/*

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.invoke.util;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodHandles.Lookup;

import java.lang.invoke.MethodType;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.EnumMap;

import java.util.List;

public class ValueConversions {

    private static final Class<?> THIS_CLASS = ValueConversions.class;

    // Do not adjust this except for special platforms:

    private static final int MAX_ARITY;

    static {

        final Object[] values = { 255 };

        AccessController.doPrivileged(new PrivilegedAction<Void>() {

                public Void run() {

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

                    return null;

                }

            });

        MAX_ARITY = (Integer) values[0];

    }

    private static final Lookup IMPL_LOOKUP = MethodHandles.lookup();

    private static EnumMap<Wrapper, MethodHandle>[] newWrapperCaches(int n) {

        @SuppressWarnings("unchecked")  // generic array creation

        EnumMap<Wrapper, MethodHandle>[] caches

                = (EnumMap<Wrapper, MethodHandle>[]) new EnumMap<?,?>[n];

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

            caches[i] = new EnumMap<>(Wrapper.class);

        return caches;

    }

    /// Converting references to values.

    // There are several levels of this unboxing conversions:

    //   no conversions:  exactly Integer.valueOf, etc.

    //   implicit conversions sanctioned by JLS 5.1.2, etc.

    //   explicit conversions as allowed by explicitCastArguments

    static int unboxInteger(Object x, boolean cast) {

        if (x instanceof Integer)

            return ((Integer) x).intValue();

        return primitiveConversion(Wrapper.INT, x, cast).intValue();

    }

    static byte unboxByte(Object x, boolean cast) {

        if (x instanceof Byte)

            return ((Byte) x).byteValue();

        return primitiveConversion(Wrapper.BYTE, x, cast).byteValue();

    }

    static short unboxShort(Object x, boolean cast) {

        if (x instanceof Short)

            return ((Short) x).shortValue();

        return primitiveConversion(Wrapper.SHORT, x, cast).shortValue();

    }

    static boolean unboxBoolean(Object x, boolean cast) {

        if (x instanceof Boolean)

            return ((Boolean) x).booleanValue();

        return (primitiveConversion(Wrapper.BOOLEAN, x, cast).intValue() & 1) != 0;

    }

    static char unboxCharacter(Object x, boolean cast) {

        if (x instanceof Character)

            return ((Character) x).charValue();

        return (char) primitiveConversion(Wrapper.CHAR, x, cast).intValue();

    }

    static long unboxLong(Object x, boolean cast) {

        if (x instanceof Long)

            return ((Long) x).longValue();

        return primitiveConversion(Wrapper.LONG, x, cast).longValue();

    }

    static float unboxFloat(Object x, boolean cast) {

        if (x instanceof Float)

            return ((Float) x).floatValue();

        return primitiveConversion(Wrapper.FLOAT, x, cast).floatValue();

    }

    static double unboxDouble(Object x, boolean cast) {

        if (x instanceof Double)

            return ((Double) x).doubleValue();

        return primitiveConversion(Wrapper.DOUBLE, x, cast).doubleValue();

    }

    private static MethodType unboxType(Wrapper wrap) {

        return MethodType.methodType(wrap.primitiveType(), Object.class, boolean.class);

    }

    private static final EnumMap<Wrapper, MethodHandle>[]

            UNBOX_CONVERSIONS = newWrapperCaches(2);

    private static MethodHandle unbox(Wrapper wrap, boolean cast) {

        EnumMap<Wrapper, MethodHandle> cache = UNBOX_CONVERSIONS[(cast?1:0)];

        MethodHandle mh = cache.get(wrap);

        if (mh != null) {

            return mh;

        }

        // slow path

        switch (wrap) {

            case OBJECT:

                mh = IDENTITY; break;

            case VOID:

                mh = IGNORE; break;

        }

        if (mh != null) {

            cache.put(wrap, mh);

            return mh;

        }

        // look up the method

        String name = "unbox" + wrap.wrapperSimpleName();

        MethodType type = unboxType(wrap);

        try {

            mh = IMPL_LOOKUP.findStatic(THIS_CLASS, name, type);

        } catch (ReflectiveOperationException ex) {

            mh = null;

        }

        if (mh != null) {

            mh = MethodHandles.insertArguments(mh, 1, cast);

            cache.put(wrap, mh);

            return mh;

        }

        throw new IllegalArgumentException("cannot find unbox adapter for " + wrap

                + (cast ? " (cast)" : ""));

    }

    public static MethodHandle unboxCast(Wrapper type) {

        return unbox(type, true);

    }

    public static MethodHandle unbox(Class<?> type) {

        return unbox(Wrapper.forPrimitiveType(type), false);

    }

    public static MethodHandle unboxCast(Class<?> type) {

        return unbox(Wrapper.forPrimitiveType(type), true);

    }

    static private final Integer ZERO_INT = 0, ONE_INT = 1;

    /// Primitive conversions

    /**

     * Produce a Number which represents the given value {@code x}

     * according to the primitive type of the given wrapper {@code wrap}.

     * Caller must invoke intValue, byteValue, longValue (etc.) on the result

     * to retrieve the desired primitive value.

     */

    public static Number primitiveConversion(Wrapper wrap, Object x, boolean cast) {

        // Maybe merge this code with Wrapper.convert/cast.

        if (x == null) {

            if (!cast)  return null;

            return ZERO_INT;

        }

        if (x instanceof Number) {

            res = (Number) x;

        } else if (x instanceof Boolean) {

            res = ((boolean)x ? ONE_INT : ZERO_INT);

        } else if (x instanceof Character) {

            res = (int)(char)x;

        } else {

            // this will fail with the required ClassCastException:

            res = (Number) x;

        }

        Wrapper xwrap = Wrapper.findWrapperType(x.getClass());

        if (xwrap == null || !cast && !wrap.isConvertibleFrom(xwrap))

            // this will fail with the required ClassCastException:

            return (Number) wrap.wrapperType().cast(x);

        return res;

    }

    /**

     * The JVM verifier allows boolean, byte, short, or char to widen to int.

     * Support exactly this conversion, from a boxed value type Boolean,

     * Byte, Short, Character, or Integer.

     */

    public static int widenSubword(Object x) {

        if (x instanceof Integer)

            return (int) x;

        else if (x instanceof Boolean)

            return fromBoolean((boolean) x);

        else if (x instanceof Character)

            return (char) x;

        else if (x instanceof Short)

            return (short) x;

        else if (x instanceof Byte)

            return (byte) x;

        else

            // Fail with a ClassCastException.

            return (int) x;

    }

    /// Converting primitives to references

    static Integer boxInteger(int x) {

        return x;

    }

    static Byte boxByte(byte x) {

        return x;

    }

    static Short boxShort(short x) {

        return x;

    }

    static Boolean boxBoolean(boolean x) {

        return x;

    }

    static Character boxCharacter(char x) {

        return x;

    }

    static Long boxLong(long x) {

        return x;

    }

    static Float boxFloat(float x) {

        return x;

    }

    static Double boxDouble(double x) {

        return x;

    }

    private static MethodType boxType(Wrapper wrap) {

        // be exact, since return casts are hard to compose

        Class<?> boxType = wrap.wrapperType();

        return MethodType.methodType(boxType, wrap.primitiveType());

    }

    private static final EnumMap<Wrapper, MethodHandle>[]

            BOX_CONVERSIONS = newWrapperCaches(2);

    private static MethodHandle box(Wrapper wrap, boolean exact) {

        EnumMap<Wrapper, MethodHandle> cache = BOX_CONVERSIONS[(exact?1:0)];

        MethodHandle mh = cache.get(wrap);

        if (mh != null) {

            return mh;

        }

        // slow path

        switch (wrap) {

            case OBJECT:

                mh = IDENTITY; break;

            case VOID:

                mh = ZERO_OBJECT;

                break;

        }

        if (mh != null) {

            cache.put(wrap, mh);

            return mh;

        }

        // look up the method

        String name = "box" + wrap.wrapperSimpleName();

        MethodType type = boxType(wrap);

        if (exact) {

            try {

                mh = IMPL_LOOKUP.findStatic(THIS_CLASS, name, type);

            } catch (ReflectiveOperationException ex) {

                mh = null;

            }

        } else {

            mh = box(wrap, !exact).asType(type.erase());

        }

        if (mh != null) {

            cache.put(wrap, mh);

            return mh;

        }

        throw new IllegalArgumentException("cannot find box adapter for "

                + wrap + (exact ? " (exact)" : ""));

    }

    public static MethodHandle box(Class<?> type) {

        boolean exact = false;

        // e.g., boxShort(short)Short if exact,

        // e.g., boxShort(short)Object if !exact

        return box(Wrapper.forPrimitiveType(type), exact);

    }

    public static MethodHandle box(Wrapper type) {

        boolean exact = false;

        return box(type, exact);

    }

    /// Constant functions

    static void ignore(Object x) {

        // no value to return; this is an unbox of null

    }

    static void empty() {

    }

    static Object zeroObject() {

        return null;

    }

    static int zeroInteger() {

        return 0;

    }

    static long zeroLong() {

        return 0;

    }

    static float zeroFloat() {

        return 0;

    }

    static double zeroDouble() {

        return 0;

    }

    private static final EnumMap<Wrapper, MethodHandle>[]

            CONSTANT_FUNCTIONS = newWrapperCaches(2);

    public static MethodHandle zeroConstantFunction(Wrapper wrap) {

        EnumMap<Wrapper, MethodHandle> cache = CONSTANT_FUNCTIONS[0];

        MethodHandle mh = cache.get(wrap);

        if (mh != null) {

            return mh;

        }

        // slow path

        MethodType type = MethodType.methodType(wrap.primitiveType());

        switch (wrap) {

            case VOID:

                mh = EMPTY;

                break;

            case OBJECT:

            case INT: case LONG: case FLOAT: case DOUBLE:

                try {

                    mh = IMPL_LOOKUP.findStatic(THIS_CLASS, "zero"+wrap.wrapperSimpleName(), type);

                } catch (ReflectiveOperationException ex) {

                    mh = null;

                }

                break;

        }

        if (mh != null) {

            cache.put(wrap, mh);

            return mh;

        }

        // use zeroInt and cast the result

        if (wrap.isSubwordOrInt() && wrap != Wrapper.INT) {

            mh = MethodHandles.explicitCastArguments(zeroConstantFunction(Wrapper.INT), type);

            cache.put(wrap, mh);

            return mh;

        }

        throw new IllegalArgumentException("cannot find zero constant for " + wrap);

    }

    /// Converting references to references.

    /**

     * Identity function.

     * @param x an arbitrary reference value

     * @return the same value x

     */

    static <T> T identity(T x) {

        return x;

    }

    /**

     * Identity function on ints.

     * @param x an arbitrary int value

     * @return the same value x

     */

    static int identity(int x) {

        return x;

    }

    static byte identity(byte x) {

        return x;

    }

    static short identity(short x) {

        return x;

    }

    static boolean identity(boolean x) {

        return x;

    }

    static char identity(char x) {

        return x;

    }

    /**

     * Identity function on longs.

     * @param x an arbitrary long value

     * @return the same value x

     */

    static long identity(long x) {

        return x;

    }

    static float identity(float x) {

        return x;

    }

    static double identity(double x) {

        return x;

    }

    /**

     * Identity function, with reference cast.

     * @param t an arbitrary reference type

     * @param x an arbitrary reference value

     * @return the same value x

     */

    static <T,U> T castReference(Class<? extends T> t, U x) {

        return t.cast(x);

    }

    static {

        try {

            MethodType idType = MethodType.genericMethodType(1);

            MethodType castType = idType.insertParameterTypes(0, Class.class);

            MethodType ignoreType = idType.changeReturnType(void.class);

            MethodType zeroObjectType = MethodType.genericMethodType(0);

            IDENTITY = IMPL_LOOKUP.findStatic(THIS_CLASS, "identity", idType);

            //CAST_REFERENCE = IMPL_LOOKUP.findVirtual(Class.class, "cast", idType);

            CAST_REFERENCE = IMPL_LOOKUP.findStatic(THIS_CLASS, "castReference", castType);

            ZERO_OBJECT = IMPL_LOOKUP.findStatic(THIS_CLASS, "zeroObject", zeroObjectType);

            IGNORE = IMPL_LOOKUP.findStatic(THIS_CLASS, "ignore", ignoreType);

            EMPTY = IMPL_LOOKUP.findStatic(THIS_CLASS, "empty", ignoreType.dropParameterTypes(0, 1));

        } catch (NoSuchMethodException | IllegalAccessException ex) {

            throw new InternalError("uncaught exception", ex);

        }

    }

    static class LazyStatics {

        private static final MethodHandle COPY_AS_REFERENCE_ARRAY, COPY_AS_PRIMITIVE_ARRAY, MAKE_LIST;

        static {

            try {

                //MAKE_ARRAY = IMPL_LOOKUP.findStatic(THIS_CLASS, "makeArray", MethodType.methodType(Object[].class, Object[].class));

                COPY_AS_REFERENCE_ARRAY = IMPL_LOOKUP.findStatic(THIS_CLASS, "copyAsReferenceArray", MethodType.methodType(Object[].class, Class.class, Object[].class));

                COPY_AS_PRIMITIVE_ARRAY = IMPL_LOOKUP.findStatic(THIS_CLASS, "copyAsPrimitiveArray", MethodType.methodType(Object.class, Wrapper.class, Object[].class));

                MAKE_LIST = IMPL_LOOKUP.findStatic(THIS_CLASS, "makeList", MethodType.methodType(List.class, Object[].class));

            } catch (ReflectiveOperationException ex) {

                throw new InternalError("uncaught exception", ex);

            }

        }

    }