functional.h

/* Copyright (c) 2024 Julian Benda
 *
 * This file is part of inkCPP which is released under MIT license.
 * See file LICENSE.txt or go to
 * https://github.com/JBenda/inkcpp for full license details.
 */
#pragma once
 
#include "config.h"
#include "list.h"
#include "traits.h"
#include "system.h"
#include "types.h"
 
#ifdef INK_ENABLE_UNREAL
#   include "../InkVar.h"
#endif
 
namespace ink::runtime::internal
{
class basic_eval_stack;
class string_table;
class list_table;
 
class callback_base
{
public:
    virtual void call(ink::runtime::value, ink::optional<ink::runtime::value>) = 0;
    virtual ~callback_base()                                                   = default;
};
 
template<typename F>
class callback final : public callback_base
{
    using traits = function_traits<F>;
    static_assert(traits::arity < 3);
 
    template<ink::runtime::value::Type Ty>
    void call_functor(ink::runtime::value new_val, ink::optional<ink::runtime::value> old_val)
    {
        if constexpr (traits::arity == 2) {
            if (old_val.has_value()) {
                functor(
                    new_val.get<Ty>(),
                    typename traits::template argument<1>::type{old_val.value().get<Ty>()}
                );
            } else {
                functor(new_val.get<Ty>(), ink::nullopt);
            }
        } else {
            functor(new_val.get<Ty>());
        }
    }
 
public:
    callback(const callback&)            = delete;
    callback(callback&&)                 = delete;
    callback& operator=(const callback&) = delete;
    callback& operator=(callback&&)      = delete;
 
    callback(F functor)
        : functor(functor)
    {
    }
 
    virtual void call(ink::runtime::value new_val, ink::optional<ink::runtime::value> old_val)
    {
        using value     = ink::runtime::value;
        auto check_type = [&new_val, &old_val](value::Type type) {
            inkAssert(
                new_val.type == type, "Missmatch type for variable observer: expected %i, got %i",
                static_cast<int>(type), static_cast<int>(new_val.type)
            );
            if constexpr (traits::arity == 2) {
                if (old_val.has_value() && old_val.value().type != type) {
                    inkFail(
                        "Missmatch type for variable observers old value: expected optional<%i> got "
                        "optional<%i>",
                        static_cast<int>(type), static_cast<int>(old_val.value().type)
                    );
                }
            }
        };
        if constexpr (traits::arity > 0) {
            using arg_t = typename remove_cvref<typename traits::template argument<0>::type>::type;
            if constexpr (is_same<arg_t, value>::value) {
                if constexpr (traits::arity == 2) {
                    functor(new_val, old_val);
                } else {
                    functor(new_val);
                }
            } else if constexpr (is_same<arg_t, bool>::value) {
                check_type(value::Type::Bool);
                call_functor<value::Type::Bool>(new_val, old_val);
            } else if constexpr (is_same<arg_t, uint32_t>::value) {
                check_type(value::Type::Uint32);
                call_functor<value::Type::Uint32>(new_val, old_val);
            } else if constexpr (is_same<arg_t, int32_t>::value) {
                check_type(value::Type::Int32);
                call_functor<value::Type::Int32>(new_val, old_val);
            } else if constexpr (is_same<arg_t, const char*>::value) {
                check_type(value::Type::String);
                call_functor<value::Type::String>(new_val, old_val);
            } else if constexpr (is_same<arg_t, float>::value) {
                check_type(value::Type::Float);
                call_functor<value::Type::Float>(new_val, old_val);
            } else if constexpr (is_same<arg_t, list_interface*>::value) {
                check_type(value::Type::List);
                call_functor<value::Type::List>(new_val, old_val);
            } else {
                static_assert(
                    always_false<arg_t>::value, "Unsupported value for variable observer callback!"
                );
            }
        } else {
            functor();
        }
    }
 
private:
    F functor;
};
 
// base function container with virtual callback methods
class function_base
{
public:
    function_base(bool lookaheadSafe)
        : _lookaheadSafe(lookaheadSafe)
    {
    }
 
    virtual ~function_base() {}
 
    // calls the underlying function object taking parameters from a stack
    // TODO: remove ?
#ifdef INK_ENABLE_UNREAL
    virtual void
        call(basic_eval_stack* stack, size_t length, string_table& strings, list_table& lists)
        = 0;
#else
    virtual void
        call(basic_eval_stack* stack, size_t length, string_table& strings, list_table& lists)
        = 0;
#endif
 
    bool lookaheadSafe() const { return _lookaheadSafe; }
 
protected:
    bool _lookaheadSafe;
    // used to hide basic_eval_stack and value definitions
    template<typename T>
    static T pop(basic_eval_stack* stack, list_table& lists);
 
    // used to hide basic_eval_stack and value definitions
    template<typename T>
    static void push(basic_eval_stack* stack, const T& value);
 
    static void push_void(basic_eval_stack* stack);
 
    // string special push
    static void push_string(basic_eval_stack* stack, const char* dynamic_string);
 
    // used to hide string_table definitions
    static char* allocate(string_table& strings, ink::size_t len);
};
 
// Stores a Callable function object and forwards calls to it
template<typename F>
class function : public function_base
{
public:
    function(F functor, bool lookaheadSafe)
        : function_base(lookaheadSafe)
        , functor(functor)
    {
    }
 
    // calls the underlying function using arguments on the stack
    virtual void call(
        basic_eval_stack* stack, size_t length, string_table& strings, list_table& lists
    ) override
    {
        call(stack, length, strings, lists, GenSeq<traits::arity>());
    }
 
private:
    // Callable functor object
    F functor;
 
    // function traits
    using traits = function_traits<F>;
 
    // argument types
    template<int index>
    using arg_type = typename function_traits<F>::template argument<index>::type;
 
    // pops an argument from the stack using the function-type
    template<int index>
    arg_type<index> pop_arg(basic_eval_stack* stack, list_table& lists)
    {
        // todo - type assert?
        return pop<arg_type<index>>(stack, lists);
    }
 
    static constexpr bool is_array_call()
    {
        if constexpr (traits::arity == 2) {
            return is_same<
                const ink::runtime::value*, typename traits::template argument<1>::type>::value;
        } else {
            return false;
        }
    }
 
    template<size_t... Is>
    void
        call(basic_eval_stack* stack, size_t length, string_table& strings, list_table& lists, seq<Is...>)
    {
        inkAssert(
            is_array_call() || sizeof...(Is) == length,
            "Attempting to call functor with too few/many arguments"
        );
        static_assert(sizeof...(Is) == traits::arity);
        if_t<is_array_call(), value[config::maxArrayCallArity], char> vals;
        if constexpr (is_array_call()) {
            inkAssert(
                length <= config::maxArrayCallArity,
                "AIttampt to call array call with more arguments then supportet, please change in "
                "config"
            );
            for (size_t i = 0; i < length; ++i) {
                vals[i] = pop<ink::runtime::value>(stack, lists);
            }
        }
        // void functions
        if constexpr (is_same<void, typename traits::return_type>::value) {
            // Just evaluevaluatelate
            if constexpr (is_array_call()) {
                functor(length, vals);
            } else {
                functor(pop_arg<Is>(stack, lists)...);
            }
 
            // Ink expects us to push something
            push_void(stack);
        } else {
            typename traits::return_type res;
            if constexpr (is_array_call()) {
                res = functor(length, vals);
            } else {
                res = functor(pop_arg<Is>(stack, lists)...);
            }
            if constexpr (is_string<typename traits::return_type>::value) {
                // SPECIAL: The result of the functor is a string type
                //  in order to store it in the inkcpp interpreter we
                //  need to store it in our allocated string table
                // Get string length
                size_t len = string_handler<typename traits::return_type>::length(res);
 
                // Get source and allocate buffer
                char* buffer = allocate(strings, len + 1);
                string_handler<typename traits::return_type>::src_copy(res, buffer);
 
                // push string result
                push_string(stack, buffer);
            } else if constexpr (is_same<value, remove_cvref<typename traits::return_type>>::value) {
                if (res.type() == ink::runtime::value::Type::String) {
                    auto   src    = res.template get<ink::runtime::value::Type::String>();
                    size_t len    = string_handler<decltype(src)>::length(src);
                    char*  buffer = allocate(strings, len + 1);
                    string_handler<decltype(src)>::src_copy(src, buffer);
                    push_string(stack, buffer);
                } else {
                    push(stack, res);
                }
            } else {
                // Evaluate and push the result onto the stack
                push(stack, res);
            }
        }
    }
};
 
#ifdef INK_ENABLE_UNREAL
template<typename D>
class function_array_delegate : public function_base
{
public:
    function_array_delegate(const D& del, bool lookaheadSafe)
        : function_base(lookaheadSafe)
        , invocableDelegate(del)
    {
    }
 
    // calls the underlying delegate using arguments on the stack
    virtual void call(
        basic_eval_stack* stack, size_t length, string_table& strings, list_table& lists
    ) override
    {
        constexpr bool RET_VOID
            = is_same<typename function_traits<decltype(&D::Execute)>::return_type, void>::value;
        // Create variable array
        TArray<FInkVar> variables;
        for (size_t i = 0; i < length; i++) {
            variables.Add(pop<FInkVar>(stack, lists));
        }
        if constexpr (RET_VOID) {
            invocableDelegate.Execute(variables);
            push(stack, 0);
        } else {
 
            auto                ret    = invocableDelegate.Execute(variables);
            ink::runtime::value result = ret.to_value();
            if (result.type == ink::runtime::value::Type::String) {
                const char* src    = result.get<ink::runtime::value::Type::String>();
                size_t      len    = string_handler<const char*>::length(src);
                char*       buffer = allocate(strings, len + 1);
                char*       ptr    = buffer;
                while (*src != '\0')
                    *(ptr++) = *(src++);
                *ptr   = 0;
                result = ink::runtime::value(buffer);
            }
            push(stack, result);
        }
    }
 
private:
    D invocableDelegate;
};
#endif
} // namespace ink::runtime::internal