use crate::*;
/** Implement `EdnCommand` for given `State` and `Command` */
#[macro_export] macro_rules! edn_command {
    ($Command:ty : |$state:ident:$State:ty| { $((
        // identifier
        $key:literal [
            // named parameters
            $(
                // argument name
                $arg:ident
                // if type is not provided defaults to EdnItem
                $(
                    // type:name separator
                    :
                    // argument type
                    $type:ty
                )?
            ),* 
            // rest of parameters
            $(, ..$rest:ident)?
        ]
        // bound command:
        $command:expr
    ))* }) => {
        impl EdnCommand<$State> for $Command {
            fn from_edn <'a> ($state: &$State, head: &EdnItem<&str>, tail: &'a [EdnItem<String>]) -> Self {
                $(if let (EdnItem::Key($key), [ // if the identifier matches
                    // bind argument ids
                    $($arg),*
                    // bind rest parameters
                    $(, $rest @ ..)?
                ]) = (head, tail) {
                    $(
                        $(let $arg: Option<$type> = EdnProvide::<$type>::get($state, $arg);)?
                    )*
                    //$(edn_command!(@bind $state => $arg $(?)? : $type);)*
                    return $command
                })*
                panic!("no such command")
            }
        }
    };
    (@bind $state:ident =>$arg:ident ? : $type:ty) => {
        let $arg: Option<$type> = EdnProvide::<$type>::get($state, $arg);
    };
    (@bind $state:ident => $arg:ident : $type:ty) => {
        let $arg: $type = EdnProvide::<$type>::get_or_fail($state, $arg);
    };
}
/// Turns an EDN symbol sequence into a command enum variant.
pub trait EdnCommand<C>: Command<C> {
    fn from_edn <'a> (state: &C, head: &EdnItem<&str>, tail: &'a [EdnItem<String>]) -> Self;
    fn get_isize (state: &C, item: &EdnItem<&str>) -> Option<isize> {
        None
    }
    fn get_usize (state: &C, item: &EdnItem<&str>) -> Option<usize> {
        None
    }
    fn get_bool  (state: &C, item: &EdnItem<&str>) -> Option<usize> {
        None
    }
}