/*

 * 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

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package jdk.jfr.internal.consumer;

import java.io.IOException;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.VarHandle;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.time.Duration;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.Objects;

import java.util.function.Consumer;

import jdk.jfr.EventType;

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.LongMap;

abstract public class EventConsumer implements Runnable {

    private final static class EventDispatcher {

        public final static EventDispatcher[] NO_DISPATCHERS = new EventDispatcher[0];

        final private String eventName;

        final Consumer<RecordedEvent> action;

        public EventDispatcher(Consumer<RecordedEvent> action) {

            this(null, action);

        }

        public EventDispatcher(String eventName, Consumer<RecordedEvent> action) {

            this.eventName = eventName;

            this.action = action;

        }

        public void offer(RecordedEvent event) {

            action.accept(event);

        }

        public boolean accepts(EventType eventType) {

            return (eventName == null || eventType.getName().equals(eventName));

        }

    }

    private final static JVM jvm = JVM.getJVM();

    private final static VarHandle closedHandle;

    private final static VarHandle consumersHandle;

    private final static VarHandle dispatcherHandle;

    private final static VarHandle flushActionsHandle;

    private final static VarHandle closeActionsHandle;

    private final static VarHandle orderedHandle;

    private final static VarHandle reuseHandle;

    static {

        try {

            MethodHandles.Lookup l = MethodHandles.lookup();

            closedHandle = l.findVarHandle(EventConsumer.class, "closed", boolean.class);

            consumersHandle = l.findVarHandle(EventConsumer.class, "consumers", EventDispatcher[].class);

            dispatcherHandle = l.findVarHandle(EventConsumer.class, "dispatcher", LongMap.class);

            flushActionsHandle = l.findVarHandle(EventConsumer.class, "flushActions", Runnable[].class);

            closeActionsHandle = l.findVarHandle(EventConsumer.class, "closeActions", Runnable[].class);

            orderedHandle = l.findVarHandle(EventConsumer.class, "ordered", boolean.class);

            reuseHandle = l.findVarHandle(EventConsumer.class, "reuse", boolean.class);

        } catch (ReflectiveOperationException e) {

            throw new InternalError(e);

        }

    }

    // set by VarHandle

    private boolean closed;

    // set by VarHandle

    private EventDispatcher[] consumers = new EventDispatcher[0];

    // set by VarHandle

    private LongMap<EventDispatcher[]> dispatcher = new LongMap<>();

    // set by VarHandle

    private Runnable[] flushActions = new Runnable[0];

    // set by VarHandle

    private Runnable[] closeActions = new Runnable[0];

    protected boolean ordered = true;

    protected boolean reuse = true;

    private final AccessControlContext accessControlContext;

    private boolean started;

    private Thread thread;

    protected long startNanos;

    public EventConsumer(AccessControlContext acc) throws IOException {

        this.accessControlContext = acc;

    }

    public void run() {

        doPriviliged(() -> execute());

    }

    void doPriviliged(Runnable r) {

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

            @Override

            public Void run() {

                r.run();

                return null;

            }

        }, accessControlContext);

    }

    private void execute() {

        jvm.exclude(Thread.currentThread());

        try {

            process();

        } catch (IOException e) {

            if (!isClosed()) {

                logException(e);

            }

        } catch (Exception e) {

            logException(e);

        } finally {

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

        }

    }

    private void logException(Exception e) {

        e.printStackTrace(); // for debugging purposes, remove before

        // integration

        Logger.log(LogTag.JFR_SYSTEM_STREAMING, LogLevel.DEBUG, "Unexpected error processing stream. " + e.getMessage());

    }

    public abstract void process() throws IOException;

    public synchronized boolean remove(Object action) {

        boolean remove = false;

        Runnable[] updatedFlushActions = removeAction(flushActions, action);

        if (updatedFlushActions != null) {

            flushActionsHandle.setVolatile(this, updatedFlushActions);

            remove = true;

        }

        Runnable[] updatedCloseActions = removeAction(closeActions, action);

        if (updatedCloseActions != null) {

            closeActionsHandle.setVolatile(this, updatedCloseActions);

            remove = true;

        }

        boolean removeConsumer = false;

        List<EventDispatcher> list = new ArrayList<>();

        for (int i = 0; i < consumers.length; i++) {

            if (consumers[i].action != action) {

                list.add(consumers[i]);

            } else {

                removeConsumer = true;

                remove = true;

            }

        }

        if (removeConsumer) {

            EventDispatcher[] array = list.toArray(new EventDispatcher[list.size()]);

            consumersHandle.setVolatile(this, array);

            dispatcherHandle.setVolatile(this, new LongMap<>()); // will reset

                                                                 // dispatch

        }

        return remove;

    }

    public void dispatch(RecordedEvent e) {

        EventDispatcher[] consumerDispatch = dispatcher.get(e.getEventType().getId());

        if (consumerDispatch == null) {

            consumerDispatch = EventDispatcher.NO_DISPATCHERS;

            for (EventDispatcher ec : consumers.clone()) {

                if (ec.accepts(e.getEventType())) {

                    consumerDispatch = merge(consumerDispatch, ec);

                }

            }

            dispatcher.put(e.getEventType().getId(), consumerDispatch);

        }

        for (int i = 0; i < consumerDispatch.length; i++) {

            try {

                consumerDispatch[i].offer(e);

            } catch (Exception exception) {

                // Is this a reasonable behavior for an exception?

                // Error will abort the stream.

            }

        }

    }

    public void onEvent(Consumer<RecordedEvent> action) {

        add(new EventDispatcher(action));

    }

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

        add(new EventDispatcher(eventName, action));

    }

    private synchronized void add(EventDispatcher e) {

        dispatcherHandle.setVolatile(this, new LongMap<>()); // will reset

    }

    public synchronized void onFlush(Runnable action) {

        flushActionsHandle.setVolatile(this, addAction(flushActions, action));

    }

    public synchronized void addCloseAction(Runnable action) {

        closeActionsHandle.setVolatile(this, addAction(closeActions, action));

    }

    public void setClosed(boolean closed) {

        closedHandle.setVolatile(this, closed);

    }

    final public boolean isClosed() {

        return closed;

    }

    public void runCloseActions() {

        Runnable[] cas = this.closeActions;

        for (int i = 0; i < cas.length; i++) {

            cas[i].run();

        }

    }

    public void runFlushActions() {

        Runnable[] fas = this.flushActions;

        for (int i = 0; i < fas.length; i++) {

            fas[i].run();

        }

    }

    public synchronized void startAsync(long startNanos) {

        if (started) {

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

        }

        started = true;

        setStartNanos(startNanos);

        thread = new Thread(this);

        thread.setDaemon(true);

        thread.start();

    }

    public void start(long startNanos) {

        synchronized (this) {

            if (started) {

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

            }

            started = true;

            setStartNanos(startNanos);

        }

        run();

    }

    public void awaitTermination(Duration timeout) {

        Objects.requireNonNull(timeout);

        Thread t = null;

        synchronized (this) {

            t = thread;

        }

        if (t != null && t != Thread.currentThread()) {

            try {

                t.join(timeout.toMillis());

            } catch (InterruptedException e) {

                // ignore

            }

        }

    }

    public void awaitTermination() {

        awaitTermination(Duration.ofMillis(0));

    }

    private void setStartNanos(long startNanos) {

        this.startNanos = startNanos;

    }

    protected static EventDispatcher[] merge(EventDispatcher[] current, EventDispatcher add) {

        EventDispatcher[] array = new EventDispatcher[current.length + 1];

        System.arraycopy(current, 0, array, 0, current.length);

        array[current.length] = add;

        return array;

    }

    private static Runnable[] removeAction(Runnable[] array, Object action) {

        if (array.length == 0) {

            return null;

        }

        boolean remove = false;

        List<Runnable> list = new ArrayList<>();

        for (int i = 0; i < array.length; i++) {

            if (array[i] != action) {

                list.add(array[i]);

            } else {

                remove = true;

            }

        }

        if (remove) {

            return list.toArray(new Runnable[list.size()]);

        }

        return null;

    }

    private static Runnable[] addAction(Runnable[] array, Runnable action) {

        ArrayList<Runnable> a = new ArrayList<>();

        a.addAll(Arrays.asList(array));

        a.add(action);

        return a.toArray(new Runnable[0]);

    }

    abstract public void close();

    public void setReuse(boolean reuse) {

        reuseHandle.setVolatile(this, reuse);

    }

    public void setOrdered(boolean ordered) {

        orderedHandle.setVolatile(this, ordered);

    }

}