skeleton_node.hpp

// Copyright Take Vos 2020.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "../formula/formula.hpp"
#include "../strings.hpp"
#include "../algorithm.hpp"
#include <memory>
#include <string_view>
#include <optional>
 
namespace tt {
 
struct skeleton_node {
    using statement_vector = typename std::vector<std::unique_ptr<skeleton_node>>;
 
    parse_location location;
 
    skeleton_node(parse_location location) :
        location(std::move(location)) {}
 
    virtual ~skeleton_node() {}
 
    [[nodiscard]] virtual bool append(std::unique_ptr<skeleton_node> x) noexcept { return false; }
 
    [[nodiscard]] virtual bool should_left_align() const noexcept { return true; } 
 
    virtual void left_align() noexcept {}
 
    [[nodiscard]] virtual bool found_elif(parse_location _location, std::unique_ptr<formula_node> expression) noexcept { return false; }
    [[nodiscard]] virtual bool found_else(parse_location _location) noexcept { return false;}
    [[nodiscard]] virtual bool found_while(parse_location _location, std::unique_ptr<formula_node> expression) noexcept { return false; }
 
    virtual void post_process(formula_post_process_context &context) {}
 
    [[nodiscard]] virtual datum evaluate(formula_evaluation_context &context) {
        tt_no_default();
    }
 
    [[nodiscard]] std::string evaluate_output(formula_evaluation_context &context) {
        auto tmp = evaluate(context);
        if (tmp.is_break()) {
            throw operation_error("{}: Found #break not inside a loop statement.", location);
 
        } else if (tmp.is_continue()) {
            throw operation_error("{}: Found #continue not inside a loop statement.", location);
 
        } else if (tmp.is_undefined()) {
            return std::move(context.output);
 
        } else {
            throw operation_error("{}: Found #return not inside a function.", location);
        }
    }
 
    [[nodiscard]] std::string evaluate_output() {
        auto context = formula_evaluation_context{};
        return evaluate_output(context);
    }
 
    [[nodiscard]] virtual std::string string() const noexcept {
        return "<skeleton_node>";
    }
 
    [[nodiscard]] friend std::string to_string(skeleton_node const &lhs) noexcept {
        return lhs.string();
    }
 
    friend std::ostream &operator<<(std::ostream &lhs, skeleton_node const &rhs) {
        return lhs << to_string(rhs);
    }
 
    static void append_child(statement_vector &children, std::unique_ptr<skeleton_node> new_child) {
        if (std::ssize(children) > 0 && new_child->should_left_align()) {
            children.back()->left_align();
        }
        children.push_back(std::move(new_child));
    }
 
    [[nodiscard]] static datum evaluate_formula_without_output(formula_evaluation_context &context, formula_node const &expression, parse_location const &location) {
        try {
            return expression.evaluate_without_output(context);
 
        } catch (std::exception const &e) {
            throw operation_error("{}: Could not evaluate.\n{}", location, e.what());
        }
    }
 
    [[nodiscard]] static datum evaluate_expression(formula_evaluation_context &context, formula_node const &expression, parse_location const &location) {
        try {
            return expression.evaluate(context);
 
        } catch (std::exception const &e) {
            throw operation_error("{}: Could not evaluate expression.\n{}", location, e.what());
        }
    }
 
    static void post_process_expression(formula_post_process_context &context, formula_node &expression, parse_location const &location) {
        try {
            return expression.post_process(context);
 
        } catch (std::exception const &e) {
            throw operation_error("{}: Could not post-process expression.\n{}", location, e.what());
        }
    }
 
    [[nodiscard]] static datum evaluate_children(formula_evaluation_context &context, statement_vector const &children) {
        for (ttlet &child: children) {
            ttlet tmp = child->evaluate(context);
            if (!tmp.is_undefined()) {
                return tmp;
            }
        }
        return {};
    }
};
 
}