/*
 * Copyright (c) 2011, 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.
 *
 * 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 jdk.vm.ci.hotspot;

import java.lang.reflect.Array;
import java.util.Objects;

import jdk.vm.ci.common.JVMCIError;
import jdk.vm.ci.meta.Constant;
import jdk.vm.ci.meta.ConstantReflectionProvider;
import jdk.vm.ci.meta.JavaConstant;
import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.MemoryAccessProvider;
import jdk.vm.ci.meta.MethodHandleAccessProvider;
import jdk.vm.ci.meta.ResolvedJavaField;
import jdk.vm.ci.meta.ResolvedJavaType;

HotSpot implementation of ConstantReflectionProvider. /**
 * HotSpot implementation of {@link ConstantReflectionProvider}.
 */
public class HotSpotConstantReflectionProvider implements ConstantReflectionProvider {

    protected final HotSpotJVMCIRuntime runtime;
    protected final HotSpotMethodHandleAccessProvider methodHandleAccess;
    private final HotSpotMemoryAccessProviderImpl memoryAccess;

    public HotSpotConstantReflectionProvider(HotSpotJVMCIRuntime runtime) {
        this.runtime = runtime;
        this.methodHandleAccess = new HotSpotMethodHandleAccessProvider(this);
        this.memoryAccess = new HotSpotMemoryAccessProviderImpl(runtime);
    }

    @Override
    public MethodHandleAccessProvider getMethodHandleAccess() {
        return methodHandleAccess;
    }

    @Override
    public MemoryAccessProvider getMemoryAccessProvider() {
        return memoryAccess;
    }

    @Override
    public Boolean constantEquals(Constant x, Constant y) {
        if (x == y) {
            return true;
        } else if (x instanceof HotSpotObjectConstantImpl) {
            return y instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) x).object() == ((HotSpotObjectConstantImpl) y).object();
        } else {
            return Objects.equals(x, y);
        }
    }

    @Override
    public Integer readArrayLength(JavaConstant array) {
        if (array == null || array.getJavaKind() != JavaKind.Object || array.isNull()) {
            return null;
        }

        Object arrayObject = ((HotSpotObjectConstantImpl) array).object();
        if (!arrayObject.getClass().isArray()) {
            return null;
        }
        return Array.getLength(arrayObject);
    }

    @Override
    public JavaConstant readArrayElement(JavaConstant array, int index) {
        if (array == null || array.getJavaKind() != JavaKind.Object || array.isNull()) {
            return null;
        }
        Object a = ((HotSpotObjectConstantImpl) array).object();

        if (!a.getClass().isArray() || index < 0 || index >= Array.getLength(a)) {
            return null;
        }

        if (a instanceof Object[]) {
            Object element = ((Object[]) a)[index];
            return HotSpotObjectConstantImpl.forObject(element);
        } else {
            return JavaConstant.forBoxedPrimitive(Array.get(a, index));
        }
    }

    
Check if the constant is a boxed value that is guaranteed to be cached by the platform.
Otherwise the generated code might be the only reference to the boxed value and since object
references from nmethods are weak this can cause GC problems.
Returns:
true if the box is cached/**
     * Check if the constant is a boxed value that is guaranteed to be cached by the platform.
     * Otherwise the generated code might be the only reference to the boxed value and since object
     * references from nmethods are weak this can cause GC problems.
     *
     * @return true if the box is cached
     */
    private static boolean isBoxCached(JavaConstant source) {
        switch (source.getJavaKind()) {
            case Boolean:
                return true;
            case Char:
                return source.asInt() <= 127;
            case Byte:
            case Short:
            case Int:
                return source.asInt() >= -128 && source.asInt() <= 127;
            case Long:
                return source.asLong() >= -128 && source.asLong() <= 127;
            case Float:
            case Double:
                return false;
            default:
                throw new IllegalArgumentException("unexpected kind " + source.getJavaKind());
        }
    }

    @Override
    public JavaConstant boxPrimitive(JavaConstant source) {
        if (source == null || !source.getJavaKind().isPrimitive() || !isBoxCached(source)) {
            return null;
        }
        return HotSpotObjectConstantImpl.forObject(source.asBoxedPrimitive());
    }

    @Override
    public JavaConstant unboxPrimitive(JavaConstant source) {
        if (source == null || !source.getJavaKind().isObject()) {
            return null;
        }
        if (source.isNull()) {
            return null;
        }
        return JavaConstant.forBoxedPrimitive(((HotSpotObjectConstantImpl) source).object());
    }

    @Override
    public JavaConstant forString(String value) {
        return HotSpotObjectConstantImpl.forObject(value);
    }

    public JavaConstant forObject(Object value) {
        return HotSpotObjectConstantImpl.forObject(value);
    }

    @Override
    public ResolvedJavaType asJavaType(Constant constant) {
        if (constant instanceof HotSpotObjectConstant) {
            Object obj = ((HotSpotObjectConstantImpl) constant).object();
            if (obj instanceof Class) {
                return runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType((Class<?>) obj);
            }
        }
        if (constant instanceof HotSpotMetaspaceConstant) {
            MetaspaceWrapperObject obj = HotSpotMetaspaceConstantImpl.getMetaspaceObject(constant);
            if (obj instanceof HotSpotResolvedObjectTypeImpl) {
                return (ResolvedJavaType) obj;
            }
        }
        return null;
    }

    @Override
    public JavaConstant readFieldValue(ResolvedJavaField field, JavaConstant receiver) {
        HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
        if (hotspotField.isStatic()) {
            HotSpotResolvedJavaType holder = (HotSpotResolvedJavaType) hotspotField.getDeclaringClass();
            if (holder.isInitialized()) {
                return memoryAccess.readFieldValue(hotspotField, holder.mirror(), field.isVolatile());
            }
        } else {
            if (receiver.isNonNull()) {
                Object object = ((HotSpotObjectConstantImpl) receiver).object();
                if (hotspotField.isInObject(receiver)) {
                    return memoryAccess.readFieldValue(hotspotField, object, field.isVolatile());
                }
            }
        }
        return null;
    }

    @Override
    public JavaConstant asJavaClass(ResolvedJavaType type) {
        return HotSpotObjectConstantImpl.forObject(((HotSpotResolvedJavaType) type).mirror());
    }

    @Override
    public Constant asObjectHub(ResolvedJavaType type) {
        if (type instanceof HotSpotResolvedObjectType) {
            return ((HotSpotResolvedObjectType) type).klass();
        } else {
            throw JVMCIError.unimplemented();
        }
    }
}