use crate::{
    generate::method_gen,
    model::{AutoImpl, ContractTrait, Method, MethodImpl},
    parse::split_path_last,
};
use proc_macro2::Ident;
use syn::{Pat, punctuated::Punctuated, token::PathSep};

/// Path to a Rust module containing a contract call proxy.
pub type ProxyModulePath = Punctuated<syn::PathSegment, PathSep>;

pub struct ProxyGetterReturnType {
    pub module_path: ProxyModulePath,
    pub proxy_obj_name: syn::PathSegment,
}

/// Return type of the proxy getter method, split into module and type segment.
pub fn proxy_getter_return_type(m: &Method) -> ProxyGetterReturnType {
    match &m.return_type {
        syn::ReturnType::Default => panic!("Missing return type from proxy getter `{}`", m.name),
        syn::ReturnType::Type(_, ty) => {
            if let syn::Type::Path(type_path) = ty.as_ref() {
                if let Some((leading_segments, last_segment)) = split_path_last(&type_path.path) {
                    ProxyGetterReturnType {
                        module_path: leading_segments,
                        proxy_obj_name: last_segment,
                    }
                } else {
                    panic!(
                        "Proxy getter return type must be specified with some module specifier (e.g. `path::to::module::Proxy`)"
                    );
                }
            } else {
                panic!("Invalid proxy getter return type")
            }
        }
    }
}

pub fn proxy_getter_return_type_token(m: &Method) -> proc_macro2::TokenStream {
    let ProxyGetterReturnType {
        module_path,
        mut proxy_obj_name,
    } = proxy_getter_return_type(m);
    if proxy_getter_address_arg_name(m).is_some() {
        // replace type name
        let span = proxy_obj_name.ident.span(); // preserve span
        proxy_obj_name.ident = Ident::new("ProxyTo", span);
    }
    quote! { #module_path #proxy_obj_name}
}

fn proxy_getter_address_arg_name(m: &Method) -> Option<Pat> {
    match m.method_args.len() {
        0 => None,
        1 => Some(m.method_args[0].pat.clone()),
        _ => panic!("Proxy getter can have at most 1 argument, which is the target address"),
    }
}

fn proxy_getter_address_snippet(m: &Method) -> proc_macro2::TokenStream {
    if let Some(address_arg_name) = proxy_getter_address_arg_name(m) {
        quote! {
            .contract(#address_arg_name)
        }
    } else {
        quote! {}
    }
}

pub fn generate_proxy_getter_impl(m: &Method) -> proc_macro2::TokenStream {
    let msig = method_gen::generate_sig_with_attributes(m);
    let parsed_return_type = proxy_getter_return_type(m);
    let module_path = &parsed_return_type.module_path;
    let address_snippet = proxy_getter_address_snippet(m);

    quote! {
        #msig {
            <#module_path Proxy<Self::Api> as multiversx_sc::contract_base::ProxyObjNew>::new_proxy_obj() #address_snippet
        }
    }
}

pub fn generate_all_proxy_trait_imports(c: &ContractTrait) -> Vec<proc_macro2::TokenStream> {
    c.methods
        .iter()
        .filter_map(|m| {
            if let MethodImpl::Generated(AutoImpl::ProxyGetter) = &m.implementation {
                let parsed_return_type = proxy_getter_return_type(m);
                let module_path = &parsed_return_type.module_path;
                Some(quote! {
                    use #module_path ProxyTrait as _;
                })
            } else {
                None
            }
        })
        .collect()
}
