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// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use syn::spanned::Spanned;

/// Derive Clone but do not bound any generic.
pub fn derive_clone_no_bound(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
	let input = syn::parse_macro_input!(input as syn::DeriveInput);

	let name = &input.ident;
	let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();

	let impl_ = match input.data {
		syn::Data::Struct(struct_) => match struct_.fields {
			syn::Fields::Named(named) => {
				let fields = named.named.iter().map(|i| &i.ident).map(|i| {
					quote::quote_spanned!(i.span() =>
						#i: ::core::clone::Clone::clone(&self.#i)
					)
				});

				quote::quote!( Self { #( #fields, )* } )
			},
			syn::Fields::Unnamed(unnamed) => {
				let fields =
					unnamed.unnamed.iter().enumerate().map(|(i, _)| syn::Index::from(i)).map(|i| {
						quote::quote_spanned!(i.span() =>
							::core::clone::Clone::clone(&self.#i)
						)
					});

				quote::quote!( Self ( #( #fields, )* ) )
			},
			syn::Fields::Unit => {
				quote::quote!(Self)
			},
		},
		syn::Data::Enum(enum_) => {
			let variants = enum_.variants.iter().map(|variant| {
				let ident = &variant.ident;
				match &variant.fields {
					syn::Fields::Named(named) => {
						let captured = named.named.iter().map(|i| &i.ident);
						let cloned = captured.clone().map(|i| {
							::quote::quote_spanned!(i.span() =>
								#i: ::core::clone::Clone::clone(#i)
							)
						});
						quote::quote!(
							Self::#ident { #( ref #captured, )* } => Self::#ident { #( #cloned, )*}
						)
					},
					syn::Fields::Unnamed(unnamed) => {
						let captured = unnamed
							.unnamed
							.iter()
							.enumerate()
							.map(|(i, f)| syn::Ident::new(&format!("_{}", i), f.span()));
						let cloned = captured.clone().map(|i| {
							quote::quote_spanned!(i.span() =>
								::core::clone::Clone::clone(#i)
							)
						});
						quote::quote!(
							Self::#ident ( #( ref #captured, )* ) => Self::#ident ( #( #cloned, )*)
						)
					},
					syn::Fields::Unit => quote::quote!( Self::#ident => Self::#ident ),
				}
			});

			quote::quote!(match self {
				#( #variants, )*
			})
		},
		syn::Data::Union(_) => {
			let msg = "Union type not supported by `derive(CloneNoBound)`";
			return syn::Error::new(input.span(), msg).to_compile_error().into()
		},
	};

	quote::quote!(
		const _: () = {
			#[automatically_derived]
			impl #impl_generics ::core::clone::Clone for #name #ty_generics #where_clause {
				fn clone(&self) -> Self {
					#impl_
				}
			}
		};
	)
	.into()
}