use proc_macro2::TokenStream as TokenStream2;
use quote::ToTokens;

/// We store description of the assets an application uses in the executable.
/// We use the `link_section` attribute embed an extra section in the executable.
/// We force rust to store a serialized representation of the asset description
/// inside a particular region of the binary, with the label "manganis".
/// After linking, the "manganis" sections of the different object files will be merged.
pub fn generate_link_section(asset: impl ToTokens, asset_hash: &str) -> TokenStream2 {
    let position = proc_macro2::Span::call_site();
    let export_name = syn::LitStr::new(&format!("__MANGANIS__{}", asset_hash), position);

    quote::quote! {
        // First serialize the asset into a constant sized buffer
        const __BUFFER: manganis::macro_helpers::const_serialize::ConstVec<u8> = manganis::macro_helpers::serialize_asset(&#asset);
        // Then pull out the byte slice
        const __BYTES: &[u8] = __BUFFER.as_ref();
        // And the length of the byte slice
        const __LEN: usize = __BYTES.len();

        // Now that we have the size of the asset, copy the bytes into a static array
        #[unsafe(export_name = #export_name)]
        static __LINK_SECTION: [u8; __LEN]  = manganis::macro_helpers::copy_bytes(__BYTES);
    }
}