/* 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 crate::eval::eval;
use crate::lex::lex;
use crate::segment::{Seg, Ctr};
use crate::sym::{SymTable, ValueType, Args, Symbol};
use std::fs;
use std::io;
use std::rc::Rc;

fn prompt_default_callback(_: &Seg, _: &mut SymTable) -> Result<Ctr, String> {
    Ok(Ctr::Symbol("λ ".to_string()))
}

/* loads defaults, evaluates config script */
pub fn configure(filename: String, syms: &mut SymTable) -> Result<(), String> {
    syms.insert("CFG_RELISH_POSIX".to_string(), Symbol {
        name: String::from("CFG_RELISH_POSIX"),
        args: Args::None,
        conditional_branches: false,
        value: ValueType::VarForm(Box::new(Ctr::String("0".to_string()))),
    });

    syms.insert("CFG_RELISH_ENV".to_string(), Symbol {
        name: String::from("CFG_RELISH_ENV"),
        args: Args::None,
        conditional_branches: false,
        value: ValueType::VarForm(Box::new(Ctr::String("1".to_string()))),
    });

    syms.insert("CFG_RELISH_PROMPT".to_string(), Symbol {
        name: String::from("default relish prompt"),
        args: Args::None,
        conditional_branches: false,
        value: ValueType::Internal(Rc::new(prompt_default_callback)),
    });

    let config_document = fs::read_to_string(filename).unwrap_or_else(|err: io::Error| err.to_string());
    let config_tree = lex(&config_document)?;
    let config_result = eval(&config_tree, syms)?;

    println!("config result: {config_result}");
    Ok(())
}