use crate::deserialize::util::{make_build_fn_name, make_build_pair};
use crate::spec::leaf_enum_spec::LeafEnumBuildSpec;
use proc_macro2::TokenStream;
use quote::{format_ident, quote};

pub fn make_leaf_enum_build_fn(leaf_enum_build_spec: &LeafEnumBuildSpec) -> TokenStream {
    let build_fn_ident = format_ident!("{}", make_build_fn_name(leaf_enum_build_spec.build()));
    let pair_ident = format_ident!("{}", make_build_pair(leaf_enum_build_spec.build()));
    let return_type_ident = format_ident!("{}", leaf_enum_build_spec.build());

    let rule_branches = leaf_enum_build_spec
        .rules()
        .map(|leaf_enum_rule| {
            let rule_ident = format_ident!("{}", leaf_enum_rule);
            quote! {
                Rule::#rule_ident => #return_type_ident::#rule_ident
            }
        })
        .collect::<Vec<_>>();

    quote! {
        fn #build_fn_ident(file_id: usize, #pair_ident: Pair<Rule>) -> #return_type_ident {
            let inner_pair = #pair_ident.into_inner().next().unwrap();
            match inner_pair.as_rule() {
                #(#rule_branches,)*
                _ => unreachable!()
            }
        }
    }
}