use macro_rules_attribute::derive;
use mini_macro_magic::export;

// An example macro that gets the name of the variant an expression is.
// It also needs to be given the enum definition to generate the match statement.
// We will use the export macro to export the enum definition for use by this macro.
//
// In some sense this macro is generic over the enum *definition* itself.
macro_rules! variant_name {
    {{
        $(#[$($attr:tt)*])*
        $vis:vis enum $name:ident {
            $($variant:ident($($stuff:tt)*)),*$(,)?
        }
    } $e:expr} => {
        match $e {
            $($name::$variant {..} => stringify!($variant)),*
        }
    };
}

// An example enum.
// Here we use the derive macro to apply export to the enum definition.
// A macro named my_enum will be generated along side the enum definition.
// The my_enum macro can be used to call any other macro with the definition of the enum.
#[derive(export!)]
#[custom(export(my_enum$))]
pub enum MyEnum {
    A(i32),
    B(String),
    C(bool),
}

#[test]
fn check_variant() {
    // Check that the macro can get the correct variant name.

    let x = MyEnum::A(1);
    assert_eq!(my_enum!(variant_name!(x)), "A");

    let x = MyEnum::B("a".into());
    assert_eq!(my_enum!(variant_name!(x)), "B");

    let x = MyEnum::C(true);
    assert_eq!(my_enum!(variant_name!(x)), "C");
}