/*

 * Copyright (c) 2008, 2015, 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.invoke;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Arrays;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.function.Function;

import jdk.internal.vm.annotation.Stable;

import sun.invoke.empty.Empty;

import sun.invoke.util.ValueConversions;

import sun.invoke.util.VerifyType;

import sun.invoke.util.Wrapper;

import sun.reflect.CallerSensitive;

import sun.reflect.Reflection;

import static java.lang.invoke.LambdaForm.*;

import static java.lang.invoke.MethodHandleStatics.*;

import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;

/**

 * Trusted implementation code for MethodHandle.

 * @author jrose

 */

/*non-public*/ abstract class MethodHandleImpl {

    // Do not adjust this except for special platforms:

    private static final int MAX_ARITY;

    static {

        final Object[] values = { 255 };

        AccessController.doPrivileged(new PrivilegedAction<>() {

            @Override

            public Void run() {

                values[0] = Integer.getInteger(MethodHandleImpl.class.getName()+".MAX_ARITY", 255);

                return null;

            }

        });

        MAX_ARITY = (Integer) values[0];

    }

    /// Factory methods to create method handles:

    static MethodHandle makeArrayElementAccessor(Class<?> arrayClass, boolean isSetter) {

        if (arrayClass == Object[].class)

            return (isSetter ? ArrayAccessor.OBJECT_ARRAY_SETTER : ArrayAccessor.OBJECT_ARRAY_GETTER);

        if (!arrayClass.isArray())

            throw newIllegalArgumentException("not an array: "+arrayClass);

        MethodHandle[] cache = ArrayAccessor.TYPED_ACCESSORS.get(arrayClass);

        int cacheIndex = (isSetter ? ArrayAccessor.SETTER_INDEX : ArrayAccessor.GETTER_INDEX);

        MethodHandle mh = cache[cacheIndex];

        if (mh != null)  return mh;

        mh = ArrayAccessor.getAccessor(arrayClass, isSetter);

        MethodType correctType = ArrayAccessor.correctType(arrayClass, isSetter);

        if (mh.type() != correctType) {

            assert(mh.type().parameterType(0) == Object[].class);

            assert((isSetter ? mh.type().parameterType(2) : mh.type().returnType()) == Object.class);

            assert(isSetter || correctType.parameterType(0).getComponentType() == correctType.returnType());

            // safe to view non-strictly, because element type follows from array type

            mh = mh.viewAsType(correctType, false);

        }

        mh = makeIntrinsic(mh, (isSetter ? Intrinsic.ARRAY_STORE : Intrinsic.ARRAY_LOAD));

        // Atomically update accessor cache.

        synchronized(cache) {

            if (cache[cacheIndex] == null) {

                cache[cacheIndex] = mh;

            } else {

                // Throw away newly constructed accessor and use cached version.

                mh = cache[cacheIndex];

            }

        }

        return mh;

    }

    static final class ArrayAccessor {

        /// Support for array element access

        static final int GETTER_INDEX = 0, SETTER_INDEX = 1, INDEX_LIMIT = 2;

        static final ClassValue<MethodHandle[]> TYPED_ACCESSORS

                = new ClassValue<MethodHandle[]>() {

                    @Override

                    protected MethodHandle[] computeValue(Class<?> type) {

                        return new MethodHandle[INDEX_LIMIT];

                    }

                };

        static final MethodHandle OBJECT_ARRAY_GETTER, OBJECT_ARRAY_SETTER;

        static {

            MethodHandle[] cache = TYPED_ACCESSORS.get(Object[].class);

            cache[GETTER_INDEX] = OBJECT_ARRAY_GETTER = makeIntrinsic(getAccessor(Object[].class, false), Intrinsic.ARRAY_LOAD);

            cache[SETTER_INDEX] = OBJECT_ARRAY_SETTER = makeIntrinsic(getAccessor(Object[].class, true),  Intrinsic.ARRAY_STORE);

            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_GETTER.internalMemberName()));

            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_SETTER.internalMemberName()));

        }

        static int     getElementI(int[]     a, int i)            { return              a[i]; }

        static long    getElementJ(long[]    a, int i)            { return              a[i]; }

        static float   getElementF(float[]   a, int i)            { return              a[i]; }

        static double  getElementD(double[]  a, int i)            { return              a[i]; }

        static boolean getElementZ(boolean[] a, int i)            { return              a[i]; }

        static byte    getElementB(byte[]    a, int i)            { return              a[i]; }

        static short   getElementS(short[]   a, int i)            { return              a[i]; }

        static char    getElementC(char[]    a, int i)            { return              a[i]; }

        static Object  getElementL(Object[]  a, int i)            { return              a[i]; }

        static void    setElementI(int[]     a, int i, int     x) {              a[i] = x; }

        static void    setElementJ(long[]    a, int i, long    x) {              a[i] = x; }

        static void    setElementF(float[]   a, int i, float   x) {              a[i] = x; }

        static void    setElementD(double[]  a, int i, double  x) {              a[i] = x; }

        static void    setElementZ(boolean[] a, int i, boolean x) {              a[i] = x; }

        static void    setElementB(byte[]    a, int i, byte    x) {              a[i] = x; }

        static void    setElementS(short[]   a, int i, short   x) {              a[i] = x; }

        static void    setElementC(char[]    a, int i, char    x) {              a[i] = x; }

        static void    setElementL(Object[]  a, int i, Object  x) {              a[i] = x; }

        static String name(Class<?> arrayClass, boolean isSetter) {

            Class<?> elemClass = arrayClass.getComponentType();

            if (elemClass == null)  throw newIllegalArgumentException("not an array", arrayClass);

            return (!isSetter ? "getElement" : "setElement") + Wrapper.basicTypeChar(elemClass);

        }

        static MethodType type(Class<?> arrayClass, boolean isSetter) {

            Class<?> elemClass = arrayClass.getComponentType();

            Class<?> arrayArgClass = arrayClass;

            if (!elemClass.isPrimitive()) {

                arrayArgClass = Object[].class;

                elemClass = Object.class;

            }

            return !isSetter ?

                    MethodType.methodType(elemClass,  arrayArgClass, int.class) :

                    MethodType.methodType(void.class, arrayArgClass, int.class, elemClass);

        }

        static MethodType correctType(Class<?> arrayClass, boolean isSetter) {

            Class<?> elemClass = arrayClass.getComponentType();

            return !isSetter ?

                    MethodType.methodType(elemClass,  arrayClass, int.class) :

                    MethodType.methodType(void.class, arrayClass, int.class, elemClass);

        }

        static MethodHandle getAccessor(Class<?> arrayClass, boolean isSetter) {

            String     name = name(arrayClass, isSetter);

            MethodType type = type(arrayClass, isSetter);

            try {

                return IMPL_LOOKUP.findStatic(ArrayAccessor.class, name, type);

            } catch (ReflectiveOperationException ex) {

                throw uncaughtException(ex);

            }

        }

    }

    /**

     * Create a JVM-level adapter method handle to conform the given method

     * handle to the similar newType, using only pairwise argument conversions.

     * For each argument, convert incoming argument to the exact type needed.

     * The argument conversions allowed are casting, boxing and unboxing,

     * integral widening or narrowing, and floating point widening or narrowing.

     * @param srcType required call type

     * @param target original method handle

     * @param strict if true, only asType conversions are allowed; if false, explicitCastArguments conversions allowed

     * @param monobox if true, unboxing conversions are assumed to be exactly typed (Integer to int only, not long or double)

     * @return an adapter to the original handle with the desired new type,

     *          or the original target if the types are already identical

     *          or null if the adaptation cannot be made

     */

    static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,

                                            boolean strict, boolean monobox) {

        MethodType dstType = target.type();

        if (srcType == dstType)

            return target;

        return makePairwiseConvertByEditor(target, srcType, strict, monobox);

    }

    private static int countNonNull(Object[] array) {

        int count = 0;

        for (Object x : array) {

            if (x != null)  ++count;

        }

        return count;

    }

    static MethodHandle makePairwiseConvertByEditor(MethodHandle target, MethodType srcType,

                                                    boolean strict, boolean monobox) {

        Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);

        int convCount = countNonNull(convSpecs);

        if (convCount == 0)

            return target.viewAsType(srcType, strict);

        MethodType basicSrcType = srcType.basicType();

        MethodType midType = target.type().basicType();

        BoundMethodHandle mh = target.rebind();

        // FIXME: Reduce number of bindings when there is more than one Class conversion.

        // FIXME: Reduce number of bindings when there are repeated conversions.

        for (int i = 0; i < convSpecs.length-1; i++) {

            Object convSpec = convSpecs[i];

            if (convSpec == null)  continue;

            MethodHandle fn;

            if (convSpec instanceof Class) {

                fn = getConstantHandle(MH_cast).bindTo(convSpec);

            } else {

                fn = (MethodHandle) convSpec;

            }

            Class<?> newType = basicSrcType.parameterType(i);

            if (--convCount == 0)

                midType = srcType;

            else

                midType = midType.changeParameterType(i, newType);

            LambdaForm form2 = mh.editor().filterArgumentForm(1+i, BasicType.basicType(newType));

            mh = mh.copyWithExtendL(midType, form2, fn);

            mh = mh.rebind();

        }

        Object convSpec = convSpecs[convSpecs.length-1];

        if (convSpec != null) {

            MethodHandle fn;

            if (convSpec instanceof Class) {

                if (convSpec == void.class)

                    fn = null;

                else

                    fn = getConstantHandle(MH_cast).bindTo(convSpec);

            } else {

                fn = (MethodHandle) convSpec;

            }

            Class<?> newType = basicSrcType.returnType();

            assert(--convCount == 0);

            midType = srcType;

            if (fn != null) {

                mh = mh.rebind();  // rebind if too complex

                LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), false);

                mh = mh.copyWithExtendL(midType, form2, fn);

            } else {

                LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), true);

                mh = mh.copyWith(midType, form2);

            }

        }

        assert(convCount == 0);

        assert(mh.type().equals(srcType));

        return mh;

    }

    static MethodHandle makePairwiseConvertIndirect(MethodHandle target, MethodType srcType,

                                                    boolean strict, boolean monobox) {

        assert(target.type().parameterCount() == srcType.parameterCount());

        // Calculate extra arguments (temporaries) required in the names array.

        Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);

        final int INARG_COUNT = srcType.parameterCount();

        int convCount = countNonNull(convSpecs);

        boolean retConv = (convSpecs[INARG_COUNT] != null);

        boolean retVoid = srcType.returnType() == void.class;

        if (retConv && retVoid) {

            convCount -= 1;

            retConv = false;

        }

        final int IN_MH         = 0;

        final int INARG_BASE    = 1;

        final int INARG_LIMIT   = INARG_BASE + INARG_COUNT;

        final int NAME_LIMIT    = INARG_LIMIT + convCount + 1;

        final int RETURN_CONV   = (!retConv ? -1         : NAME_LIMIT - 1);

        final int OUT_CALL      = (!retConv ? NAME_LIMIT : RETURN_CONV) - 1;

        final int RESULT        = (retVoid ? -1 : NAME_LIMIT - 1);

        // Now build a LambdaForm.

        MethodType lambdaType = srcType.basicType().invokerType();

        Name[] names = arguments(NAME_LIMIT - INARG_LIMIT, lambdaType);

        // Collect the arguments to the outgoing call, maybe with conversions:

        final int OUTARG_BASE = 0;  // target MH is Name.function, name Name.arguments[0]

        Object[] outArgs = new Object[OUTARG_BASE + INARG_COUNT];

        int nameCursor = INARG_LIMIT;

        for (int i = 0; i < INARG_COUNT; i++) {

            Object convSpec = convSpecs[i];

            if (convSpec == null) {

                // do nothing: difference is trivial

                outArgs[OUTARG_BASE + i] = names[INARG_BASE + i];

                continue;

            }

            Name conv;

            if (convSpec instanceof Class) {

                Class<?> convClass = (Class<?>) convSpec;

                conv = new Name(getConstantHandle(MH_cast), convClass, names[INARG_BASE + i]);

            } else {

                MethodHandle fn = (MethodHandle) convSpec;

                conv = new Name(fn, names[INARG_BASE + i]);

            }

            assert(names[nameCursor] == null);

            names[nameCursor++] = conv;

            assert(outArgs[OUTARG_BASE + i] == null);

            outArgs[OUTARG_BASE + i] = conv;

        }

        // Build argument array for the call.

        assert(nameCursor == OUT_CALL);

        names[OUT_CALL] = new Name(target, outArgs);

        Object convSpec = convSpecs[INARG_COUNT];

        if (!retConv) {

            assert(OUT_CALL == names.length-1);

        } else {

            Name conv;

            if (convSpec == void.class) {

                conv = new Name(LambdaForm.constantZero(BasicType.basicType(srcType.returnType())));

            } else if (convSpec instanceof Class) {

                Class<?> convClass = (Class<?>) convSpec;

                conv = new Name(getConstantHandle(MH_cast), convClass, names[OUT_CALL]);

            } else {

                MethodHandle fn = (MethodHandle) convSpec;

                if (fn.type().parameterCount() == 0)

                    conv = new Name(fn);  // don't pass retval to void conversion

                else

                    conv = new Name(fn, names[OUT_CALL]);

            }

            assert(names[RETURN_CONV] == null);

            names[RETURN_CONV] = conv;

            assert(RETURN_CONV == names.length-1);

        }

        LambdaForm form = new LambdaForm("convert", lambdaType.parameterCount(), names, RESULT);

        return SimpleMethodHandle.make(srcType, form);

    }

    static Object[] computeValueConversions(MethodType srcType, MethodType dstType,

                                            boolean strict, boolean monobox) {

        final int INARG_COUNT = srcType.parameterCount();

        Object[] convSpecs = new Object[INARG_COUNT+1];

        for (int i = 0; i <= INARG_COUNT; i++) {

            boolean isRet = (i == INARG_COUNT);

            Class<?> src = isRet ? dstType.returnType() : srcType.parameterType(i);

            Class<?> dst = isRet ? srcType.returnType() : dstType.parameterType(i);

            if (!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict)) {

                convSpecs[i] = valueConversion(src, dst, strict, monobox);

            }

        }

        return convSpecs;

    }

    static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,

                                            boolean strict) {

        return makePairwiseConvert(target, srcType, strict, /*monobox=*/ false);

    }

    /**

     * Find a conversion function from the given source to the given destination.

     * This conversion function will be used as a LF NamedFunction.

     * Return a Class object if a simple cast is needed.

     * Return void.class if void is involved.

     */

    static Object valueConversion(Class<?> src, Class<?> dst, boolean strict, boolean monobox) {

        assert(!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict));  // caller responsibility

        if (dst == void.class)

            return dst;

        MethodHandle fn;

        if (src.isPrimitive()) {

            if (src == void.class) {

                return void.class;  // caller must recognize this specially

            } else if (dst.isPrimitive()) {

                // Examples: int->byte, byte->int, boolean->int (!strict)

                fn = ValueConversions.convertPrimitive(src, dst);

            } else {

                // Examples: int->Integer, boolean->Object, float->Number

                Wrapper wsrc = Wrapper.forPrimitiveType(src);

                fn = ValueConversions.boxExact(wsrc);

                assert(fn.type().parameterType(0) == wsrc.primitiveType());

                assert(fn.type().returnType() == wsrc.wrapperType());

                if (!VerifyType.isNullConversion(wsrc.wrapperType(), dst, strict)) {

                    // Corner case, such as int->Long, which will probably fail.

                    MethodType mt = MethodType.methodType(dst, src);

                    if (strict)

                        fn = fn.asType(mt);

                    else

                        fn = MethodHandleImpl.makePairwiseConvert(fn, mt, /*strict=*/ false);

                }

            }

        } else if (dst.isPrimitive()) {

            Wrapper wdst = Wrapper.forPrimitiveType(dst);

            if (monobox || src == wdst.wrapperType()) {

                // Use a strongly-typed unboxer, if possible.

                fn = ValueConversions.unboxExact(wdst, strict);

            } else {

                // Examples:  Object->int, Number->int, Comparable->int, Byte->int

                // must include additional conversions

                // src must be examined at runtime, to detect Byte, Character, etc.

                fn = (strict

                        ? ValueConversions.unboxWiden(wdst)

                        : ValueConversions.unboxCast(wdst));

            }

        } else {

            // Simple reference conversion.

            // Note:  Do not check for a class hierarchy relation

            // between src and dst.  In all cases a 'null' argument

            // will pass the cast conversion.

            return dst;

        }

        assert(fn.type().parameterCount() <= 1) : "pc"+Arrays.asList(src.getSimpleName(), dst.getSimpleName(), fn);

        return fn;

    }

    static MethodHandle makeVarargsCollector(MethodHandle target, Class<?> arrayType) {

        MethodType type = target.type();

        int last = type.parameterCount() - 1;

        if (type.parameterType(last) != arrayType)

            target = target.asType(type.changeParameterType(last, arrayType));

        target = target.asFixedArity();  // make sure this attribute is turned off

        return new AsVarargsCollector(target, arrayType);

    }

    private static final class AsVarargsCollector extends DelegatingMethodHandle {

        private final MethodHandle target;

        private final Class<?> arrayType;

        private @Stable MethodHandle asCollectorCache;

        AsVarargsCollector(MethodHandle target, Class<?> arrayType) {

            this(target.type(), target, arrayType);

        }

        AsVarargsCollector(MethodType type, MethodHandle target, Class<?> arrayType) {

            super(type, target);

            this.target = target;

            this.arrayType = arrayType;

            this.asCollectorCache = target.asCollector(arrayType, 0);

        }

        @Override

        public boolean isVarargsCollector() {

            return true;

        }

        @Override

        protected MethodHandle getTarget() {

            return target;

        }

        @Override

        public MethodHandle asFixedArity() {

            return target;

        }

        @Override

        MethodHandle setVarargs(MemberName member) {

            if (member.isVarargs())  return this;

            return asFixedArity();

        }

        @Override

        public MethodHandle asTypeUncached(MethodType newType) {

            MethodType type = this.type();

            int collectArg = type.parameterCount() - 1;

            int newArity = newType.parameterCount();

            if (newArity == collectArg+1 &&

                type.parameterType(collectArg).isAssignableFrom(newType.parameterType(collectArg))) {

                // if arity and trailing parameter are compatible, do normal thing

                return asTypeCache = asFixedArity().asType(newType);

            }

            // check cache

            MethodHandle acc = asCollectorCache;

            if (acc != null && acc.type().parameterCount() == newArity)

                return asTypeCache = acc.asType(newType);

            // build and cache a collector

            int arrayLength = newArity - collectArg;

            MethodHandle collector;

            try {

                collector = asFixedArity().asCollector(arrayType, arrayLength);

                assert(collector.type().parameterCount() == newArity) : "newArity="+newArity+" but collector="+collector;

            } catch (IllegalArgumentException ex) {

                throw new WrongMethodTypeException("cannot build collector", ex);

            }

            asCollectorCache = collector;

            return asTypeCache = collector.asType(newType);

        }