void alert_parse(struct state *state) { }

int disambiguator(struct state *old, struct state *new) {
    // fprintf(stderr, "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
    // print_parse_tree(old, 0, stderr);
    // print_parse_tree(new, 0, stderr);
    // fprintf(stderr, "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n");

    if (old->n_poisoned < new->n_poisoned) return 0;
    if (new->n_poisoned < old->n_poisoned) return 1;

    // Prefer the earlier parsings in the grammar when two entirely different
    // productions are taken.
    if (old->production_id != new->production_id)
        return (old->production_id < new->production_id) ? 0 : 1;

    // If they're the same production ...
    prod_id_t prod = old->production_id;

    if (PRODUCTION_ID_TO_SYMBOL[prod] == START_SYMBOL
            && PRODUCTION_ID_TO_PRODUCTION[prod][1] != DONE_SYMBOL) {
        struct token *old_tok = find_token(old, 1),
                     *new_tok = find_token(new, 1);
        if (old_tok < new_tok)      return 0;
        else if (old_tok > new_tok) return 1;
    }

    if (PRODUCTION_ID_TO_PRODUCTION[prod][0] == SYMBOL_ERROR && PRODUCTION_ID_TO_PRODUCTION[prod][1] != DONE_SYMBOL) {
        struct token *old_tok = find_token(old, 1),
                     *new_tok = find_token(new, 1);
        if (old_tok < new_tok)      return 0;
        else if (old_tok > new_tok) return 1;
    } else if (PRODUCTION_ID_TO_PRODUCTION[prod][1] == SYMBOL_ERROR) {
        struct token *old_tok = find_token(old, 1),
                     *new_tok = find_token(new, 1);
        if (old_tok < new_tok)      return 1;
        else if (old_tok > new_tok) return 0;
    } else if (PRODUCTION_ID_TO_SYMBOL[prod] == SYMBOL_EXPR) {
        if (PRODUCTION_ID_TO_PRODUCTION[prod][1] == SYMBOL_OP) {
            struct token *old_tok = find_token(old, 1),
                         *new_tok = find_token(new, 1);
            char *old_s = old_tok->string, *new_s = new_tok->string;
            const char *precedence[] = {".", "->", "*", "/", "%", "+", "-",
                "<<", ">>", "<", "<=", ">", ">=", "==", "!=", "&", "|", "&&",
                "||", "=", "+=", "-=", "*=", "/=", "%=", "<<=", ">>=", "&=",
                "^=", "|=", ",", ":", 0};
            if (strcmp(old_s, new_s)) {
                for (const char **p = precedence; *p; p++) {
                    if (!strcmp(old_s, *p)) {
                        return 1;
                    } else if (!strcmp(new_s, *p)) {
                        return 0;
                    }
                }
                fprintf(stderr, "ERROR: didn't find operator '%s'\n", old_s);
                exit(1);
            } else {
                if (old_tok < new_tok)      return 1;
                else if (old_tok > new_tok) return 0;
            }
        }
    }

    // Generally speaking, we want left associativity to avoid long chains of
    // completions.
    struct token *old_tok = find_token(old, 1),
                 *new_tok = find_token(new, 1);
    if (old_tok < new_tok)      return 1;
    else if (old_tok > new_tok) return 0;

    fprintf(stderr, "TOTALLY UNKNOWN!\n");
    fprintf(stderr, "~~~~~~~~~~~~~~~~~~~~~\n");
    pprint_state(old);
    // print_parse_tree(old, 0, stderr);
    fprintf(stderr, "~~~~~~~~~~~~~~~~~~~~~\n");
    pprint_state(new);
    // print_parse_tree(new, 0, stderr);
    fprintf(stderr, "~~~~~~~~~~~~~~~~~~~~~\n");
    exit(1);
    return 2;
}