elna/shell/state.cpp

#include <algorithm>
#include <boost/endian.hpp>

#include "elna/shell/state.hpp"

namespace elna
{
    std::string cursor_to_column(const std::uint16_t position)
    {
        std::string code = std::to_string(position);
        code.insert(0, "\x1b[");
        code.push_back('G');

        return code;
    }

    key::key()
        : store(0x1bu)
    {
    }

    key::key(const char_t c, const std::uint8_t modifiers)
        : store(c), modifiers(modifiers == 0 ? 0 : modifiers - 1)
    {
    }

    key::key(const char_t c, const modifier modifiers)
        : store(c), modifiers(static_cast<uint8_t>(modifiers))
    {
    }

    key::key(const special_key control, const std::uint8_t modifiers)
        : store(control), modifiers(modifiers == 0 ? 0 : modifiers - 1)
    {
    }

    key::key(const special_key control, const modifier modifiers)
        : store(control), modifiers(static_cast<uint8_t>(modifiers))
    {
    }

    key::char_t key::character() const
    {
        return std::get<char_t>(this->store);
    }

    special_key key::control() const
    {
        return std::get<special_key>(this->store);
    }

    bool key::modified(const std::uint8_t modifiers) const noexcept
    {
        return this->modifiers == modifiers;
    }

    bool key::modified(const modifier modifiers) const noexcept
    {
        return this->modifiers == static_cast<std::uint8_t>(modifiers);
    }

    bool key::operator==(const char_t c) const
    {
        return std::holds_alternative<char_t>(this->store)
            && std::get<char_t>(this->store) == c;
    }

    bool key::operator==(const special_key control) const
    {
        return std::holds_alternative<special_key>(this->store)
            && std::get<special_key>(this->store) == control;
    }

    bool key::operator==(const key& that) const
    {
        return this->store == that.store;
    }

    bool key::operator!=(const char_t c) const
    {
        return !(*this == c);
    }

    bool key::operator!=(const special_key control) const
    {
        return !(*this == control);
    }

    bool key::operator!=(const key& that) const
    {
        return !(*this == that);
    }

    bool key::is_character() const noexcept
    {
        return std::holds_alternative<char_t>(this->store);
    }

    bool key::is_control() const noexcept
    {
        return std::holds_alternative<special_key>(this->store);
    }

    bool key::empty() const noexcept
    {
        return *this == '\x1b';
    }

    bool operator==(const special_key control, const key& that)
    {
        return that == control;
    }

    bool operator==(const char c, const key& that)
    {
        return that == c;
    }

    bool operator!=(const special_key control, const key& that)
    {
        return that != control;
    }

    bool operator!=(const char c, const key& that)
    {
        return that != c;
    }

    editor_state::editor_state()
    {
        this->input.reserve(1024);
    }

    void editor_state::load(const std::string& text)
    {
        this->input = text;
        this->position = this->input.size() + 1;
    }

    const std::string& editor_state::command_line() const noexcept
    {
        return this->input;
    }

    std::size_t editor_state::absolute_position() const noexcept
    {
        return this->prompt.size() + this->position;
    }

    std::size_t editor_state::relative_position() const noexcept
    {
        return this->position;
    }

    void editor_state::insert(const std::string& text)
    {
        this->input.insert(this->position - 1, text);
        this->position += text.size();
    }

    void editor_state::insert(const key::char_t text)
    {
        if (text == 0u)
        {
            this->input.insert(this->position - 1, '\0', 1);
            ++this->position;
            return;
        }
        key::char_t buffer = boost::endian::native_to_big<key::char_t>(text);

        const char *begin = reinterpret_cast<char *>(&buffer);
        const char *end = begin + sizeof(key::char_t);
        const char *significant = std::find_if(begin, end,
                [](const char byte) {
                    return byte != 0;
                });

        this->input.insert(this->position - 1, significant, end - significant);
        this->position += end - significant;
    }

    action editor_state::process_keypress(const key& press)
    {
        if (press.is_control())
        {
            switch (press.control())
            {
                case special_key::arrow_left:
                    if (this->position > 1)
                    {
                        --this->position;
                    }
                    return action::move;
                case special_key::arrow_right:
                    if (this->position + 1 < this->input.size() + this->prompt.size())
                    {
                        ++this->position;
                    }
                    return action::move;
                case special_key::arrow_up:
                case special_key::arrow_down:
                    return action::history;
                case special_key::home_key:
                    this->position = 1;
                    return action::move;
                case special_key::end_key:
                    this->position = this->input.size() + 1;
                    return action::move;
                default:
                    return action::ignore;
            }
        }
        else if (press.modified(modifier::ctrl))
        {
            switch (press.character())
            {
                case 'd':
                    return action::finalize;
                case 't':
                    return action::complete;
                default:
                    return action::ignore;
            }
        }
        else
        {
            switch (press.character())
            {
                case 127: // Backspace.
                    if (this->position <= this->input.size() + 1 && this->position > 1)
                    {
                        --this->position;
                        this->input.erase(this->position - 1, 1);
                    }
                    return action::redraw;
                case 9: // Tab.
                    return action::complete;
                case '\r':
                    return action::finalize;
                default:
                    if (this->position - 1 < input.size())
                    {
                        insert(press.character());
                        return action::redraw;
                    }
                    else
                    {
                        insert(press.character());
                        return action::write;
                    }
            }
        }
    }
}