fish-shell/src/parse_productions.h

// Programmatic representation of fish code.
#ifndef FISH_PARSE_TREE_CONSTRUCTION_H
#define FISH_PARSE_TREE_CONSTRUCTION_H

#include <stdbool.h>
#include <sys/types.h>

#include "parse_constants.h"

struct parse_token_t;

namespace parse_productions {

#define MAX_SYMBOLS_PER_PRODUCTION 6

// A production is an array of unsigned char. Symbols are encoded directly as their symbol value.
// Keywords are encoded with an offset of LAST_TOKEN_OR_SYMBOL + 1. So essentially we glom together
// keywords and symbols.
typedef uint8_t production_element_t;
typedef production_element_t const production_t[MAX_SYMBOLS_PER_PRODUCTION];

/// Resolve the type from a production element.
inline parse_token_type_t production_element_type(production_element_t elem) {
    if (elem > LAST_TOKEN_OR_SYMBOL) {
        return parse_token_type_string;
    } else {
        return static_cast<parse_token_type_t>(elem);
    }
}

/// Resolve the keyword from a production element.
inline parse_keyword_t production_element_keyword(production_element_t elem) {
    if (elem > LAST_TOKEN_OR_SYMBOL) {
        // First keyword is LAST_TOKEN_OR_SYMBOL + 1.
        return static_cast<parse_keyword_t>(elem - LAST_TOKEN_OR_SYMBOL - 1);
    } else {
        return parse_keyword_none;
    }
}

/// Check if an element is valid.
inline bool production_element_is_valid(production_element_t elem) {
    return elem != token_type_invalid;
}

/// Fetch a production. We are passed two input tokens. The first input token is guaranteed to not
/// be invalid; the second token may be invalid if there's no more tokens. We may also set flags.
const production_t *production_for_token(parse_token_type_t node_type, const parse_token_t &input1,
                                         const parse_token_t &input2, uint8_t *out_tag);
}

#endif