/*

 * Copyright (c) 2016, 2018, 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;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.util.ArrayList;

import java.util.HashSet;

import java.util.List;

import java.util.Objects;

import java.util.Set;

import jdk.jfr.internal.EventClassBuilder;

import jdk.jfr.internal.JVMSupport;

import jdk.jfr.internal.MetadataRepository;

import jdk.jfr.internal.Type;

import jdk.jfr.internal.Utils;

/**

 * Class for defining an event at runtime.

 * <p>

 * It's highly recommended that the event is defined at compile time, if the

 * field layout is known, so the Java Virtual Machine (JVM) can optimize the

 * code, possibly remove all instrumentation if Flight Recorder is inactive or

 * if the enabled setting for this event is set to {@code false}.

 * <p>

 * To define an event at compile time, see {@link Event}.

 * <p>

 * The following example shows how to implement a dynamic {@code Event} class.

 *

 * <pre>

 * {@code

 * List<ValueDescriptor> fields = new ArrayList<>();

 * List<AnnotationElement> messageAnnotations = Collections.singletonList(new AnnotationElement(Label.class, "Message"));

 * fields.add(new ValueDescriptor(String.class, "message", messageAnnotations));

 * List<AnnotationElement> numberAnnotations = Collections.singletonList(new AnnotationElement(Label.class, "Number"));

 * fields.add(new ValueDescriptor(int.class, "number", numberAnnotations));

 *

 * String[] category = { "Example", "Getting Started" };

 * List<AnnotationElement> eventAnnotations = new ArrayList<>();

 * eventAnnotations.add(new AnnotationElement(Name.class, "com.example.HelloWorld"));

 * eventAnnotations.add(new AnnotationElement(Label.class, "Hello World"));

 * eventAnnotations.add(new AnnotationElement(Description.class, "Helps programmer getting started"));

 * eventAnnotations.add(new AnnotationElement(Category.class, category));

 *

 * EventFactory f = EventFactory.create(eventAnnotations, fields);

 *

 * Event event = f.newEvent();

 * event.set(0, "hello, world!");

 * event.set(1, 4711);

 * event.commit();

 * }

 * </pre>

 *

 * @since 9

 */

public final class EventFactory {

    private static final long REGISTERED_ID = Type.getTypeId(Registered.class);

    private final Class<? extends Event> eventClass;

    private final MethodHandle constructorHandle;

    private final List<AnnotationElement> sanitizedAnnotation;

    private final List<ValueDescriptor> sanitizedFields;

    private EventFactory(Class<? extends Event> eventClass, List<AnnotationElement> sanitizedAnnotation, List<ValueDescriptor> sanitizedFields) throws IllegalAccessException, NoSuchMethodException, SecurityException {

        this.constructorHandle = MethodHandles.lookup().unreflectConstructor(eventClass.getConstructor());

        this.eventClass = eventClass;

        this.sanitizedAnnotation = sanitizedAnnotation;

        this.sanitizedFields = sanitizedFields;

    }

    /**

     * Creates an {@code EventFactory} object.

     * <p>

     * The order of the value descriptors specifies the index to use when setting

     * event values.

     *

     * @param annotationElements list of annotation elements that describes the

     *        annotations on the event, not {@code null}

     *

     * @param fields list of descriptors that describes the fields of the event, not

     *        {@code null}

     *

     * @return event factory, not {@code null}

     *

     * @throws IllegalArgumentException if the input is not valid. For example,

     *         input might not be valid if the field type or name is not valid in

     *         the Java language or an annotation element references a type that

     *         can't be found.

     *

     * @throws SecurityException if a security manager exists and the caller does

     *         not have {@code FlightRecorderPermission("registerEvent")}

     *

     * @see Event#set(int, Object)

     */

    public static EventFactory create(List<AnnotationElement> annotationElements, List<ValueDescriptor> fields) {

        Objects.requireNonNull(fields);

        Objects.requireNonNull(annotationElements);

        JVMSupport.ensureWithInternalError();

        Utils.checkRegisterPermission();

        List<AnnotationElement> sanitizedAnnotation = Utils.sanitizeNullFreeList(annotationElements, AnnotationElement.class);

        List<ValueDescriptor> sanitizedFields = Utils.sanitizeNullFreeList(fields, ValueDescriptor.class);

        Set<String> nameSet = new HashSet<>();

        for (ValueDescriptor v : sanitizedFields) {

            String name = v.getName();

            if (v.isArray()) {

                throw new IllegalArgumentException("Array types are not allowed for fields");

            }

            if (!Type.isValidJavaFieldType(v.getTypeName())) {

                throw new IllegalArgumentException(v.getTypeName() + " is not a valid type for an event field");

            }

            if (!Type.isValidJavaIdentifier(v.getName())) {

                throw new IllegalArgumentException(name + " is not a valid name for an event field");

            }

            if (nameSet.contains(name)) {

                throw new IllegalArgumentException("Name of fields must be unique. Found two instances of " + name);

            }

            nameSet.add(name);

        }

        // Prevent event from being registered in <clinit>

        // and only use annotations that can be resolved (those in boot class loader)

        boolean needRegister = true;

        List<AnnotationElement> bootAnnotations = new ArrayList<>();

        for (AnnotationElement ae : sanitizedAnnotation) {

            long id = ae.getTypeId();

            if (ae.isInBoot()) {

                if (id == REGISTERED_ID) {

                    if (Boolean.FALSE.equals(ae.getValue("value"))) {

                        needRegister = false;

                    }

                } else {

                    bootAnnotations.add(ae);

                }

            }

        }

        bootAnnotations.add(new AnnotationElement(Registered.class, false));

        EventClassBuilder ecb = new EventClassBuilder(bootAnnotations, sanitizedFields);

        Class<? extends Event> eventClass = ecb.build();

        if (needRegister) {

            MetadataRepository.getInstance().register(eventClass, sanitizedAnnotation, sanitizedFields);

        }

        try {

            return new EventFactory(eventClass, sanitizedAnnotation, sanitizedFields);

        } catch (IllegalAccessException e) {

            throw new IllegalAccessError("Could not accees constructor of generated event handler, " + e.getMessage());

        } catch (NoSuchMethodException e) {

            throw new InternalError("Could not find constructor in generated event handler, " + e.getMessage());

        }

    }

    /**

     * Instantiates an event, so it can be populated with data and written to the

     * Flight Recorder system.

     * <p>

     * Use the {@link Event#set(int, Object)} method to set a value.

     *

     * @return an event instance, not {@code null}

     */

    public Event newEvent() {

        try {

            return (Event) constructorHandle.invoke();

        } catch (Throwable e) {

            throw new InstantiationError("Could not instantaite dynamically generated event class " + eventClass.getName() + ". " + e.getMessage());

        }

    }

    /**

     * Returns the event type that is associated with this event factory.

     *

     * @return event type that is associated with this event factory, not

     *         {@code null}

     *

     * @throws java.lang.IllegalStateException if the event factory is created with

     *         the {@code Registered(false)} annotation and the event class is not

     *         manually registered before the invocation of this method

     */

    public EventType getEventType() {

        return EventType.getEventType(eventClass);

    }

    /**

     * Registers an unregistered event.

     * <p>

     * By default, the event class associated with this event factory is registered

     * when the event factory is created, unless the event has the

     * {@link Registered} annotation.

     * <p>

     * A registered event class can write data to Flight Recorder and event metadata

     * can be obtained by invoking {@link FlightRecorder#getEventTypes()}.

     * <p>

     * If the event class associated with this event factory is already registered,

     * the call to this method is ignored.

     *

     * @throws SecurityException if a security manager exists and the caller

     *         does not have {@code FlightRecorderPermission("registerEvent")}

     * @see Registered

     * @see FlightRecorder#register(Class)

     */

    public void register() {

        MetadataRepository.getInstance().register(eventClass, sanitizedAnnotation, sanitizedFields);

    }

    /**

     * Unregisters the event that is associated with this event factory.

     * <p>

     * A unregistered event class can't write data to Flight Recorder and event

     * metadata can't be obtained by invoking

     * {@link FlightRecorder#getEventTypes()}.

     * <p>

     * If the event class associated with this event factory is not already

     * registered, the call to this method is ignored.

     *

     * @throws SecurityException if a security manager exists and the caller does

     *         not have {@code FlightRecorderPermission("registerEvent")}

     * @see Registered

     * @see FlightRecorder#unregister(Class)

     */

    public void unregister() {

        MetadataRepository.getInstance().unregister(eventClass);

    }

}