use super::{Repl, InterpreterDirectiveOutput};
use crate::language::{LangMetaRequest, LangMetaResponse, DebugAsk, DebugResponse}; 
use itertools::Itertools;
use std::fmt::Write as FmtWrite;

#[derive(Debug, Clone)]
pub enum DirectiveAction {
  Null,
  Help,
  QuitProgram,
  ListPasses,
}

impl DirectiveAction {
  pub fn perform(&self, repl: &mut Repl, arguments: &[&str]) -> InterpreterDirectiveOutput {
    use DirectiveAction::*;
    match self {
      Null => None,
      Help => Some(repl.print_help_message(arguments)),
      QuitProgram => {
        repl.save_before_exit();
        ::std::process::exit(0)
      },
      ListPasses => {
        let language_state = repl.get_cur_language_state();
        let pass_names = match language_state.request_meta(LangMetaRequest::StageNames) {
          LangMetaResponse::StageNames(names) => names,
          _ => vec![],
        };

        let mut buf = String::new();
        for pass in pass_names.iter().map(|name| Some(name)).intersperse(None) {
          match pass {
            Some(pass) => write!(buf, "{}", pass).unwrap(),
            None => write!(buf, " -> ").unwrap(),
          }
        }
        Some(buf)
      }
    }
  }
}