/* 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 std::env;
use crate::segment::{Ctr, Ast, ast_to_string};
use crate::eval::eval;
use crate::func::{Function, Operation, InternalOperation, 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(env_cfg: bool) -> Function {
    return Function{
        name: String::from("export"),
        loose_syms: true,
        eval_lazy: true,
        args: Args::Lazy(2),
        function: Operation::Internal(get_export_callback(env_cfg)),
    };
}

fn get_export_callback(env_cfg: bool) -> InternalOperation {
    |a: Ast, b: Rc<RefCell<VTable>>, c: Rc<RefCell<FTable>>| -> Ctr {
        let inner = a.borrow_mut();
        match &inner.car {
            Ctr::Symbol(identifier) => {
                match &inner.cdr {
                    Ctr::Seg(tree) => {
                        match eval(tree.clone(), b.clone(), c.clone(), false) {
                            Ok(seg) => {
                                match seg {
                                    Ctr::Seg(val) => {
                                        let val_tmp = val.borrow().clone();
                                        define(b, identifier.to_string(), Rc::new(val_tmp.car));
                                        if env_cfg {
                                            match val_tmp.car {
                                                Ctr::Symbol(s)  => env::set_var(identifier, s),
                                                Ctr::String(s)  => env::set_var(identifier, s),
                                                Ctr::Integer(i) => env::set_var(identifier, format!("{}", i)),
                                                Ctr::Float(f)   => env::set_var(identifier, format!("{}", f)),
                                                Ctr::Bool(b)    => env::set_var(identifier, format!("{}", b)),
                                                Ctr::Seg(c)     => env::set_var(identifier, ast_to_string(c)),
                                                Ctr::None       => ()
                                            }
                                        }
                                    },

                                    _ => eprintln!("impossible args to export")
                                }
                            },

                            Err(e) => eprintln!("couldnt eval symbol: {}", e)
                        }
                    },

                    Ctr::None => {
                        (*b).borrow_mut().remove(identifier);
                        if env_cfg {
                            // TODO: unset variable
                        }
                    },

                    _ => eprintln!("args not in standard form")
                }
            },

            _ => eprintln!("first argument to export must be a symbol")
        }

        return Ctr::None;
    }
}