qmk_firmware/users/dennytom/chording_engine/engine.part.1

enum chord_states {
    IDLE,
    READY,
    ACTIVATED,
    DEACTIVATED,
    PRESS_FROM_ACTIVE,
    FINISHED_FROM_ACTIVE,
    IDLE_IN_DANCE,
    READY_IN_DANCE,
    FINISHED,
    LOCKED,
    READY_LOCKED,
    RESTART,
    IN_ONE_SHOT
};

struct Chord {
    uint32_t keycodes_hash;
    uint8_t pseudolayer;
    uint8_t* state;
    uint8_t* counter;
    uint16_t value1;
    uint8_t value2;
    void (*function) (const struct Chord*);
};

uint8_t current_pseudolayer = DEFAULT_PSEUDOLAYER;
bool lock_next = false;
uint16_t chord_timer = 0;
uint16_t dance_timer = 0;
bool autoshift_mode = true;
uint8_t keycode_index = 0;
uint8_t command_mode = 0;
uint8_t command_ind = 0;
bool in_leader_mode = false;
uint8_t leader_ind = 0;
uint16_t leader_timer = 0;
uint8_t dynamic_macro_mode = false;
uint8_t dynamic_macro_ind = 0;
bool a_key_went_through = false;
struct Chord* last_chord = NULL;

bool handle_US_ANSI_shifted_keys(int16_t keycode, bool in) {
    bool is_US_ANSI_shifted = true;
    
    int16_t regular_keycode = KC_NO;
    switch (keycode) {
        case KC_TILDE:
            regular_keycode = KC_GRAVE;
            break;
        case KC_EXCLAIM:
            regular_keycode = KC_1;
            break;
        case KC_AT:
            regular_keycode = KC_2;
            break;
        case KC_HASH:
            regular_keycode = KC_3;
            break;
        case KC_DOLLAR:
            regular_keycode = KC_4;
            break;
        case KC_PERCENT:
            regular_keycode = KC_5;
            break;
        case KC_CIRCUMFLEX:
            regular_keycode = KC_6;
            break;
        case KC_AMPERSAND:
            regular_keycode = KC_7;
            break;
        case KC_ASTERISK:
            regular_keycode = KC_8;
            break;
        case KC_LEFT_PAREN:
            regular_keycode = KC_9;
            break;
        case KC_RIGHT_PAREN:
            regular_keycode = KC_0;
            break;
        case KC_UNDERSCORE:
            regular_keycode = KC_MINUS;
            break;
        case KC_PLUS:
            regular_keycode = KC_EQUAL;
            break;
        case KC_LEFT_CURLY_BRACE:
            regular_keycode = KC_LBRACKET;
            break;
        case KC_RIGHT_CURLY_BRACE:
            regular_keycode = KC_RBRACKET;
            break;
        case KC_PIPE:
            regular_keycode = KC_BSLASH;
            break;
        case KC_COLON:
            regular_keycode = KC_SCOLON;
            break;
        case KC_DOUBLE_QUOTE:
            regular_keycode = KC_QUOTE;
            break;
        case KC_LEFT_ANGLE_BRACKET:
            regular_keycode = KC_COMMA;
            break;
        case KC_RIGHT_ANGLE_BRACKET:
            regular_keycode = KC_DOT;
            break;
        case KC_QUESTION:
            regular_keycode = KC_SLASH;
            break;
        default:
            is_US_ANSI_shifted = false;
    }
    if (is_US_ANSI_shifted) {
        if (in) {
            register_code(KC_LSFT);
            register_code(regular_keycode);
        } else {
            unregister_code(regular_keycode);
            unregister_code(KC_LSFT);
        }
    }
    return is_US_ANSI_shifted;
}

void key_in(int16_t keycode) {
    if (command_mode == 1 && command_ind < COMMAND_MAX_LENGTH) {
        command_buffer[command_ind] = keycode;
        command_ind++;
        a_key_went_through = true;
    } else if (in_leader_mode && leader_ind < LEADER_MAX_LENGTH) {
        leader_buffer[leader_ind] = keycode;
        leader_ind++;
        a_key_went_through = true;
    } else if (dynamic_macro_mode && dynamic_macro_ind < DYNAMIC_MACRO_MAX_LENGTH) {
        dynamic_macro_buffer[dynamic_macro_ind] = keycode;
        dynamic_macro_ind++;
        a_key_went_through = true;
    } else {
        if (!handle_US_ANSI_shifted_keys(keycode, true)) {
            register_code(keycode);
        }
        send_keyboard_report();
        a_key_went_through = true;
    }
}

void key_out(int16_t keycode) {
    if (command_mode == 0) {
        if (!handle_US_ANSI_shifted_keys(keycode, false)) {
            if (command_mode == 0 && in_leader_mode == false && dynamic_macro_mode == false) {
                unregister_code(keycode);
            }
        }
        send_keyboard_report();
    }
}

void tap_key(int16_t keycode) {
    key_in(keycode);
    wait_ms(TAP_TIMEOUT);
    key_out(keycode);
}