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use proc_macro2::TokenStream;
use syn;

use crate::helpers::{case_style::CaseStyle, extract_meta, CaseStyleHelpers, MetaIteratorHelpers};

pub fn enum_variant_names_inner(ast: &syn::DeriveInput) -> TokenStream {
    let name = &ast.ident;
    let gen = &ast.generics;
    let (impl_generics, ty_generics, where_clause) = gen.split_for_impl();

    let variants = match ast.data {
        syn::Data::Enum(ref v) => &v.variants,
        _ => panic!("EnumVariantNames only works on Enums"),
    };

    // Derives for the generated enum
    let type_meta = extract_meta(&ast.attrs);
    let case_style = type_meta
        .find_unique_property("strum", "serialize_all")
        .map(|style| CaseStyle::from(style.as_ref()));

    let names = variants
        .iter()
        .map(|v| v.ident.convert_case(case_style))
        .collect::<Vec<_>>();

    quote! {
        impl #impl_generics ::strum::VariantNames for #name #ty_generics #where_clause {
            const VARIANTS: &'static [&'static str] = &[ #(#names),* ];
        }
    }
}