formula.hpp

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/*
    Copyright (C) 2003 - 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.
*/
 
#pragma once
 
#include "formula/debugger_fwd.hpp"
#include "formula/formula_fwd.hpp"
#include "formula/tokenizer.hpp"
#include "formula/variant.hpp"
#include <memory>
 
namespace wfl
{
class formula_expression;
class function_symbol_table;
 
using expression_ptr = std::shared_ptr<formula_expression>;
 
// Namespace alias for shorter typing
namespace tk = tokenizer;
 
class formula
{
public:
    formula(const std::string& str, function_symbol_table* symbols = nullptr, bool manage_symbols = false);
    formula(const tk::token* i1, const tk::token* i2, function_symbol_table* symbols = nullptr);
 
    formula(formula&&) noexcept = default;
    formula& operator=(formula&&) noexcept = default;
 
    // Since function_symbol_table is an incomplete type at this point,
    // a destructor must be defined out-of-line once its definition is
    // complete, otherwise compilation fails when used with unique_ptr.
    ~formula();
 
    static variant evaluate(
            const const_formula_ptr& f,
            const formula_callable& variables,
            formula_debugger* fdb = nullptr,
            variant default_res = variant(0))
    {
        if(f) {
            return f->evaluate(variables, fdb);
        } else {
            return default_res;
        }
    }
 
    static formula_ptr create_optional_formula(const std::string& str, function_symbol_table* symbols = nullptr);
 
    variant evaluate(const formula_callable& variables, formula_debugger* fdb = nullptr) const
    {
        if(fdb != nullptr) {
            return evaluate_formula_callback(*fdb, *this, variables);
        } else {
            return execute(variables, fdb);
        }
    }
 
    variant evaluate(formula_debugger* fdb = nullptr) const
    {
        if(fdb != nullptr) {
            return evaluate_formula_callback(*fdb,*this);
        } else {
            return execute(fdb);
        }
    }
 
    const std::string& str() const { return str_; }
 
    static const char* const id_chars;
 
private:
    variant execute(const formula_callable& variables, formula_debugger* fdb = nullptr) const;
    variant execute(formula_debugger* fdb) const;
 
    expression_ptr expr_;
    std::string str_;
    std::unique_ptr<function_symbol_table> managed_symbols_;
    function_symbol_table* symbols_;
 
    friend class formula_debugger;
};
 
struct formula_error : public game::error
{
    formula_error()
        : error()
        , type()
        , formula()
        , filename()
        , line(0)
    {}
 
    formula_error(const std::string& type, const std::string& formula,
            const std::string& file, int line);
 
    ~formula_error() noexcept {}
 
    std::string type;
    std::string formula;
    std::string filename;
    int line;
};
 
} // namespace wfl