/* relish: versatile lisp shell
 * 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 std::rc::Rc;
use std::cell::RefCell;
use crate::segment::{Ast, Ctr};
use crate::func::FTable;
use crate::vars::VTable;

/* iterates over a syntax tree
 * returns a NEW LIST of values
 * representing the simplest possible form of the input
 */
pub fn eval(
    ast: Ast,
    vars: Rc<RefCell<VTable>>,
    funcs: Rc<RefCell<FTable>>,
    sym_loose: bool
) -> Result<Ast, String> {
    eval_inner(ast, vars, funcs, sym_loose, true)
}

fn eval_inner(
    ast: Ast,
    vars: Rc<RefCell<VTable>>,
    funcs: Rc<RefCell<FTable>>,
    sym_loose: bool,
    first_item: bool
) -> Result<Ast, String> {
    /* TODO:
     * 1. make new ast
     * 2. call process_ctr on ast.car
     * 3. set new.car to result
     * 3. if cdr is an AST
     *   - set first_item to false
     *   - set new.cdr to recur of this
     * 4. else call process_ctr on cdr
     *    (and set new.cdr to result)
     * 5. return new ast
     */
}

fn process_ctr(
    ctr: Ctr,
    vars: Rc<RefCell<VTable>>,
    funcs: Rc<RefCell<FTable>>,
    sym_loose: bool,
    first_item: bool
) -> Result<Ctr, String> {
    /* TODO:
     *   1. if symbol, unwrap (DEEP COPY)
     *   2. if first_item and symbol, call function?
     *      (else: return var copy)
     *   3. if list return result of eval()
     *   4. finally, return a clone (shallow copy) of datum
}