sapphire/src/Parser.h

#pragma once
#include <memory>
#include "Lexer.h"
#include "AST/NumberNode.h"
#include "Error.h"
#include <cassert>

/* Parser class for the Sapphire compiler. */
class Parser
{
    /* Struct to store a parsing result which can be either a parsing error or a success, in which case it contains a pointer to the result. */
    template<typename T>
    struct ErrorOr
    {
        /* Return the stored pointer. */
        std::shared_ptr<T> get()
        {
            assert(!m_is_error);
            return m_ptr;
        }

        /* Call Error::throw_error() with the stored error's location, line text, and the error string provided to this struct instance. */
        void ethrow()
        {
            assert(m_is_error);
            Error::throw_error(error_tok->loc,error_tok->line(),m_error);
        }

        /* Construct a new successful ErrorOr with a heap-allocated pointer to the result class. */
        ErrorOr(T* ptr) : m_ptr(ptr), m_is_error(false) {}
        /* Construct a new failed ErrorOr with the error details and the token where parsing failed. */
        ErrorOr(const std::string& error, const Token& error_tok) : m_error(error), m_is_error(true), error_tok(error_tok) {}

        /* Is this ErrorOr instance successful or failed? */
        bool is_error() { return m_is_error; }

    private:
        bool m_is_error;
        std::string m_error;
        std::shared_ptr<Token> error_tok;
        std::shared_ptr<T> m_ptr;
    };
private:
    Parser(const TokenStream& tokens);
    TokenStream tokens;

    ErrorOr<ExprNode> walk_expr();
    ErrorOr<NumberNode> walk_number();

    int m_index;
    int saved_m_index;

    void save_current_position();
    void restore_current_position();
public:
    ~Parser();

    /* Construct a new Parser with the given TokenStream. */
    static std::shared_ptr<Parser> new_parser(const TokenStream& tokens);
    /* Parse the stored TokenStream and return the top-level node of the result Abstract Syntax Tree. */
    std::shared_ptr<ASTNode> parse();
};