xml-data-derive 0.0.1

use crate::{
	element::{
		Field,
		FieldAttribute,
		Meta,
	},
};
use proc_macro2::TokenStream;
use quote::{quote, quote_spanned};

pub fn build_serialize(meta: &Meta, impl_element: bool) -> TokenStream {
	let Meta { xml_data_crate, name, tag, .. } = meta;

	let serializer = if impl_element {
		quote!{ &mut serializer }
	} else {
		quote!{ serializer }
	};

	let el_attrs: TokenStream = meta.fields.iter().filter_map(|field| {
		if let Some(attr) = &field.attr {
			if !impl_element {
				panic!("attributes now allowed in `Inner` data");
			}
			let FieldAttribute { key: attr_key, .. } = attr;
			let Field { name, span, .. } = field;
			let value_t = if attr.is_string {
				quote!(ValueString)
			} else {
				quote!(ValueDefault)
			};
			Some(if attr.optional {
				quote_spanned! {*span=>
					if let Some(#name) = &self.#name {
						serializer.serialize_attribute(#attr_key, #value_t::serialize_value(#name)?)?;
					}
				}
			} else {
				quote_spanned! {*span=>
					serializer.serialize_attribute(#attr_key, #value_t::serialize_value(&self.#name)?)?;
				}
			})
		} else {
			None
		}
	}).collect();
	let el_inner: TokenStream = meta.fields.iter().filter_map(|field| {
		if field.attr.is_none() {
			let Field { name, span, .. } = field;
			Some(quote_spanned! {*span=>
				self.#name.serialize_elements(#serializer)?;
			})
		} else {
			None
		}
	}).collect();

	let actual_impl = if impl_element {
		quote! {
			impl FixedElement for #name {
				const TAG: &'static str = #tag;

				fn serialize<S: Serializer>(&self, mut serializer: S) -> Result<()> {
					#el_attrs
					#el_inner
					Ok(())
				}
			}
		}
	} else {
		quote! {
			impl Inner for #name {
				fn serialize_elements<S: Serializer>(&self, serializer: &mut S) -> Result<()> {
					#el_inner
					Ok(())
				}
			}
		}
	};

	quote! {
		const _: () = {
			use #xml_data_crate::{
				serializer::{
					FixedElement,
					Inner,
					Serializer,
					Value,
					ValueString,
					ValueDefault,
				},
				Result,
			};

			#actual_impl
		};
	}
}