/* Copyright (C) 2021 Aidan Hahn
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

use crate::segment::{Ctr, Seg};
use crate::sym::{SymTable};

// Some essential operations below
pub fn append_callback (ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
    // if car is a list, append cdr
    // otherwise create a list out of all arguments
    if let Ctr::Seg(ref s) = *ast.car {
        let mut temp = s.clone();
        temp.append(ast.cdr.clone());
        Ok(Ctr::Seg(temp))
    } else {
        let mut temp = Seg::new();
        let mut car_iter = &ast.car;
        let mut cdr_iter = &ast.cdr;
        loop {
            temp.append(car_iter.clone());
            if let Ctr::Seg(ref s) = **cdr_iter {
                car_iter = &s.car;
                cdr_iter = &s.cdr;
            } else {
                break;
            }
        }

        Ok(Ctr::Seg(temp))
    }
}

pub fn expand_callback (ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
    if let Ctr::Seg(_) = *ast.car {
        Ok(*ast.car.clone())
    } else {
        Err("non list passed to expand!".to_string())
    }
}