#![feature(box_patterns)]
#![recursion_limit="128"]
extern crate proc_macro;
#[macro_use]
extern crate quote;
#[macro_use]
extern crate syn;

use self::proc_macro::TokenStream;
use self::syn::fold::Fold;

struct RecursiveDescentFn {
}

impl Fold for RecursiveDescentFn {
  fn fold_item_fn(&mut self, mut i: syn::ItemFn) -> syn::ItemFn {
    let box block = i.block;
    let ref ident = i.ident;

    let new_block: syn::Block = parse_quote! {
      {
        let next_token_before_parse = self.token_handler.peek();
        let record = ParseRecord {
          production_name: stringify!(#ident).to_string(),
          next_token: format!("{}", next_token_before_parse.to_string_with_metadata()),
          level: self.parse_level,
        };
        self.parse_level += 1;
        self.parse_record.push(record);
        let result = { #block };

        if self.parse_level != 0 {
          self.parse_level -= 1;
        }

        result.map_err(|mut parse_error: ParseError| {
          parse_error.production_name = Some(stringify!(#ident).to_string());
          parse_error
        })
      }
    };
    i.block = Box::new(new_block);
    i
  }
}

#[proc_macro_attribute]
pub fn recursive_descent_method(_attr: TokenStream, item: TokenStream) -> TokenStream {

  let input: syn::ItemFn = parse_macro_input!(item as syn::ItemFn);
  let mut folder = RecursiveDescentFn {};
  let output = folder.fold_item_fn(input);
  TokenStream::from(quote!(#output))
}