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extern crate proc_macro;

use proc_macro::TokenStream;
use quote::{quote, quote_spanned};
use syn::{parse_macro_input, Lit, Expr, spanned::Spanned};

fn lit_to_bytes(lit: &Lit) -> Option<Vec<u8>> {
    match lit {
        Lit::Str(lit_str) => {
            Some(lit_str.value().into_bytes())
        }
        Lit::ByteStr(lit_str) => {
            Some(lit_str.value())
        }
        _ => {
            None
        }
    }
}

fn expr_to_bytes(expr: &Expr) -> Option<Vec<u8>> {
    match expr {
        Expr::Lit(lit) => lit_to_bytes(&lit.lit),
        Expr::Path(path) => {
            let ident = path.path.get_ident()?;
            Some(Vec::from(ident.to_string().as_bytes()))
        }
        Expr::Group(group) => {
            expr_to_bytes(&group.expr)
        }
        _ => None
    }
}

use std::sync::atomic::{AtomicBool, Ordering};

static EXIT: AtomicBool = AtomicBool::new(false);

#[proc_macro]
pub fn lua_bind_hash(input: TokenStream) -> TokenStream {
    if EXIT.load(Ordering::SeqCst) {
        return quote!{}.into();
    }

    let expr = parse_macro_input!(input as Expr);

    match expr_to_bytes(&expr) {
        Some(string) => {
            let lua_bind_hash = lua_bind_hash::lua_bind_hash(&string);
            
            TokenStream::from(quote! {
                (#lua_bind_hash)
            })
        }
        None => {
            let span = expr.span();
            EXIT.store(true, Ordering::SeqCst);
            panic!("Invalid input: '{:?}'", expr);
            TokenStream::from(quote_spanned!{span =>
                compile_error!("Invalid input");
            })
        }
    }
}