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use proc_macro::TokenStream;
use proc_macro2::{Ident as Ident2, TokenStream as TokenStream2};
use quote::{quote, TokenStreamExt};
use syn::{parse_macro_input, Data, DataStruct, DeriveInput, Fields};

#[proc_macro_derive(CLTyped)]
pub fn derive_cl_typed(input: TokenStream) -> TokenStream {
  let input = parse_macro_input!(input as DeriveInput);
  let ident = input.ident;

  let expanded = quote! {
    impl casper_types::CLTyped for #ident {
      fn cl_type() -> casper_types::CLType {
        casper_types::CLType::Any
      }
    }
  };

  TokenStream::from(expanded)
}

fn named_fields(input: DeriveInput) -> Result<Vec<Ident2>, TokenStream> {
  let fields = match input.data {
    Data::Struct(DataStruct {
      fields: Fields::Named(named_fields),
      ..
    }) => named_fields
      .named
      .into_iter()
      .map(|x| x.ident.unwrap())
      .collect::<Vec<_>>(),
    _ => {
      return Err(TokenStream::from(
        quote! { compile_error!("Expected a struct with named fields."); },
      ))
    }
  };
  Ok(fields)
}

#[proc_macro_derive(FromBytes)]
pub fn derive_from_bytes(input: TokenStream) -> TokenStream {
  let input = parse_macro_input!(input as DeriveInput);
  let struct_ident = input.ident.clone();
  let fields = match named_fields(input) {
    Ok(fields) => fields,
    Err(error_stream) => return error_stream,
  };

  let mut deserialize_fields = TokenStream2::new();
  deserialize_fields.append_all(fields.iter().map(|ident| {
    quote! {
      let (#ident, bytes) = casper_types::bytesrepr::FromBytes::from_bytes(bytes)?;
    }
  }));

  let mut construct_struct = TokenStream2::new();
  construct_struct.append_all(fields.iter().map(|ident| quote! { #ident, }));

  let expanded = quote! {
    impl casper_types::bytesrepr::FromBytes for #struct_ident {
      fn from_bytes(bytes: &[u8]) -> Result<(Self, &[u8]), casper_types::bytesrepr::Error> {
        #deserialize_fields
        let value = #struct_ident {
          #construct_struct
        };
        Ok((value, bytes))
      }
    }
  };

  TokenStream::from(expanded)
}

#[proc_macro_derive(ToBytes)]
pub fn derive_to_bytes(input: TokenStream) -> TokenStream {
  let input = parse_macro_input!(input as DeriveInput);
  let struct_ident = input.ident.clone();
  let fields = match named_fields(input) {
    Ok(fields) => fields,
    Err(error_stream) => return error_stream,
  };

  let mut sum_serialized_lengths = TokenStream2::new();
  sum_serialized_lengths.append_all(fields.iter().map(|ident| {
    quote! {
      size += self.#ident.serialized_length();
    }
  }));

  let mut append_bytes = TokenStream2::new();
  append_bytes.append_all(fields.iter().map(|ident| {
    quote! {
      vec.extend(self.#ident.to_bytes()?);
    }
  }));

  let expanded = quote! {
    impl casper_types::bytesrepr::ToBytes for #struct_ident {
      fn serialized_length(&self) -> usize {
        let mut size = 0;
        #sum_serialized_lengths
        return size;
      }

      fn to_bytes(&self) -> Result<Vec<u8>, casper_types::bytesrepr::Error> {
        let mut vec = Vec::with_capacity(self.serialized_length());
        #append_bytes
        Ok(vec)
      }
    }
  };

  TokenStream::from(expanded)
}