function.cpp

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/*
    Copyright (C) 2008 - 2025
    by David White <dave@whitevine.net>
    Part of the Battle for Wesnoth Project https://www.wesnoth.org/
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY.
 
    See the COPYING file for more details.
*/
 
#include "formula/function.hpp"
 
#include "color.hpp"
#include "formula/callable_objects.hpp"
#include "formula/debugger.hpp"
#include "game_config.hpp"
#include "game_display.hpp"
#include "log.hpp"
#include "pathutils.hpp"
#include "serialization/unicode.hpp"
 
#include <boost/algorithm/string.hpp>
#include <boost/math/constants/constants.hpp>
#include <cctype>
#include <chrono>
#include <deque>
#include <utility>
 
using namespace boost::math::constants;
 
static lg::log_domain log_engine("engine");
#define DBG_NG LOG_STREAM(debug, log_engine)
static lg::log_domain log_scripting_formula("scripting/formula");
#define LOG_SF LOG_STREAM(info, log_scripting_formula)
#define WRN_SF LOG_STREAM(warn, log_scripting_formula)
#define ERR_SF LOG_STREAM(err, log_scripting_formula)
 
namespace wfl
{
/**
 * For printing error messages when WFL parsing or evaluation fails, this contains the names of the WFL functions being evaluated.
 *
 * Two C++ threads might be evaluating WFL at the same; declaring this thread_local is a quick bugfix which should probably be replaced
 * by having a context-object for each WFL evaluation.
 */
thread_local static std::deque<std::string> call_stack;
 
call_stack_manager::call_stack_manager(const std::string& str)
{
    call_stack.push_back(str);
}
 
call_stack_manager::~call_stack_manager()
{
    call_stack.pop_back();
}
 
std::string call_stack_manager::get()
{
    std::ostringstream res;
    for(const auto& frame : call_stack) {
        if(!frame.empty()) {
            res << "  " << frame << "\n";
        }
    }
 
    return res.str();
}
 
std::string function_expression::str() const
{
    std::stringstream s;
    s << get_name();
    s << '(';
    bool first_arg = true;
    for(expression_ptr a : args()) {
        if(!first_arg) {
            s << ',';
        } else {
            first_arg = false;
        }
        s << a->str();
    }
    s << ')';
    return s.str();
}
 
namespace builtins
{
DEFINE_WFL_FUNCTION(debug, 0, 1)
{
    std::shared_ptr<formula_debugger> fdbp;
    bool need_wrapper = false;
 
    if(fdb == nullptr) {
        fdbp.reset(new formula_debugger());
        fdb = fdbp.get();
        need_wrapper = true;
    }
 
    if(args().size() == 1) {
        if(!need_wrapper) {
            return args()[0]->evaluate(variables, fdb);
        } else {
            return wrapper_formula(args()[0]).evaluate(variables, fdb);
        }
    }
 
    return wrapper_formula().evaluate(variables, fdb);
}
 
DEFINE_WFL_FUNCTION(dir, 1, 1)
{
    variant var = args()[0]->evaluate(variables, fdb);
 
    auto callable = var.as_callable();
    formula_input_vector inputs = callable->inputs();
 
    std::vector<variant> res;
    for(std::size_t i = 0; i < inputs.size(); ++i) {
        const formula_input& input = inputs[i];
        res.emplace_back(input.name);
    }
 
    return variant(std::move(res));
}
 
DEFINE_WFL_FUNCTION(if, 2, -1)
{
    for(std::size_t n = 0; n < args().size() - 1; n += 2) {
        if(args()[n]->evaluate(variables, fdb).as_bool()) {
            return args()[n + 1]->evaluate(variables, fdb);
        }
    }
 
    if((args().size() % 2) != 0) {
        return args().back()->evaluate(variables, fdb);
    } else {
        return variant();
    }
}
 
DEFINE_WFL_FUNCTION(switch, 3, -1)
{
    variant var = args()[0]->evaluate(variables, fdb);
 
    for(std::size_t n = 1; n < args().size() - 1; n += 2) {
        variant val = args()[n]->evaluate(variables, fdb);
 
        if(val == var) {
            return args()[n + 1]->evaluate(variables, fdb);
        }
    }
 
    if((args().size() % 2) == 0) {
        return args().back()->evaluate(variables, fdb);
    } else {
        return variant();
    }
}
 
DEFINE_WFL_FUNCTION(abs, 1, 1)
{
    const variant input = args()[0]->evaluate(variables, fdb);
    if(input.is_decimal()) {
        const int n = input.as_decimal();
        return variant(n >= 0 ? n : -n, variant::DECIMAL_VARIANT);
    } else {
        const int n = input.as_int();
        return variant(n >= 0 ? n : -n);
    }
}
 
DEFINE_WFL_FUNCTION(min, 1, -1)
{
    variant res = args()[0]->evaluate(variables, fdb);
    if(res.is_list()) {
        if(res.is_empty()) {
            throw formula_error("min(list): list is empty", "", "", 0);
        }
 
        res = *std::min_element(res.begin(), res.end());
    }
 
    for(std::size_t n = 1; n < args().size(); ++n) {
        variant v = args()[n]->evaluate(variables, fdb);
 
        if(v.is_list()) {
            if(v.is_empty()) {
                continue;
            }
 
            v = *std::min_element(v.begin(), v.end());
        }
 
        if(res.is_null() || v < res) {
            res = v;
        }
    }
 
    return res;
}
 
DEFINE_WFL_FUNCTION(max, 1, -1)
{
    variant res = args()[0]->evaluate(variables, fdb);
    if(res.is_list()) {
        if(res.is_empty()) {
            throw formula_error("max(list): list is empty", "", "", 0);
        }
 
        res = *std::max_element(res.begin(), res.end());
    }
 
    for(std::size_t n = 1; n < args().size(); ++n) {
        variant v = args()[n]->evaluate(variables, fdb);
 
        if(v.is_list()) {
            if(v.is_empty()) {
                continue;
            }
 
            v = *std::max_element(v.begin(), v.end());
        }
 
        if(res.is_null() || v > res) {
            res = v;
        }
    }
 
    return res;
}
 
namespace
{
void display_float(const map_location& location, const std::string& text)
{
    if(auto gd = game_display::get_singleton()) {
        gd->float_label(location, text, color_t(255, 0, 0));
    }
}
} // end anon namespace
 
DEFINE_WFL_FUNCTION(debug_float, 2, 3)
{
    const args_list& arguments = args();
    const variant var0 = arguments[0]->evaluate(variables, fdb);
    variant var1 = arguments[1]->evaluate(variables, fdb);
 
    const map_location location = callable_cast<location_callable&>(var0).loc();
    std::string text;
 
    if(arguments.size() == 2) {
        text = var1.to_debug_string();
        display_float(location, text);
        return var1;
    } else {
        const variant var2 = arguments[2]->evaluate(variables, fdb);
        text = var1.string_cast() + var2.to_debug_string();
        display_float(location, text);
        return var2;
    }
}
 
DEFINE_WFL_FUNCTION(debug_print, 1, 2)
{
    std::string speaker = "WFL";
    int i_value = 0;
 
    if(args().size() == 2) {
        speaker = args()[0]->evaluate(variables, fdb).string_cast();
        i_value = 1;
    }
 
    variant value = args()[i_value]->evaluate(variables, fdb);
    const std::string str = value.to_debug_string(true);
 
    LOG_SF << speaker << ": " << str;
 
    if(game_config::debug && game_display::get_singleton()) {
        game_display::get_singleton()->get_chat_manager().add_chat_message(
            std::chrono::system_clock::now(), speaker, 0, str, events::chat_handler::MESSAGE_PUBLIC, false);
    }
 
    return value;
}
 
DEFINE_WFL_FUNCTION(debug_profile, 1, 2)
{
    std::string speaker = "WFL";
    int i_value = 0;
 
    if(args().size() == 2) {
        speaker = args()[0]->evaluate(variables, fdb).string_cast();
        i_value = 1;
    }
 
    const variant value = args()[i_value]->evaluate(variables, fdb);
    const int run_count = 1000;
    std::chrono::steady_clock::duration run_time;
 
    for(int i = 0; i < run_count; i++) {
        const auto start = std::chrono::steady_clock::now();
        args()[i_value]->evaluate(variables, fdb);
        run_time += std::chrono::steady_clock::now() - start;
    }
 
    // Average execution time over all runs
    auto average_ms = std::chrono::duration_cast<std::chrono::milliseconds>(run_time / run_count);
 
    std::ostringstream str;
#ifdef __cpp_lib_format
    str << "Evaluated in " << average_ms << " on average";
#else
    str << "Evaluated in " << average_ms.count() << " ms on average";
#endif
 
    LOG_SF << speaker << ": " << str.str();
 
    if(game_config::debug && game_display::get_singleton()) {
        game_display::get_singleton()->get_chat_manager().add_chat_message(
            std::chrono::system_clock::now(), speaker, 0, str.str(), events::chat_handler::MESSAGE_PUBLIC, false);
    }
 
    return value;
}
 
DEFINE_WFL_FUNCTION(keys, 1, 1)
{
    const variant map = args()[0]->evaluate(variables, fdb);
    return map.get_keys();
}
 
DEFINE_WFL_FUNCTION(values, 1, 1)
{
    const variant map = args()[0]->evaluate(variables, fdb);
    return map.get_values();
}
 
DEFINE_WFL_FUNCTION(tolist, 1, 1)
{
    const variant var = args()[0]->evaluate(variables, fdb);
 
    std::vector<variant> tmp;
    for(variant_iterator it = var.begin(); it != var.end(); ++it) {
        tmp.push_back(*it);
    }
 
    return variant(std::move(tmp));
}
 
DEFINE_WFL_FUNCTION(tomap, 1, 2)
{
    const variant var_1 = args()[0]->evaluate(variables, fdb);
 
    std::map<variant, variant> tmp;
 
    if(args().size() == 2) {
        const variant var_2 = args()[1]->evaluate(variables, fdb);
        if(var_1.num_elements() != var_2.num_elements()) {
            return variant();
        }
 
        for(std::size_t i = 0; i < var_1.num_elements(); ++i) {
            tmp[var_1[i]] = var_2[i];
        }
    } else {
        for(variant_iterator it = var_1.begin(); it != var_1.end(); ++it) {
            if(auto kv = callable_cast<key_value_pair*>(*it)) {
                tmp[kv->query_value("key")] = kv->query_value("value");
            } else {
                auto map_it = tmp.find(*it);
 
                if(map_it == tmp.end()) {
                    tmp[*it] = variant(1);
                } else {
                    map_it->second = variant(map_it->second.as_int() + 1);
                }
            }
        }
    }
 
    return variant(std::move(tmp));
}
 
DEFINE_WFL_FUNCTION(substring, 2, 3)
{
    std::string result = args()[0]->evaluate(variables, fdb).as_string();
 
    int offset = args()[1]->evaluate(variables, fdb).as_int();
    if(offset < 0) {
        offset += result.size();
 
        if(offset < 0) {
            offset = 0;
        }
    } else {
        if(static_cast<std::size_t>(offset) >= result.size()) {
            return variant(std::string());
        }
    }
 
    if(args().size() > 2) {
        int size = args()[2]->evaluate(variables, fdb).as_int();
 
        if(size < 0) {
            size = -size;
            offset = std::max(0, offset - size + 1);
        }
 
        return variant(result.substr(offset, size));
    }
 
    return variant(result.substr(offset));
}
 
DEFINE_WFL_FUNCTION(replace, 3, 4)
{
    std::string result = args()[0]->evaluate(variables, fdb).as_string();
    std::string replacement = args().back()->evaluate(variables, fdb).as_string();
 
    int offset = args()[1]->evaluate(variables, fdb).as_int();
    if(offset < 0) {
        offset += result.size();
 
        if(offset < 0) {
            offset = 0;
        }
    } else {
        if(static_cast<std::size_t>(offset) >= result.size()) {
            return variant(result);
        }
    }
 
    if(args().size() > 3) {
        int size = args()[2]->evaluate(variables, fdb).as_int();
 
        if(size < 0) {
            size = -size;
            offset = std::max(0, offset - size + 1);
        }
 
        return variant(result.replace(offset, size, replacement));
    }
 
    return variant(result.replace(offset, std::string::npos, replacement));
}
 
DEFINE_WFL_FUNCTION(replace_all, 3, 3)
{
    std::string result = args()[0]->evaluate(variables, fdb).as_string();
    std::string needle = args()[1]->evaluate(variables, fdb).as_string();
    std::string replacement = args().back()->evaluate(variables, fdb).as_string();
    boost::replace_all(result, needle, replacement);
    return variant(result);
}
 
DEFINE_WFL_FUNCTION(starts_with, 2, 2)
{
    std::string str = args()[0]->evaluate(variables, fdb).as_string();
    std::string prefix = args()[1]->evaluate(variables, fdb).as_string();
    return variant(boost::starts_with(str, prefix));
}
 
DEFINE_WFL_FUNCTION(ends_with, 2, 2)
{
    std::string str = args()[0]->evaluate(variables, fdb).as_string();
    std::string prefix = args()[1]->evaluate(variables, fdb).as_string();
    return variant(boost::ends_with(str, prefix));
}
 
DEFINE_WFL_FUNCTION(insert, 3, 3)
{
    std::string result = args()[0]->evaluate(variables, fdb).as_string();
    std::string insert = args().back()->evaluate(variables, fdb).as_string();
 
    int offset = args()[1]->evaluate(variables, fdb).as_int();
    if(offset < 0) {
        offset += result.size();
 
        if(offset < 0) {
            offset = 0;
        }
    } else if(static_cast<std::size_t>(offset) >= result.size()) {
        return variant(result + insert);
    }
 
    return variant(result.insert(offset, insert));
}
 
DEFINE_WFL_FUNCTION(length, 1, 1)
{
    return variant(args()[0]->evaluate(variables, fdb).as_string().length());
}
 
DEFINE_WFL_FUNCTION(byte_index, 2, 2)
{
    return variant(utf8::index(
        args()[0]->evaluate(variables, fdb).as_string(),
        args()[1]->evaluate(variables, fdb).as_int()));
}
 
DEFINE_WFL_FUNCTION(concatenate, 1, -1)
{
    std::string result;
    for(expression_ptr arg : args()) {
        result += arg->evaluate(variables, fdb).string_cast();
    }
 
    return variant(result);
}
 
DEFINE_WFL_FUNCTION(str_upper, 1, 1)
{
    std::string str = args()[0]->evaluate(variables, fdb).as_string();
    std::transform(str.begin(), str.end(), str.begin(), static_cast<int (*)(int)>(std::toupper));
    return variant(str);
}
 
DEFINE_WFL_FUNCTION(str_lower, 1, 1)
{
    std::string str = args()[0]->evaluate(variables, fdb).as_string();
    std::transform(str.begin(), str.end(), str.begin(), static_cast<int (*)(int)>(std::tolower));
    return variant(str);
}
 
DEFINE_WFL_FUNCTION(sin, 1, 1)
{
    const double angle = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::sin(angle * pi<double>() / 180.0);
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(cos, 1, 1)
{
    const double angle = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::cos(angle * pi<double>() / 180.0);
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(tan, 1, 1)
{
    const double angle = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::tan(angle * pi<double>() / 180.0);
    if(std::isnan(result) || result <= std::numeric_limits<int>::min() || result >= std::numeric_limits<int>::max()) {
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(asin, 1, 1)
{
    const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::asin(num) * 180.0 / pi<double>();
    if(std::isnan(result)) {
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(acos, 1, 1)
{
    const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::acos(num) * 180.0 / pi<double>();
    if(std::isnan(result)) {
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(atan, 1, 2)
{
    if(args().size() == 1) {
        const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
        const double result = std::atan(num) * 180.0 / pi<double>();
        return variant(result, variant::DECIMAL_VARIANT);
    } else {
        const double y = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
        const double x = args()[1]->evaluate(variables, fdb).as_decimal() / 1000.0;
        const double result = std::atan2(y, x) * 180.0 / pi<double>();
        return variant(result, variant::DECIMAL_VARIANT);
    }
}
 
DEFINE_WFL_FUNCTION(sqrt, 1, 1)
{
    const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::sqrt(num);
    if(std::isnan(result)) {
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(cbrt, 1, 1)
{
    const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = num < 0 ? -std::pow(-num, 1.0 / 3.0) : std::pow(num, 1.0 / 3.0);
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(root, 2, 2)
{
    const double base = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double root = args()[1]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = base < 0 && std::fmod(root, 2) == 1 ? -std::pow(-base, 1.0 / root) : std::pow(base, 1.0 / root);
    if(std::isnan(result)) {
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(log, 1, 2)
{
    const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    if(args().size() == 1) {
        const double result = std::log(num);
        if(std::isnan(result)) {
            return variant();
        }
 
        return variant(result, variant::DECIMAL_VARIANT);
    }
 
    const double base = args()[1]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::log(num) / std::log(base);
    if(std::isnan(result)) {
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(exp, 1, 1)
{
    const double num = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double result = std::exp(num);
    if(result == 0 || result >= std::numeric_limits<int>::max()) {
        // These are range errors rather than NaNs,
        // but I figure it's better than returning INT_MIN.
        return variant();
    }
 
    return variant(result, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(pi, 0, 0)
{
    return variant(pi<double>(), variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(hypot, 2, 2)
{
    const double x = args()[0]->evaluate(variables, fdb).as_decimal() / 1000.0;
    const double y = args()[1]->evaluate(variables, fdb).as_decimal() / 1000.0;
    return variant(std::hypot(x, y), variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(index_of, 2, 2)
{
    const variant value = args()[0]->evaluate(variables, fdb);
    const variant list = args()[1]->evaluate(variables, fdb);
 
    for(std::size_t i = 0; i < list.num_elements(); ++i) {
        if(list[i] == value) {
            return variant(i);
        }
    }
 
    return variant(-1);
}
 
DEFINE_WFL_FUNCTION(choose, 2, 3)
{
    const variant items = args()[0]->evaluate(variables, fdb);
    variant max_value;
    variant_iterator max;
 
    if(args().size() == 2) {
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            const variant val = args().back()->evaluate(formula_variant_callable_with_backup(*it, variables), fdb);
 
            if(max == variant_iterator() || val > max_value) {
                max = it;
                max_value = val;
            }
        }
    } else {
        map_formula_callable self_callable;
        const std::string self = args()[1]->evaluate(variables, fdb).as_string();
 
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            self_callable.add(self, *it);
 
            const variant val = args().back()->evaluate(
                formula_callable_with_backup(self_callable, formula_variant_callable_with_backup(*it, variables)), fdb);
 
            if(max == variant_iterator() || val > max_value) {
                max = it;
                max_value = val;
            }
        }
    }
 
    if(max == variant_iterator()) {
        return variant();
    }
 
    return *max;
}
 
DEFINE_WFL_FUNCTION(wave, 1, 1)
{
    const int value = args()[0]->evaluate(variables, fdb).as_int() % 1000;
    const double angle = 2.0 * pi<double>() * (static_cast<double>(value) / 1000.0);
    return variant(static_cast<int>(std::sin(angle) * 1000.0));
}
 
DEFINE_WFL_FUNCTION(lerp, 3, 3)
{
    const double lo = args()[0]->evaluate(variables, add_debug_info(fdb, 0, "lerp:lo")).as_decimal() / 1000.0;
    const double hi = args()[1]->evaluate(variables, add_debug_info(fdb, 1, "lerp:hi")).as_decimal() / 1000.0;;
    const double alpha = args()[2]->evaluate(variables, add_debug_info(fdb, 2, "lerp:alpha")).as_decimal() / 1000.0;;
    return variant(static_cast<int>((lo + alpha * (hi - lo)) * 1000.0), variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(lerp_index, 2, 2)
{
    const std::vector<variant> items = args()[0]->evaluate(variables, fdb).as_list();
    if(items.empty()) return variant();
    const double alpha = args()[1]->evaluate(variables, fdb).as_decimal() / 1000.0;
    // Same formula as red_to_green etc
    const double val_scaled = std::clamp(0.01 * alpha, 0.0, 1.0);
    const int idx = int(std::nearbyint((items.size() - 1) * val_scaled));
    return items[idx];
}
 
DEFINE_WFL_FUNCTION(get_palette, 1, 1)
{
    const std::string name = args()[0]->evaluate(variables, fdb).as_string();
    std::vector<color_t> colors;
    if(name == "red_green_scale") {
        colors = game_config::red_green_scale;
    } else if(name == "red_green_scale_text") {
        colors = game_config::red_green_scale_text;
    } else if(name == "blue_white_scale") {
        colors = game_config::blue_white_scale;
    } else if(name == "blue_white_scale_text") {
        colors = game_config::blue_white_scale_text;
    } else {
        colors = game_config::tc_info(name);
    }
    std::vector<variant> result;
    result.reserve(colors.size());
    for(auto clr : colors) {
        result.emplace_back(std::make_shared<color_callable>(clr));
    }
    return variant(std::move(result));
}
 
DEFINE_WFL_FUNCTION(clamp, 3, 3)
{
    const variant val = args()[0]->evaluate(variables, add_debug_info(fdb, 0, "clamp:value"));
    const variant lo = args()[1]->evaluate(variables, add_debug_info(fdb, 1, "clamp:lo"));
    const variant hi = args()[2]->evaluate(variables, add_debug_info(fdb, 2, "clamp:hi"));
    if(val.is_int() && lo.is_int() && hi.is_int()) {
        return variant(std::clamp<int>(val.as_int(), lo.as_int(), hi.as_int()));
    }
    return variant(static_cast<int>(std::clamp<int>(val.as_decimal(), lo.as_decimal(), hi.as_decimal())), variant::DECIMAL_VARIANT);
}
 
namespace
{
class variant_comparator : public formula_callable
{
public:
    variant_comparator(const expression_ptr& expr, const formula_callable& fallback)
        : expr_(expr)
        , fallback_(&fallback)
        , a_()
        , b_()
    {
    }
 
    bool operator()(const variant& a, const variant& b) const
    {
        a_ = a;
        b_ = b;
        return expr_->evaluate(*this).as_bool();
    }
 
private:
    variant get_value(const std::string& key) const
    {
        if(key == "a") {
            return a_;
        } else if(key == "b") {
            return b_;
        } else {
            return fallback_->query_value(key);
        }
    }
 
    void get_inputs(formula_input_vector& inputs) const
    {
        fallback_->get_inputs(inputs);
    }
 
    expression_ptr expr_;
    const formula_callable* fallback_;
    mutable variant a_, b_;
};
} // end anon namespace
 
DEFINE_WFL_FUNCTION(sort, 1, 2)
{
    variant list = args()[0]->evaluate(variables, fdb);
 
    std::vector<variant> vars;
    vars.reserve(list.num_elements());
 
    for(std::size_t n = 0; n != list.num_elements(); ++n) {
        vars.push_back(list[n]);
    }
 
    if(args().size() == 1) {
        std::sort(vars.begin(), vars.end());
    } else {
        std::sort(vars.begin(), vars.end(), variant_comparator(args()[1], variables));
    }
 
    return variant(std::move(vars));
}
 
DEFINE_WFL_FUNCTION(reverse, 1, 1)
{
    const variant& arg = args()[0]->evaluate(variables, fdb);
 
    if(arg.is_string()) {
        std::string str = args()[0]->evaluate(variables, fdb).as_string();
        std::reverse(str.begin(), str.end());
 
        return variant(std::move(str));
    } else if(arg.is_list()) {
        std::vector<variant> list = args()[0]->evaluate(variables, fdb).as_list();
        std::reverse(list.begin(), list.end());
 
        return variant(std::move(list));
    }
 
    return variant();
}
 
DEFINE_WFL_FUNCTION(contains_string, 2, 2)
{
    std::string str = args()[0]->evaluate(variables, fdb).as_string();
    std::string key = args()[1]->evaluate(variables, fdb).as_string();
 
    return variant(str.find(key) != std::string::npos);
}
 
DEFINE_WFL_FUNCTION(find_string, 2, 2)
{
    const std::string str = args()[0]->evaluate(variables, fdb).as_string();
    const std::string key = args()[1]->evaluate(variables, fdb).as_string();
 
    std::size_t pos = str.find(key);
    return variant(static_cast<int>(pos));
}
 
DEFINE_WFL_FUNCTION(filter, 2, 3)
{
    std::vector<variant> list_vars;
    std::map<variant, variant> map_vars;
 
    const variant items = args()[0]->evaluate(variables, fdb);
 
    if(args().size() == 2) {
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            const variant val = args()[1]->evaluate(formula_variant_callable_with_backup(*it, variables), fdb);
 
            if(val.as_bool()) {
                if(items.is_map()) {
                    map_vars[(*it).get_member("key")] = (*it).get_member("value");
                } else {
                    list_vars.push_back(*it);
                }
            }
        }
    } else {
        map_formula_callable self_callable;
        const std::string self = args()[1]->evaluate(variables, fdb).as_string();
 
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            self_callable.add(self, *it);
 
            const variant val = args()[2]->evaluate(
                formula_callable_with_backup(self_callable, formula_variant_callable_with_backup(*it, variables)), fdb);
 
            if(val.as_bool()) {
                if(items.is_map()) {
                    map_vars[(*it).get_member("key")] = (*it).get_member("value");
                } else {
                    list_vars.push_back(*it);
                }
            }
        }
    }
 
    if(items.is_map()) {
        return variant(std::move(map_vars));
    }
 
    return variant(std::move(list_vars));
}
 
DEFINE_WFL_FUNCTION(find, 2, 3)
{
    const variant items = args()[0]->evaluate(variables, fdb);
 
    if(args().size() == 2) {
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            const variant val = args()[1]->evaluate(formula_variant_callable_with_backup(*it, variables), fdb);
            if(val.as_bool()) {
                return *it;
            }
        }
    } else {
        map_formula_callable self_callable;
        const std::string self = args()[1]->evaluate(variables, fdb).as_string();
 
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            self_callable.add(self, *it);
 
            const variant val = args().back()->evaluate(
                formula_callable_with_backup(self_callable, formula_variant_callable_with_backup(*it, variables)), fdb);
 
            if(val.as_bool()) {
                return *it;
            }
        }
    }
 
    return variant();
}
 
DEFINE_WFL_FUNCTION(map, 2, 3)
{
    std::vector<variant> list_vars;
    std::map<variant, variant> map_vars;
    const variant items = args()[0]->evaluate(variables, fdb);
 
    if(args().size() == 2) {
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            const variant val = args().back()->evaluate(formula_variant_callable_with_backup(*it, variables), fdb);
            if(items.is_map()) {
                map_vars[(*it).get_member("key")] = val;
            } else {
                list_vars.push_back(val);
            }
        }
    } else {
        map_formula_callable self_callable;
        const std::string self = args()[1]->evaluate(variables, fdb).as_string();
 
        for(variant_iterator it = items.begin(); it != items.end(); ++it) {
            self_callable.add(self, *it);
 
            const variant val = args().back()->evaluate(
                formula_callable_with_backup(self_callable, formula_variant_callable_with_backup(*it, variables)), fdb);
 
            if(items.is_map()) {
                map_vars[(*it).get_member("key")] = val;
            } else {
                list_vars.push_back(val);
            }
        }
    }
 
    if(items.is_map()) {
        return variant(std::move(map_vars));
    }
 
    return variant(std::move(list_vars));
}
 
DEFINE_WFL_FUNCTION(take_while, 2, 2)
{
    const variant& items = args()[0]->evaluate(variables, fdb);
 
    variant_iterator it = items.begin();
    for(; it != items.end(); ++it) {
        const variant matches = args().back()->evaluate(formula_variant_callable_with_backup(*it, variables), fdb);
 
        if(!matches.as_bool()) {
            break;
        }
    }
 
    return variant(std::vector(items.begin(), it));
}
 
namespace
{
struct indexer
{
    explicit indexer(std::size_t i)
        : i(i)
    {
    }
 
    variant operator()(const variant& v) const
    {
        if(i >= v.num_elements()) {
            return variant();
        } else {
            return v[i];
        }
    }
 
    std::size_t i;
};
 
/** @todo: replace with lambda? */
struct comparator
{
    bool operator()(const variant& a, const variant& b) const
    {
        return a.num_elements() < b.num_elements();
    }
};
 
std::vector<variant> get_input(
        const function_expression::args_list& args,
        const formula_callable& variables,
        formula_debugger* fdb)
{
    if(args.size() == 1) {
        const variant list = args[0]->evaluate(variables, fdb);
        return std::vector<variant>(list.begin(), list.end());
    } else {
        std::vector<variant> input;
        input.reserve(args.size());
 
        for(expression_ptr expr : args) {
            input.push_back(expr->evaluate(variables, fdb));
        }
 
        return input;
    }
}
} // end anon namespace
 
DEFINE_WFL_FUNCTION(zip, 1, -1)
{
    const std::vector<variant> input = get_input(args(), variables, fdb);
    std::vector<variant> output;
 
    // So basically this does [[a,b,c],[d,e,f],[x,y,z]] -> [[a,d,x],[b,e,y],[c,f,z]]
    // Or [[a,b,c,d],[x,y,z]] -> [[a,x],[b,y],[c,z],[d,null()]]
    std::size_t max_i = std::max_element(input.begin(), input.end(), comparator())->num_elements();
    output.reserve(max_i);
 
    for(std::size_t i = 0; i < max_i; i++) {
        std::vector<variant> elem(input.size());
        std::transform(input.begin(), input.end(), elem.begin(), indexer(i));
        output.emplace_back(elem);
    }
 
    return variant(std::move(output));
}
 
DEFINE_WFL_FUNCTION(reduce, 2, 3)
{
    const variant items = args()[0]->evaluate(variables, fdb);
    variant initial = args().size() == 2 ? variant() : args()[1]->evaluate(variables, fdb);
 
    if(items.num_elements() == 0) {
        return initial;
    }
 
    variant_iterator it = items.begin();
    variant res(initial.is_null() ? *it : initial);
    if(res != initial) {
        ++it;
    }
 
    map_formula_callable self_callable;
    for(; it != items.end(); ++it) {
        self_callable.add("a", res);
        self_callable.add("b", *it);
        res = args().back()->evaluate(
            formula_callable_with_backup(self_callable, formula_variant_callable_with_backup(*it, variables)), fdb);
    }
 
    return res;
}
 
DEFINE_WFL_FUNCTION(sum, 1, 2)
{
    variant res(0);
    const variant items = args()[0]->evaluate(variables, fdb);
    if(items.num_elements() > 0) {
        if(items[0].is_list()) {
            res = variant(std::vector<variant>{});
            if(args().size() >= 2) {
                res = args()[1]->evaluate(variables, fdb);
                if(!res.is_list())
                    return variant();
            }
        } else if(items[0].is_map()) {
            res = variant(std::map<variant, variant>{});
            if(args().size() >= 2) {
                res = args()[1]->evaluate(variables, fdb);
                if(!res.is_map())
                    return variant();
            }
        } else {
            if(args().size() >= 2) {
                res = args()[1]->evaluate(variables, fdb);
            }
        }
    }
 
    for(std::size_t n = 0; n != items.num_elements(); ++n) {
        res = res + items[n];
    }
 
    return res;
}
 
DEFINE_WFL_FUNCTION(head, 1, 2)
{
    const variant items = args()[0]->evaluate(variables, fdb);
    variant_iterator it = items.begin();
    if(it == items.end()) {
        return variant();
    }
 
    if(args().size() == 1) {
        return *it;
    }
 
    const int n = items.num_elements(), req = args()[1]->evaluate(variables, fdb).as_int();
    const int count = req < 0 ? n - std::min(-req, n) : std::min(req, n);
 
    variant_iterator end = it;
    std::advance(end, count);
 
    std::vector<variant> res;
    std::copy(it, end, std::back_inserter(res));
    return variant(std::move(res));
}
 
DEFINE_WFL_FUNCTION(tail, 1, 2)
{
    const variant items = args()[0]->evaluate(variables, fdb);
    variant_iterator it = items.end();
    if(it == items.begin()) {
        return variant();
    }
 
    if(args().size() == 1) {
        return *--it;
    }
 
    const int n = items.num_elements(), req = args()[1]->evaluate(variables, fdb).as_int();
    const int count = req < 0 ? n - std::min(-req, n) : std::min(req, n);
 
    std::advance(it, -count);
    std::vector<variant> res;
 
    std::copy(it, items.end(), std::back_inserter(res));
    return variant(std::move(res));
}
 
DEFINE_WFL_FUNCTION(size, 1, 1)
{
    const variant items = args()[0]->evaluate(variables, fdb);
    return variant(static_cast<int>(items.num_elements()));
}
 
DEFINE_WFL_FUNCTION(null, 0, -1)
{
    if(!args().empty()) {
        for(std::size_t i = 0; i < args().size(); ++i) {
            args()[i]->evaluate(variables, fdb);
        }
    }
 
    return variant();
}
 
DEFINE_WFL_FUNCTION(ceil, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_decimal();
 
    if((d >= 0) && (d % 1000 != 0)) {
        d /= 1000;
        return variant(++d);
    } else {
        d /= 1000;
        return variant(d);
    }
}
 
DEFINE_WFL_FUNCTION(round, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_decimal();
    int f = d % 1000;
 
    if(f >= 500) {
        d /= 1000;
        return variant(++d);
    } else if(f <= -500) {
        d /= 1000;
        return variant(--d);
    } else {
        d /= 1000;
        return variant(d);
    }
}
 
DEFINE_WFL_FUNCTION(floor, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_decimal();
 
    if((d < 0) && (d % 1000 != 0)) {
        d /= 1000;
        return variant(--d);
    } else {
        d /= 1000;
        return variant(d);
    }
}
 
DEFINE_WFL_FUNCTION(trunc, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_int();
 
    return variant(d);
}
 
DEFINE_WFL_FUNCTION(frac, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_decimal();
 
    d %= 1000;
    return variant(d, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(sgn, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_decimal();
 
    if(d != 0) {
        d = d > 0 ? 1 : -1;
    }
 
    return variant(d);
}
 
DEFINE_WFL_FUNCTION(as_decimal, 1, 1)
{
    variant decimal = args()[0]->evaluate(variables, fdb);
    int d = decimal.as_decimal();
 
    return variant(d, variant::DECIMAL_VARIANT);
}
 
DEFINE_WFL_FUNCTION(loc, 2, 2)
{
    return make_callable<location_callable>(map_location(
        args()[0]->evaluate(variables, add_debug_info(fdb, 0, "loc:x")).as_int(),
        args()[1]->evaluate(variables, add_debug_info(fdb, 1, "loc:y")).as_int(), wml_loc()
    ));
}
 
DEFINE_WFL_FUNCTION(pair, 2, 2)
{
    return make_callable<key_value_pair>(
        args()[0]->evaluate(variables, add_debug_info(fdb, 0, "pair:key")),
        args()[1]->evaluate(variables, add_debug_info(fdb, 1, "pair_value"))
    );
}
 
DEFINE_WFL_FUNCTION(distance_between, 2, 2)
{
    map_location loc1, loc2;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "distance_between:location_A")))) {
        loc1 = loc_c->loc();
    }
 
    if (auto loc_c = callable_cast<location_callable*>(args()[1]->evaluate(variables, add_debug_info(fdb, 1, "distance_between:location_B")))) {
        loc2 = loc_c->loc();
    }
 
    if (!loc1.valid() || !loc2.valid()) {
        return variant();
    }
 
    return variant(distance_between(loc1, loc2));
}
 
DEFINE_WFL_FUNCTION(nearest_loc, 2, 2)
{
    map_location loc;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "nearest_loc:location")))) {
        loc = loc_c->loc();
    }
 
    if(!loc.valid()) {
        return variant();
    }
 
    const std::vector<variant> locations = args()[1]
        ->evaluate(variables, add_debug_info(fdb, 1, "nearest_loc:locations"))
        .as_list();
 
#ifdef __cpp_lib_ranges
    auto nearest = std::ranges::min_element(locations, {},
        [&](const variant& cmp) { return distance_between(loc, callable_cast<location_callable&>(cmp).loc()); });
#else
    auto nearest = std::min_element(locations.begin(), locations.end(), [&](const variant& cmp1, const variant& cmp2) {
        return std::less{}(
            distance_between(loc, callable_cast<location_callable&>(cmp1).loc()),
            distance_between(loc, callable_cast<location_callable&>(cmp2).loc())
        );
    });
#endif
 
    if(nearest != locations.end()) {
        return make_callable<location_callable>(callable_cast<location_callable&>(*nearest).loc());
    } else {
        return variant();
    }
}
 
DEFINE_WFL_FUNCTION(adjacent_locs, 1, 1)
{
    map_location loc;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "adjacent_locs:location")))) {
        loc = loc_c->loc();
    }
 
    if(!loc.valid()) {
        return variant();
    }
 
    std::vector<variant> v;
    for(const map_location& adj : get_adjacent_tiles(loc)) {
        v.emplace_back(std::make_shared<location_callable>(adj));
    }
 
    return variant(std::move(v));
}
 
DEFINE_WFL_FUNCTION(locations_in_radius, 2, 2)
{
    map_location loc;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, fdb))) {
        loc = loc_c->loc();
    }
 
    if(!loc.valid()) {
        return variant();
    }
 
    int range = args()[1]->evaluate(variables, fdb).as_int();
 
    if(range < 0) {
        return variant();
    }
 
    if(!range) {
        return make_callable<location_callable>(loc);
    }
 
    std::vector<map_location> res;
 
    get_tiles_in_radius(loc, range, res);
 
    std::vector<variant> v;
    v.reserve(res.size() + 1);
    v.emplace_back(std::make_shared<location_callable>(loc));
 
    for(std::size_t n = 0; n != res.size(); ++n) {
        v.emplace_back(std::make_shared<location_callable>(res[n]));
    }
 
    return variant(std::move(v));
}
 
DEFINE_WFL_FUNCTION(are_adjacent, 2, 2)
{
    map_location loc1, loc2;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "are_adjacent:location_A")))) {
        loc1 = loc_c->loc();
    }
 
    if (auto loc_c = callable_cast<location_callable*>(args()[1]->evaluate(variables, add_debug_info(fdb, 1, "are_adjacent:location_B")))) {
        loc2 = loc_c->loc();
    }
 
    if (!loc1.valid() || !loc2.valid()) {
        return variant();
    }
 
    return variant(tiles_adjacent(loc1, loc2) ? 1 : 0);
}
 
DEFINE_WFL_FUNCTION(relative_dir, 2, 2)
{
    map_location loc1, loc2;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "relative_dir:location_A")))) {
        loc1 = loc_c->loc();
    }
 
    if (auto loc_c = callable_cast<location_callable*>(args()[1]->evaluate(variables, add_debug_info(fdb, 1, "relative_dir:location_B")))) {
        loc2 = loc_c->loc();
    }
 
    if (!loc1.valid() || !loc2.valid()) {
        return variant();
    }
 
    return variant(map_location::write_direction(loc1.get_relative_dir(loc2)));
}
 
DEFINE_WFL_FUNCTION(direction_from, 2, 3)
{
    map_location loc;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "direction_from:location")))) {
        loc = loc_c->loc();
    }
 
    const std::string dir_str =
        args()[1]->evaluate(variables, add_debug_info(fdb, 1, "direction_from:dir")).as_string();
 
    int n = args().size() == 3
        ? args()[2]->evaluate(variables, add_debug_info(fdb, 2, "direction_from:count")).as_int()
        : 1;
 
    if (!loc.valid()) {
        return variant();
    }
    return make_callable<location_callable>(loc.get_direction(map_location::parse_direction(dir_str), n));
}
 
DEFINE_WFL_FUNCTION(rotate_loc_around, 2, 3)
{
    map_location center, loc;
    if (auto loc_c = callable_cast<location_callable*>(args()[0]->evaluate(variables, add_debug_info(fdb, 0, "direction_from:center")))) {
        center = loc_c->loc();
    }
 
    if (auto loc_c = callable_cast<location_callable*>(args()[1]->evaluate(variables, add_debug_info(fdb, 1, "direction_from:location")))) {
        loc = loc_c->loc();
    }
 
    if (!center.valid() || !loc.valid()) {
        return variant();
    }
 
    int n = args().size() == 3
        ? args()[2]->evaluate(variables, add_debug_info(fdb, 2, "direction_from:count")).as_int()
        : 1;
 
    return make_callable<location_callable>(loc.rotate_right_around_center(center, n));
}
 
DEFINE_WFL_FUNCTION(type, 1, 1)
{
    const variant& v = args()[0]->evaluate(variables, fdb);
    return variant(formula_variant::get_string(v.type()));
}
 
} // namespace builtins
 
namespace actions
{
DEFINE_WFL_FUNCTION(safe_call, 2, 2)
{
    const variant main = args()[0]->evaluate(variables, fdb);
    const expression_ptr backup_formula = args()[1];
 
    return make_callable<safe_call_callable>(main, backup_formula);
}
 
DEFINE_WFL_FUNCTION(set_var, 2, 2)
{
    return make_callable<set_var_callable>(
        args()[0]->evaluate(variables, add_debug_info(fdb, 0, "set_var:key")).as_string(),
        args()[1]->evaluate(variables, add_debug_info(fdb, 1, "set_var:value")));
}
 
} // namespace actions
 
variant key_value_pair::get_value(const std::string& key) const
{
    if(key == "key") {
        return key_;
    } else if(key == "value") {
        return value_;
    }
 
    return variant();
}
 
void key_value_pair::get_inputs(formula_input_vector& inputs) const
{
    add_input(inputs, "key");
    add_input(inputs, "value");
}
 
std::string key_value_pair::serialize_to_string() const
{
    std::ostringstream ss;
    ss << "pair(";
    ss << key_.serialize_to_string();
    ss << ",";
    ss << value_.serialize_to_string();
    ss << ")";
    return ss.str();
}
 
formula_function_expression::formula_function_expression(const std::string& name,
        const args_list& args,
        const_formula_ptr formula,
        const_formula_ptr precondition,
        const std::vector<std::string>& arg_names)
    : function_expression(name, args, arg_names.size(), arg_names.size())
    , formula_(std::move(formula))
    , precondition_(std::move(precondition))
    , arg_names_(arg_names)
    , star_arg_(-1)
{
    for(std::size_t n = 0; n != arg_names_.size(); ++n) {
        if(arg_names_[n].empty() == false && arg_names_[n].back() == '*') {
            arg_names_[n].resize(arg_names_[n].size() - 1);
            star_arg_ = n;
            break;
        }
    }
}
 
variant formula_function_expression::execute(const formula_callable& variables, formula_debugger* fdb) const
{
    static std::string indent;
    indent += "  ";
 
    DBG_NG << indent << "executing '" << formula_->str() << "'";
 
    const auto begin_time = std::chrono::steady_clock::now();
    map_formula_callable callable;
 
    for(std::size_t n = 0; n != arg_names_.size(); ++n) {
        variant var = args()[n]->evaluate(variables, fdb);
        callable.add(arg_names_[n], var);
 
        if(static_cast<int>(n) == star_arg_) {
            callable.set_fallback(var.as_callable());
        }
    }
 
    if(precondition_) {
        if(!precondition_->evaluate(callable, fdb).as_bool()) {
            DBG_NG << "FAILED function precondition for function '" << formula_->str() << "' with arguments: ";
 
            for(std::size_t n = 0; n != arg_names_.size(); ++n) {
                DBG_NG << "  arg " << (n + 1) << ": " << args()[n]->evaluate(variables, fdb).to_debug_string();
            }
        }
    }
 
    variant res = formula_->evaluate(callable, fdb);
 
    const auto taken = std::chrono::steady_clock::now() - begin_time;
    DBG_NG << indent << "returning: " << taken.count();
 
    indent.resize(indent.size() - 2);
 
    return res;
}
 
function_expression_ptr user_formula_function::generate_function_expression(
        const std::vector<expression_ptr>& args) const
{
    return std::make_shared<formula_function_expression>(name_, args, formula_, precondition_, args_);
}
 
function_symbol_table::function_symbol_table(const std::shared_ptr<function_symbol_table>& parent)
    : parent(parent ? parent : get_builtins())
{
}
 
void function_symbol_table::add_function(const std::string& name, formula_function_ptr&& fcn)
{
    custom_formulas_.insert_or_assign(name, std::move(fcn));
}
 
expression_ptr function_symbol_table::create_function(
        const std::string& fn, const std::vector<expression_ptr>& args) const
{
    const auto i = custom_formulas_.find(fn);
    if(i != custom_formulas_.end()) {
        return i->second->generate_function_expression(args);
    }
 
    if(parent) {
        expression_ptr res(parent->create_function(fn, args));
        if(res) {
            return res;
        }
    }
 
    throw formula_error("Unknown function: " + fn, "", "", 0);
}
 
std::set<std::string> function_symbol_table::get_function_names() const
{
    std::set<std::string> res;
    if(parent) {
        res = parent->get_function_names();
    }
 
    for(const auto& formula : custom_formulas_) {
        res.insert(formula.first);
    }
 
    return res;
}
 
std::shared_ptr<function_symbol_table> function_symbol_table::get_builtins()
{
    static function_symbol_table functions_table(builtins_tag);
 
    if(functions_table.empty()) {
        functions_table.parent = nullptr;
 
        using namespace builtins;
        DECLARE_WFL_FUNCTION(debug);
        DECLARE_WFL_FUNCTION(dir);
        DECLARE_WFL_FUNCTION(if);
        DECLARE_WFL_FUNCTION(switch);
        DECLARE_WFL_FUNCTION(abs);
        DECLARE_WFL_FUNCTION(min);
        DECLARE_WFL_FUNCTION(max);
        DECLARE_WFL_FUNCTION(choose);
        DECLARE_WFL_FUNCTION(debug_float);
        DECLARE_WFL_FUNCTION(debug_print);
        DECLARE_WFL_FUNCTION(debug_profile);
        DECLARE_WFL_FUNCTION(wave);
        DECLARE_WFL_FUNCTION(sort);
        DECLARE_WFL_FUNCTION(contains_string);
        DECLARE_WFL_FUNCTION(find_string);
        DECLARE_WFL_FUNCTION(reverse);
        DECLARE_WFL_FUNCTION(filter);
        DECLARE_WFL_FUNCTION(find);
        DECLARE_WFL_FUNCTION(map);
        DECLARE_WFL_FUNCTION(zip);
        DECLARE_WFL_FUNCTION(take_while);
        DECLARE_WFL_FUNCTION(reduce);
        DECLARE_WFL_FUNCTION(sum);
        DECLARE_WFL_FUNCTION(head);
        DECLARE_WFL_FUNCTION(tail);
        DECLARE_WFL_FUNCTION(size);
        DECLARE_WFL_FUNCTION(null);
        DECLARE_WFL_FUNCTION(ceil);
        DECLARE_WFL_FUNCTION(floor);
        DECLARE_WFL_FUNCTION(trunc);
        DECLARE_WFL_FUNCTION(frac);
        DECLARE_WFL_FUNCTION(sgn);
        DECLARE_WFL_FUNCTION(round);
        DECLARE_WFL_FUNCTION(as_decimal);
        DECLARE_WFL_FUNCTION(pair);
        DECLARE_WFL_FUNCTION(loc);
        DECLARE_WFL_FUNCTION(distance_between);
        DECLARE_WFL_FUNCTION(nearest_loc);
        DECLARE_WFL_FUNCTION(adjacent_locs);
        DECLARE_WFL_FUNCTION(locations_in_radius);
        DECLARE_WFL_FUNCTION(are_adjacent);
        DECLARE_WFL_FUNCTION(relative_dir);
        DECLARE_WFL_FUNCTION(direction_from);
        DECLARE_WFL_FUNCTION(rotate_loc_around);
        DECLARE_WFL_FUNCTION(index_of);
        DECLARE_WFL_FUNCTION(keys);
        DECLARE_WFL_FUNCTION(values);
        DECLARE_WFL_FUNCTION(tolist);
        DECLARE_WFL_FUNCTION(tomap);
        DECLARE_WFL_FUNCTION(substring);
        DECLARE_WFL_FUNCTION(replace);
        DECLARE_WFL_FUNCTION(replace_all);
        DECLARE_WFL_FUNCTION(starts_with);
        DECLARE_WFL_FUNCTION(ends_with);
        DECLARE_WFL_FUNCTION(length);
        DECLARE_WFL_FUNCTION(byte_index);
        DECLARE_WFL_FUNCTION(concatenate);
        DECLARE_WFL_FUNCTION(sin);
        DECLARE_WFL_FUNCTION(cos);
        DECLARE_WFL_FUNCTION(tan);
        DECLARE_WFL_FUNCTION(asin);
        DECLARE_WFL_FUNCTION(acos);
        DECLARE_WFL_FUNCTION(atan);
        DECLARE_WFL_FUNCTION(sqrt);
        DECLARE_WFL_FUNCTION(cbrt);
        DECLARE_WFL_FUNCTION(root);
        DECLARE_WFL_FUNCTION(log);
        DECLARE_WFL_FUNCTION(exp);
        DECLARE_WFL_FUNCTION(pi);
        DECLARE_WFL_FUNCTION(hypot);
        DECLARE_WFL_FUNCTION(type);
        DECLARE_WFL_FUNCTION(lerp);
        DECLARE_WFL_FUNCTION(lerp_index);
        DECLARE_WFL_FUNCTION(clamp);
        DECLARE_WFL_FUNCTION(get_palette);
    }
 
    return std::shared_ptr<function_symbol_table>(&functions_table, [](function_symbol_table*) {});
}
 
action_function_symbol_table::action_function_symbol_table(const std::shared_ptr<function_symbol_table>& parent)
    : function_symbol_table(parent)
{
    using namespace actions;
    function_symbol_table& functions_table = *this;
    DECLARE_WFL_FUNCTION(safe_call);
    DECLARE_WFL_FUNCTION(set_var);
}
}