/*

 * Copyright (c) 2010, 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

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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

 * license:

 */

/*

   Copyright 2009-2013 Attila Szegedi

*/

package jdk.dynalink.beans;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodType;

import java.lang.reflect.Array;

import java.util.StringTokenizer;

import jdk.dynalink.CallSiteDescriptor;

import jdk.dynalink.linker.LinkerServices;

import jdk.dynalink.linker.support.Guards;

import jdk.dynalink.linker.support.Lookup;

/**

 * Base class for dynamic methods that dispatch to a single target Java method or constructor. Handles adaptation of the

 * target method to a call site type (including mapping variable arity methods to a call site signature with different

 * arity).

 */

abstract class SingleDynamicMethod extends DynamicMethod {

    private static final MethodHandle CAN_CONVERT_TO = Lookup.findOwnStatic(MethodHandles.lookup(), "canConvertTo", boolean.class, LinkerServices.class, Class.class, Object.class);

    SingleDynamicMethod(final String name) {

        super(name);

    }

    /**

     * Returns true if this method is variable arity.

     * @return true if this method is variable arity.

     */

    abstract boolean isVarArgs();

    /**

     * Returns this method's native type.

     * @return this method's native type.

     */

    abstract MethodType getMethodType();

    /**

     * Given a specified call site descriptor, returns a method handle to this method's target. The target

     * should only depend on the descriptor's lookup, and it should only retrieve it (as a privileged

     * operation) when it is absolutely needed.

     * @param desc the call site descriptor to use.

     * @return the handle to this method's target method.

     */

    abstract MethodHandle getTarget(CallSiteDescriptor desc);

    @Override

    MethodHandle getInvocation(final CallSiteDescriptor callSiteDescriptor, final LinkerServices linkerServices) {

        return linkerServices.getWithLookup(()->getInvocation(getTarget(callSiteDescriptor),

                callSiteDescriptor.getMethodType(), linkerServices), callSiteDescriptor);

    }

    @Override

    SingleDynamicMethod getMethodForExactParamTypes(final String paramTypes) {

        return typeMatchesDescription(paramTypes, getMethodType()) ? this : null;

    }

    @Override

    boolean contains(final SingleDynamicMethod method) {

        return getMethodType().parameterList().equals(method.getMethodType().parameterList());

    }

    static String getMethodNameWithSignature(final MethodType type, final String methodName, final boolean withReturnType) {

        final String typeStr = type.toString();

        final int retTypeIndex = typeStr.lastIndexOf(')') + 1;

        int secondParamIndex = typeStr.indexOf(',') + 1;

        if(secondParamIndex == 0) {

            secondParamIndex = retTypeIndex - 1;

        }

        final StringBuilder b = new StringBuilder();

        if (withReturnType) {

            b.append(typeStr, retTypeIndex, typeStr.length()).append(' ');

        }

        return b.append(methodName).append('(').append(typeStr, secondParamIndex, retTypeIndex).toString();

    }

    /**

     * Given a method handle and a call site type, adapts the method handle to the call site type. Performs type

     * conversions as needed using the specified linker services, and in case that the method handle is a vararg

     * collector, matches it to the arity of the call site. The type of the return value is only changed if it can be

     * converted using a conversion that loses neither precision nor magnitude, see

     * {@link LinkerServices#asTypeLosslessReturn(MethodHandle, MethodType)}.

     * @param target the method handle to adapt

     * @param callSiteType the type of the call site

     * @param linkerServices the linker services used for type conversions

     * @return the adapted method handle.

     */

    static MethodHandle getInvocation(final MethodHandle target, final MethodType callSiteType, final LinkerServices linkerServices) {

        final MethodHandle filteredTarget = linkerServices.filterInternalObjects(target);

        final MethodType methodType = filteredTarget.type();

        final int paramsLen = methodType.parameterCount();

        final boolean varArgs = target.isVarargsCollector();

        final MethodHandle fixTarget = varArgs ? filteredTarget.asFixedArity() : filteredTarget;

        final int fixParamsLen = varArgs ? paramsLen - 1 : paramsLen;

        final int argsLen = callSiteType.parameterCount();

        if(argsLen < fixParamsLen) {

            // Less actual arguments than number of fixed declared arguments; can't invoke.

            return null;

        }

        // Method handle has the same number of fixed arguments as the call site type

        if(argsLen == fixParamsLen) {

            // Method handle that matches the number of actual arguments as the number of fixed arguments

            final MethodHandle matchedMethod;

            if(varArgs) {

                // If vararg, add a zero-length array of the expected type as the last argument to signify no variable

                // arguments.

                matchedMethod = MethodHandles.insertArguments(fixTarget, fixParamsLen, Array.newInstance(

                        methodType.parameterType(fixParamsLen).getComponentType(), 0));

            } else {

                // Otherwise, just use the method

                matchedMethod = fixTarget;

            }

            return createConvertingInvocation(matchedMethod, linkerServices, callSiteType);

        }

        // What's below only works for varargs

        if(!varArgs) {

            return null;

        }

        final Class<?> varArgType = methodType.parameterType(fixParamsLen);

        // Handle a somewhat sinister corner case: caller passes exactly one argument in the vararg position, and we

        // must handle both a prepacked vararg array as well as a genuine 1-long vararg sequence.

        if(argsLen == paramsLen) {

            final Class<?> callSiteLastArgType = callSiteType.parameterType(fixParamsLen);

            if(varArgType.isAssignableFrom(callSiteLastArgType)) {

                // Call site signature guarantees we'll always be passed a single compatible array; just link directly

                // to the method, introducing necessary conversions. Also, preserve it being a variable arity method.

                return createConvertingInvocation(filteredTarget, linkerServices, callSiteType).asVarargsCollector(

                        callSiteLastArgType);

            }

            // This method handle takes the single argument and packs it into a newly allocated single-element array. It

            // will be used when the incoming argument can't be converted to the vararg array type (the "vararg packer"

            // method).

            final MethodHandle varArgCollectingInvocation = createConvertingInvocation(collectArguments(fixTarget,

                    argsLen), linkerServices, callSiteType);

            // Is call site type assignable from an array type (e.g. Object:int[], or Object[]:String[])

            final boolean isAssignableFromArray = callSiteLastArgType.isAssignableFrom(varArgType);

            // Do we have a custom conversion that can potentially convert the call site type to an array?

            final boolean isCustomConvertible = linkerServices.canConvert(callSiteLastArgType, varArgType);

            if(!isAssignableFromArray && !isCustomConvertible) {

                // Call site signature guarantees the argument can definitely not be converted to an array (i.e. it is

                // primitive), and no conversion can help with it either. Link immediately to a vararg-packing method

                // handle.

                return varArgCollectingInvocation;

            }

            // This method handle employs language-specific conversions to convert the last argument into an array of

            // vararg type.

            final MethodHandle arrayConvertingInvocation = createConvertingInvocation(MethodHandles.filterArguments(

                    fixTarget, fixParamsLen, linkerServices.getTypeConverter(callSiteLastArgType, varArgType)),

                    linkerServices, callSiteType);

            // This method handle determines whether the value can be converted to the array of vararg type using a

            // language-specific conversion.

            final MethodHandle canConvertArgToArray = MethodHandles.insertArguments(CAN_CONVERT_TO, 0, linkerServices,

                    varArgType);

            // This one adjusts the previous one for the location of the argument and the call site type.

            final MethodHandle canConvertLastArgToArray = MethodHandles.dropArguments(canConvertArgToArray, 0,

                    MethodType.genericMethodType(fixParamsLen).parameterList()).asType(callSiteType.changeReturnType(boolean.class));

            // This one takes the previous ones and combines them into a method handle that converts the argument into

            // a vararg array when it can, otherwise falls back to the vararg packer.

            final MethodHandle convertToArrayWhenPossible = MethodHandles.guardWithTest(canConvertLastArgToArray,

                    arrayConvertingInvocation, varArgCollectingInvocation);

            if(isAssignableFromArray) {

                return MethodHandles.guardWithTest(

                        // Is incoming parameter already a compatible array?

                        Guards.isInstance(varArgType, fixParamsLen, callSiteType),

                        // Yes: just pass it to the method

                        createConvertingInvocation(fixTarget, linkerServices, callSiteType),

                        // No: either go through a custom conversion, or if it is not possible, go directly to the

                        // vararg packer.

                        isCustomConvertible ? convertToArrayWhenPossible : varArgCollectingInvocation);

            }

            // Just do the custom conversion with fallback to the vararg packer logic.

            assert isCustomConvertible;

            return convertToArrayWhenPossible;

        }

        // Remaining case: more than one vararg.

        return createConvertingInvocation(collectArguments(fixTarget, argsLen), linkerServices, callSiteType);

    }

    @SuppressWarnings("unused")

    private static boolean canConvertTo(final LinkerServices linkerServices, final Class<?> to, final Object obj) {

        return obj == null ? false : linkerServices.canConvert(obj.getClass(), to);

    }

    /**

     * Creates a method handle out of the original target that will collect the varargs for the exact component type of

     * the varArg array. Note that this will nicely trigger language-specific type converters for exactly those varargs

     * for which it is necessary when later passed to linkerServices.convertArguments().

     *

     * @param target the original method handle

     * @param parameterCount the total number of arguments in the new method handle

     * @return a collecting method handle

     */

    static MethodHandle collectArguments(final MethodHandle target, final int parameterCount) {

        final MethodType methodType = target.type();

        final int fixParamsLen = methodType.parameterCount() - 1;

        final Class<?> arrayType = methodType.parameterType(fixParamsLen);

        return target.asCollector(arrayType, parameterCount - fixParamsLen);

    }

    private static MethodHandle createConvertingInvocation(final MethodHandle sizedMethod,

            final LinkerServices linkerServices, final MethodType callSiteType) {

        return linkerServices.asTypeLosslessReturn(sizedMethod, callSiteType);

    }

    private static boolean typeMatchesDescription(final String paramTypes, final MethodType type) {

        final StringTokenizer tok = new StringTokenizer(paramTypes, ", ");

        for(int i = 1; i < type.parameterCount(); ++i) { // i = 1 as we ignore the receiver

            if(!(tok.hasMoreTokens() && typeNameMatches(tok.nextToken(), type.parameterType(i)))) {

                return false;

            }

        }

        return !tok.hasMoreTokens();

    }

    private static boolean typeNameMatches(final String typeName, final Class<?> type) {

        return  typeName.equals(typeName.indexOf('.') == -1 ? type.getSimpleName() : type.getCanonicalName());

    }

}