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 * Copyright (c) 2018, 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,

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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.

 *

 * @see ConstantDescs

 *

 * @since 12

 */

public sealed interface ClassDesc

        extends ConstantDesc,

                TypeDescriptor.OfField<ClassDesc>

        permits PrimitiveClassDescImpl,

                ReferenceClassDescImpl {

    /**

     * 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 the 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));

        if (packageName.isEmpty()) {

            return of(className);

        }

        validateMemberName(requireNonNull(className), false);

        return ofDescriptor("L" + 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

     * ({@code "J", "I", "C", "S", "B", "D", "F", "Z", "V"}), or the letter {@code "L"}, followed

     * by the fully qualified binary name of a class, followed by {@code ";"}.

     * A field type descriptor for an array type is the character {@code "["}

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

     * valid type descriptor strings include {@code "Ljava/lang/String;"}, {@code "I"},

     * {@code "[I"}, {@code "V"}, {@code "[Ljava/lang/String;"}, etc.

     * See JVMS 4.3.2 ("Field Descriptors") for more detail.

     *

     * @param descriptor a field descriptor string

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

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

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

     * correct format

     * @jvms 4.3.2 Field Descriptors

     * @jvms 4.4.1 The CONSTANT_Class_info Structure

     */

    static ClassDesc ofDescriptor(String descriptor) {

        requireNonNull(descriptor);

        if (descriptor.isEmpty()) {

            throw new IllegalArgumentException(

                    "not a valid reference type descriptor: " + descriptor);

        }

        int depth = ConstantUtils.arrayDepth(descriptor);

        if (depth > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {

            throw new IllegalArgumentException(

                    "Cannot create an array type descriptor with more than " +

                    ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS + " dimensions");

        }

        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

     * @throws IllegalStateException if the resulting {@linkplain ClassDesc} would have an array rank of greater than 255

     * @jvms 4.4.1 The CONSTANT_Class_info Structure

     */

    default ClassDesc arrayType() {

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

        if (depth >= ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS) {

            throw new IllegalStateException(

                    "Cannot create an array type descriptor with more than " +

                    ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS + " dimensions");

        }

        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

     * @throws IllegalArgumentException if the rank is less than or equal to zero or if the rank of the resulting array type is

     * greater than 255

     * @jvms 4.4.1 The CONSTANT_Class_info Structure

     */

    default ClassDesc arrayType(int rank) {

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

        if (rank <= 0 || currentDepth + rank > ConstantUtils.MAX_ARRAY_TYPE_DESC_DIMENSIONS)

            throw new IllegalArgumentException("rank: " + currentDepth + 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}.

     *

     * @apiNote

     *

     * Example: If descriptor {@code d} describes the class {@code java.util.Map}, a

     * descriptor for the class {@code java.util.Map.Entry} could be obtained

     * by {@code d.nested("Entry")}.

     *

     * @param nestedName the unqualified name of the nested class

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

     * @throws NullPointerException if the 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, false);

        if (!isClassOrInterface())

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

        return ClassDesc.ofDescriptor(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 or its contents 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");

        validateMemberName(firstNestedName, false);

        requireNonNull(moreNestedNames);

        for (String addNestedNames : moreNestedNames) {

            validateMemberName(addNestedNames, false);

        }

        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);

}