use std::fmt::Write as FmtWrite;
use itertools::Itertools;

use crate::repl::Repl;
use crate::repl::command_tree::CommandTree;
use crate::language::{ProgrammingLanguageInterface, LangMetaRequest, LangMetaResponse, DebugAsk, DebugResponse}; 

pub fn get_directives(language_state: &mut Box<ProgrammingLanguageInterface>) -> CommandTree {
  let pass_names = match language_state.request_meta(LangMetaRequest::StageNames) {
    LangMetaResponse::StageNames(names) => names,
    _ => vec![],
  };

  let passes_directives: Vec<CommandTree> = pass_names.iter()
    .map(|pass_name| { CommandTree::nonterm_no_further_tab_completions(pass_name, None) })
    .collect();

  CommandTree::Top(vec![
    CommandTree::terminal("exit", Some("exit the REPL"), vec![], Box::new(|repl: &mut Repl, _cmds: &[&str]| {
      repl.save_before_exit();
      ::std::process::exit(0)
    })),
    CommandTree::terminal("quit", Some("exit the REPL"), vec![], Box::new(|repl: &mut Repl, _cmds: &[&str]| {
      repl.save_before_exit();
      ::std::process::exit(0)
    })),
    CommandTree::terminal("help", Some("Print this help message"), vec![], Box::new(|repl: &mut Repl, cmds: &[&str]| {
      Some(repl.print_help_message(cmds))
    })),
    CommandTree::nonterm("debug",
      Some("Configure debug information"),
      vec![
        CommandTree::terminal("list-passes", Some("List all registered compiler passes"), vec![], Box::new(|repl: &mut Repl, _cmds: &[&str]| {
          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)
        })),
        CommandTree::terminal("show-immediate", None, passes_directives.clone(),
        Box::new(|repl: &mut Repl, cmds: &[&str]| {
          let cur_state = repl.get_cur_language_state();
          let stage_name = match cmds.get(1) {
            Some(s) => s.to_string(),
            None => return Some(format!("Must specify a thing to debug")),
          };
          let meta = LangMetaRequest::ImmediateDebug(DebugAsk::ByStage { stage_name: stage_name.clone() });

          let response = match cur_state.request_meta(meta) {
            LangMetaResponse::ImmediateDebug(DebugResponse { ask, value }) => {
              if (ask != DebugAsk::ByStage { stage_name: stage_name }) {
                return Some(format!("Didn't get debug stage requested"));
              }
              value
            },
            _ => return Some(format!("Invalid language meta response")),
          };
          Some(response)
        })),
        CommandTree::terminal("show", None, passes_directives.clone(), Box::new(|repl: &mut Repl, cmds: &[&str]| {
          let stage_name = match cmds.get(0) {
            Some(s) => s.to_string(),
            None => return Some(format!("Must specify a stage to show")),
          };
          let ask = DebugAsk::ByStage { stage_name };
          repl.options.debug_asks.insert(ask);
          None
        })),
        CommandTree::terminal("hide", None, passes_directives.clone(), Box::new(|repl: &mut Repl, cmds: &[&str]| {
          let stage_name = match cmds.get(0) {
            Some(s) => s.to_string(),
            None => return Some(format!("Must specify a stage to hide")),
          };
          let ask = DebugAsk::ByStage { stage_name };
          repl.options.debug_asks.remove(&ask);
          None
        })),
        CommandTree::nonterm("total-time", None, vec![
          CommandTree::terminal("on", None, vec![], Box::new(|repl: &mut Repl, _: &[&str]| {
            repl.options.show_total_time = true;
            None
          })),
          CommandTree::terminal("off", None, vec![], Box::new(turn_off)),
        ])
      ]
    ),
    CommandTree::nonterm("lang",
      Some("switch between languages, or go directly to a langauge by name"),
      vec![
        CommandTree::nonterm_no_further_tab_completions("next", None),
        CommandTree::nonterm_no_further_tab_completions("prev", None),
        CommandTree::nonterm("go", None, vec![]),
      ]
    ),
    CommandTree::terminal("doc", Some("Get language-specific help for an item"), vec![], Box::new(|repl: &mut Repl, cmds: &[&str]| {
      cmds.get(0).map(|cmd| {
        let source = cmd.to_string();
        let meta = LangMetaRequest::Docs { source };
        let cur_state = repl.get_cur_language_state();
        match cur_state.request_meta(meta) {
          LangMetaResponse::Docs { doc_string } => Some(doc_string),
          _ => Some(format!("Invalid doc response"))
        }
      }).unwrap_or(Some(format!(":docs needs an argument")))
    }))
  ])
}

fn turn_off(repl: &mut Repl, _cmds: &[&str]) -> Option<String> {
  repl.options.show_total_time = false;
  None
}