/*

 * 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

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

 * questions.

 */

package jdk.jfr;

import java.lang.annotation.Annotation;

import java.lang.reflect.Method;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Objects;

import java.util.Set;

import java.util.StringJoiner;

import jdk.jfr.internal.Type;

import jdk.jfr.internal.TypeLibrary;

import jdk.jfr.internal.Utils;

/**

 * Describes event metadata, such as labels, descriptions and units.

 * <p>

 * The following example shows how {@code AnnotationElement} can be used to dynamically define events.

 *

 * <pre>

 * <code>

 *   List{@literal <}AnnotationElement{@literal >} typeAnnotations = new ArrayList{@literal <}{@literal >}();

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

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

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

 *

 *   List{@literal <}AnnotationElement{@literal >} fieldAnnotations = new ArrayList{@literal <}{@literal >}();

 *   fieldAnnotations.add(new AnnotationElement(Label.class, "Message"));

 *

 *   List{@literal <}ValueDescriptor{@literal >} fields = new ArrayList{@literal <}{@literal >}();

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

 *

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

 *   Event event = f.newEvent();

 *   event.commit();

 * </code>

 * </pre>

 *

 * @since 9

 */

public final class AnnotationElement {

    private final Type type;

    private final List<Object> annotationValues;

    private final List<String> annotationNames;

    private final boolean inBootClassLoader;

    // package private

    AnnotationElement(Type type, List<Object> objects, boolean boot) {

        Objects.requireNonNull(type);

        Objects.requireNonNull(objects);

        this.type = type;

        if (objects.size() != type.getFields().size()) {

            StringJoiner descriptors = new StringJoiner(",", "[", "]");

            for (ValueDescriptor v : type.getFields()) {

                descriptors.add(v.getName());

            }

            StringJoiner values = new StringJoiner(",", "[", "]");

            for (Object object : objects) {

                descriptors.add(String.valueOf(object));

            }

            throw new IllegalArgumentException("Annotation " + descriptors + " for " + type.getName() + " doesn't match number of values " + values);

        }

        List<String> n = new ArrayList<>();

        List<Object> v = new ArrayList<>();

        int index = 0;

        for (ValueDescriptor valueDescriptor : type.getFields()) {

            Object object = objects.get(index);

            if (object == null) {

                throw new IllegalArgumentException("Annotation value can't be null");

            }

            Class<?> valueType = object.getClass();

            if (valueDescriptor.isArray()) {

                valueType = valueType.getComponentType();

            }

            checkType(Utils.unboxType(valueType));

            n.add(valueDescriptor.getName());

            v.add(object);

            index++;

        }

        this.annotationValues = Utils.smallUnmodifiable(v);

        this.annotationNames = Utils.smallUnmodifiable(n);

        this.inBootClassLoader = boot;

    }

    /**

     * Creates an annotation element to use for dynamically defined events.

     * <p>

     * Supported value types are {@code byte}, {@code int}, {@code short},

     * {@code long}, {@code double}, {@code float}, {@code boolean}, {@code char},

     * and {@code String}. Enums, arrays and classes, are not supported.

     * <p>

     * If {@code annotationType} has annotations (directly present, indirectly

     * present, or associated), then those annotation are recursively included.

     * However, both the {@code annotationType} and any annotation found recursively

     * must have the {@link MetadataDefinition} annotation.

     * <p>

     * To statically define events, see {@link Event} class.

     *

     * @param annotationType interface extending

     *        {@code java.lang.annotation.Annotation}, not {@code null}

     * @param values a {@code Map} with keys that match method names of the specified

     *        annotation interface

     * @throws IllegalArgumentException if value/key is {@code null}, an unsupported

     *         value type is used, or a value/key is used that doesn't match the

     *         signatures in the {@code annotationType}

     */

    public AnnotationElement(Class<? extends Annotation> annotationType, Map<String, Object> values) {

        Objects.requireNonNull(annotationType);

        Objects.requireNonNull(values);

        Utils.checkRegisterPermission();

        // copy values to avoid modification after validation

        HashMap<String, Object> map = new HashMap<>(values);

        for (Map.Entry<String, Object> entry : map.entrySet()) {

            if (entry.getKey() == null) {

                throw new NullPointerException("Name of annotation method can't be null");

            }

            if (entry.getValue() == null) {

                throw new NullPointerException("Return value for annotation method can't be null");

            }

        }

        if (AnnotationElement.class.isAssignableFrom(annotationType) && annotationType.isInterface()) {

            throw new IllegalArgumentException("Must be interface extending " + Annotation.class.getName());

        }

        if (!isKnownJFRAnnotation(annotationType) && annotationType.getAnnotation(MetadataDefinition.class) == null) {

            throw new IllegalArgumentException("Annotation class must be annotated with jdk.jfr.MetadataDefinition to be valid");

        }

        if (isKnownJFRAnnotation(annotationType)) {

            this.type = new Type(annotationType.getCanonicalName(), Type.SUPER_TYPE_ANNOTATION, Type.getTypeId(annotationType));

        } else {

            this.type = TypeLibrary.createAnnotationType(annotationType);

        }

        Method[] methods = annotationType.getDeclaredMethods();

        if (methods.length != map.size()) {

            throw new IllegalArgumentException("Number of declared methods must match size of value map");

        }

        List<String> n = new ArrayList<>();

        List<Object> v = new ArrayList<>();

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

        for (Method method : methods) {

            String fieldName = method.getName();

            Object object = map.get(fieldName);

            if (object == null) {

                throw new IllegalArgumentException("No method in annotation interface " + annotationType.getName() + " matching name " + fieldName);

            }

            Class<?> fieldType = object.getClass();

            if (fieldType == Class.class) {

                throw new IllegalArgumentException("Annotation value for " + fieldName + " can't be class");

            }

            if (object instanceof Enum) {

                throw new IllegalArgumentException("Annotation value for " + fieldName + " can't be enum");

            }

            if (!fieldType.equals(object.getClass())) {

                throw new IllegalArgumentException("Return type of annotation " + fieldType.getName() + " must match type of object" + object.getClass());

            }

            if (fieldType.isArray()) {

                Class<?> componentType = fieldType.getComponentType();

                checkType(componentType);

                if (componentType.equals(String.class)) {

                    String[] stringArray = (String[]) object;

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

                        if (stringArray[i] == null) {

                            throw new IllegalArgumentException("Annotation value for " + fieldName + " contains null");

                        }

                    }

                }

            } else {

                fieldType = Utils.unboxType(object.getClass());

                checkType(fieldType);

            }

            if (nameSet.contains(fieldName)) {

                throw new IllegalArgumentException("Value with name '" + fieldName + "' already exists");

            }

            if (isKnownJFRAnnotation(annotationType)) {

                ValueDescriptor vd = new ValueDescriptor(fieldType, fieldName, Collections.emptyList(), true);

                type.add(vd);

            }

            n.add(fieldName);

            v.add(object);

        }

        this.annotationValues = Utils.smallUnmodifiable(v);

        this.annotationNames = Utils.smallUnmodifiable(n);

        this.inBootClassLoader = annotationType.getClassLoader() == null;

    }

    /**

     * Creates an annotation element to use for dynamically defined events.

     * <p>

     * Supported value types are {@code byte}, {@code int}, {@code short},

     * {@code long}, {@code double}, {@code float}, {@code boolean}, {@code char},

     * and {@code String}. Enums, arrays, and classes are not supported.

     * <p>

     * If {@code annotationType} has annotations (directly present, indirectly

     * present, or associated), then those annotations are recursively included.

     * However, both {@code annotationType} and any annotation found recursively

     * must have the {@link MetadataDefinition} annotation.

     * <p>

     * To statically define events, see {@link Event} class.

     *

     * @param annotationType interface extending

     *        {@code java.lang.annotation.Annotation,} not {@code null}

     * @param value the value that matches the {@code value} method of the specified

     *        {@code annotationType}

     * @throws IllegalArgumentException if value/key is {@code null}, an unsupported

     *         value type is used, or a value/key is used that doesn't match the

     *         signatures in the {@code annotationType}

     */

    public AnnotationElement(Class<? extends Annotation> annotationType, Object value) {

        this(annotationType, Collections.singletonMap("value", Objects.requireNonNull(value)));

    }

    /**

     * Creates an annotation element to use for dynamically defined events.

     * <p>

     * Supported value types are {@code byte}, {@code short}, {@code int},

     * {@code long}, {@code double}, {@code float}, {@code boolean}, {@code char},

     * and {@code String}. Enums, arrays, and classes are not supported.

     * <p>

     * If {@code annotationType} has annotations (directly present, indirectly

     * present or associated), then those annotation are recursively included.

     * However, both {@code annotationType} and any annotation found recursively

     * must have the {@link MetadataDefinition} annotation.

     * <p>

     * To statically define events, see {@link Event} class.

     *

     * @param annotationType interface extending java.lang.annotation.Annotation,

     *        not {@code null}

     */

    public AnnotationElement(Class<? extends Annotation> annotationType) {

        this(annotationType, Collections.emptyMap());

    }

    /**

     * Returns an immutable list of annotation values in an order that matches the

     * value descriptors for this {@code AnnotationElement}.

     *

     * @return list of values, not {@code null}

     */

    public List<Object> getValues() {

        return annotationValues;

    }

    /**

     * Returns an immutable list of descriptors that describes the annotation values

     * for this {@code AnnotationElement}.

     *

     * @return the list of value descriptors for this {@code Annotation}, not

     *         {@code null}

     */

    public List<ValueDescriptor> getValueDescriptors() {

        return Collections.unmodifiableList(type.getFields());

    }

    /**

     * Returns an immutable list of annotation elements for this

     * {@code AnnotationElement}.

     *

     * @return a list of meta annotation, not {@code null}

     */

    public List<AnnotationElement> getAnnotationElements() {

        return type.getAnnotationElements();

    }

    /**

     * Returns the fully qualified name of the annotation type that corresponds to

     * this {@code AnnotationElement} (for example, {@code "jdk.jfr.Label"}).

     *

     * @return type name, not {@code null}

     */

    public String getTypeName() {

        return type.getName();

    }

    /**

     * Returns a value for this {@code AnnotationElement}.

     *

     * @param name the name of the method in the annotation interface, not

     *        {@code null}.

     *

     * @return the annotation value, not {@code null}.

     *

     * @throws IllegalArgumentException if a method with the specified name does

     *         not exist in the annotation

     */

    public Object getValue(String name) {

        Objects.requireNonNull(name);

        int index = 0;

        for (String n : annotationNames) {

            if (name.equals(n)) {

                return annotationValues.get(index);

            }

            index++;

        }

        StringJoiner valueNames = new StringJoiner(",", "[", "]");

        for (ValueDescriptor v : type.getFields()) {

            valueNames.add(v.getName());

        }

        throw new IllegalArgumentException("No value with name '" + name + "'. Valid names are " + valueNames);

    }

    /**

     * Returns {@code true} if an annotation value with the specified name exists in

     * this {@code AnnotationElement}.

     *

     * @param name name of the method in the annotation interface to find, not

     *        {@code null}

     *

     * @return {@code true} if method exists, {@code false} otherwise

     */

    public boolean hasValue(String name) {

        Objects.requireNonNull(name);

        for (String n : annotationNames) {

            if (name.equals(n)) {

                return true;

            }

        }

        return false;

    }

    /**

     * Returns the first annotation for the specified type if an

     * {@code AnnotationElement} with the same name exists, else {@code null}.

     *

     * @param <A> the type of the annotation to query for and return if it exists

     * @param annotationType the {@code Class object} corresponding to the annotation type,

     *        not {@code null}

     * @return this element's annotation for the specified annotation type if

     *         it it exists, else {@code null}

     */

    public final <A> A getAnnotation(Class<? extends Annotation> annotationType) {

        Objects.requireNonNull(annotationType);

        return type.getAnnotation(annotationType);

    }

    /**

     * Returns the type ID for this {@code AnnotationElement}.

     * <p>

     * The ID is a unique identifier for the type in the Java Virtual Machine (JVM). The ID might not

     * be the same between JVM instances.

     *

     * @return the type ID, not negative

     */

    public long getTypeId() {

        return type.getId();

    }

    // package private

    Type getType() {

        return type;

    }

    private static void checkType(Class<?> type) {

        if (type.isPrimitive()) {

            return;

        }

        if (type == String.class) {

            return;

        }

        throw new IllegalArgumentException("Only primitives types or java.lang.String are allowed");

    }

    // Whitelist of annotation classes that are allowed, even though

    // they don't have @MetadataDefinition.

    private static boolean isKnownJFRAnnotation(Class<? extends Annotation> annotationType) {

        if (annotationType == Registered.class) {

            return true;

        }

        if (annotationType == Threshold.class) {

            return true;

        }

        if (annotationType == StackTrace.class) {

            return true;

        }

        if (annotationType == Period.class) {

            return true;

        }

        if (annotationType == Enabled.class) {

            return true;

        }

        return false;

    }

    // package private

    boolean isInBoot() {

        return inBootClassLoader;

    }

}