/* 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::cell::RefCell;
use std::rc::Rc;
use std::collections::HashMap;
use crate::segment::{Ctr, Ast};
use crate::func::{Function, Operation, Args, FTable};
/* Mapping between a string token and a tree of Segments
 * The string token can be found in any Ctr::Symbol value
 * it is expected that the trees stored are already evaluated
 */
pub type VTable = HashMap<String, Rc<Ctr>>;

// WARNING: make sure var_tree is properly evaluated before storing
pub fn define(
    vt: Rc<RefCell<VTable>>,
    identifier: String,
    var_tree: Rc<Ctr>
) {
    if let Some(rc_segment) = vt.borrow_mut().insert(identifier, var_tree) {
        drop(rc_segment);
    }
}

pub fn get_export() -> Function {
    return Function{
        name: String::from("export"),
        loose_syms: true,
        eval_lazy: false,
        args: Args::Lazy(2),
        function: Operation::Internal(
            |a: Ast, b: Rc<RefCell<VTable>>, _c: Rc<RefCell<FTable>>| -> Ctr {
                let inner = a.borrow_mut();
                match &inner.car {
                    Ctr::Symbol(identifier) => {
                        define(b, identifier.to_string(), Rc::new(inner.cdr.clone()));
                        return Ctr::None;
                    },
                    _ => {
                        eprintln!("first argument to export must be a symbol");
                        return Ctr::None;
                    }
                }
            }
        )
    };
}