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

#[proc_macro_attribute]
pub fn scanner(name: TokenStream, input: TokenStream) -> TokenStream {
  let name_str = parse_macro_input!(name as syn::LitStr).value();
  let input = parse_macro_input!(input as ItemFn);

  let _fn_name = input.sig.ident.clone();
  let body = &input.block;

  let result = quote! {
      #[no_mangle]
      pub extern "C" fn pscand_scanner() -> *mut std::os::raw::c_void {
          struct ScannerImpl;

          impl pscand_core::Scanner for ScannerImpl {
              fn name(&self) -> &'static str {
                  #name_str
              }

              fn interval(&self) -> std::time::Duration {
                  std::time::Duration::from_secs(1)
              }

              fn init(&mut self, _config: &toml::Value) -> pscand_core::Result<()> {
                  Ok(())
              }

              fn collect(&self) -> pscand_core::Result<std::collections::HashMap<String, pscand_core::MetricValue>> {
                  #body
              }

              fn cleanup(&mut self) -> pscand_core::Result<()> {
                  Ok(())
              }
          }

          let handle = unsafe { pscand_core::register_scanner(Box::new(ScannerImpl)) };
          handle as *mut std::os::raw::c_void
      }
  };

  result.into()
}

#[proc_macro]
pub fn register_scanner(input: TokenStream) -> TokenStream {
  let input = parse_macro_input!(input as ItemFn);
  let fn_name = input.sig.ident.clone();

  let result = quote! {
      #input

      #[no_mangle]
      pub extern "C" fn pscand_scanner() -> *mut std::os::raw::c_void {
          let handle = unsafe { pscand_core::register_scanner(Box::new(#fn_name())) };
          handle as *mut std::os::raw::c_void
      }
  };

  result.into()
}