use crate::deserialize::util::{make_build_fn_name, make_build_pair};
use crate::spec::leaf_struct_spec::{LeafStructBuildSpec, LeafStructMemberKind};
use proc_macro2::TokenStream;
use quote::{format_ident, quote};

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

    let child_builders = build_spec
        .members()
        .map(|member| {
            let child_ident = format_ident!("{}", member.name());
            match member.kind() {
                LeafStructMemberKind::String => {
                    quote! {
                        let #child_ident = #pair_ident.as_str()
                    }
                }
                LeafStructMemberKind::FileId => {
                    quote! {
                        let #child_ident = file_id
                    }
                }
                LeafStructMemberKind::Range => {
                    quote! {
                        let #child_ident = {
                            let as_span = #pair_ident.as_span();
                            Range {
                                start: as_span.start(),
                                end: as_span.end()
                            }
                        }
                    }
                }
            }
        })
        .collect::<Vec<_>>();

    let child_args = build_spec
        .members()
        .map(|member| format_ident!("{}", member.name()))
        .collect::<Vec<_>>();

    quote! {
        fn #build_fn_ident(file_id: usize, #pair_ident: Pair<Rule>) -> #return_type_ident {
            #(#child_builders;)*
            #return_type_ident::new(
                #(#child_args,)*
            )
        }
    }
}