shutdownThreadPoolsAwaitingKilled();

    protected final void beforeRunQuietly() {
        shutdownStatus.setDescriptionsBeforeShutdown(hasTimeout() ? scheduleShutdown() : null);
        forcedShutdownStatus.setDescriptionsBeforeShutdown(hasTimeoutForced() ? scheduleForcedShutdown() : null);
    }

    protected final boolean afterRunQuietly() {
        shutdownStatus.tryFinish();
        forcedShutdownStatus.tryFinish();
        boolean notInterrupted = true;
        if (shutdownScheduler != null) {
            shutdownScheduler.shutdownNow();
            /**
             * Clear <i>interrupted status</i> of the (main) Thread.
             * Could be previously interrupted by {@link InvokerStrategy} after triggering immediate shutdown.
             */
            Thread.interrupted();
            try {
                shutdownScheduler.awaitTermination(Long.MAX_VALUE, NANOSECONDS);
            } catch (InterruptedException e) {
                notInterrupted = false;
            }
        }
        notInterrupted &= shutdownThreadPoolsAwaitingKilled();
        return notInterrupted;
    }

    public String describeElapsedTimeout() throws TestSetFailedException {
        final StringBuilder msg = new StringBuilder();
        final boolean isShutdownTimeout = shutdownStatus.isTimeoutElapsed();
        final boolean isForcedShutdownTimeout = forcedShutdownStatus.isTimeoutElapsed();
        if (isShutdownTimeout || isForcedShutdownTimeout) {
            msg.append("The test run has finished abruptly after timeout of ");
            msg.append(nanosToSeconds(minTimeout(timeoutNanos, timeoutForcedNanos)));
            msg.append(" seconds.\n");

            try {
                final TreeSet<String> executedTests = new TreeSet<>();
                final TreeSet<String> incompleteTests = new TreeSet<>();

                if (isShutdownTimeout) {
                    printShutdownHook(executedTests, incompleteTests, shutdownStatus.getDescriptionsBeforeShutdown());
                }

                if (isForcedShutdownTimeout) {
                    printShutdownHook(
                            executedTests, incompleteTests, forcedShutdownStatus.getDescriptionsBeforeShutdown());
                }

                if (!executedTests.isEmpty()) {
                    msg.append("These tests were executed in prior to the shutdown operation:\n");
                    for (String executedTest : executedTests) {
                        msg.append(executedTest).append('\n');
                    }
                }

                if (!incompleteTests.isEmpty()) {
                    msg.append("These tests are incomplete:\n");
                    for (String incompleteTest : incompleteTests) {
                        msg.append(incompleteTest).append('\n');
                    }
                }
            } catch (InterruptedException e) {
                throw new TestSetFailedException("Timed termination was interrupted.", e);
            } catch (ExecutionException e) {
                throw new TestSetFailedException(e.getLocalizedMessage(), e.getCause());
            }
        }
        return msg.toString();
    }

    private Future<ShutdownResult> scheduleShutdown() {
        return getShutdownScheduler().schedule(createShutdownTask(), timeoutNanos, NANOSECONDS);
    }

    private Future<ShutdownResult> scheduleForcedShutdown() {
        return getShutdownScheduler().schedule(createForcedShutdownTask(), timeoutForcedNanos, NANOSECONDS);
    }

    private ScheduledExecutorService getShutdownScheduler() {
        if (shutdownScheduler == null) {
            shutdownScheduler = Executors.newScheduledThreadPool(2, DAEMON_THREAD_FACTORY);
        }
        return shutdownScheduler;
    }

    private Callable<ShutdownResult> createShutdownTask() {
        return new Callable<ShutdownResult>() {
            @Override
            public ShutdownResult call() throws Exception {
                boolean stampedStatusWithTimeout = ParallelComputer.this.shutdownStatus.tryTimeout();
                return stampedStatusWithTimeout ? ParallelComputer.this.describeStopped(false) : null;
            }
        };
    }

    private Callable<ShutdownResult> createForcedShutdownTask() {
        return new Callable<ShutdownResult>() {
            @Override
            public ShutdownResult call() throws Exception {
                boolean stampedStatusWithTimeout = ParallelComputer.this.forcedShutdownStatus.tryTimeout();
                return stampedStatusWithTimeout ? ParallelComputer.this.describeStopped(true) : null;
            }
        };
    }

    private double nanosToSeconds(long nanos) {
        return (double) nanos / NANOS_IN_A_SECOND;
    }

    private boolean hasTimeout() {
        return timeoutNanos > 0;
    }

    private boolean hasTimeoutForced() {
        return timeoutForcedNanos > 0;
    }

    private static long secondsToNanos(double seconds) {
        double nanos = seconds > 0 ? seconds * NANOS_IN_A_SECOND : 0;
        return Double.isInfinite(nanos) || nanos >= Long.MAX_VALUE ? 0 : (long) nanos;
    }

    private static long minTimeout(long timeout1, long timeout2) {
        if (timeout1 == 0) {
            return timeout2;
        } else if (timeout2 == 0) {
            return timeout1;
        } else {
            return Math.min(timeout1, timeout2);
        }
    }

    private static void printShutdownHook(
            Collection<String> executedTests,
            Collection<String> incompleteTests,
            Future<ShutdownResult> testsBeforeShutdown)
            throws ExecutionException, InterruptedException {
        if (testsBeforeShutdown != null) {
            final ShutdownResult shutdownResult = testsBeforeShutdown.get();
            if (shutdownResult != null) {
                for (final Description test : shutdownResult.getTriggeredTests()) {
                    if (test != null && test.getDisplayName() != null) {
                        executedTests.add(test.getDisplayName());
                    }
                }

                for (final Description test : shutdownResult.getIncompleteTests()) {
                    if (test != null && test.getDisplayName() != null) {
                        incompleteTests.add(test.getDisplayName());
                    }
                }
            }
        }
    }
}
