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module;
#include <algorithm>
#include <boost/sml.hpp>
#include <queue>
#include <span>
#include <string>
export module ttwhy.terminal:scanner;
import :events;
import :policies;
import ttwhy.core;
namespace ttwhy::terminal::detail
{
/// Events
struct byte_received
{
char value;
};
struct c1_received
{
unsigned char value;
};
struct timeout_expired
{
};
/// States
constexpr auto idle = boost::sml::state<class idle>;
constexpr auto escape_sequence = boost::sml::state<class escape_sequence>;
constexpr auto csi_sequence = boost::sml::state<class csi_sequence>;
constexpr auto ss3_sequence = boost::sml::state<class ss3_sequence>;
/// Guards
constexpr auto is_backspace = [](byte_received e) {
return e.value == '\x08' || e.value == '\x7f';
};
constexpr auto is_tab = [](byte_received e) {
return e.value == '\x09';
};
constexpr auto is_enter = [](byte_received e) {
return e.value == '\x0a' || e.value == '\x0d';
};
constexpr auto is_escape = [](byte_received e) {
return e.value == '\x1b';
};
constexpr auto is_printable = [](byte_received e) {
return e.value >= ' ' && e.value <= '~';
};
constexpr auto is_c0_chord = [](byte_received e) {
return e.value >= '\0' && e.value <= '\x1f' && !is_backspace(e) && !is_tab(e) && !is_enter(e) && !is_escape(e);
};
constexpr auto is_fe = [](byte_received e) {
return e.value >= '@' && e.value <= '_';
};
constexpr auto is_csi = [](c1_received e) {
return e.value == u'\x9b';
};
constexpr auto is_ss3 = [](c1_received e) {
return e.value == u'\x8f';
};
constexpr auto is_unhandled_c1 = [](c1_received e) {
return !(is_csi(e) || is_ss3(e));
};
constexpr auto is_csi_param = [](byte_received e) {
return e.value >= ' ' && e.value <= '?';
};
constexpr auto is_vt100_terminator = [](byte_received e) {
return e.value >= '@' && e.value <= '}';
};
constexpr auto is_vt220_terminator = [](byte_received e) {
return e.value == '~';
};
/// Transitions
template<event_sink Sink, typename TerminalPolicy>
struct transition_table
{
auto operator()() const noexcept
{
using namespace boost::sml;
constexpr auto push_character = [](byte_received event, Sink & sink) {
sink(character_event{event.value});
};
constexpr auto push_backspace = [](Sink & sink) {
sink(control_event{control_key::backspace});
};
constexpr auto push_tab = [](Sink & sink) {
sink(control_event(control_key::tab));
};
constexpr auto push_enter = [](Sink & sink) {
sink(control_event(control_key::enter));
};
constexpr auto push_c0_chord = [](byte_received event, Sink & sink) {
sink(ctrl_chord_event{static_cast<char>(event.value + 0x40)});
};
constexpr auto dispatch_c1 = [](byte_received event, back::process<c1_received> process) {
process(c1_received{static_cast<unsigned char>(event.value + 0x40)});
};
constexpr auto fallback_fe = [](c1_received event, Sink & sink) {
sink(control_event{control_key::escape});
sink(character_event{static_cast<char>(event.value - 0x40)});
};
constexpr auto emit_timeout_escape = [](Sink & sink, std::string & buffer) {
sink(control_event{control_key::escape});
buffer.clear();
};
constexpr auto fallback_escape = [](byte_received event, Sink & sink) {
sink(control_event{control_key::escape});
if (event.value >= ' ' && event.value <= '~')
{
sink(character_event{event.value});
}
};
constexpr auto clear_csi = [](std::string & buffer) {
buffer.clear();
};
constexpr auto push_csi_parameter = [](byte_received const & event, std::string & buffer) {
buffer.push_back(event.value);
};
constexpr auto resolve_vt100_cursor = [](byte_received event, std::string & buffer, Sink & sink) {
TerminalPolicy::resolve_vt100_cursor(event.value, buffer, sink);
buffer.clear();
};
constexpr auto resolve_vt220_keypad = [](std::string & buffer, Sink & sink) {
TerminalPolicy::resolve_vt220_keypad(buffer, sink);
buffer.clear();
};
constexpr auto resolve_ss3 = [](byte_received event, Sink & sink) {
TerminalPolicy::resolve_ss3(event.value, sink);
};
// clang-format off
return make_transition_table(
*idle + event<byte_received>[is_escape] = escape_sequence,
idle + event<byte_received>[is_backspace] / push_backspace = idle,
idle + event<byte_received>[is_tab] / push_tab = idle,
idle + event<byte_received>[is_enter] / push_enter = idle,
idle + event<byte_received>[is_c0_chord] / push_c0_chord = idle,
idle + event<byte_received>[is_printable] / push_character = idle,
escape_sequence + event<byte_received>[is_fe] / dispatch_c1 = idle,
escape_sequence + event<byte_received>[!is_fe] / fallback_escape = idle,
escape_sequence + event<timeout_expired> / emit_timeout_escape = idle,
idle + event<c1_received>[is_csi] / clear_csi = csi_sequence,
idle + event<c1_received>[is_ss3] = ss3_sequence,
idle + event<c1_received>[is_unhandled_c1] / fallback_fe = idle,
csi_sequence + event<byte_received>[is_csi_param] / push_csi_parameter = csi_sequence,
csi_sequence + event<byte_received>[is_vt220_terminator] / resolve_vt220_keypad = idle,
csi_sequence + event<byte_received>[is_vt100_terminator] / resolve_vt100_cursor = idle,
csi_sequence + event<timeout_expired> / emit_timeout_escape = idle,
ss3_sequence + event<byte_received> / resolve_ss3 = idle,
ss3_sequence + event<timeout_expired> / emit_timeout_escape = idle
);
// clang-format on
}
};
} // namespace ttwhy::terminal::detail
export namespace ttwhy::terminal
{
//! State machine tokenizer that decodes terminal escape sequences into input events.
//!
//! @tparam Sink The event sink callable type.
//! @tparam TerminalPolicy The terminal escape policy.
template<event_sink Sink, typename TerminalPolicy>
struct scanner
{
//! Construct a terminal scanner bound to an event sink.
//!
//! @param sink The event sink to deliver decoded input events to.
explicit scanner(Sink & sink)
: m_state_machine{sink, m_csi_buffer}
{}
//! Process a buffer of incoming raw bytes through the state machine.
//!
//! @param buffer The view of raw bytes to decode.
auto process(std::span<char const> buffer) -> void
{
std::ranges::for_each(buffer, [&](auto byte) { m_state_machine.process_event(detail::byte_received{byte}); });
}
//! Notify the state machine that an inter-byte timeout expired.
auto timeout()
{
m_state_machine.process_event(detail::timeout_expired{});
}
//! Check if an escape sequence is currently pending completion.
//!
//! @return True if a sequence is incomplete, false otherwise.
[[nodiscard]] auto is_pending() const -> bool
{
return m_state_machine.is(detail::escape_sequence) || //
m_state_machine.is(detail::csi_sequence) || //
m_state_machine.is(detail::ss3_sequence);
}
private:
std::string m_csi_buffer{};
boost::sml::sm<detail::transition_table<Sink, TerminalPolicy>, boost::sml::process_queue<std::queue>>
m_state_machine;
};
//! Convenience alias for a terminal scanner configured with the ANSI policy.
//!
//! @tparam Sink The event sink callable type.
template<event_sink Sink>
using ansi = scanner<Sink, ansi_policy>;
//! Convenience alias for a terminal scanner configured with the xterm policy.
//!
//! @tparam Sink The event sink callable type.
template<event_sink Sink>
using xterm = scanner<Sink, xterm_policy>;
} // namespace ttwhy::terminal
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