/*
 * Copyright (c) 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 java.lang.constant;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandleInfo;
import java.util.OptionalInt;
import java.util.stream.Stream;

import jdk.internal.vm.annotation.Stable;

import static java.lang.invoke.MethodHandleInfo.REF_getField;
import static java.lang.invoke.MethodHandleInfo.REF_getStatic;
import static java.lang.invoke.MethodHandleInfo.REF_invokeInterface;
import static java.lang.invoke.MethodHandleInfo.REF_invokeSpecial;
import static java.lang.invoke.MethodHandleInfo.REF_invokeStatic;
import static java.lang.invoke.MethodHandleInfo.REF_invokeVirtual;
import static java.lang.invoke.MethodHandleInfo.REF_newInvokeSpecial;
import static java.lang.invoke.MethodHandleInfo.REF_putField;
import static java.lang.invoke.MethodHandleInfo.REF_putStatic;

A nominal descriptor for a direct MethodHandle. A DirectMethodHandleDesc corresponds to a Constant_MethodHandle_info entry in the constant pool of a classfile. 
API Note:
In the future, if the Java language permits, DirectMethodHandleDesc may become a sealed interface, which would prohibit subclassing except by explicitly permitted types. Non-platform classes should not implement DirectMethodHandleDesc directly.
Since:
12/**
 * A <a href="package-summary.html#nominal">nominal descriptor</a> for a direct
 * {@link MethodHandle}.  A {@linkplain DirectMethodHandleDesc} corresponds to
 * a {@code Constant_MethodHandle_info} entry in the constant pool of a classfile.
 *
 * @apiNote In the future, if the Java language permits, {@linkplain DirectMethodHandleDesc}
 * may become a {@code sealed} interface, which would prohibit subclassing except
 * by explicitly permitted types.  Non-platform classes should not implement
 * {@linkplain DirectMethodHandleDesc} directly.
 *
 * @since 12
 */
public interface DirectMethodHandleDesc extends MethodHandleDesc {
    
Kinds of method handles that can be described with DirectMethodHandleDesc. 
Since:
12/**
     * Kinds of method handles that can be described with {@linkplain DirectMethodHandleDesc}.
     *
     * @since 12
     */
    enum Kind {
        
A method handle for a method invoked as with invokestatic /** A method handle for a method invoked as with {@code invokestatic} */
        STATIC(REF_invokeStatic),
        
A method handle for a method invoked as with invokestatic /** A method handle for a method invoked as with {@code invokestatic} */
        INTERFACE_STATIC(REF_invokeStatic, true),
        
A method handle for a method invoked as with invokevirtual /** A method handle for a method invoked as with {@code invokevirtual} */
        VIRTUAL(REF_invokeVirtual),
        
A method handle for a method invoked as with invokeinterface /** A method handle for a method invoked as with {@code invokeinterface} */
        INTERFACE_VIRTUAL(REF_invokeInterface, true),
        
A method handle for a method invoked as with invokespecial /** A method handle for a method invoked as with {@code invokespecial} */
        SPECIAL(REF_invokeSpecial),
        
A method handle for an interface method invoked as with invokespecial /** A method handle for an interface method invoked as with {@code invokespecial} */
        INTERFACE_SPECIAL(REF_invokeSpecial, true),
        
A method handle for a constructor /** A method handle for a constructor */
        CONSTRUCTOR(REF_newInvokeSpecial),
        
A method handle for a read accessor for an instance field  /** A method handle for a read accessor for an instance field  */
        GETTER(REF_getField),
        
A method handle for a write accessor for an instance field  /** A method handle for a write accessor for an instance field  */
        SETTER(REF_putField),
        
A method handle for a read accessor for a static field  /** A method handle for a read accessor for a static field  */
        STATIC_GETTER(REF_getStatic),
        
A method handle for a write accessor for a static field  /** A method handle for a write accessor for a static field  */
        STATIC_SETTER(REF_putStatic);

        
The corresponding refKind value for this kind of method handle, as defined by MethodHandleInfo /** The corresponding {@code refKind} value for this kind of method handle,
         * as defined by {@link MethodHandleInfo}
         */
        public final int refKind;

        
Is this an interface
/** Is this an interface
         */
        public final boolean isInterface;
        Kind(int refKind) {
            this(refKind, false);
        }

        Kind(int refKind, boolean isInterface) { this.refKind = refKind; this.isInterface = isInterface; }

        
Returns the enumeration member with the given refKind field. Behaves as if valueOf(refKind, false). As a special case, if refKind is REF_invokeInterface (9) then the isInterface field will be true. 
Params:
refKind – refKind of desired member
Throws:
IllegalArgumentException – if there is no such member
Returns:
the matching enumeration member/**
         * Returns the enumeration member with the given {@code refKind} field.
         * Behaves as if {@code valueOf(refKind, false)}.  As a special case,
         * if {@code refKind} is {@code REF_invokeInterface} (9) then the
         * {@code isInterface} field will be true.
         *
         * @param refKind refKind of desired member
         * @return the matching enumeration member
         * @throws IllegalArgumentException if there is no such member
         */
        public static Kind valueOf(int refKind) {
            return valueOf(refKind, false);
        }

        
Returns the enumeration member with the given the refKind and isInterface arguments. For most values of refKind there is an exact match regardless of the value of isInterface. These are: 

    
REF_invokeVirtual which matches to VIRTUAL 
REF_invokeInterface which matches to INTERFACE_VIRTUAL 
REF_newInvokeSpecial which matches to CONSTRUCTOR 
REF_getField which matches to GETTER 
REF_putField which matches to SETTER 
REF_getStatic which matches to STATIC_GETTER 
REF_putStatic which matches to STATIC_SETTER 
 As for the rest, the returned kind will depend on the value (false or true accordingly) of isInterface: 

    
REF_invokeStatic which matches to STATIC or INTERFACE_STATIC 
REF_invokeSpecial which matches to SPECIAL or INTERFACE_SPECIAL 
Params:
refKind – refKind of desired member
isInterface – whether desired member is for interface methods
Throws:
IllegalArgumentException – if there is no such member
Returns:
the matching enumeration member/**
         * Returns the enumeration member with the given the {@code refKind} and
         * {@code isInterface} arguments.
         * For most values of {@code refKind} there is an exact match regardless of the value of {@code isInterface}.
         * These are:
         * <UL>
         *     <LI>{@code REF_invokeVirtual} which matches to {@code VIRTUAL}
         *     <LI>{@code REF_invokeInterface} which matches to {@code INTERFACE_VIRTUAL}
         *     <LI>{@code REF_newInvokeSpecial} which matches to {@code CONSTRUCTOR}
         *     <LI>{@code REF_getField} which matches to {@code GETTER}
         *     <LI>{@code REF_putField} which matches to {@code SETTER}
         *     <LI>{@code REF_getStatic} which matches to {@code STATIC_GETTER}
         *     <LI>{@code REF_putStatic} which matches to {@code STATIC_SETTER}
         * </UL>
         * As for the rest, the returned kind will depend on the value (false or true accordingly) of {@code isInterface}:
         * <UL>
         *     <LI>{@code REF_invokeStatic} which matches to {@code STATIC} or {@code INTERFACE_STATIC}
         *     <LI>{@code REF_invokeSpecial} which matches to {@code SPECIAL} or {@code INTERFACE_SPECIAL}
         * </UL>
         * @param refKind refKind of desired member
         * @param isInterface whether desired member is for interface methods
         * @return the matching enumeration member
         * @throws IllegalArgumentException if there is no such member
         */
        public static Kind valueOf(int refKind, boolean isInterface) {
            int i = tableIndex(refKind, isInterface);
            if (i >= 0 && i < TABLE.length) {
                Kind kind = TABLE[i];
                if (kind == null) {
                    throw new IllegalArgumentException(String.format("refKind=%d", refKind));
                }
                if (kind.refKind == refKind && kind.isInterface == isInterface) {
                    return kind;
                }
            }
            throw new IllegalArgumentException(String.format("refKind=%d", refKind));
        }

        private static int tableIndex(int refKind, boolean isInterface) {
            if (refKind < 0)  return refKind;
            return (refKind * 2) + (isInterface ? 1 : 0);
        }

        private static final @Stable Kind[] TABLE;

        static {
            // Pack the static table.
            int max = 0;
            for (Kind k : values())
                max = Math.max(max, tableIndex(k.refKind, true));

            TABLE = new Kind[max+1];
            for (Kind kind : values()) {
                int i = tableIndex(kind.refKind, kind.isInterface);
                if (i >= TABLE.length || TABLE[i] != null)
                    throw new AssertionError("TABLE entry for " + kind);
                TABLE[i] = kind;
            }

            // Pack in some aliases also.
            int ii = tableIndex(REF_invokeInterface, false);
            if (TABLE[ii] != null)
                throw new AssertionError("TABLE entry for (invokeInterface, false) used by " + TABLE[ii]);
            TABLE[ii] = INTERFACE_VIRTUAL;

            for (Kind kind : values()) {
                if (!kind.isInterface) {
                    // Add extra cache entry to alias the isInterface case.
                    // For example, (REF_getStatic, X) will produce STATIC_GETTER
                    // for either truth value of X.
                    int i = tableIndex(kind.refKind, true);
                    if (TABLE[i] == null) {
                        // There is not a specific Kind for interfaces
                        if (kind == VIRTUAL)  kind = INTERFACE_VIRTUAL;
                        if (TABLE[i] == null)  TABLE[i] = kind;
                    }
                }
            }
        }

        
Does this Kind correspond to a virtual method invocation? 
Returns:
if this Kind corresponds to a virtual method invocation/**
         * Does this {@code Kind} correspond to a virtual method invocation?
         *
         * @return if this {@code Kind} corresponds to a virtual method invocation
         */
        boolean isVirtualMethod() {
            switch (this) {
                case VIRTUAL:
                case SPECIAL:
                case INTERFACE_VIRTUAL:
                case INTERFACE_SPECIAL:
                    return true;
                default:
                    return false;
            }
        }
    }

    
Returns the kind of the method handle described by this nominal descriptor. 
Returns:
the Kind/**
     * Returns the {@code kind} of the method handle described by this nominal
     * descriptor.
     *
     * @return the {@link Kind}
     */
    Kind kind();

    
Returns the refKind of the method handle described by this nominal reference, as defined by MethodHandleInfo. 
Returns:
the reference kind/**
     * Returns the {@code refKind} of the method handle described by this nominal
     * reference, as defined by {@link MethodHandleInfo}.
     *
     * @return the reference kind
     */
    int refKind();

    
Indicates if the method is declared by an interface
Returns:
true if the method is declared by an interface/**
     * Indicates if the method is declared by an interface
     *
     * @return true if the method is declared by an interface
     */
    boolean isOwnerInterface();

    
Returns a ClassDesc describing the class declaring the method or field described by this nominal descriptor. 
Returns:
the class declaring the method or field/**
     * Returns a {@link ClassDesc} describing the class declaring the
     * method or field described by this nominal descriptor.
     *
     * @return the class declaring the method or field
     */
    ClassDesc owner();

    
Returns the name of the method or field described by this nominal descriptor. For constructors, returns the reserved name "<init>". 
Returns:
the name of the method or field/**
     * Returns the name of the method or field described by this nominal descriptor.
     * For constructors, returns the reserved name {@code "<init>"}.
     *
     * @return the name of the method or field
     */
    String methodName();

    
Returns the lookup descriptor of the method handle described by this descriptor, after adjusting for the invocation mode. This will correspond to either a method type descriptor string (for methods and constructors), or a field descriptor string (for field access method handles). The lookup descriptor string is in the same format as accepted by MethodHandleDesc.of(Kind, ClassDesc, String, String). 
Returns:
the lookup descriptor string/**
     * Returns the lookup descriptor of the method handle described by this descriptor,
     * after adjusting for the invocation mode.  This will correspond to either
     * a method type descriptor string (for methods and constructors), or a field
     * descriptor string (for field access method handles).  The lookup descriptor
     * string is in the same format as accepted by {@link MethodHandleDesc#of(Kind, ClassDesc, String, String)}.
     *
     * @return the lookup descriptor string
     */
    String lookupDescriptor();
}