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extern crate proc_macro;

mod helper;
mod r#enum;
mod r#struct;


use r#enum::EnumStructure;
use r#struct::StructStructure;
use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use syn::{parse_macro_input, DeriveInput, Data, Error, Meta, NestedMeta, Lit};
use helper::{MOD_PATH};
use crate::helper::IROHA;
use std::str::FromStr;

#[proc_macro_derive(ToTokens, attributes(Iroha))]
pub fn derive_to_tokens(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!{input as DeriveInput};
    let mut mod_path_tokens: Result<Option<TokenStream2>, Error> = Ok(None);

    for attr in &input.attrs {
        if attr.path == IROHA {
            match attr.parse_meta() {
                Ok(Meta::List(list)) => {
                    for item in list.nested.iter() {
                        mod_path_tokens = match item {
                            NestedMeta::Meta(Meta::NameValue(mod_path)) => {
                                if mod_path.path != MOD_PATH {
                                    Err(Error::new_spanned(
                                        &attr,
                                        "Attribute `Iroha` only support argument `mod_path`"
                                    ))
                                } else {
                                     match match &mod_path.lit {
                                         Lit::Str(path_str) => Ok(path_str.value()),
                                         _ => Err(Error::new_spanned(
                                            &mod_path,
                                            "`mod_path` must be a string"
                                         ))
                                     }.map(
                                         |path| TokenStream2::from_str(path.as_str()).map_err(
                                             |_| Error::new_spanned(
                                                 &mod_path,
                                                 "Value of mod_path must be a mod path"
                                             )
                                         )
                                     ) {
                                         Ok(Ok(tokens)) => Ok(Some(tokens)),
                                         Ok(Err(e)) => Err(e),
                                         Err(e) => Err(e)
                                     }
                                }
                            }
                            _ => Err(
                                Error::new_spanned(
                                    &attr,
                                    "Argument of `Iroha` must be a meta."
                                )
                            )
                        };
                    }
                }
                Err(e) => mod_path_tokens = Err(e),
                _ => mod_path_tokens = Err(
                    Error::new_spanned(
                        &attr,
                        "Attribute `Iroha` only support list."
                    )
                )
            }
        }
    }

    let mod_path_tokens = match mod_path_tokens {
        Ok(result) => result,
        Err(e) => return TokenStream::from(e.to_compile_error())
    };

    let result = match &input.data {
        Data::Enum(_) => EnumStructure::from_ast(&input, mod_path_tokens).map(
            |s| s.get_implement()
        ),
        Data::Struct(_) => StructStructure::from_ast(&input, mod_path_tokens).map(
            |s| s.get_implement()
        ),
        _ => Err(Error::new_spanned(&input, "Unknown data type"))
    };

    //panic!(result.unwrap().unwrap().to_string());

    TokenStream::from(match result {
        Ok(Ok(tokens)) => tokens,
        Ok(Err(e)) => e.to_compile_error(),
        Err(e) => e.to_compile_error()
    })
}