//
// SqratTable: Table Binding
//

//
// Copyright (c) 2009 Brandon Jones
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
//  1. The origin of this software must not be misrepresented; you must not
//  claim that you wrote the original software. If you use this software
//  in a product, an acknowledgment in the product documentation would be
//  appreciated but is not required.
//
//  2. Altered source versions must be plainly marked as such, and must not be
//  misrepresented as being the original software.
//
//  3. This notice may not be removed or altered from any source
//  distribution.
//

#pragma once

#include <squirrelex.h>

#include <string.h>

#include "sqratObject.h"
#include "sqratFunction.h"
#include "sqratGlobalMethods.h"

namespace Sqrat {

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// The base class for Table that implements almost all of its functionality
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class TableBase : public Object {
public:

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Default constructor (null)
    ///
    /// \param v VM that the table will exist in
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase() : Object(true) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the TableBase from an Object that already exists
    ///
    /// \param obj An Object that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(const Object& obj) : Object(obj) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the TableBase from an Object that already exists
    ///
    /// \param obj An Object that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(Object&& obj) noexcept : Object(std::move(obj)) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the TableBase from an Object that already exists
    ///
    /// \param obj An Object that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(const LightObj& obj) : Object(obj) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the TableBase from an Object that already exists
    ///
    /// \param obj An Object that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(LightObj&& obj) : Object(std::move(obj)) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the TableBase from a HSQOBJECT and HSQUIRRELVM that already exist
    ///
    /// \param o Squirrel object that should already represent a Squirrel table
    /// \param v Squirrel VM that contains the Squirrel object given
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(HSQOBJECT o, HSQUIRRELVM v = SqVM()) : Object(o, v) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Copy constructor
    ///
    /// \param st TableBase to copy
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(const TableBase& st) : Object(st) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Move constructor
    ///
    /// \param st TableBase to move
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase(TableBase&& st) noexcept : Object(std::move(st)) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Assignment operator
    ///
    /// \param st TableBase to copy
    ///
    /// \return The TableBase itself
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase& operator=(const TableBase& st) {
        Object::operator = (st);
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Assignment operator
    ///
    /// \param st TableBase to move
    ///
    /// \return The TableBase itself
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase& operator=(TableBase&& st) noexcept {
        Object::operator = (std::move(st));
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Binds a Table or Class to the Table (can be used to facilitate namespaces)
    ///
    /// \param name The key in the table being assigned a Table or Class
    /// \param obj  Table or Class that is being placed in the table
    ///
    /// \remarks
    /// Bind cannot be called "inline" like other functions because it introduces order-of-initialization bugs.
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    void Bind(const SQChar* name, Object& obj) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, GetObj());
        sq_pushstring(vm, name, -1);
        sq_pushobject(vm, obj.GetObj());
        sq_newslot(vm, -3, false);
        sq_pop(vm,1); // pop table
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Binds a Table or Class to the Table (can be used to facilitate namespaces)
    ///
    /// \param name The key in the table being assigned a Table or Class
    /// \param obj  Table or Class that is being placed in the table
    ///
    /// \remarks
    /// Bind cannot be called "inline" like other functions because it introduces order-of-initialization bugs.
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    void Bind(const SQChar* name, LightObj& obj) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, GetObj());
        sq_pushstring(vm, name, -1);
        sq_pushobject(vm, obj.GetObj());
        sq_newslot(vm, -3, false);
        sq_pop(vm,1); // pop table
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Binds a raw Squirrel closure to the Table
    ///
    /// \param name The key in the table being assigned a function
    /// \param func Squirrel function that is being placed in the Table
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase& SquirrelFunc(const SQChar* name, SQFUNCTION func) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, GetObj());
        sq_pushstring(vm, name, -1);
        sq_newclosure(vm, func, 0);
        // Set the closure name (for debug purposes)
        sq_setnativeclosurename(vm, -1, name);
        sq_newslot(vm, -3, false);
        sq_pop(vm,1); // pop table
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Binds a raw Squirrel closure to the Table
    ///
    /// \param name The key in the table being assigned a function
    /// \param func Squirrel function that is being placed in the Table
    /// \param pnum Number of parameters the function expects.
    /// \param mask Types of parameters the function expects.
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    TableBase& SquirrelFunc(const SQChar* name, SQFUNCTION func, SQInteger pnum, const SQChar * mask) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, GetObj());
        sq_pushstring(vm, name, -1);
        sq_newclosure(vm, func, 0);
        // Set the closure name (for debug purposes)
        sq_setnativeclosurename(vm, -1, name);
        // Set parameter validation
        sq_setparamscheck(vm, pnum, mask);
        sq_newslot(vm, -3, false);
        sq_pop(vm,1); // pop table
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets a key in the Table to a specific value
    ///
    /// \param name The key in the table being assigned a value
    /// \param val  Value that is being placed in the Table
    ///
    /// \tparam V Type of value (usually doesnt need to be defined explicitly)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class V>
    TableBase& SetValue(const SQChar* name, const V& val) {
        BindValue<V>(name, val, false);
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets an index in the Table to a specific value
    ///
    /// \param index The index in the table being assigned a value
    /// \param val   Value that is being placed in the Table
    ///
    /// \tparam V Type of value (usually doesnt need to be defined explicitly)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class V>
    TableBase& SetValue(const SQInteger index, const V& val) {
        BindValue<V>(index, val, false);
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets a key in the Table to a specific instance (like a reference)
    ///
    /// \param name The key in the table being assigned a value
    /// \param val  Pointer to the instance that is being placed in the Table
    ///
    /// \tparam V Type of instance (usually doesnt need to be defined explicitly)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class V>
    TableBase& SetInstance(const SQChar* name, V* val) {
        BindInstance<V>(name, val, false);
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets an index in the Table to a specific instance (like a reference)
    ///
    /// \param index The index in the table being assigned a value
    /// \param val   Pointer to the instance that is being placed in the Table
    ///
    /// \tparam V Type of instance (usually doesnt need to be defined explicitly)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class V>
    TableBase& SetInstance(const SQInteger index, V* val) {
        BindInstance<V>(index, val, false);
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets a key in the Table to a specific function
    ///
    /// \param name   The key in the table being assigned a value
    /// \param method Function that is being placed in the Table
    ///
    /// \tparam F Type of function (only define this if you need to choose a certain template specialization or overload)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class F>
    TableBase& Func(const SQChar* name, F method) {
        BindFunc(name, &method, sizeof(method), SqGlobalFunc(method));
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets a key in the Table to a specific function with formatting support
    ///
    /// \param name   The key in the table being assigned a value
    /// \param method Function that is being placed in the Table
    ///
    /// \tparam F Type of function (only define this if you need to choose a certain template specialization or overload)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class F>
    TableBase& FmtFunc(const SQChar* name, F method) {
        BindFunc(name, &method, sizeof(method), SqGlobalFunc(method));
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Sets a key in the Table to a specific function and allows the key to be overloaded with functions of a different amount of arguments
    ///
    /// \param name   The key in the table being assigned a value
    /// \param method Function that is being placed in the Table
    ///
    /// \tparam F Type of function (only define this if you need to choose a certain template specialization or overload)
    ///
    /// \return The Table itself so the call can be chained
    ///
    /// \remarks
    /// Overloading in Sqrat does not work for functions with the same amount of arguments (just like in Squirrel).
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template<class F>
    TableBase& Overload(const SQChar* name, F method) {
        BindOverload(name, &method, sizeof(method), SqGlobalOverloadedFunc(method), SqOverloadFunc(method), SqGetArgCount(method));
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Checks if the given key exists in the table
    ///
    /// \param name Key to check
    ///
    /// \return True on success, otherwise false
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    bool HasKey(const SQChar* name) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, mObj);
        sq_pushstring(vm, name, -1);
        if (SQ_FAILED(sq_get(vm, -2))) {
            sq_pop(vm, 1);
            return false;
        }
        sq_pop(vm, 2);
        return true;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Returns the value at a given key
    ///
    /// \param name Key of the element
    ///
    /// \tparam T Type of value (fails if value is not of this type)
    ///
    /// \return SharedPtr containing the value (or null if failed)
    ///
    /// \remarks
    /// This function MUST have its Error handled if it occurred.
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template <typename T>
    SharedPtr<T> GetValue(const SQChar* name) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, mObj);
        sq_pushstring(vm, name, -1);
#if !defined (SCRAT_NO_ERROR_CHECKING)
        if (SQ_FAILED(sq_get(vm, -2))) {
            sq_pop(vm, 1);
            SQTHROW(vm, _SC("illegal index"));
            return SharedPtr<T>();
        }
#else
        sq_get(vm, -2);
#endif
        SQTRY()
        Var<SharedPtr<T> > entry(vm, -1);
        SQCATCH_NOEXCEPT(vm) {
            sq_pop(vm, 2);
            return SharedPtr<T>();
        }
        sq_pop(vm, 2);
        return entry.value;
        SQCATCH(vm) {
#if defined (SCRAT_USE_EXCEPTIONS)
            SQUNUSED(e); // avoid "unreferenced local variable" warning
#endif
            sq_pop(vm, 2);
            SQRETHROW(vm);
        }
        return SharedPtr<T>(); // avoid "not all control paths return a value" warning
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Returns the value at a given index
    ///
    /// \param index Index of the element
    ///
    /// \tparam T Type of value (fails if value is not of this type)
    ///
    /// \return SharedPtr containing the value (or null if failed)
    ///
    /// \remarks
    /// This function MUST have its Error handled if it occurred.
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    template <typename T>
    SharedPtr<T> GetValue(int index) {
        HSQUIRRELVM vm = SqVM();
        sq_pushobject(vm, mObj);
        sq_pushinteger(vm, index);
#if !defined (SCRAT_NO_ERROR_CHECKING)
        if (SQ_FAILED(sq_get(vm, -2))) {
            sq_pop(vm, 1);
            SQTHROW(vm, _SC("illegal index"));
            return SharedPtr<T>();
        }
#else
        sq_get(vm, -2);
#endif
        SQTRY()
        Var<SharedPtr<T> > entry(vm, -1);
        SQCATCH_NOEXCEPT(vm) {
            sq_pop(vm, 2);
            return SharedPtr<T>();
        }
        sq_pop(vm, 2);
        return entry.value;
        SQCATCH(vm) {
#if defined (SCRAT_USE_EXCEPTIONS)
            SQUNUSED(e); // avoid "unreferenced local variable" warning
#endif
            sq_pop(vm, 2);
            SQRETHROW(vm);
        }
        return SharedPtr<T>(); // avoid "not all control paths return a value" warning
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Gets a Function from a key in the Table
    ///
    /// \param name The key in the table that contains the Function
    ///
    /// \return Function found in the Table (null if failed)
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Function GetFunction(const SQChar* name) {
        HSQUIRRELVM vm = SqVM();
        HSQOBJECT funcObj;
        sq_pushobject(vm, GetObj());
        sq_pushstring(vm, name, -1);
#if !defined (SCRAT_NO_ERROR_CHECKING)
        if(SQ_FAILED(sq_get(vm, -2))) {
            sq_pop(vm, 1);
            return Function();
        }
        SQObjectType value_type = sq_gettype(vm, -1);
        if (value_type != OT_CLOSURE && value_type != OT_NATIVECLOSURE) {
            sq_pop(vm, 2);
            return Function();
        }
#else
        sq_get(vm, -2);
#endif
        sq_getstackobj(vm, -1, &funcObj);
        Function ret(GetObj(), funcObj, vm); // must addref before the pop!
        sq_pop(vm, 2);
        return ret;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Gets a Function from an index in the Table
    ///
    /// \param index The index in the table that contains the Function
    ///
    /// \return Function found in the Table (null if failed)
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Function GetFunction(const SQInteger index) {
        HSQUIRRELVM vm = SqVM();
        HSQOBJECT funcObj;
        sq_pushobject(vm, GetObj());
        sq_pushinteger(vm, index);
#if !defined (SCRAT_NO_ERROR_CHECKING)
        if(SQ_FAILED(sq_get(vm, -2))) {
            sq_pop(vm, 1);
            return Function();
        }
        SQObjectType value_type = sq_gettype(vm, -1);
        if (value_type != OT_CLOSURE && value_type != OT_NATIVECLOSURE) {
            sq_pop(vm, 2);
            return Function();
        }
#else
        sq_get(vm, -2);
#endif
        sq_getstackobj(vm, -1, &funcObj);
        Function ret(GetObj(), funcObj, vm); // must addref before the pop!
        sq_pop(vm, 2);
        return ret;
    }
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// Represents a table in Squirrel
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class Table : public TableBase {
public:
    using TableBase::TableBase;
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Default constructor (null)
    ///
    /// \remarks
    /// The Table is invalid until it is given a VM to exist in.
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table() : TableBase() {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Constructs a Table
    ///
    /// \param v VM to create the Table in
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(HSQUIRRELVM vm) : TableBase() {
        sq_newtable(vm);
        sq_getstackobj(vm,-1,&mObj);
        sq_addref(vm, &mObj);
        sq_pop(vm,1);
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the Table from an Object that already exists
    ///
    /// \param obj An Object that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(const Object& obj) : TableBase(obj) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the Table from an Object that already exists
    ///
    /// \param obj An Object that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(Object&& obj) noexcept : TableBase(std::move(obj)) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the Table from an LightObj that already exists
    ///
    /// \param obj An LightObj that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(const LightObj& obj) : TableBase(obj) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the Table from an LightObj that already exists
    ///
    /// \param obj An LightObj that should already represent a Squirrel table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(LightObj&& obj) noexcept : TableBase(std::move(obj)) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the Table from a HSQOBJECT and HSQUIRRELVM that already exist
    ///
    /// \param o Squirrel object that should already represent a Squirrel table
    /// \param v Squirrel VM that contains the Squirrel object given
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(HSQOBJECT o, HSQUIRRELVM v = SqVM()) : TableBase(o, v) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Construct the TableBase with an initial capacity
    ///
    /// \param v VM to create the Table in
    /// \param c The initial capacity of the created table
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(HSQUIRRELVM vm, SQInteger c) : TableBase() {
        sq_newtableex(vm, c);
        sq_getstackobj(vm,-1,&mObj);
        sq_addref(vm, &mObj);
        sq_pop(vm,1);
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Copy constructor
    ///
    /// \param st Table to copy
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(const Table& st) : TableBase(st) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Move constructor
    ///
    /// \param st Table to move
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table(Table&& st) noexcept : TableBase(std::move(st)) {
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Assignment operator
    ///
    /// \param st Table to copy
    ///
    /// \return The Table itself
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table& operator=(const Table& st) {
        TableBase::operator = (st);
        return *this;
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Assignment operator
    ///
    /// \param st Table to move
    ///
    /// \return The Table itself
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Table& operator=(Table&& st) noexcept {
        TableBase::operator = (std::move(st));
        return *this;
    }

};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// Table that is a reference to the Squirrel root table for a given VM
/// The Squirrel root table is usually where all globals are stored by the Squirrel language.
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class RootTable : public TableBase {
public:
    using TableBase::TableBase;
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Constructs a RootTable object to represent the given VM's root table
    ///
    /// \param v VM to get the RootTable for
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    RootTable(HSQUIRRELVM vm = SqVM()) : TableBase() {
        sq_pushroottable(vm);
        sq_getstackobj(vm,-1,&mObj);
        sq_addref(vm, &mObj);
        sq_pop(vm,1); // pop root table
    }
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// Table that is a reference to the Squirrel registry table for a given VM
/// The Squirrel registry table is where non-Squirrel code can store Squirrel objects without worrying about Squirrel code messing with them.
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class RegistryTable : public TableBase {
public:
    using TableBase::TableBase;
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Constructs a RegistryTable object to represent the given VM's registry table
    ///
    /// \param v VM to get the RegistryTable for
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    RegistryTable(HSQUIRRELVM vm = SqVM()) : TableBase() {
        sq_pushregistrytable(vm);
        sq_getstackobj(vm,-1,&mObj);
        sq_addref(vm, &mObj);
        sq_pop(vm,1); // pop the registry table
    }
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// Used to get and push Table instances to and from the stack as references (tables are always references in Squirrel)
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
template<>
struct Var<Table> {

    Table value; ///< The actual value of get operations

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Attempts to get the value off the stack at idx as a Table
    ///
    /// \param vm  Target VM
    /// \param idx Index trying to be read
    ///
    /// \remarks
    /// This function MUST have its Error handled if it occurred.
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    Var(HSQUIRRELVM vm, SQInteger idx) {
        HSQOBJECT obj;
        sq_resetobject(&obj);
        sq_getstackobj(vm,idx,&obj);
        value = Table(obj, vm);
#if !defined (SCRAT_NO_ERROR_CHECKING)
        SQObjectType value_type = sq_gettype(vm, idx);
        if (value_type != OT_TABLE) {
            SQTHROW(vm, FormatTypeError(vm, idx, _SC("table")));
        }
#endif
    }

    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    /// Called by Sqrat::PushVar to put an Table reference on the stack
    ///
    /// \param vm    Target VM
    /// \param value Value to push on to the VM's stack
    ///
    /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    static void push(HSQUIRRELVM vm, const Table& value) {
        HSQOBJECT obj;
        sq_resetobject(&obj);
        obj = value.GetObj();
        sq_pushobject(vm,obj);
    }
};


/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// Used to get and push Table instances to and from the stack as references (tables are always references in Squirrel)
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
template<>
struct Var<Table&> : Var<Table> {Var(HSQUIRRELVM vm, SQInteger idx) : Var<Table>(vm, idx) {}};


/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
/// Used to get and push Table instances to and from the stack as references (tables are always references in Squirrel)
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
template<>
struct Var<const Table&> : Var<Table> {Var(HSQUIRRELVM vm, SQInteger idx) : Var<Table>(vm, idx) {}};

}