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Capture output written to System.out and System.err
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/*
  The MIT License (MIT)

  Copyright (c) 2018 Paul Campbell

  Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  and associated documentation files (the "Software"), to deal in the Software without restriction,
  including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
  and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
  subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all copies
  or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
  AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package net.kemitix.outputcapture;

import lombok.val;

import java.io.ByteArrayOutputStream;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Function;

/**
 * Run a callable in a new thread and capture its output.
 *
 * @author Paul Campbell ([email protected])
 *
 * @see SynchronousOutputCapturer
 */
class AsynchronousOutputCapturer extends AbstractCaptureOutput {

    private final Function routerFactory;
    private final Long maxAwaitMilliseconds;
    private final ExecutorService executor;

    /**
     * Constructor.
     * @param routerFactory        The Router to direct where written output is sent
     * @param maxAwaitMilliseconds The maximum number of milliseconds to await for the capture to complete
     * @param executor             The executor service
     */
    AsynchronousOutputCapturer(
            final Function routerFactory,
            final Long maxAwaitMilliseconds,
            final ExecutorService executor
    ) {
        this.routerFactory = routerFactory;
        this.maxAwaitMilliseconds = maxAwaitMilliseconds;
        this.executor = executor;
    }

    /**
     * Captures the output of the callable asynchronously.
     *
     * This implementation launches the callable in a background thread then returns immediately.
     *
     * @param callable     The Runnable to capture the output of
     *
     * @return an instance of OngoingCapturedOutput
     */
    OngoingCapturedOutput capture(final ThrowingCallable callable) {
        val capturedOutput = new AtomicReference();
        val started = new SafeLatch(1, maxAwaitMilliseconds, executor::shutdown);
        execute(callable, capturedOutput, started);
        started.await();
        return capturedOutput.get();
    }

    private void execute(
            final ThrowingCallable callable,
            final AtomicReference capturedOutput,
            final SafeLatch started
    ) {
        val completedLatch = new SafeLatch(1, maxAwaitMilliseconds, executor::shutdown);
        executor.submit(buildCaptor(capturedOutput, completedLatch));
        executor.submit(started::countDown);
        executor.submit(() -> enable(capturedOutput.get()));
        executor.submit(() -> invokeCallable(callable));
        executor.submit(() -> disable(capturedOutput.get()));
        executor.submit(() -> {
            executor.shutdown();
            completedLatch.countDown();
        });
    }

    private Runnable buildCaptor(
            final AtomicReference capturedOutput,
            final SafeLatch completedLatch
    ) {
        return () -> capturedOutput.set(outputCaptor(completedLatch));
    }

    private OngoingCapturedOutput outputCaptor(final SafeLatch completedLatch) {
        val capturedOut = new ByteArrayOutputStream();
        val capturedErr = new ByteArrayOutputStream();
        val router = routerFactory.apply(RouterParameters.createDefault());
        val capturedLines = router.getCapturedLines();
        return new DefaultOngoingCapturedOutput(
                capturedOut,
                capturedErr,
                completedLatch,
                getThrownExceptionReference(),
                router,
                executor,
                capturedLines
        );
    }

}