// Copyright 2024 Gabriel Bjørnager Jensen.
//
// This file is part of bZipper.
//
// bZipper is free software: you can redistribute
// it and/or modify it under the terms of the GNU
// Lesser General Public License as published by
// the Free Software Foundation, either version 3
// of the License, or (at your option) any later
// version.
//
// bZipper is distributed in the hope that it will
// be useful, but WITHOUT ANY WARRANTY; without
// even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Less-
// er General Public License along with bZipper. If
// not, see <https://www.gnu.org/licenses/>.

use proc_macro2::TokenStream;
use quote::quote;
use syn::{DataStruct, Fields, Token};
use syn::punctuated::Punctuated;

#[must_use]
pub fn decode_struct(data: &DataStruct) -> TokenStream {
	let mut chain_commands = Punctuated::<TokenStream, Token![,]>::new();

	for field in &data.fields {
		let command = field.ident
			.as_ref()
			.map_or_else(
				||           quote! { ::bzipper::Decode::decode(stream)? },
				|field_name| quote! { #field_name: ::bzipper::Decode::decode(stream)? },
			);

		chain_commands.push(command);
	}

	let value = match data.fields {
		Fields::Named(  ..) => quote! { Self { #chain_commands } },
		Fields::Unnamed(..) => quote! { Self(#chain_commands) },
		Fields::Unit        => quote! { Self },
	};

	quote! {
		#[inline]
		fn decode(stream: &mut ::bzipper::IStream) -> ::core::result::Result<Self, ::bzipper::error::DecodeError> {
			let value = #value;
			Ok(value)
		}
	}
}