use std::fmt::Write as FmtWrite;

use super::command_tree::CommandTree;
use super::{Repl, InterpreterDirectiveOutput};

pub fn help(repl: &mut Repl, arguments: &[&str]) -> InterpreterDirectiveOutput {
  match arguments {
    [] =>  return global_help(repl),
    commands => {
      let dirs = repl.get_directives();
      Some(match get_directive_from_commands(commands, &dirs) {
        None => format!("Directive `{}` not found", commands.last().unwrap()),
        Some(dir) => format!("`{}` - {}", dir.get_cmd(), dir.get_help())
      })
    }
  }
}

fn get_directive_from_commands<'a>(commands: &[&str], dirs: &'a CommandTree) -> Option<&'a CommandTree> {
  let mut directive_list = dirs.get_children();
  let mut matched_directive = None;
  for cmd in commands {
    let found = directive_list.iter().find(|directive| directive.get_cmd() == *cmd);
    if let Some(dir) = found {
      directive_list = dir.get_children();
    }

    matched_directive = found;
  }
  matched_directive
}

fn global_help(repl: &mut Repl) -> InterpreterDirectiveOutput {
  let mut buf = String::new();

  writeln!(buf, "MetaInterpreter options").unwrap();
  writeln!(buf, "-----------------------").unwrap();

  for directive in repl.get_directives().get_children() {
    let trailer = " ";
    writeln!(buf, "{}{}- {}", directive.get_cmd(), trailer, directive.get_help()).unwrap();
  }

  let ref lang = repl.get_cur_language_state();
  writeln!(buf, "").unwrap();
  writeln!(buf, "Language-specific help for {}", lang.get_language_name()).unwrap();
  writeln!(buf, "-----------------------").unwrap();
  Some(buf)
}