// arg_util.rs

// *************************************************************************
// * Copyright (C) 2019 Daniel Mueller (deso@posteo.net)                   *
// *                                                                       *
// * 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/>. *
// *************************************************************************

/// A macro for generating an enum with a set of simple (i.e., no
/// parameters) variants and their textual representations.
// TODO: Right now we hard code the derives we create. We may want to
//       make this set configurable.
macro_rules! Enum {
  ( $name:ident, [ $( $var:ident => $str:expr ), *] ) => {
    #[derive(Clone, Copy, Debug, PartialEq)]
    #[allow(unused)]
    pub enum $name {
      $(
        $var,
      )*
    }

    impl AsRef<str> for $name {
      fn as_ref(&self) -> &'static str {
        match *self {
          $(
            $name::$var => $str,
          )*
        }
      }
    }

    impl ::std::fmt::Display for $name {
      fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
        write!(f, "{}", self.as_ref())
      }
    }

    impl ::std::str::FromStr for $name {
      type Err = ();

      fn from_str(s: &str) -> ::std::result::Result<Self, Self::Err> {
        match s {
          $(
            $str => Ok($name::$var),
          )*
          _ => Err(()),
        }
      }
    }
  }
}

#[cfg(test)]
mod tests {
  Enum! {Command, [
    Var1 => "var1",
    Var2 => "2",
    Var3 => "crazy"
  ]}

  #[test]
  fn text_representations() {
    assert_eq!(Command::Var1.as_ref(), "var1");
    assert_eq!(Command::Var2.as_ref(), "2");
    assert_eq!(Command::Var3.as_ref(), "crazy");
  }
}