/* 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::segment::{Ctr, Seg, Type};
use crate::sym::{Args, SymTable, Symbol, UserFn, ValueType};
use std::env;
use std::rc::Rc;

pub mod append;
pub mod control;
pub mod boolean;
//pub mod str;

/// static_stdlib
/// inserts all stdlib functions that can be inserted without
/// any kind of further configuration data into a symtable
pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
    syms.insert(
        "append".to_string(),
        Symbol {
            name: String::from("append"),
            args: Args::Infinite,
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(append::append_callback)),
        },
    );

    syms.insert(
        "expand".to_string(),
        Symbol {
            name: String::from("expand"),
            args: Args::Strict(vec![Type::Seg]),
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(append::expand_callback)),
        },
    );

    syms.insert(
        "echo".to_string(),
        Symbol {
            name: String::from("echo"),
            args: Args::Infinite,
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(_echo_callback)),
        },
    );

    syms.insert(
        "if".to_string(),
        Symbol {
            name: String::from("if"),
            args: Args::Lazy(3),
            conditional_branches: true,
            value: ValueType::Internal(Rc::new(control::if_callback)),
        },
    );

    syms.insert(
        "let".to_string(),
        Symbol {
            name: String::from("let"),
            args: Args::Infinite,
            conditional_branches: true,
            value: ValueType::Internal(Rc::new(control::let_callback)),
        },
    );

    syms.insert(
        "while".to_string(),
        Symbol {
            name: String::from("while"),
            args: Args::Infinite,
            conditional_branches: true,
            value: ValueType::Internal(Rc::new(control::while_callback)),
        },
    );

    syms.insert(
        "circuit".to_string(),
        Symbol {
            name: String::from("circuit"),
            args: Args::Infinite,
            conditional_branches: true,
            value: ValueType::Internal(Rc::new(control::circuit_callback)),
        },
    );

    syms.insert(
        "and".to_string(),
        Symbol {
            name: String::from("and"),
            args: Args::Infinite,
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(boolean::bool_and_callback)),
        }
    );

    syms.insert(
        "or".to_string(),
        Symbol {
            name: String::from("or"),
            args: Args::Infinite,
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(boolean::bool_or_callback)),
        }
    );

    syms.insert(
        "not".to_string(),
        Symbol {
            name: String::from("not"),
            args: Args::Strict(vec![Type::Bool]),
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(boolean::bool_not_callback)),
        }
    );

    syms.insert(
        "eq?".to_string(),
        Symbol {
            name: String::from("eq?"),
            args: Args::Infinite,
            conditional_branches: false,
            value: ValueType::Internal(Rc::new(boolean::bool_iseq_callback)),
        }
    );

    syms.insert(
        "toggle".to_string(),
        Symbol {
            name: String::from("toggle"),
            args: Args::Lazy(1),
            conditional_branches: true,
            value: ValueType::Internal(Rc::new(boolean::bool_toggle_callback)),
        }
    );

    Ok(())
}

/// dynamic_stdlib
/// takes configuration data and uses it to insert dynamic
/// callbacks with configuration into a symtable
pub fn dynamic_stdlib(syms: &mut SymTable) -> Result<(), String> {
    //get CFG_RELISH_ENV from syms
    let env_cfg_user_form = syms
        .call_symbol(&"CFG_RELISH_ENV".to_string(), &Seg::new(), true)
        .unwrap_or_else(|_: String| Box::new(Ctr::None))
        .to_string()
        .ne("");

    syms.insert(
        "def".to_string(),
        Symbol {
            name: String::from("define"),
            args: Args::Infinite,
            conditional_branches: true,
            value: ValueType::Internal(Rc::new(
                move |ast: &Seg, syms: &mut SymTable| -> Result<Ctr, String> {
                    _store_callback(ast, syms, env_cfg_user_form)
                },
            )),
        },
    );

    Ok(())
}

fn _echo_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
    if ast.len() == 1 {
        println!("{}", ast.car);
    } else {
        ast.circuit(&mut |arg: &Ctr| print!("{}", arg) == ());
    }

    Ok(Ctr::None)
}

fn _store_callback(ast: &Seg, syms: &mut SymTable, env_cfg: bool) -> Result<Ctr, String> {
    let is_var = ast.len() == 2;
    if let Ctr::Symbol(ref identifier) = *ast.car {
        match &*ast.cdr {
            Ctr::Seg(data_tree) if is_var => match eval(&Box::new(data_tree), syms) {
                Ok(seg) => {
                    if let Ctr::Seg(ref val) = *seg {
                        syms.insert(
                            identifier.clone(),
                            Symbol {
                                value: ValueType::VarForm(val.car.clone()),
                                name: identifier.clone(),
                                args: Args::None,
                                conditional_branches: false,
                            },
                        );
                        if env_cfg {
                            env::set_var(identifier.clone(), val.car.to_string());
                        }
                    } else {
                        return Err("impossible args to export".to_string());
                    }
                }
                Err(e) => return Err(format!("couldnt eval symbol: {}", e)),
            },
            Ctr::Seg(data_tree) if !is_var => {
                if let Ctr::Seg(ref args) = *data_tree.car {
                    let mut arg_list = vec![];
                    if !args.circuit(&mut |c: &Ctr| -> bool {
                        if let Ctr::Symbol(ref arg) = c {
                            arg_list.push(arg.clone());
                            true
                        } else {
                            false
                        }
                    }) {
                        return Err(
                            "all arguments defined for function must be of type symbol".to_string()
                        );
                    };

                    if let Ctr::Seg(ref bodies) = *data_tree.cdr {
                        syms.insert(
                            identifier.clone(),
                            Symbol {
                                value: ValueType::FuncForm(UserFn {
                                    ast: Box::new(bodies.clone()),
                                    arg_syms: arg_list.clone(),
                                }),
                                name: identifier.clone(),
                                args: Args::Lazy(arg_list.len() as u128),
                                conditional_branches: false,
                            },
                        );
                    } else {
                        return Err(
                            "expected one or more function bodies in function definition"
                                .to_string(),
                        );
                    }
                } else {
                    return Err("expected list of arguments in function definition".to_string());
                }
            }
            Ctr::None => {
                syms.remove(&identifier.to_string());
                if env_cfg {
                    env::remove_var(identifier);
                }
            }
            _ => return Err("args not in standard form".to_string()),
        }
    } else {
        return Err("first argument to export must be a symbol".to_string());
    }
    Ok(Ctr::None)
}