use quote::quote;

use syn::DeriveInput;

pub(crate) fn expand_ideal_gas(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream> {

let variants = match input.data {

syn::Data::Enum(syn::DataEnum { ref variants, .. }) => variants,

_ => panic!("this derive macro only works on enums"),

};

let ideal_gas = impl_ideal_gas(variants);

Ok(quote! {

#ideal_gas

})

}

fn impl_ideal_gas(

variants: &syn::punctuated::Punctuated<syn::Variant, syn::token::Comma>,

) -> proc_macro2::TokenStream {

let ideal_gas_model = variants.iter().map(|v| {

let name = &v.ident;

if name == "NoModel" {

quote! {

Self::#name(_) => panic!("No ideal gas model initialized!")

}

} else {

quote! {

Self::#name(ideal_gas) => ideal_gas.ideal_gas_model()

}

}

});

quote! {

impl IdealGas for IdealGasModel {

fn ideal_gas_model(&self) -> &dyn DeBroglieWavelength {

match self {

#(#ideal_gas_model,)*

}

}

}

}

}