// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QV4JSCALL_H
#define QV4JSCALL_H

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//

#include "qv4object_p.h"
#include "qv4function_p.h"
#include "qv4functionobject_p.h"
#include "qv4context_p.h"
#include "qv4scopedvalue_p.h"
#include "qv4stackframe_p.h"
#include "qv4qobjectwrapper_p.h"
#include <private/qv4alloca_p.h>

QT_BEGIN_NAMESPACE

namespace QV4 {

template<typename Args>
CallData *callDatafromJS(const Scope &scope, const Args *args, const FunctionObject *f = nullptr)
{
    int size = int(offsetof(QV4::CallData, args)/sizeof(QV4::Value)) + args->argc;
    CallData *ptr = reinterpret_cast<CallData *>(scope.alloc<Scope::Uninitialized>(size));
    ptr->function = Encode::undefined();
    ptr->context = Encode::undefined();
    ptr->accumulator = Encode::undefined();
    ptr->thisObject = args->thisObject ? args->thisObject->asReturnedValue() : Encode::undefined();
    ptr->newTarget = Encode::undefined();
    ptr->setArgc(args->argc);
    if (args->argc)
        memcpy(ptr->args, args->args, args->argc*sizeof(Value));
    if (f)
        ptr->function = f->asReturnedValue();
    return ptr;
}

struct JSCallArguments
{
    JSCallArguments(const Scope &scope, int argc = 0)
        : thisObject(scope.alloc()), args(scope.alloc(argc)), argc(argc)
    {
    }

    CallData *callData(const Scope &scope, const FunctionObject *f = nullptr) const
    {
        return callDatafromJS(scope, this, f);
    }

    Value *thisObject;
    Value *args;
    const int argc;
};

struct JSCallData
{
    JSCallData(const Value *thisObject, const Value *argv, int argc)
        : thisObject(thisObject), args(argv), argc(argc)
    {
    }

    Q_IMPLICIT JSCallData(const JSCallArguments &args)
        : thisObject(args.thisObject), args(args.args), argc(args.argc)
    {
    }

    CallData *callData(const Scope &scope, const FunctionObject *f = nullptr) const
    {
        return callDatafromJS(scope, this, f);
    }

    const Value *thisObject;
    const Value *args;
    const int argc;
};

inline
ReturnedValue FunctionObject::callAsConstructor(const JSCallData &data) const
{
    return callAsConstructor(data.args, data.argc, this);
}

inline
ReturnedValue FunctionObject::call(const JSCallData &data) const
{
    return call(data.thisObject, data.args, data.argc);
}

void populateJSCallArguments(ExecutionEngine *v4, JSCallArguments &jsCall, int argc,
                             void **args, const QMetaType *types);

struct ScopedStackFrame
{
    ScopedStackFrame(const Scope &scope, ExecutionContext *context)
        : engine(scope.engine)
    {
        if (auto currentFrame = engine->currentStackFrame) {
            frame.init(currentFrame->v4Function, nullptr, context, nullptr, nullptr, 0);
            frame.instructionPointer = currentFrame->instructionPointer;
        } else {
            frame.init(nullptr, nullptr, context, nullptr, nullptr, 0);
        }
        frame.push(engine);
    }

    ~ScopedStackFrame()
    {
        frame.pop(engine);
    }

private:
    ExecutionEngine *engine = nullptr;
    MetaTypesStackFrame frame;
};

template<typename Callable>
ReturnedValue convertAndCall(
        ExecutionEngine *engine, const QQmlPrivate::TypedFunction *aotFunction,
        const Value *thisObject, const Value *argv, int argc, Callable call)
{
    const qsizetype numFunctionArguments = aotFunction->argumentTypes.size();
    Q_ALLOCA_VAR(void *, values, (numFunctionArguments + 1) * sizeof(void *));
    Q_ALLOCA_VAR(QMetaType, types, (numFunctionArguments + 1) * sizeof(QMetaType));

    for (qsizetype i = 0; i < numFunctionArguments; ++i) {
        const QMetaType argumentType = aotFunction->argumentTypes[i];
        types[i + 1] = argumentType;
        if (const qsizetype argumentSize = argumentType.sizeOf()) {
            Q_ALLOCA_VAR(void, argument, argumentSize);
            argumentType.construct(argument);
            if (i < argc)
                ExecutionEngine::metaTypeFromJS(argv[i], argumentType, argument);
            values[i + 1] = argument;
        } else {
            values[i + 1] = nullptr;
        }
    }

    Q_ALLOCA_DECLARE(void, returnValue);
    types[0] = aotFunction->returnType;
    if (const qsizetype returnSize = types[0].sizeOf()) {
        Q_ALLOCA_ASSIGN(void, returnValue, returnSize);
        values[0] = returnValue;
    } else {
        values[0] = nullptr;
    }

    if (const QV4::QObjectWrapper *cppThisObject = thisObject
                ? thisObject->as<QV4::QObjectWrapper>()
                : nullptr) {
        call(cppThisObject->object(), values, types, argc);
    } else {
        call(nullptr, values, types, argc);
    }

    ReturnedValue result;
    if (values[0]) {
        result = engine->metaTypeToJS(types[0], values[0]);
        types[0].destruct(values[0]);
    } else {
        result = Encode::undefined();
    }

    for (qsizetype i = 1, end = numFunctionArguments + 1; i < end; ++i)
        types[i].destruct(values[i]);

    return result;
}

template<typename Callable>
bool convertAndCall(ExecutionEngine *engine, QObject *thisObject,
                    void **a, const QMetaType *types, int argc, Callable call)
{
    Scope scope(engine);
    QV4::JSCallArguments jsCallData(scope, argc);

    for (int ii = 0; ii < argc; ++ii)
        jsCallData.args[ii] = engine->metaTypeToJS(types[ii + 1], a[ii + 1]);

    ScopedObject jsThisObject(scope);
    if (thisObject) {
        // The result of wrap() can only be null, undefined, or an object.
        jsThisObject = QV4::QObjectWrapper::wrap(engine, thisObject);
        if (!jsThisObject)
            jsThisObject = engine->globalObject;
    } else {
        jsThisObject = engine->globalObject;
    }

    ScopedValue jsResult(scope, call(jsThisObject, jsCallData.args, argc));
    void *result = a[0];
    if (!result)
        return !jsResult->isUndefined();

    const QMetaType resultType = types[0];
    if (scope.hasException()) {
        // Clear the return value
        resultType.construct(result);
    } else {
        // When the return type is QVariant, JS objects are to be returned as
        // QJSValue wrapped in QVariant. metaTypeFromJS unwraps them, unfortunately.
        if (resultType == QMetaType::fromType<QVariant>()) {
            new (result) QVariant(ExecutionEngine::toVariant(jsResult, QMetaType {}));
        } else {
            resultType.construct(result);
            ExecutionEngine::metaTypeFromJS(jsResult, resultType, result);
        }
    }
    return !jsResult->isUndefined();
}

template<typename Callable>
ReturnedValue coerceAndCall(
        ExecutionEngine *engine, const QQmlPrivate::TypedFunction *typedFunction,
        const Value *thisObject, const Value *argv, int argc, Callable call)
{
    Scope scope(engine);
    QV4::JSCallArguments jsCallData(scope, argc);

    const qsizetype numFunctionArguments = typedFunction->argumentTypes.size();
    for (qsizetype i = 0; i < numFunctionArguments; ++i) {
        const QMetaType argumentType = typedFunction->argumentTypes[i];
        if (const qsizetype argumentSize = argumentType.sizeOf()) {
            Q_ALLOCA_VAR(void, argument, argumentSize);
            argumentType.construct(argument);
            if (i < argc)
                ExecutionEngine::metaTypeFromJS(argv[i], argumentType, argument);
            jsCallData.args[i] = engine->metaTypeToJS(argumentType, argument);
        } else {
            jsCallData.args[i] = argv[i];
        }
    }

    ScopedValue result(scope, call(thisObject, jsCallData.args, argc));
    const QMetaType returnType = typedFunction->returnType;
    if (const qsizetype returnSize = returnType.sizeOf()) {
        Q_ALLOCA_VAR(void, returnValue, returnSize);
        if (scope.hasException()) {
            returnType.construct(returnValue);
        } else if (returnType == QMetaType::fromType<QVariant>()) {
            new (returnValue) QVariant(ExecutionEngine::toVariant(result, QMetaType {}));
        } else {
            returnType.construct(returnValue);
            ExecutionEngine::metaTypeFromJS(result, returnType, returnValue);
        }
        return engine->metaTypeToJS(returnType, returnValue);
    }
    return result->asReturnedValue();
}

// Note: \a to is unininitialized here! This is in contrast to most other related functions.
inline void coerce(
        ExecutionEngine *engine, QMetaType fromType, const void *from, QMetaType toType, void *to)
{
    if ((fromType.flags() & QMetaType::PointerToQObject)
        && (toType.flags() & QMetaType::PointerToQObject)) {
        QObject *fromObj = *static_cast<QObject * const*>(from);
        *static_cast<QObject **>(to)
                = (fromObj && fromObj->metaObject()->inherits(toType.metaObject()))
                ? fromObj
                : nullptr;
        return;
    }

    if (toType == QMetaType::fromType<QVariant>()) {
        new (to) QVariant(fromType, from);
        return;
    }

    if (toType == QMetaType::fromType<QJSPrimitiveValue>()) {
        new (to) QJSPrimitiveValue(fromType, from);
        return;
    }

    if (fromType == QMetaType::fromType<QVariant>()) {
        const QVariant *fromVariant = static_cast<const QVariant *>(from);
        if (fromVariant->metaType() == toType)
            toType.construct(to, fromVariant->data());
        else
            coerce(engine, fromVariant->metaType(), fromVariant->data(), toType, to);
        return;
    }

    // TODO: This is expensive. We might establish a direct C++-to-C++ type coercion, like we have
    //       will generate code that passes the right arguments.
    //       for JS-to-JS. However, we shouldn't need this very often. Most of the time the compiler
    if (toType.flags() & QMetaType::NeedsConstruction)
        toType.construct(to);
    QV4::Scope scope(engine);
    QV4::ScopedValue value(scope, engine->fromData(fromType, from));
    if (!ExecutionEngine::metaTypeFromJS(value, toType, to))
        QMetaType::convert(fromType, from, toType, to);
}

template<typename TypedFunction, typename Callable>
void coerceAndCall(
        ExecutionEngine *engine, const TypedFunction *typedFunction,
        void **argv, const QMetaType *types, int argc, Callable call)
{
    const qsizetype numFunctionArguments = typedFunction->parameterCount();

    Q_ALLOCA_DECLARE(void *, transformedArguments);
    Q_ALLOCA_DECLARE(void, transformedResult);

    const QMetaType returnType = typedFunction->returnMetaType();
    const QMetaType frameReturn = types[0];
    bool returnsQVariantWrapper = false;
    if (argv[0] && returnType != frameReturn) {
        Q_ALLOCA_ASSIGN(void *, transformedArguments, (numFunctionArguments + 1) * sizeof(void *));
        memcpy(transformedArguments, argv, (argc + 1) * sizeof(void *));

        if (frameReturn == QMetaType::fromType<QVariant>()) {
            QVariant *returnValue = static_cast<QVariant *>(argv[0]);
            *returnValue = QVariant(returnType);
            transformedResult = transformedArguments[0] = returnValue->data();
            returnsQVariantWrapper = true;
        } else if (returnType.sizeOf() > 0) {
            Q_ALLOCA_ASSIGN(void, transformedResult, returnType.sizeOf());
            transformedArguments[0] = transformedResult;
            if (returnType.flags() & QMetaType::NeedsConstruction)
                returnType.construct(transformedResult);
        } else {
            transformedResult = transformedArguments[0] = &argc; // Some non-null marker value
        }
    }

    for (qsizetype i = 0; i < numFunctionArguments; ++i) {
        const bool isValid = argc > i;
        const QMetaType frameType = isValid ? types[i + 1] : QMetaType();

        const QMetaType argumentType = typedFunction->parameterMetaType(i);
        if (isValid && argumentType == frameType)
            continue;

        if (transformedArguments == nullptr) {
            Q_ALLOCA_ASSIGN(void *, transformedArguments, (numFunctionArguments + 1) * sizeof(void *));
            memcpy(transformedArguments, argv, (argc + 1) * sizeof(void *));
        }

        if (argumentType.sizeOf() == 0) {
            transformedArguments[i + 1] = nullptr;
            continue;
        }

        void *frameVal = isValid ? argv[i + 1] : nullptr;
        if (isValid && frameType == QMetaType::fromType<QVariant>()) {
            QVariant *variant = static_cast<QVariant *>(frameVal);

            const QMetaType variantType = variant->metaType();
            if (variantType == argumentType) {
                // Slightly nasty, but we're allowed to do this.
                // We don't want to destruct() the QVariant's data() below.
                transformedArguments[i + 1] = argv[i + 1] = variant->data();
            } else {
                Q_ALLOCA_VAR(void, arg, argumentType.sizeOf());
                coerce(engine, variantType, variant->constData(), argumentType, arg);
                transformedArguments[i + 1] = arg;
            }
            continue;
        }

        Q_ALLOCA_VAR(void, arg, argumentType.sizeOf());

        if (isValid)
            coerce(engine, frameType, frameVal, argumentType, arg);
        else
            argumentType.construct(arg);

        transformedArguments[i + 1] = arg;
    }

    if (!transformedArguments) {
        call(argv, numFunctionArguments);
        return;
    }

    call(transformedArguments, numFunctionArguments);

    if (transformedResult && !returnsQVariantWrapper) {
        if (frameReturn.sizeOf() > 0) {
            if (frameReturn.flags() & QMetaType::NeedsDestruction)
                frameReturn.destruct(argv[0]);
            coerce(engine, returnType, transformedResult, frameReturn, argv[0]);
        }
        if (returnType.flags() & QMetaType::NeedsDestruction)
            returnType.destruct(transformedResult);
    }

    for (qsizetype i = 0; i < numFunctionArguments; ++i) {
        void *arg = transformedArguments[i + 1];
        if (arg == nullptr)
            continue;
        if (i >= argc || arg != argv[i + 1]) {
            const QMetaType argumentType = typedFunction->parameterMetaType(i);
            if (argumentType.flags() & QMetaType::NeedsDestruction)
                argumentType.destruct(arg);
        }
    }
}

} // namespace QV4

QT_END_NAMESPACE

#endif // QV4JSCALL_H