//! Declares macros to help implementing parsers.

// https://github.com/rust-lang/rust-clippy/issues/6860

#![allow(renamed_and_removed_lints, clippy::unknown_clippy_lints)]

/// Macro for declaring a keyword enumeration to help parse a document.

///

/// A keyword enumeration implements the Keyword trait.

///

/// These enums are a bit different from those made by `caret`, in a

/// few ways.  Notably, they are optimized for parsing, they are

/// required to be compact, and they allow multiple strings to be mapped to

/// a single index.

///

/// ```ignore

/// decl_keyword! {

///    Location {

//         "start" => START,

///        "middle" | "center" => MID,

///        "end" => END

///    }

/// }

///

/// assert_eq!(Location::from_str("start"), Location::START);

/// assert_eq!(Location::from_str("stfff"), Location::UNRECOGNIZED);

/// ```

#[allow(unused_macro_rules)]

macro_rules! decl_keyword {

    { $(#[$meta:meta])* $v:vis

      $name:ident { $( $($anno:ident)? $($s:literal)|+ => $i:ident),* $(,)? } } => {

        #[derive(Copy,Clone,Eq,PartialEq,Debug,std::hash::Hash)]

        #[allow(non_camel_case_types)]

        $(#[$meta])*

        #[allow(unknown_lints)]

        // https://github.com/rust-lang/rust-clippy/issues/6860

        #[allow(renamed_and_removed_lints, clippy::unknown_clippy_lints)]

        #[allow(clippy::upper_case_acronyms)]

        $v enum $name {

            $( $i , )*

            UNRECOGNIZED,

            ANN_UNRECOGNIZED

        }

        impl $crate::parse::keyword::Keyword for $name {

                // Note usage of phf crate to create a perfect hash over

                // the possible keywords.  It will be even better if someday

                // the phf crate can find hash functions that are better

                // than siphash.

                const KEYWORD: phf::Map<&'static str, $name> = phf::phf_map! {

                    $( $( $s => $name::$i , )+ )*

                };

                    } else {

                    }

                }

                // Note looking up the value in a vec.  This may or may

                // not be faster than a case statement would be.

                static VALS: once_cell::sync::Lazy<Vec<$name>> =

                    once_cell::sync::Lazy::new(

                use $name::*;

                }

                use $name::*;

                }

        }

    };

    [ @impl is_anno annotation ] => ( true );

    [ @impl is_anno $x:ident ] => ( compile_error!("unrecognized keyword; not annotation") );

    [ @impl is_anno ] => ( false );

    [ @impl join $s:literal ] => ( $s );

    [ @impl join $s:literal , $($ss:literal),+ ] => (

        concat! { $s, "/", decl_keyword![@impl join $($ss),*] }

    );

}

#[cfg(test)]

pub(crate) mod test {

    #![allow(clippy::cognitive_complexity)]

    decl_keyword! {

        pub(crate) Fruit {

            "apple" => APPLE,

            "orange" => ORANGE,

            "lemon" => LEMON,

            "guava" => GUAVA,

            "cherry" | "plum" => STONEFRUIT,

            "banana" => BANANA,

            annotation "@tasty" => ANN_TASTY,

        }

    }

    #[test]

    fn kwd() {

        use crate::parse::keyword::Keyword;

        use Fruit::*;

        assert_eq!(Fruit::from_str("lemon"), LEMON);

        assert_eq!(Fruit::from_str("cherry"), STONEFRUIT);

        assert_eq!(Fruit::from_str("plum"), STONEFRUIT);

        assert_eq!(Fruit::from_str("pear"), UNRECOGNIZED);

        assert_eq!(Fruit::from_str("@tasty"), ANN_TASTY);

        assert_eq!(Fruit::from_str("@tastier"), ANN_UNRECOGNIZED);

        assert_eq!(APPLE.idx(), 0);

        assert_eq!(ORANGE.idx(), 1);

        assert_eq!(ANN_UNRECOGNIZED.idx(), 8);

        assert_eq!(Fruit::n_vals(), 9);

        assert_eq!(Fruit::from_idx(0), Some(APPLE));

        assert_eq!(Fruit::from_idx(8), Some(ANN_UNRECOGNIZED));

        assert_eq!(Fruit::from_idx(9), None);

        assert_eq!(Fruit::idx_to_str(3), "guava");

        assert_eq!(Fruit::idx_to_str(999), "<out of range>");

        assert_eq!(APPLE.to_str(), "apple");

        assert_eq!(GUAVA.to_str(), "guava");

        assert_eq!(ANN_TASTY.to_str(), "@tasty");

        assert_eq!(STONEFRUIT.to_str(), "cherry/plum");

        assert_eq!(UNRECOGNIZED.to_str(), "<unrecognized>");

        assert_eq!(ANN_UNRECOGNIZED.to_str(), "<unrecognized annotation>");

        assert!(!GUAVA.is_annotation());

        assert!(!STONEFRUIT.is_annotation());

        assert!(!UNRECOGNIZED.is_annotation());

        assert!(ANN_TASTY.is_annotation());

        assert!(ANN_UNRECOGNIZED.is_annotation());

    }

}