/*
 * Copyright (c) 2016, 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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 * questions.
 */

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 8
 */
@jdk.Exported
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);
    }

}
