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 * Copyright (c) 2008, 2011, 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

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package java.lang.invoke;

import sun.invoke.util.VerifyType;

import sun.invoke.util.Wrapper;

import sun.invoke.util.ValueConversions;

import java.util.Arrays;

import java.util.ArrayList;

import java.util.Collections;

import static java.lang.invoke.MethodHandleNatives.Constants.*;

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

/**

 * This method handle performs simple conversion or checking of a single argument.

 * @author jrose

 */

class AdapterMethodHandle extends BoundMethodHandle {

    //MethodHandle vmtarget;   // next AMH or BMH in chain or final DMH

    //Object       argument;   // parameter to the conversion if needed

    //int          vmargslot;  // which argument slot is affected

    private final int conversion;  // the type of conversion: RETYPE_ONLY, etc.

    // Constructors in this class *must* be package scoped or private.

    private AdapterMethodHandle(MethodHandle target, MethodType newType,

                long conv, Object convArg) {

        super(newType, convArg, newType.parameterSlotDepth(1+convArgPos(conv)));

        this.conversion = convCode(conv);

        // JVM might update VM-specific bits of conversion (ignore)

        MethodHandleNatives.init(this, target, convArgPos(conv));

    }

    private AdapterMethodHandle(MethodHandle target, MethodType newType,

                long conv) {

        this(target, newType, conv, null);

    }

    int getConversion() { return conversion; }

    // TO DO:  When adapting another MH with a null conversion, clone

    // the target and change its type, instead of adding another layer.

    /** Can a JVM-level adapter directly implement the proposed

     *  argument conversions, as if by fixed-arity MethodHandle.asType?

     */

    static boolean canPairwiseConvert(MethodType newType, MethodType oldType, int level) {

        // same number of args, of course

        int len = newType.parameterCount();

        if (len != oldType.parameterCount())

            return false;

        // Check return type.

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

        Class<?> ret = oldType.returnType();

        if (!VerifyType.isNullConversion(ret, exp)) {

            if (!convOpSupported(OP_COLLECT_ARGS))

                return false;

            if (!canConvertArgument(ret, exp, level))

                return false;

        }

        // Check args pairwise.

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

            Class<?> src = newType.parameterType(i); // source type

            Class<?> dst = oldType.parameterType(i); // destination type

            if (!canConvertArgument(src, dst, level))

                return false;

        }

        return true;

    }

    /** Can a JVM-level adapter directly implement the proposed

     *  argument conversion, as if by fixed-arity MethodHandle.asType?

     */

    static boolean canConvertArgument(Class<?> src, Class<?> dst, int level) {

        // ? Retool this logic to use RETYPE_ONLY, CHECK_CAST, etc., as opcodes,

        // so we don't need to repeat so much decision making.

        if (VerifyType.isNullConversion(src, dst)) {

            return true;

        } else if (convOpSupported(OP_COLLECT_ARGS)) {

            // If we can build filters, we can convert anything to anything.

            return true;

        } else if (src.isPrimitive()) {

            if (dst.isPrimitive())

                return canPrimCast(src, dst);

            else

                return canBoxArgument(src, dst);

        } else {

            if (dst.isPrimitive())

                return canUnboxArgument(src, dst, level);

            else

                return true;  // any two refs can be interconverted

        }

    }

    /**

     * 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 newType required call type

     * @param target original method handle

     * @param level which strength of conversion is allowed

     * @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(MethodType newType, MethodHandle target, int level) {

        MethodType oldType = target.type();

        if (newType == oldType)  return target;

        if (!canPairwiseConvert(newType, oldType, level))

            return null;

        // (after this point, it is an assertion error to fail to convert)

        // Find last non-trivial conversion (if any).

        int lastConv = newType.parameterCount()-1;

        while (lastConv >= 0) {

            Class<?> src = newType.parameterType(lastConv); // source type

            Class<?> dst = oldType.parameterType(lastConv); // destination type

            if (isTrivialConversion(src, dst, level)) {

                --lastConv;

            } else {

                break;

            }

        }

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

        Class<?> haveReturn = oldType.returnType();

        boolean retConv = !isTrivialConversion(haveReturn, needReturn, level);

        // Now build a chain of one or more adapters.

        MethodHandle adapter = target, adapter2;

        MethodType midType = oldType;

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

            Class<?> src = newType.parameterType(i); // source type

            Class<?> dst = midType.parameterType(i); // destination type

            if (isTrivialConversion(src, dst, level)) {

                // do nothing: difference is trivial

                continue;

            }

            // Work the current type backward toward the desired caller type:

            midType = midType.changeParameterType(i, src);

            if (i == lastConv) {

                // When doing the last (or only) real conversion,

                // force all remaining null conversions to happen also.

                MethodType lastMidType = newType;

                if (retConv)  lastMidType = lastMidType.changeReturnType(haveReturn);

                assert(VerifyType.isNullConversion(lastMidType, midType));

                midType = lastMidType;

            }

            // Tricky case analysis follows.

            // It parallels canConvertArgument() above.

            if (src.isPrimitive()) {

                if (dst.isPrimitive()) {

                    adapter2 = makePrimCast(midType, adapter, i, dst);

                } else {

                    adapter2 = makeBoxArgument(midType, adapter, i, src);

                }

            } else {

                if (dst.isPrimitive()) {

                    // Caller has boxed a primitive.  Unbox it for the target.

                    // The box type must correspond exactly to the primitive type.

                    // This is simpler than the powerful set of widening

                    // conversions supported by reflect.Method.invoke.

                    // Those conversions require a big nest of if/then/else logic,

                    // which we prefer to make a user responsibility.

                    adapter2 = makeUnboxArgument(midType, adapter, i, dst, level);

                } 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.

                    adapter2 = makeCheckCast(midType, adapter, i, dst);

                }

            }

            assert(adapter2 != null) : Arrays.asList(src, dst, midType, adapter, i, target, newType);

            assert(adapter2.type() == midType);

            adapter = adapter2;

        }

        if (retConv) {

            adapter2 = makeReturnConversion(adapter, haveReturn, needReturn);

            assert(adapter2 != null);

            adapter = adapter2;

        }

        if (adapter.type() != newType) {

            // Only trivial conversions remain.

            adapter2 = makeRetypeOnly(newType, adapter);

            assert(adapter2 != null);

            adapter = adapter2;

            // Actually, that's because there were no non-trivial ones:

            assert(lastConv == -1 || retConv);

        }

        assert(adapter.type() == newType);

        return adapter;

    }

    private static boolean isTrivialConversion(Class<?> src, Class<?> dst, int level) {

        if (src == dst || dst == void.class)  return true;

        if (!VerifyType.isNullConversion(src, dst))  return false;

        if (level > 1)  return true;  // explicitCastArguments

        boolean sp = src.isPrimitive();

        boolean dp = dst.isPrimitive();

        if (sp != dp)  return false;

        if (sp) {

            // in addition to being a null conversion, forbid boolean->int etc.

            return Wrapper.forPrimitiveType(dst)

                    .isConvertibleFrom(Wrapper.forPrimitiveType(src));

        } else {

            return dst.isAssignableFrom(src);

        }

    }

    private static MethodHandle makeReturnConversion(MethodHandle target, Class<?> haveReturn, Class<?> needReturn) {

        MethodHandle adjustReturn;

        if (haveReturn == void.class) {

            // synthesize a zero value for the given void

            Object zero = Wrapper.forBasicType(needReturn).zero();

            adjustReturn = MethodHandles.constant(needReturn, zero);

        } else {

            MethodType needConversion = MethodType.methodType(needReturn, haveReturn);

            adjustReturn = MethodHandles.identity(needReturn).asType(needConversion);

        }

        return makeCollectArguments(adjustReturn, target, 0, false);

    }

    /**

     * Create a JVM-level adapter method handle to permute the arguments

     * of the given method.

     * @param newType required call type

     * @param target original method handle

     * @param argumentMap for each target argument, position of its source in newType

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

     *          or the original target if the types are already identical

     *          and the permutation is null

     * @throws IllegalArgumentException if the adaptation cannot be made

     *          directly by a JVM-level adapter, without help from Java code

     */

    static MethodHandle makePermutation(MethodType newType, MethodHandle target,

                int[] argumentMap) {

        MethodType oldType = target.type();

        boolean nullPermutation = true;

        for (int i = 0; i < argumentMap.length; i++) {

            int pos = argumentMap[i];

            if (pos != i)

                nullPermutation = false;

            if (pos < 0 || pos >= newType.parameterCount()) {

                argumentMap = new int[0]; break;

            }

        }

        if (argumentMap.length != oldType.parameterCount())

            throw newIllegalArgumentException("bad permutation: "+Arrays.toString(argumentMap));

        if (nullPermutation) {

            MethodHandle res = makePairwiseConvert(newType, target, 0);

            // well, that was easy

            if (res == null)

                throw newIllegalArgumentException("cannot convert pairwise: "+newType);

            return res;

        }

        // Check return type.  (Not much can be done with it.)

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

        Class<?> ret = oldType.returnType();

        if (!VerifyType.isNullConversion(ret, exp))

            throw newIllegalArgumentException("bad return conversion for "+newType);

        // See if the argument types match up.

        for (int i = 0; i < argumentMap.length; i++) {

            int j = argumentMap[i];

            Class<?> src = newType.parameterType(j);

            Class<?> dst = oldType.parameterType(i);

            if (!VerifyType.isNullConversion(src, dst))

                throw newIllegalArgumentException("bad argument #"+j+" conversion for "+newType);

        }

        // Now figure out a nice mix of SWAP, ROT, DUP, and DROP adapters.

        // A workable greedy algorithm is as follows:

        // Drop unused outgoing arguments (right to left: shallowest first).

        // Duplicate doubly-used outgoing arguments (left to right: deepest first).

        // Then the remaining problem is a true argument permutation.

        // Marshal the outgoing arguments as required from left to right.

        // That is, find the deepest outgoing stack position that does not yet

        // have the correct argument value, and correct at least that position

        // by swapping or rotating in the misplaced value (from a shallower place).

        // If the misplaced value is followed by one or more consecutive values

        // (also misplaced)  issue a rotation which brings as many as possible

        // into position.  Otherwise make progress with either a swap or a

        // rotation.  Prefer the swap as cheaper, but do not use it if it

        // breaks a slot pair.  Prefer the rotation over the swap if it would

        // preserve more consecutive values shallower than the target position.

        // When more than one rotation will work (because the required value

        // is already adjacent to the target position), then use a rotation

        // which moves the old value in the target position adjacent to

        // one of its consecutive values.  Also, prefer shorter rotation

        // spans, since they use fewer memory cycles for shuffling.

        throw new UnsupportedOperationException("NYI");

    }

    private static byte basicType(Class<?> type) {

        if (type == null)  return T_VOID;

        switch (Wrapper.forBasicType(type)) {

            case BOOLEAN:  return T_BOOLEAN;

            case CHAR:     return T_CHAR;

            case FLOAT:    return T_FLOAT;

            case DOUBLE:   return T_DOUBLE;

            case BYTE:     return T_BYTE;

            case SHORT:    return T_SHORT;

            case INT:      return T_INT;

            case LONG:     return T_LONG;

            case OBJECT:   return T_OBJECT;

            case VOID:     return T_VOID;

        }

        return 99; // T_ILLEGAL or some such

    }

    /** Number of stack slots for the given type.

     *  Two for T_DOUBLE and T_FLOAT, one for the rest.

     */

    private static int type2size(int type) {

        assert(type >= T_BOOLEAN && type <= T_OBJECT);

        return (type == T_LONG || type == T_DOUBLE) ? 2 : 1;

    }

    private static int type2size(Class<?> type) {

        return type2size(basicType(type));

    }

    /** The given stackMove is the number of slots pushed.

     * It might be negative.  Scale it (multiply) by the

     * VM's notion of how an address changes with a push,

     * to get the raw SP change for stackMove.

     * Then shift and mask it into the correct field.

     */

    private static long insertStackMove(int stackMove) {

        // following variable must be long to avoid sign extension after '<<'

        long spChange = stackMove * MethodHandleNatives.JVM_STACK_MOVE_UNIT;

        return (spChange & CONV_STACK_MOVE_MASK) << CONV_STACK_MOVE_SHIFT;

    }

    static int extractStackMove(int convOp) {

        int spChange = convOp >> CONV_STACK_MOVE_SHIFT;

        return spChange / MethodHandleNatives.JVM_STACK_MOVE_UNIT;

    }

    static int extractStackMove(MethodHandle target) {

        if (target instanceof AdapterMethodHandle) {

            AdapterMethodHandle amh = (AdapterMethodHandle) target;

            return extractStackMove(amh.getConversion());

        } else {

            return 0;

        }

    }

    /** Construct an adapter conversion descriptor for a single-argument conversion. */

    private static long makeConv(int convOp, int argnum, int src, int dest) {

        assert(src  == (src  & CONV_TYPE_MASK));

        assert(dest == (dest & CONV_TYPE_MASK));

        assert(convOp >= OP_CHECK_CAST && convOp <= OP_PRIM_TO_REF || convOp == OP_COLLECT_ARGS);

        int stackMove = type2size(dest) - type2size(src);

        return ((long) argnum << 32 |

                (long) convOp << CONV_OP_SHIFT |

                (int)  src    << CONV_SRC_TYPE_SHIFT |

                (int)  dest   << CONV_DEST_TYPE_SHIFT |

                insertStackMove(stackMove)

                );

    }

    private static long makeDupConv(int convOp, int argnum, int stackMove) {

        // simple argument motion, requiring one slot to specify

        assert(convOp == OP_DUP_ARGS || convOp == OP_DROP_ARGS);

        byte src = 0, dest = 0;

        return ((long) argnum << 32 |

                (long) convOp << CONV_OP_SHIFT |

                (int)  src    << CONV_SRC_TYPE_SHIFT |

                (int)  dest   << CONV_DEST_TYPE_SHIFT |

                insertStackMove(stackMove)

                );

    }

    private static long makeSwapConv(int convOp, int srcArg, byte srcType, int destSlot, byte destType) {

        // more complex argument motion, requiring two slots to specify

        assert(convOp == OP_SWAP_ARGS || convOp == OP_ROT_ARGS);

        return ((long) srcArg << 32 |

                (long) convOp << CONV_OP_SHIFT |

                (int)  srcType << CONV_SRC_TYPE_SHIFT |

                (int)  destType << CONV_DEST_TYPE_SHIFT |

                (int)  destSlot << CONV_VMINFO_SHIFT

                );

    }

    private static long makeSpreadConv(int convOp, int argnum, int src, int dest, int stackMove) {

        // spreading or collecting, at a particular slot location

        assert(convOp == OP_SPREAD_ARGS || convOp == OP_COLLECT_ARGS || convOp == OP_FOLD_ARGS);

        // src  = spread ? T_OBJECT (for array)  : common type of collected args (else void)

        // dest = spread ? element type of array : result type of collector (can be void)

        return ((long) argnum << 32 |

                (long) convOp << CONV_OP_SHIFT |

                (int)  src    << CONV_SRC_TYPE_SHIFT |

                (int)  dest   << CONV_DEST_TYPE_SHIFT |

                insertStackMove(stackMove)

                );

    }

    private static long makeConv(int convOp) {

        assert(convOp == OP_RETYPE_ONLY || convOp == OP_RETYPE_RAW);

        return ((long)-1 << 32) | (convOp << CONV_OP_SHIFT);   // stackMove, src, dst all zero

    }

    private static int convCode(long conv) {

        return (int)conv;

    }

    private static int convArgPos(long conv) {

        return (int)(conv >>> 32);

    }

    private static boolean convOpSupported(int convOp) {

        assert(convOp >= 0 && convOp <= CONV_OP_LIMIT);

        return ((1<<convOp) & MethodHandleNatives.CONV_OP_IMPLEMENTED_MASK) != 0;

    }

    /** One of OP_RETYPE_ONLY, etc. */

    int conversionOp() { return (conversion & CONV_OP_MASK) >> CONV_OP_SHIFT; }

    /* Return one plus the position of the first non-trivial difference

     * between the given types.  This is not a symmetric operation;

     * we are considering adapting the targetType to adapterType.

     * Trivial differences are those which could be ignored by the JVM

     * without subverting the verifier.  Otherwise, adaptable differences

     * are ones for which we could create an adapter to make the type change.

     * Return zero if there are no differences (other than trivial ones).

     * Return 1+N if N is the only adaptable argument difference.

     * Return the -2-N where N is the first of several adaptable

     * argument differences.

     * Return -1 if there there are differences which are not adaptable.

     */

    private static int diffTypes(MethodType adapterType,

                                 MethodType targetType,

                                 boolean raw) {

        int diff;

        diff = diffReturnTypes(adapterType, targetType, raw);

        if (diff != 0)  return diff;

        int nargs = adapterType.parameterCount();

        if (nargs != targetType.parameterCount())

            return -1;

        diff = diffParamTypes(adapterType, 0, targetType, 0, nargs, raw);

        //System.out.println("diff "+adapterType);

        //System.out.println("  "+diff+" "+targetType);

        return diff;

    }

    private static int diffReturnTypes(MethodType adapterType,

                                       MethodType targetType,

                                       boolean raw) {

        Class<?> src = targetType.returnType();

        Class<?> dst = adapterType.returnType();

        if ((!raw

             ? VerifyType.canPassUnchecked(src, dst)

             : VerifyType.canPassRaw(src, dst)

             ) > 0)

            return 0;  // no significant difference

        if (raw && !src.isPrimitive() && !dst.isPrimitive())

            return 0;  // can force a reference return (very carefully!)

        //if (false)  return 1;  // never adaptable!

        return -1;  // some significant difference

    }

    private static int diffParamTypes(MethodType adapterType, int astart,

                                      MethodType targetType, int tstart,

                                      int nargs, boolean raw) {

        assert(nargs >= 0);

        int res = 0;

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

            Class<?> src  = adapterType.parameterType(astart+i);

            Class<?> dest = targetType.parameterType(tstart+i);

            if ((!raw

                 ? VerifyType.canPassUnchecked(src, dest)

                 : VerifyType.canPassRaw(src, dest)

                ) <= 0) {

                // found a difference; is it the only one so far?

                if (res != 0)

                    return -1-res; // return -2-i for prev. i

                res = 1+i;

            }

        }

        return res;

    }

    /** Can a retyping adapter (alone) validly convert the target to newType? */

    static boolean canRetypeOnly(MethodType newType, MethodType targetType) {

        return canRetype(newType, targetType, false);

    }