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 * 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 java.lang.reflect;

import java.lang.annotation.*;

import java.util.HashMap;

import java.util.Map;

import java.util.Objects;

import sun.reflect.annotation.AnnotationSupport;

/**

 * Information about method parameters.

 *

 * A {@code Parameter} provides information about method parameters,

 * including its name and modifiers.  It also provides an alternate

 * means of obtaining attributes for the parameter.

 *

 * @since 1.8

 */

public final class Parameter implements AnnotatedElement {

    private final String name;

    private final int modifiers;

    private final Executable executable;

    private final int index;

    /**

     * Package-private constructor for {@code Parameter}.

     *

     * If method parameter data is present in the classfile, then the

     * JVM creates {@code Parameter} objects directly.  If it is

     * absent, however, then {@code Executable} uses this constructor

     * to synthesize them.

     *

     * @param name The name of the parameter.

     * @param modifiers The modifier flags for the parameter.

     * @param executable The executable which defines this parameter.

     * @param index The index of the parameter.

     */

    Parameter(String name,

              int modifiers,

              Executable executable,

              int index) {

        this.name = name;

        this.modifiers = modifiers;

        this.executable = executable;

        this.index = index;

    }

    /**

     * Compares based on the executable and the index.

     *

     * @param obj The object to compare.

     * @return Whether or not this is equal to the argument.

     */

    public boolean equals(Object obj) {

        if(obj instanceof Parameter) {

            Parameter other = (Parameter)obj;

            return (other.executable.equals(executable) &&

                    other.index == index);

        }

        return false;

    }

    /**

     * Returns a hash code based on the executable's hash code and the

     * index.

     *

     * @return A hash code based on the executable's hash code.

     */

    public int hashCode() {

        return executable.hashCode() ^ index;

    }

    /**

     * Returns true if the parameter has a name according to the class

     * file; returns false otherwise. Whether a parameter has a name

     * is determined by the {@literal MethodParameters} attribute of

     * the method which declares the parameter.

     *

     * @return true if and only if the parameter has a name according

     * to the class file.

     */

    public boolean isNamePresent() {

        return executable.hasRealParameterData() && name != null;

    }

    /**

     * Returns a string describing this parameter.  The format is the

     * modifiers for the parameter, if any, in canonical order as

     * recommended by <cite>The Java&trade; Language

     * Specification</cite>, followed by the fully- qualified type of

     * the parameter (excluding the last [] if the parameter is

     * variable arity), followed by "..." if the parameter is variable

     * arity, followed by a space, followed by the name of the

     * parameter.

     *

     * @return A string representation of the parameter and associated

     * information.

     */

    public String toString() {

        final StringBuilder sb = new StringBuilder();

        final Type type = getParameterizedType();

        final String typename = type.getTypeName();

        sb.append(Modifier.toString(getModifiers()));

        if(0 != modifiers)

            sb.append(' ');

        if(isVarArgs())

            sb.append(typename.replaceFirst("\\[\\]$", "..."));

        else

            sb.append(typename);

        sb.append(' ');

        sb.append(getName());

        return sb.toString();

    }

    /**

     * Return the {@code Executable} which declares this parameter.

     *

     * @return The {@code Executable} declaring this parameter.

     */

    public Executable getDeclaringExecutable() {

        return executable;

    }

    /**

     * Get the modifier flags for this the parameter represented by

     * this {@code Parameter} object.

     *

     * @return The modifier flags for this parameter.

     */

    public int getModifiers() {

        return modifiers;

    }

    /**

     * Returns the name of the parameter.  If the parameter's name is

     * {@linkplain #isNamePresent() present}, then this method returns

     * the name provided by the class file. Otherwise, this method

     * synthesizes a name of the form argN, where N is the index of

     * the parameter in the descriptor of the method which declares

     * the parameter.

     *

     * @return The name of the parameter, either provided by the class

     *         file or synthesized if the class file does not provide

     *         a name.

     */

    public String getName() {

        // Note: empty strings as parameter names are now outlawed.

        // The .equals("") is for compatibility with current JVM

        // behavior.  It may be removed at some point.

        if(name == null || name.equals(""))

            return "arg" + index;

        else

            return name;

    }

    // Package-private accessor to the real name field.

    String getRealName() {

        return name;

    }

    /**

     * Returns a {@code Type} object that identifies the parameterized

     * type for the parameter represented by this {@code Parameter}

     * object.

     *

     * @return a {@code Type} object identifying the parameterized

     * type of the parameter represented by this object

     */

    public Type getParameterizedType() {

        Type tmp = parameterTypeCache;

        if (null == tmp) {

            tmp = executable.getGenericParameterTypes()[index];

            parameterTypeCache = tmp;

        }

        return tmp;

    }

    private transient volatile Type parameterTypeCache = null;

    /**

     * Returns a {@code Class} object that identifies the

     * declared type for the parameter represented by this

     * {@code Parameter} object.

     *

     * @return a {@code Class} object identifying the declared

     * type of the parameter represented by this object

     */

    public Class<?> getType() {

        Class<?> tmp = parameterClassCache;

        if (null == tmp) {

            tmp = executable.getParameterTypes()[index];

            parameterClassCache = tmp;

        }

        return tmp;

    }

    /**

     * Returns an AnnotatedType object that represents the use of a type to

     * specify the type of the formal parameter represented by this Parameter.

     *

     * @return an {@code AnnotatedType} object representing the use of a type

     *         to specify the type of the formal parameter represented by this

     *         Parameter

     */

    public AnnotatedType getAnnotatedType() {

        // no caching for now

        return executable.getAnnotatedParameterTypes()[index];

    }

    private transient volatile Class<?> parameterClassCache = null;

    /**

     * Returns {@code true} if this parameter is implicitly declared

     * in source code; returns {@code false} otherwise.

     *

     * @return true if and only if this parameter is implicitly

     * declared as defined by <cite>The Java&trade; Language

     * Specification</cite>.

     */

    public boolean isImplicit() {

        return Modifier.isMandated(getModifiers());

    }

    /**

     * Returns {@code true} if this parameter is neither implicitly

     * nor explicitly declared in source code; returns {@code false}

     * otherwise.

     *

     * @jls 13.1 The Form of a Binary

     * @return true if and only if this parameter is a synthetic

     * construct as defined by

     * <cite>The Java&trade; Language Specification</cite>.

     */

    public boolean isSynthetic() {

        return Modifier.isSynthetic(getModifiers());

    }

    /**

     * Returns {@code true} if this parameter represents a variable

     * argument list; returns {@code false} otherwise.

     *

     * @return {@code true} if an only if this parameter represents a

     * variable argument list.

     */

    public boolean isVarArgs() {

        return executable.isVarArgs() &&

            index == executable.getParameterCount() - 1;

    }

    /**

     * {@inheritDoc}

     * @throws NullPointerException {@inheritDoc}

     */

    public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {

        Objects.requireNonNull(annotationClass);

        return annotationClass.cast(declaredAnnotations().get(annotationClass));

    }

    /**

     * {@inheritDoc}

     * @throws NullPointerException {@inheritDoc}

     */

    @Override

    public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {

        Objects.requireNonNull(annotationClass);

        return AnnotationSupport.getDirectlyAndIndirectlyPresent(declaredAnnotations(), annotationClass);

    }

    /**

     * {@inheritDoc}

     */

    public Annotation[] getDeclaredAnnotations() {

        return executable.getParameterAnnotations()[index];

    }

    /**

     * @throws NullPointerException {@inheritDoc}

     */

    public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {

        // Only annotations on classes are inherited, for all other

        // objects getDeclaredAnnotation is the same as

        // getAnnotation.

        return getAnnotation(annotationClass);

    }

    /**

     * @throws NullPointerException {@inheritDoc}

     */

    @Override

    public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {

        // Only annotations on classes are inherited, for all other

        // objects getDeclaredAnnotations is the same as

        // getAnnotations.

        return getAnnotationsByType(annotationClass);

    }

    /**

     * {@inheritDoc}

     */

    public Annotation[] getAnnotations() {

        return getDeclaredAnnotations();

    }

    private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations;

    private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() {

        if(null == declaredAnnotations) {

            declaredAnnotations = new HashMap<>();

            for (Annotation a : getDeclaredAnnotations())

                declaredAnnotations.put(a.annotationType(), a);

        }

        return declaredAnnotations;

   }

}