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use super::{parse_args, parse_pyo3_attrs, quote_option, ArgInfo, Attr, Signature};

use proc_macro2::TokenStream as TokenStream2;
use quote::{quote, ToTokens, TokenStreamExt};
use syn::{Error, ImplItemFn, Result};

#[derive(Debug)]
pub struct NewInfo {
    args: Vec<ArgInfo>,
    sig: Option<Signature>,
}

impl NewInfo {
    pub fn is_candidate(item: &ImplItemFn) -> Result<bool> {
        let attrs = parse_pyo3_attrs(&item.attrs)?;
        Ok(attrs.iter().any(|attr| matches!(attr, Attr::New)))
    }
}

impl TryFrom<ImplItemFn> for NewInfo {
    type Error = Error;
    fn try_from(item: ImplItemFn) -> Result<Self> {
        assert!(Self::is_candidate(&item)?);
        let ImplItemFn { attrs, sig, .. } = item;
        let attrs = parse_pyo3_attrs(&attrs)?;
        let mut new_sig = None;
        for attr in attrs {
            if let Attr::Signature(text_sig) = attr {
                new_sig = Some(text_sig);
            }
        }
        Ok(NewInfo {
            args: parse_args(sig.inputs)?,
            sig: new_sig,
        })
    }
}

impl ToTokens for NewInfo {
    fn to_tokens(&self, tokens: &mut TokenStream2) {
        let Self { args, sig } = self;
        let sig_tt = quote_option(sig);
        tokens.append_all(quote! {
            ::pyo3_stub_gen::type_info::NewInfo {
                args: &[ #(#args),* ],
                signature: #sig_tt,
            }
        })
    }
}