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use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, DeriveInput};

#[proc_macro_derive(Store)]
pub fn store(input: TokenStream) -> TokenStream {
	// Parse the token stream
	let input = parse_macro_input!(input as DeriveInput);
	// Fetch the struct name
	let name = &input.ident;
	// Add derived implementations
	let output = quote! {

		impl From<Vec<u8>> for #name {
			fn from(v: Vec<u8>) -> Self {
				Self::from(&v)
			}
		}

		impl From<#name> for Vec<u8> {
			fn from(v: #name) -> Vec<u8> {
				Self::from(&v)
			}
		}

		impl From<&#name> for Vec<u8> {
			fn from(v: &#name) -> Vec<u8> {
				let mut out:Vec<u8> = vec![];
				revision::Revisioned::serialize_revisioned(v, &mut out).unwrap();
				out
			}
		}

		impl From<&Vec<u8>> for #name {
			fn from(v: &Vec<u8>) -> Self {
				revision::Revisioned::deserialize_revisioned(&mut v.as_slice()).unwrap()
			}
		}

		// TODO: for a future pull request

		// impl TryFrom<&#name> for Vec<u8> {
		// 	type Error = crate::err::Error;
		// 	fn try_from(v: &#name) -> Result<Self, Self::Error> {
		// 		let mut out:Vec<u8> = vec![];
		// 		revision::Revisioned::serialize_revisioned(v, &mut out)?;
		// 		Ok(out)
		// 	}
		// }

		// impl TryFrom<&Vec<u8>> for #name {
		// 	type Error = crate::err::Error;
		// 	fn try_from(v: &Vec<u8>) -> Result<Self, Self::Error> {
		// 		revision::Revisioned::deserialize_revisioned(&mut v.as_slice())
		// 	}
		// }

	};
	//
	output.into()
}

#[proc_macro_derive(Key)]
pub fn key(input: TokenStream) -> TokenStream {
	// Parse the token stream
	let input = parse_macro_input!(input as DeriveInput);
	// Fetch the struct name
	let name = &input.ident;
	// Compute the generics
	let generics = input.generics;
	let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
	assert!(generics.lifetimes().count() <= 1);
	let (lifetime, from_owned) = if let Some(lifetime_def) = generics.lifetimes().next() {
		let lifetime = &lifetime_def.lifetime;
		(quote! {#lifetime}, quote! {})
	} else {
		(
			quote! {},
			quote! {
				impl #impl_generics From<Vec<u8>> for #name #ty_generics #where_clause {
					fn from(v: Vec<u8>) -> Self {
						Self::decode(&v).unwrap()
					}
				}
			},
		)
	};

	// Generate the output
	let output = quote! {

		impl #impl_generics From<#name #ty_generics> for Vec<u8> #where_clause {
			fn from(v: #name #ty_generics) -> Vec<u8> {
				v.encode().unwrap_or_default()
			}
		}

		impl #impl_generics From<&#name #ty_generics> for Vec<u8> #where_clause {
			fn from(v: &#name #ty_generics) -> Vec<u8> {
				v.encode().unwrap_or_default()
			}
		}

		#from_owned

		impl #impl_generics From<&#lifetime Vec<u8>> for #name #ty_generics #where_clause {
			fn from(v: &#lifetime Vec<u8>) -> Self {
				Self::decode(v).unwrap()
			}
		}

		impl #impl_generics #name #ty_generics #where_clause {

			pub fn encode(&self) -> Result<Vec<u8>, crate::err::Error> {
				let v = storekey::serialize(self);
				Ok(v?)
			}

			pub fn decode(v: &#lifetime[u8]) -> Result<Self, crate::err::Error> {
				let v = storekey::deserialize(v);
				Ok(v?)
			}

		}

	};

	output.into()
}