/*

 * Copyright (c) 2008, 2013, 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.util.EnumMap;

public class ValueConversions {

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

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

    /** Thread-safe canonicalized mapping from Wrapper to MethodHandle

     * with unsynchronized reads and synchronized writes.

     * It's safe to publish MethodHandles by data race because they are immutable. */

    private static class WrapperCache {

        /** EnumMap uses preconstructed array internally, which is constant during it's lifetime. */

        private final EnumMap<Wrapper, MethodHandle> map = new EnumMap<>(Wrapper.class);

        public MethodHandle get(Wrapper w) {

            return map.get(w);

        }

        public synchronized MethodHandle put(final Wrapper w, final MethodHandle mh) {

            // Simulate CAS to avoid racy duplication

            MethodHandle prev = map.putIfAbsent(w, mh);

            if (prev != null)  return prev;

            return mh;

        }

    }

    private static WrapperCache[] newWrapperCaches(int n) {

        WrapperCache[] caches = new WrapperCache[n];

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

            caches[i] = new WrapperCache();

        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(Integer x) {

        return x;

    }

    static int unboxInteger(Object x, boolean cast) {

        if (x instanceof Integer)

            return (Integer) x;

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

    }

    static byte unboxByte(Byte x) {

        return x;

    }

    static byte unboxByte(Object x, boolean cast) {

        if (x instanceof Byte)

            return (Byte) x;

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

    }

    static short unboxShort(Short x) {

        return x;

    }

    static short unboxShort(Object x, boolean cast) {

        if (x instanceof Short)

            return (Short) x;

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

    }

    static boolean unboxBoolean(Boolean x) {

        return x;

    }

    static boolean unboxBoolean(Object x, boolean cast) {

        if (x instanceof Boolean)

            return (Boolean) x;

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

    }

    static char unboxCharacter(Character x) {

        return x;

    }

    static char unboxCharacter(Object x, boolean cast) {

        if (x instanceof Character)

            return (Character) x;

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

    }

    static long unboxLong(Long x) {

        return x;

    }

    static long unboxLong(Object x, boolean cast) {

        if (x instanceof Long)

            return (Long) x;

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

    }

    static float unboxFloat(Float x) {

        return x;

    }

    static float unboxFloat(Object x, boolean cast) {

        if (x instanceof Float)

            return (Float) x;

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

    }

    static double unboxDouble(Double x) {

        return x;

    }

    static double unboxDouble(Object x, boolean cast) {

        if (x instanceof Double)

            return (Double) x;

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

    }

    private static MethodType unboxType(Wrapper wrap, int kind) {

        if (kind == 0)

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

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

    }

    private static final WrapperCache[] UNBOX_CONVERSIONS = newWrapperCaches(4);

    private static MethodHandle unbox(Wrapper wrap, int kind) {

        // kind 0 -> strongly typed with NPE

        // kind 1 -> strongly typed but zero for null,

        // kind 2 -> asType rules: accept multiple box types but only widening conversions with NPE

        // kind 3 -> explicitCastArguments rules: allow narrowing conversions, zero for null

        WrapperCache cache = UNBOX_CONVERSIONS[kind];

        MethodHandle mh = cache.get(wrap);

        if (mh != null) {

            return mh;

        }

        // slow path

        switch (wrap) {

            case OBJECT:

            case VOID:

                throw new IllegalArgumentException("unbox "+wrap);

        }

        // look up the method

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

        MethodType type = unboxType(wrap, kind);

        try {

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

        } catch (ReflectiveOperationException ex) {

            mh = null;

        }

        if (mh != null) {

            if (kind > 0) {

                boolean cast = (kind != 2);

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

            }

            if (kind == 1) {  // casting but exact (null -> zero)

                mh = mh.asType(unboxType(wrap, 0));

            }

            return cache.put(wrap, mh);

        }

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

                + (kind <= 1 ? " (exact)" : kind == 3 ? " (cast)" : ""));

    }

    /** Return an exact unboxer for the given primitive type. */

    public static MethodHandle unboxExact(Wrapper type) {

        return unbox(type, 0);

    }

    /** Return an exact unboxer for the given primitive type, with optional null-to-zero conversion.

     *  The boolean says whether to throw an NPE on a null value (false means unbox a zero).

     *  The type of the unboxer is of a form like (Integer)int.

     */

    public static MethodHandle unboxExact(Wrapper type, boolean throwNPE) {

        return unbox(type, throwNPE ? 0 : 1);

    }

    /** Return a widening unboxer for the given primitive type.

     *  Widen narrower primitive boxes to the given type.

     *  Do not narrow any primitive values or convert null to zero.

     *  The type of the unboxer is of a form like (Object)int.

     */

    public static MethodHandle unboxWiden(Wrapper type) {

        return unbox(type, 2);

    }

    /** Return a casting unboxer for the given primitive type.

     *  Widen or narrow primitive values to the given type, or convert null to zero, as needed.

     *  The type of the unboxer is of a form like (Object)int.

     */

    public static MethodHandle unboxCast(Wrapper type) {

        return unbox(type, 3);

    }

    /// 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.

        Number res;

        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 WrapperCache[] BOX_CONVERSIONS = newWrapperCaches(1);

    public static MethodHandle boxExact(Wrapper wrap) {

        WrapperCache cache = BOX_CONVERSIONS[0];

        MethodHandle mh = cache.get(wrap);

        if (mh != null) {

            return mh;

        }

        // look up the method

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

        MethodType type = boxType(wrap);

        try {

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

        } catch (ReflectiveOperationException ex) {

            mh = null;

        }

        if (mh != null) {

            return cache.put(wrap, mh);

        }

        throw new IllegalArgumentException("cannot find box adapter for " + wrap);

    }

    /// 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 WrapperCache[] CONSTANT_FUNCTIONS = newWrapperCaches(2);

    public static MethodHandle zeroConstantFunction(Wrapper wrap) {

        WrapperCache 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) {

            return cache.put(wrap, mh);

        }

        // use zeroInt and cast the result

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

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

            return cache.put(wrap, mh);

        }

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

    }

    private static final MethodHandle CAST_REFERENCE, IGNORE, EMPTY;

    static {

        try {

            MethodType idType = MethodType.genericMethodType(1);

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

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

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

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

        } catch (NoSuchMethodException | IllegalAccessException ex) {

            throw newInternalError("uncaught exception", ex);

        }

    }

    public static MethodHandle ignore() {

        return IGNORE;

    }

    /** Return a method that casts its second argument (an Object) to the given type (a Class). */

    public static MethodHandle cast() {

        return CAST_REFERENCE;

    }

    /// Primitive conversions.

    // These are supported directly by the JVM, usually by a single instruction.

    // In the case of narrowing to a subword, there may be a pair of instructions.

    // In the case of booleans, there may be a helper routine to manage a 1-bit value.

    // This is the full 8x8 matrix (minus the diagonal).

    // narrow double to all other types:

    static float doubleToFloat(double x) {  // bytecode: d2f

        return (float) x;

    }

    static long doubleToLong(double x) {  // bytecode: d2l

        return (long) x;

    }

    static int doubleToInt(double x) {  // bytecode: d2i

        return (int) x;

    }

    static short doubleToShort(double x) {  // bytecodes: d2i, i2s

        return (short) x;

    }

    static char doubleToChar(double x) {  // bytecodes: d2i, i2c

        return (char) x;

    }

    static byte doubleToByte(double x) {  // bytecodes: d2i, i2b

        return (byte) x;

    }

    static boolean doubleToBoolean(double x) {

        return toBoolean((byte) x);

    }

    // widen float:

    static double floatToDouble(float x) {  // bytecode: f2d

        return x;

    }

    // narrow float:

    static long floatToLong(float x) {  // bytecode: f2l

        return (long) x;

    }

    static int floatToInt(float x) {  // bytecode: f2i

        return (int) x;

    }

    static short floatToShort(float x) {  // bytecodes: f2i, i2s

        return (short) x;

    }

    static char floatToChar(float x) {  // bytecodes: f2i, i2c

        return (char) x;

    }

    static byte floatToByte(float x) {  // bytecodes: f2i, i2b

        return (byte) x;

    }

    static boolean floatToBoolean(float x) {

        return toBoolean((byte) x);

    }

    // widen long:

    static double longToDouble(long x) {  // bytecode: l2d

        return x;

    }

    static float longToFloat(long x) {  // bytecode: l2f

        return x;

    }

    // narrow long:

    static int longToInt(long x) {  // bytecode: l2i

        return (int) x;

    }

    static short longToShort(long x) {  // bytecodes: f2i, i2s

        return (short) x;

    }

    static char longToChar(long x) {  // bytecodes: f2i, i2c

        return (char) x;

    }

    static byte longToByte(long x) {  // bytecodes: f2i, i2b

        return (byte) x;

    }

    static boolean longToBoolean(long x) {

        return toBoolean((byte) x);

    }