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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file, and Oracle licenses the original version of this file under the BSD
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/*
   Copyright 2009-2015 Attila Szegedi

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:
   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in the
     documentation and/or other materials provided with the distribution.
   * Neither the name of the copyright holder nor the names of
     contributors may be used to endorse or promote products derived from
     this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
   BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
   BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package jdk.dynalink.linker.support;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import jdk.dynalink.DynamicLinkerFactory;
import jdk.dynalink.linker.MethodHandleTransformer;

Default implementation for a DynamicLinkerFactory.setInternalObjectsFilter(MethodHandleTransformer) that delegates to a pair of filtering method handles. It takes a method handle of Object(Object) type for filtering parameter values and another one of the same type for filtering return values. It applies them as parameter and return value filters on method handles passed to its transform(MethodHandle) method, on those parameters and return values that are declared to have type Object. Also handles method handles that support variable
arity calls with a last Object[] parameter. You can broadly think of the parameter filter as being a wrapping method for exposing internal runtime objects wrapped into an adapter with some public interface, and the return value filter as being its inverse unwrapping method. /**
 * Default implementation for a
 * {@link DynamicLinkerFactory#setInternalObjectsFilter(MethodHandleTransformer)}
 * that delegates to a pair of filtering method handles. It takes a method
 * handle of {@code Object(Object)} type for filtering parameter values and
 * another one of the same type for filtering return values. It applies them as
 * parameter and return value filters on method handles passed to its
 * {@link #transform(MethodHandle)} method, on those parameters and return values
 * that are declared to have type {@link Object}. Also handles
 * {@link MethodHandle#isVarargsCollector() method handles that support variable
 * arity calls} with a last {@code Object[]} parameter. You can broadly think of
 * the parameter filter as being a wrapping method for exposing internal runtime
 * objects wrapped into an adapter with some public interface, and the return
 * value filter as being its inverse unwrapping method.
 */
public class DefaultInternalObjectFilter implements MethodHandleTransformer {
    private static final MethodHandle FILTER_VARARGS = new Lookup(MethodHandles.lookup()).findStatic(
            DefaultInternalObjectFilter.class, "filterVarArgs", MethodType.methodType(Object[].class, MethodHandle.class, Object[].class));

    private final MethodHandle parameterFilter;
    private final MethodHandle returnFilter;
    private final MethodHandle varArgFilter;

    
Creates a new filter.
Params:
parameterFilter – the filter for method parameters. Must be of type Object(Object), or null.
returnFilter – the filter for return values. Must be of type Object(Object), or null.
Throws:
IllegalArgumentException – if one or both filters are not of the
expected type./**
     * Creates a new filter.
     * @param parameterFilter the filter for method parameters. Must be of type
     * {@code Object(Object)}, or {@code null}.
     * @param returnFilter the filter for return values. Must be of type
     * {@code Object(Object)}, or {@code null}.
     * @throws IllegalArgumentException if one or both filters are not of the
     * expected type.
     */
    public DefaultInternalObjectFilter(final MethodHandle parameterFilter, final MethodHandle returnFilter) {
        this.parameterFilter = checkHandle(parameterFilter, "parameterFilter");
        this.returnFilter = checkHandle(returnFilter, "returnFilter");
        this.varArgFilter = parameterFilter == null ? null : FILTER_VARARGS.bindTo(parameterFilter);
    }

    @Override
    public MethodHandle transform(final MethodHandle target) {
        assert target != null;
        MethodHandle[] filters = null;
        final MethodType type = target.type();
        final boolean isVarArg = target.isVarargsCollector();
        final int paramCount = type.parameterCount();
        final MethodHandle paramsFiltered;
        // Filter parameters
        if (parameterFilter != null) {
            int firstFilter = -1;
            // Ignore receiver, start from argument 1
            for(int i = 1; i < paramCount; ++i) {
                final Class<?> paramType = type.parameterType(i);
                final boolean filterVarArg = isVarArg && i == paramCount - 1 && paramType == Object[].class;
                if (filterVarArg || paramType == Object.class) {
                    if (filters == null) {
                        firstFilter = i;
                        filters = new MethodHandle[paramCount - firstFilter];
                    }
                    filters[i - firstFilter] = filterVarArg ? varArgFilter : parameterFilter;
                }
            }
            paramsFiltered = filters != null ? MethodHandles.filterArguments(target, firstFilter, filters) : target;
        } else {
            paramsFiltered = target;
        }
        // Filter return value if needed
        final MethodHandle returnFiltered = returnFilter != null && type.returnType() == Object.class ? MethodHandles.filterReturnValue(paramsFiltered, returnFilter) : paramsFiltered;
        // Preserve varargs collector state
        return isVarArg && !returnFiltered.isVarargsCollector() ? returnFiltered.asVarargsCollector(type.parameterType(paramCount - 1)) : returnFiltered;

    }

    private static MethodHandle checkHandle(final MethodHandle handle, final String handleKind) {
        if (handle != null) {
            final MethodType objectObjectType = MethodType.methodType(Object.class, Object.class);
            if (!handle.type().equals(objectObjectType)) {
                throw new IllegalArgumentException("Method type for " + handleKind + " must be " + objectObjectType);
            }
        }
        return handle;
    }

    @SuppressWarnings("unused")
    private static Object[] filterVarArgs(final MethodHandle parameterFilter, final Object[] args) throws Throwable {
        Object[] newArgs = null;
        for(int i = 0; i < args.length; ++i) {
            final Object arg = args[i];
            final Object newArg = parameterFilter.invokeExact(arg);
            if (arg != newArg) {
                if (newArgs == null) {
                    newArgs = args.clone();
                }
                newArgs[i] = newArg;
            }
        }
        return newArgs == null ? args : newArgs;
    }
}