/*

 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.jfr.internal.consumer;

import java.io.IOException;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.time.Duration;

import java.time.Instant;

import java.util.Objects;

import java.util.concurrent.atomic.AtomicLong;

import java.util.function.Consumer;

import jdk.jfr.consumer.EventStream;

import jdk.jfr.consumer.RecordedEvent;

import jdk.jfr.internal.JVM;

import jdk.jfr.internal.LogLevel;

import jdk.jfr.internal.LogTag;

import jdk.jfr.internal.Logger;

import jdk.jfr.internal.SecuritySupport;

/*

 * Purpose of this class is to simplify the implementation of

 * an event stream. In particular, it handles:

 *

 * - configuration storage

 * - atomic updates to a configuration

 * - dispatch mechanism

 * - error handling

 * - security

 *

 */

public abstract class AbstractEventStream implements EventStream {

    private final static AtomicLong counter = new AtomicLong(1);

    private final Object terminated = new Object();

    private final boolean active;

    private final Runnable flushOperation = () -> dispatcher().runFlushActions();

    private final AccessControlContext accessControllerContext;

    private final StreamConfiguration configuration = new StreamConfiguration();

    private volatile Thread thread;

    private Dispatcher dispatcher;

    private volatile boolean closed;

    public AbstractEventStream(AccessControlContext acc, boolean active) throws IOException {

        this.accessControllerContext = Objects.requireNonNull(acc);

        this.active = active;

    }

    @Override

    abstract public void start();

    @Override

    abstract public void startAsync();

    @Override

    abstract public void close();

    protected final Dispatcher dispatcher() {

        if (configuration.hasChanged()) {

            synchronized (configuration) {

                dispatcher = new Dispatcher(configuration);

            }

        }

        return dispatcher;

    }

    @Override

    public final void setOrdered(boolean ordered) {

        configuration.setOrdered(ordered);

    }

    @Override

    public final void setReuse(boolean reuse) {

        configuration.setReuse(reuse);

    }

    @Override

    public final void setStartTime(Instant startTime) {

        Objects.nonNull(startTime);

        synchronized (configuration) {

            if (configuration.started) {

                throw new IllegalStateException("Stream is already started");

            }

            if (startTime.isBefore(Instant.EPOCH)) {

                startTime = Instant.EPOCH;

            }

            configuration.setStartTime(startTime);

        }

    }

    @Override

    public final void setEndTime(Instant endTime) {

        Objects.requireNonNull(endTime);

        synchronized (configuration) {

            if (configuration.started) {

                throw new IllegalStateException("Stream is already started");

            }

            configuration.setEndTime(endTime);

        }

    }

    @Override

    public final void onEvent(Consumer<RecordedEvent> action) {

        Objects.requireNonNull(action);

        configuration.addEventAction(action);

    }

    @Override

    public final void onEvent(String eventName, Consumer<RecordedEvent> action) {

        Objects.requireNonNull(eventName);

        Objects.requireNonNull(action);

        configuration.addEventAction(eventName, action);

    }

    @Override

    public final void onFlush(Runnable action) {

        Objects.requireNonNull(action);

        configuration.addFlushAction(action);

    }

    @Override

    public final void onClose(Runnable action) {

        Objects.requireNonNull(action);

        configuration.addCloseAction(action);

    }

    @Override

    public final void onError(Consumer<Throwable> action) {

        Objects.requireNonNull(action);

        configuration.addErrorAction(action);

    }

    @Override

    public final boolean remove(Object action) {

        Objects.requireNonNull(action);

        return configuration.remove(action);

    }

    @Override

    public final void awaitTermination() throws InterruptedException {

        awaitTermination(Duration.ofMillis(0));

    }

    @Override

    public final void awaitTermination(Duration timeout) throws InterruptedException {

        Objects.requireNonNull(timeout);

        if (timeout.isNegative()) {

            throw new IllegalArgumentException("timeout value is negative");

        }

        long base = System.currentTimeMillis();

        long now = 0;

        long millis;

        try {

            millis = Math.multiplyExact(timeout.getSeconds(), 1000);

        } catch (ArithmeticException a) {

            millis = Long.MAX_VALUE;

        }

        int nanos = timeout.toNanosPart();

        if (nanos == 0 && millis == 0) {

            synchronized (terminated) {

                while (!isClosed()) {

                    terminated.wait(0);

                }

            }

        } else {

            while (!isClosed()) {

                long delay = millis - now;

                if (delay <= 0) {

                    break;

                }

                synchronized (terminated) {

                    terminated.wait(delay, nanos);

                }

                now = System.currentTimeMillis() - base;

            }

        }

    }

    protected abstract void process() throws IOException;

    protected final void setClosed(boolean closed) {

        this.closed = closed;

    }

    protected final boolean isClosed() {

        return closed;

    }

    public final void startAsync(long startNanos) {

        startInternal(startNanos);

        Runnable r = () -> run(accessControllerContext);

        thread = SecuritySupport.createThreadWitNoPermissions(nextThreadName(), r);

        thread.start();

    }

    public final void start(long startNanos) {

        startInternal(startNanos);

        thread = Thread.currentThread();

        run(accessControllerContext);

    }

    protected final Runnable getFlushOperation() {

        return flushOperation;

    }

    private void startInternal(long startNanos) {

        synchronized (configuration) {

            if (configuration.started) {

                throw new IllegalStateException("Event stream can only be started once");

            }

            if (active) {

                configuration.setStartNanos(startNanos);

            }

            configuration.setStarted(true);

        }

    }

    private void execute() {

        JVM.getJVM().exclude(Thread.currentThread());

        try {

            process();

        } catch (IOException ioe) {

            // This can happen if a chunk file is removed, or

            // a file is access that has been closed

            // This is "normal" behavior for streaming and the

            // stream will be closed when this happens.

        } finally {

            Logger.log(LogTag.JFR_SYSTEM_STREAMING, LogLevel.DEBUG, "Execution of stream ended.");

            try {

                close();

            } finally {

                synchronized (terminated) {

                    terminated.notifyAll();

                }

            }

        }

    }

    private void run(AccessControlContext accessControlContext) {

        AccessController.doPrivileged(new PrivilegedAction<Void>() {

            @Override

            public Void run() {

                execute();

                return null;

            }

        }, accessControlContext);

    }

    private String nextThreadName() {

        counter.incrementAndGet();

        return "JFR Event Stream " + counter;

    }