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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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

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 *

 * 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

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 *

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package java.lang.constant;

import java.lang.invoke.TypeDescriptor;

import java.util.stream.Stream;

import sun.invoke.util.Wrapper;

import static java.lang.constant.ConstantUtils.binaryToInternal;

import static java.lang.constant.ConstantUtils.dropLastChar;

import static java.lang.constant.ConstantUtils.internalToBinary;

import static java.lang.constant.ConstantUtils.validateMemberName;

import static java.util.Objects.requireNonNull;

import static java.util.stream.Collectors.joining;

/**

 * A <a href="package-summary.html#nominal">nominal descriptor</a> for a

 * {@link Class} constant.

 *

 * <p>For common system types, including all the primitive types, there are

 * predefined {@linkplain ClassDesc} constants in {@link ConstantDescs}.

 * (The {@code java.lang.constant} APIs consider {@code void} to be a primitive type.)

 * To create a {@linkplain ClassDesc} for a class or interface type, use {@link #of} or

 * {@link #ofDescriptor(String)}; to create a {@linkplain ClassDesc} for an array

 * type, use {@link #ofDescriptor(String)}, or first obtain a

 * {@linkplain ClassDesc} for the component type and then call the {@link #arrayType()}

 * or {@link #arrayType(int)} methods.

 *

 * @apiNote In the future, if the Java language permits, {@linkplain ClassDesc}

 * may become a {@code sealed} interface, which would prohibit subclassing except

 * by explicitly permitted types.  Non-platform classes should not implement

 * {@linkplain ClassDesc} directly.

 *

 * @see ConstantDescs

 *

 * @since 12

 */

public interface ClassDesc

        extends ConstantDesc,

                TypeDescriptor.OfField<ClassDesc> {

    /**

     * Returns a {@linkplain ClassDesc} for a class or interface type,

     * given the name of the class or interface, such as {@code "java.lang.String"}.

     * (To create a descriptor for an array type, either use {@link #ofDescriptor(String)}

     * or {@link #arrayType()}; to create a descriptor for a primitive type, use

     * {@link #ofDescriptor(String)} or use the predefined constants in

     * {@link ConstantDescs}).

     *

     * @param name the fully qualified (dot-separated) binary class name

     * @return a {@linkplain ClassDesc} describing the desired class

     * @throws NullPointerException if any argument is {@code null}

     * @throws IllegalArgumentException if the name string is not in the

     * correct format

     */

    static ClassDesc of(String name) {

        ConstantUtils.validateBinaryClassName(requireNonNull(name));

        return ClassDesc.ofDescriptor("L" + binaryToInternal(name) + ";");

    }

    /**

     * Returns a {@linkplain ClassDesc} for a class or interface type,

     * given a package name and the unqualified (simple) name for the

     * class or interface.

     *

     * @param packageName the package name (dot-separated); if the package

     *                    name is the empty string, the class is considered to

     *                    be in the unnamed package

     * @param className the unqualified (simple) class name

     * @return a {@linkplain ClassDesc} describing the desired class

     * @throws NullPointerException if any argument is {@code null}

     * @throws IllegalArgumentException if the package name or class name are

     * not in the correct format

     */

    static ClassDesc of(String packageName, String className) {

        ConstantUtils.validateBinaryClassName(requireNonNull(packageName));

        validateMemberName(requireNonNull(className));

        return ofDescriptor(String.format("L%s%s%s;",

                                          binaryToInternal(packageName),

                                          (packageName.length() > 0 ? "/" : ""),

                                          className));

    }

    /**

     * Returns a {@linkplain ClassDesc} given a descriptor string for a class,

     * interface, array, or primitive type.

     *

     * @apiNote

     *

     * A field type descriptor string for a non-array type is either

     * a one-letter code corresponding to a primitive type

     * followed by the field descriptor for the component type.  Examples of

     *

     * @param descriptor a field descriptor string

     * @return a {@linkplain ClassDesc} describing the desired class

     * @throws NullPointerException if any argument is {@code null}

     * @throws IllegalArgumentException if the name string is not in the

     * correct format

     * @jvms 4.3.2 Field Descriptors

     */

    static ClassDesc ofDescriptor(String descriptor) {

        requireNonNull(descriptor);

        return (descriptor.length() == 1)

               ? new PrimitiveClassDescImpl(descriptor)

               : new ReferenceClassDescImpl(descriptor);

    }

    /**

     * Returns a {@linkplain ClassDesc} for an array type whose component type

     * is described by this {@linkplain ClassDesc}.

     *

     * @return a {@linkplain ClassDesc} describing the array type

     */

    default ClassDesc arrayType() {

        return arrayType(1);

    }

    /**

     * Returns a {@linkplain ClassDesc} for an array type of the specified rank,

     * whose component type is described by this {@linkplain ClassDesc}.

     *

     * @param rank the rank of the array

     * @return a {@linkplain ClassDesc} describing the array type

     */

    default ClassDesc arrayType(int rank) {

        return ClassDesc.ofDescriptor("[".repeat(rank) + descriptorString());

    }

    /**

     * Returns a {@linkplain ClassDesc} for a nested class of the class or

     * interface type described by this {@linkplain ClassDesc}.

     *

     * @param nestedName the unqualified name of the nested class

     * @return a {@linkplain ClassDesc} describing the nested class

     * @throws NullPointerException if any argument is {@code null}

     * @throws IllegalStateException if this {@linkplain ClassDesc} does not

     * describe a class or interface type

     * @throws IllegalArgumentException if the nested class name is invalid

     */

    default ClassDesc nested(String nestedName) {

        validateMemberName(nestedName);

        if (!isClassOrInterface())

            throw new IllegalStateException("Outer class is not a class or interface type");

        return ClassDesc.ofDescriptor(String.format("%s$%s;", dropLastChar(descriptorString()), nestedName));

    }

    /**

     * Returns a {@linkplain ClassDesc} for a nested class of the class or

     * interface type described by this {@linkplain ClassDesc}.

     *

     * @param firstNestedName the unqualified name of the first level of nested class

     * @param moreNestedNames the unqualified name(s) of the remaining levels of

     *                       nested class

     * @return a {@linkplain ClassDesc} describing the nested class

     * @throws NullPointerException if any argument is {@code null}

     * @throws IllegalStateException if this {@linkplain ClassDesc} does not

     * describe a class or interface type

     * @throws IllegalArgumentException if the nested class name is invalid

     */

    default ClassDesc nested(String firstNestedName, String... moreNestedNames) {

        if (!isClassOrInterface())

            throw new IllegalStateException("Outer class is not a class or interface type");

        return moreNestedNames.length == 0

               ? nested(firstNestedName)

               : nested(firstNestedName + Stream.of(moreNestedNames).collect(joining("$", "$", "")));

    }

    /**

     * Returns whether this {@linkplain ClassDesc} describes an array type.

     *

     * @return whether this {@linkplain ClassDesc} describes an array type

     */

    default boolean isArray() {

        return descriptorString().startsWith("[");

    }

    /**

     * Returns whether this {@linkplain ClassDesc} describes a primitive type.

     *

     * @return whether this {@linkplain ClassDesc} describes a primitive type

     */

    default boolean isPrimitive() {

        return descriptorString().length() == 1;

    }

    /**

     * Returns whether this {@linkplain ClassDesc} describes a class or interface type.

     *

     * @return whether this {@linkplain ClassDesc} describes a class or interface type

     */

    default boolean isClassOrInterface() {

        return descriptorString().startsWith("L");

    }

    /**

     * Returns the component type of this {@linkplain ClassDesc}, if it describes

     * an array type, or {@code null} otherwise.

     *

     * @return a {@linkplain ClassDesc} describing the component type, or {@code null}

     * if this descriptor does not describe an array type

     */

    default ClassDesc componentType() {

        return isArray() ? ClassDesc.ofDescriptor(descriptorString().substring(1)) : null;

    }

    /**

     * Returns the package name of this {@linkplain ClassDesc}, if it describes

     * a class or interface type.

     *

     * @return the package name, or the empty string if the class is in the

     * default package, or this {@linkplain ClassDesc} does not describe a class or interface type

     */

    default String packageName() {

        if (!isClassOrInterface())

            return "";

        String className = internalToBinary(ConstantUtils.dropFirstAndLastChar(descriptorString()));

        int index = className.lastIndexOf('.');

        return (index == -1) ? "" : className.substring(0, index);

    }

    /**

     * Returns a human-readable name for the type described by this descriptor.

     *

     * @implSpec

     * <p>The default implementation returns the simple name

     * (e.g., {@code int}) for primitive types, the unqualified class name

     * for class or interface types, or the display name of the component type

     * suffixed with the appropriate number of {@code []} pairs for array types.

     *

     * @return the human-readable name

     */

    default String displayName() {

        if (isPrimitive())

            return Wrapper.forBasicType(descriptorString().charAt(0)).primitiveSimpleName();

        else if (isClassOrInterface()) {

            return descriptorString().substring(Math.max(1, descriptorString().lastIndexOf('/') + 1),

                                                descriptorString().length() - 1);

        }

        else if (isArray()) {

            int depth = ConstantUtils.arrayDepth(descriptorString());

            ClassDesc c = this;

            for (int i=0; i<depth; i++)

                c = c.componentType();

            return c.displayName() + "[]".repeat(depth);

        }

        else

            throw new IllegalStateException(descriptorString());

    }

    /**

     * Returns a field type descriptor string for this type

     *

     * @return the descriptor string

     * @jvms 4.3.2 Field Descriptors

     */

    String descriptorString();

    /**

     * Compare the specified object with this descriptor for equality.  Returns

     * {@code true} if and only if the specified object is also a

     * {@linkplain ClassDesc} and both describe the same type.

     *

     * @param o the other object

     * @return whether this descriptor is equal to the other object

     */

    boolean equals(Object o);

}