bok/bok-macro/src/pkgs.rs

/*
 * Copyright 2024 Luca Fulchir <luca.fulchir@runesauth.com>
 *
 * Licensed under the Apache License, Version 2.0 with LLVM exception (the
 * "License"); you may not use this file except in compliance with the
 * License. You may obtain a copy of the License and of the exception at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *     https://spdx.org/licenses/LLVM-exception.html
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

use ::proc_macro::TokenStream;
use ::quote::quote;
use ::syn::{parse::Parser, parse_macro_input, DeriveInput};
use syn::{parse_quote, spanned::Spanned};

pub(crate) fn pkg_fn_to_code(
    _attrs: TokenStream,
    input: TokenStream,
) -> TokenStream {
    let ast_orig: ::syn::ItemFn = parse_macro_input!(input as ::syn::ItemFn);

    let mut ast_new = ast_orig.clone();

    let new_fn_name = quote::format_ident!("{}_code", ast_orig.sig.ident);
    ast_new.sig.ident = quote::format_ident!("{}_code", new_fn_name);
    use ::quote::ToTokens;
    let fn_block = ast_orig.block.to_token_stream();

    let asdf = quote! {
        #ast_orig
        fn #new_fn_name (&self) -> ::proc_macro2::TokenStream {
            ::quote::quote! #fn_block
        }
    };

    asdf.into()
}

pub(crate) fn package(attrs: TokenStream, input: TokenStream) -> TokenStream {
    let local = parse_macro_input!(input as ::syn::ItemStruct);
    let mut path = parse_macro_input!(attrs as ::syn::Path);

    let last = path.segments.last().unwrap();
    if last.arguments.is_empty() {
        // make sure all the packages have generics, and if not add the
        // repo as generic aka: rewrite
        //   "#[package(my::pkg)]" -->> "#[package(my::pkg<R>)])"
        //   unless it's '::bok::PkgEmpty'
        if path.segments.len() != 2
            || path.segments[0].ident.to_string() != "bok"
            || path.segments[1].ident.to_string() != "PkgEmpty"
        {
            let repo_argument = {
                let generic_id: ::syn::Path = ::syn::parse_quote!(id<R>);
                generic_id.segments.last().unwrap().arguments.clone()
            };
            path.segments.last_mut().unwrap().arguments = repo_argument;
        }
    }

    return quote! {
        use ::bok_macro::package_path;
        #[::bok_macro::package_path(#path)]
        #local
    }
    .into();
}

pub(crate) fn package_path(
    attrs: TokenStream,
    input: TokenStream,
    __source_path: TokenStream,
) -> TokenStream {
    use ::syn::{spanned::Spanned, Fields, ItemStruct};
    let local = parse_macro_input!(input as ItemStruct);
    let local_span = local.span();
    let Fields::Named(local_fields) = local.fields else {
        use ::syn::spanned::Spanned;
        return ::syn::Error::new(
            local.fields.span(),
            "#[::bok::package()]: unnamed fields are not supported",
        )
        .to_compile_error()
        .into();
    };
    let local_attrs = local.attrs.iter();
    let ident = local.ident;
    let vis = local.vis;
    let local_generics = local.generics;
    if local_generics.params.len() != 0 {
        return ::syn::Error::new(
            local_span,
            "#[::bok::package()]: a package can not have generics",
        )
        .to_compile_error()
        .into();
    };
    let generic_struct: ::syn::ItemStruct = ::syn::parse_quote! {
        pub struct test<R> where R: ::bok::Repository + 'static {}
    };
    let (_, generics, where_clause) = generic_struct.generics.split_for_impl();

    let source_path = parse_macro_input!(__source_path as ::syn::Path);

    let base = parse_macro_input!(attrs as ItemStruct);
    let Fields::Named(base_fields) = &base.fields else {
        use ::syn::spanned::Spanned;
        return ::syn::Error::new(
            base.fields.span(),
            "#[::bok::package(..)]: base: unnamed fields are not supported",
        )
        .to_compile_error()
        .into();
    };
    // make sure the 'version' field is the first after the user's fields
    // we will use as a separator from the other imported fields
    let mut base_fields_extra = Vec::with_capacity(base.fields.len());
    match base_fields.named.iter().find(|&x| match &x.ident {
        Some(id_local) => id_local == "version",
        _ => false,
    }) {
        Some(_) => {
            let pkg_version = ::syn::Field::parse_named
                .parse2(quote! {
                    version: ::bok::Version
                })
                .unwrap();
            let base_marker = ::syn::Field::parse_named
                .parse2(quote! {
                    _bok_base: ::std::marker::PhantomData<#source_path>
                })
                .unwrap();
            let repo_marker = ::syn::Field::parse_named
                .parse2(quote! {
                    _bok_repo: ::std::marker::PhantomData<R>
                })
                .unwrap();
            base_fields_extra.push(pkg_version);
            base_fields_extra.push(base_marker);
            base_fields_extra.push(repo_marker);
        }
        None => {
            return ::syn::Error::new(
                local_span,
                "pkg: \"".to_owned()
                    + &ident.to_string()
                    + "\" base package \""
                    + &base.ident.to_string()
                    + "\" does not have 'version' field",
            )
            .to_compile_error()
            .into();
        }
    }
    for f in base_fields.named.iter() {
        let Some(id) = &f.ident else { continue };
        // don't add 'version' again
        if id.to_string() == "version"
            || id.to_string() == "_bok_base"
            || id.to_string() == "_bok_repo"
        {
            continue;
        }
        // compiler error if you try to extend a package while
        // reusing its fields names
        if let Some(repeated) = local_fields.named.iter().find(|&x| {
            let Some(id_local) = &x.ident else {
                return false;
            };
            id_local.to_string() == id.to_string()
        }) {
            return ::syn::Error::new(
                local_span,
                "pkg: \"".to_owned()
                    + &ident.to_string()
                    + "\" field \""
                    + &repeated.ident.as_ref().unwrap().to_string()
                    + "\" is already in package "
                    + &base.ident.to_string()
                    + "\" or its base",
            )
            .to_compile_error()
            .into();
        }
        base_fields_extra.push(f.clone());
    }

    let mut all_fields = Vec::new();
    all_fields.extend(local_fields.named.iter());
    all_fields.extend(base_fields_extra.iter());

    quote! {
        #(#local_attrs)
        *
        #[::macro_magic::export_tokens]
        #[derive(::bok::Package, ::std::fmt::Debug, Clone)]
        #vis struct #ident #generics #where_clause{
            #(#all_fields),
            *
        }
    }
    .into()
}

pub(crate) fn deps_build(
    attrs: TokenStream,
    input: TokenStream,
) -> TokenStream {
    let mut packages = parse_macro_input!(attrs as crate::PathList);
    let local = parse_macro_input!(input as ::syn::ItemStruct);

    // make sure all the packages have generics, and if not add the repo as
    // generic aka: rewrite
    //   "#[deps_build(my::pkg)]" -->> "#[deps_build(my::pkg<R>)])"
    let mut rewrite = false;
    let repo_argument = {
        let generic_id: ::syn::Path = ::syn::parse_quote!(id<R>);
        generic_id.segments.last().unwrap().arguments.clone()
    };
    for p in packages.0.iter_mut() {
        let last = p.segments.last_mut().unwrap();
        if last.arguments.is_empty() {
            rewrite = true;
            last.arguments = repo_argument.clone();
        }
    }
    if rewrite {
        let p_list = packages.0.into_iter();
        return quote! {
            #[::bok::deps_build(#(#p_list,)*)]
            #local
        }
        .into();
    }
    let packages = packages; // remove mut;

    let ::syn::Fields::Named(local_fields) = local.fields else {
        use ::syn::spanned::Spanned;
        return ::syn::Error::new(
            local.fields.span(),
            "unnamed fields are not supported",
        )
        .to_compile_error()
        .into();
    };
    let local_attrs = local.attrs.iter();
    let local_fields = local_fields.named.iter();
    let (_, generics, where_clause) = local.generics.split_for_impl();
    let ident = local.ident;
    let vis = local.vis;

    let pkg_trait = quote::format_ident!("BokDeps{}", ident);

    use ::convert_case::{Case, Casing};
    let deps = packages
        .0
        .iter()
        .map(|x| {
            let ident = x.segments.last().unwrap().ident.clone();
            quote::format_ident!("{}", ident.to_string().to_case(Case::Snake))
        })
        .collect::<Vec<::syn::Ident>>();

    quote! {
        #(#local_attrs)
        *
        #vis struct #ident #generics #where_clause{
            #(#local_fields),
            *
        }
        #[::macro_magic::export_tokens(#pkg_trait)]
        pub trait #pkg_trait: ::bok::Repository {
            #(fn #deps(&self) -> ::std::boxed::Box<dyn ::bok::Pkg>;)
            *
        }
    }
    .into()
}

// package_impl has 3 stages, and uses macro_magic import for the last two:
// * called without parameters => add default ::bok::Pkg functions, then add the
//   same macro with the package type as argument
// * called with the package type as argument => get the base type, then add the
//   same macro with the base type IMPL as argument
// * called with the a package impl as argument, copy the non-implemented
//   functions from the base
pub(crate) fn package_impl(
    _attrs: TokenStream,
    input: TokenStream,
) -> TokenStream {
    let mut ast = parse_macro_input!(input as ::syn::ItemImpl);

    if let Some((_, trait_name, _)) = &ast.trait_ {
        let s = &trait_name.segments;
        if s.len() != 2
            || s[0].ident.to_string() != "bok"
            || s[1].ident.to_string() != "Pkg"
        {
            //
            // only add the generic parameter and nothing else
            //
            let ::syn::Type::Path(t_id) = &ast.self_ty.as_ref() else {
                return ::syn::Error::new(
                    ast.span(),
                    "package_impl: Type is not Path",
                )
                .to_compile_error()
                .into();
            };
            let trait_deps = ::quote::format_ident!(
                "BokDeps{}",
                t_id.path.segments.last().unwrap().ident
            );
            let g: ::syn::ItemImpl = ::syn::parse_quote! {
                impl<R> trait_name for #t_id<R> where R: ::bok::Repository + #trait_deps {}
            };
            ast.generics = g.generics;
            ast.self_ty = g.self_ty;
            // TODO: if the trait is `::std::default::Default`
            //   then add the `_bok_base` and `_bok_repo` defaults automatically
            return quote! {
                #ast
            }
            .into();
        }
    }
    let ast = ast; // remove mut

    let name_pkg = match &*ast.self_ty {
        ::syn::Type::Path(tp) => match tp.path.get_ident() {
            Some(id) => id.clone(),
            _ => {
                return ::syn::Error::new(
                    ast.span(),
                    "package_impl: type::Path but no ident",
                )
                .to_compile_error()
                .into()
            }
        },
        _ => {
            return ::syn::Error::new(
                ast.span(),
                "package_impl: not a type::Path",
            )
            .to_compile_error()
            .into()
        }
    };
    let full_path_name = proc_macro2::Ident::new(
        &("_bok_pkg_".to_owned() + &name_pkg.to_string()),
        proc_macro2::Span::call_site(),
    );

    quote! {
        use ::bok_macro::package_impl_base;
        #[::bok_macro::package_impl_base(#name_pkg)]
        #[::macro_magic::export_tokens(#full_path_name)]
        #ast
    }
    .into()
}

// get the actual base type and re-call the macro with the impl symbols
pub(crate) fn package_impl_base(
    attrs: TokenStream,
    input: TokenStream,
) -> TokenStream {
    // This is a two-phase macro
    // * The first time this is called the argument will be the same path as the
    //   struct that implements  ::bok::Pkg
    // * The macro will be rewritten with the base package name that is extended
    //   by the package
    // And now that we have the proper base name we can add the missing
    // methods from the base

    let mut ast = parse_macro_input!(input as ::syn::ItemImpl);
    let name_pkg = match &*ast.self_ty {
        ::syn::Type::Path(tp) => match tp.path.get_ident() {
            Some(id) => id.clone(),
            _ => panic!("::bok::package_impl expected path ident"),
        },
        _ => panic!("::bok::package_impl expected path"),
    };
    let Ok(syntax_tree) = syn::parse::<::syn::ItemStruct>(attrs.clone()) else {
        return package_impl_base_add(attrs, &mut ast);
    };
    // we were passed an exported struct. first phase.
    if syntax_tree.ident.to_string() != name_pkg.to_string() {
        return ::syn::Error::new(
            ast.span(),
            "package_impl: called on \"".to_owned()
                + &name_pkg.to_string()
                + "\" with wrong initial name"
                + &syntax_tree.ident.to_string()
                + "\" ",
        )
        .to_compile_error()
        .into();
    }
    // go through the struct definition, extract the base type
    // from the `_bok_base` phantom data marker
    let base_path = match syntax_tree.fields.iter().find(|&x| {
        let Some(id) = &x.ident else {
            return false;
        };
        return id.to_string() == "_bok_base";
    }) {
        Some(field) => match &field.ty {
            ::syn::Type::Path(tp) => {
                if tp.path.segments.len() != 3
                    || tp.path.segments[0].ident.to_string() != "std"
                    || tp.path.segments[1].ident.to_string() != "marker"
                    || tp.path.segments[2].ident.to_string() != "PhantomData"
                {
                    return ::syn::Error::new(
                        ast.span(),
                        "package_impl: called on \"".to_owned()
                            + &name_pkg.to_string()
                            + "\" base is not PhantomData, "
                            + "what are you doing?",
                    )
                    .to_compile_error()
                    .into();
                }
                let ::syn::PathArguments::AngleBracketed(psa) =
                    &tp.path.segments[2].arguments
                else {
                    return ::syn::Error::new(
                        ast.span(),
                        "package_impl: called on \"".to_owned()
                            + &name_pkg.to_string()
                            + "\" base PhantomData has no arguments "
                            + "what are you doing?",
                    )
                    .to_compile_error()
                    .into();
                };
                if psa.args.len() != 1 {
                    return ::syn::Error::new(
                        ast.span(),
                        "package_impl: called on \"".to_owned()
                            + &name_pkg.to_string()
                            + "\" base PhantomData has too many arguments "
                            + "what are you doing?",
                    )
                    .to_compile_error()
                    .into();
                }
                let ::syn::GenericArgument::Type(::syn::Type::Path(
                    base_pkg_path,
                )) = &psa.args[0]
                else {
                    return ::syn::Error::new(
                        ast.span(),
                        "package_impl: called on \"".to_owned()
                            + &name_pkg.to_string()
                            + "\" base PhantomData has wrong argument type "
                            + "what are you doing?",
                    )
                    .to_compile_error()
                    .into();
                };
                base_pkg_path.path.clone()
            }
            _ => {
                return ::syn::Error::new(
                    ast.span(),
                    "package_impl: called on \"".to_owned()
                        + &name_pkg.to_string()
                        + "\" base of unknown type",
                )
                .to_compile_error()
                .into();
            }
        },
        None => {
            return ::syn::Error::new(
                ast.span(),
                "package_impl: called on \"".to_owned()
                    + &name_pkg.to_string()
                    + "\" can't find base",
            )
            .to_compile_error()
            .into();
        }
    };
    // now, `base_path` is an absolute path.
    // but it does not mean that it is in our crate
    // we need to maintain the whole path and change only the last ident,
    // to the one generated by us instead of by macro_magic

    // now `base_type` is the base struct. but what we actually want is
    // to import the `impl ::bok::Pkg` for `base_type`
    let mut exported_impl_name = base_path.clone();
    let last_segment_n = exported_impl_name.segments.len() - 1;
    let last_segment = &mut exported_impl_name.segments[last_segment_n];
    last_segment.ident =
        ::quote::format_ident!("_bok_pkg_{}", last_segment.ident);

    return quote! {
        #[::bok_macro::package_impl_base(#exported_impl_name)]
        #ast
    }
    .into();
}

// implements ::bok::Pkg:
// * add base methods
// * copy the non-implemented methods from the base
pub(crate) fn package_impl_base_add(
    attrs: TokenStream,
    ast: &mut ::syn::ItemImpl,
) -> TokenStream {
    let name_pkg = match &*ast.self_ty {
        ::syn::Type::Path(tp) => match tp.path.get_ident() {
            Some(id) => id.clone(),
            _ => panic!("::bok::package_impl expected path ident"),
        },
        _ => panic!("::bok::package_impl expected path"),
    };
    let base_ast = parse_macro_input!(attrs as ::syn::ItemImpl);
    let name: ::syn::ImplItem = ::syn::parse_quote! {
        fn name(&self) -> ::bok::PkgName {
            (module_path!().to_owned() + "::" + ::std::stringify!(#name_pkg)).as_str().into()
        }
    };
    let path: ::syn::ImplItem = ::syn::parse_quote! {
        fn path(&self) -> ::bok::Path<::bok::PkgName> {
            (module_path!().to_owned() + "::" + ::std::stringify!(#name_pkg)).as_str().into()
        }
    };
    let version: ::syn::ImplItem = ::syn::parse_quote! {
        fn version(&self) -> ::bok::Version {
            self.version.clone()
        }
    };
    let any: ::syn::ImplItem = ::syn::parse_quote! {
        fn as_any(&self) -> &dyn ::std::any::Any {
            self
        }
    };
    let any_mut: ::syn::ImplItem = ::syn::parse_quote! {
        fn as_any_mut(&mut self) -> &mut dyn ::std::any::Any {
            self
        }
    };
    let hash: ::syn::ImplItem = ::syn::parse_quote! {
        fn hash(&self) -> ::bok::Hash {
            use ::sha3::{Digest};
            let mut hasher = ::sha3::Sha3_256::new();
            let mut pkg_vars = String::new();
            use ::std::fmt::Write;
            write!(&mut pkg_vars,
                "{:?}",
                self,
            ).ok();
            hasher.update(&pkg_vars);
            hasher.update(self.to_string());
            let hash = hasher.finalize();
            ::bok::Hash::Sha3(hash)
        }
    };
    let hash_code: ::syn::ImplItem = ::syn::parse_quote! {
        fn hash_code(&self) -> ::bok::Hash {
            use ::sha3::{Digest};
            let mut hasher = ::sha3::Sha3_256::new();
            hasher.update(self.to_string());
            let hash = hasher.finalize();
            ::bok::Hash::Sha3(hash)
        }
    };

    for mut impl_item in ast.items.iter_mut() {
        if let ::syn::ImplItem::Fn(ref mut fn_impl) = &mut impl_item {
            if ["prepare", "configure", "build", "check", "install"]
                .iter()
                .find(|&f| *f == fn_impl.sig.ident.to_string().as_str())
                .is_none()
            {
                continue;
            }
            let fn_with_code: ::syn::ImplItemFn = ::syn::parse_quote! {
                #[::bok::pkg_fn_to_code]
                #fn_impl
            };
            *fn_impl = fn_with_code;
        } else {
            panic!("wtf");
        }
    }

    let trait_deps = ::quote::format_ident!("BokDeps{}", name_pkg);
    let generic_struct: ::syn::ItemImpl = ::syn::parse_quote! {
        impl<R> test for #name_pkg <R>
        where
            R: ::bok::Repository + 'static + #trait_deps,
        {}
    };

    ast.generics = generic_struct.generics;
    ast.self_ty = generic_struct.self_ty;

    ast.items.push(name);
    ast.items.push(path);
    ast.items.push(version);
    ast.items.push(any);
    ast.items.push(any_mut);
    ast.items.push(hash);
    ast.items.push(hash_code);

    fn maybe_add_fn(
        name_pkg: &str,
        ast: &mut ::syn::ItemImpl,
        base_ast: &::syn::ItemImpl,
        name: &str,
    ) -> Result<(), TokenStream> {
        let Some(base_fn) = base_ast.items.iter().find(|&f| {
            let ::syn::ImplItem::Fn(func) = f else {
                return false;
            };
            return func.sig.ident.to_string() == name;
        }) else {
            return Err(::syn::Error::new(
                ast.span(),
                "package_impl: called on \"".to_owned()
                    + name_pkg
                    + "\" maybe_add_fn can't find "
                    + name
                    + " on base",
            )
            .to_compile_error()
            .into());
        };
        let ::syn::ImplItem::Fn(mut base_fn_no_code) = base_fn.clone() else {
            return Err(::syn::Error::new(
                ast.span(),
                "package_impl: called on \"".to_owned()
                    + name_pkg
                    + "\" what was Fn is not anymore",
            )
            .to_compile_error()
            .into());
        };
        base_fn_no_code.attrs.retain_mut(|a| {
            let ::syn::Meta::Path(mp) = &a.meta else {
                return true;
            };
            if mp.segments.len() == 2
                && mp.segments[0].ident.to_string() == "bok"
                && mp.segments[1].ident.to_string() == "pkg_fn_to_code"
            {
                return false;
            }

            return true;
        });
        if ast
            .items
            .iter()
            .find(|&f| {
                let ::syn::ImplItem::Fn(func) = f else {
                    return false;
                };
                return func.sig.ident.to_string() == name;
            })
            .is_none()
        {
            let new_fn: ::syn::ImplItem = parse_quote!(
                #[::bok::pkg_fn_to_code]
                #base_fn_no_code
            );
            ast.items.push(new_fn);
        }
        Ok(())
    }
    for name in
        ["prepare", "configure", "build", "check", "install"].into_iter()
    {
        let Err(e) = maybe_add_fn(&name_pkg.to_string(), ast, &base_ast, name)
        else {
            continue;
        };
        return e;
    }
    quote! {
        #ast
    }
    .into()
}

pub(crate) fn derive_package(input: TokenStream) -> TokenStream {
    let mut input = parse_macro_input!(input as DeriveInput);

    let name = input.ident.clone();
    let name_builder = quote::format_ident!("{name}Builder");
    let name_builder2 = name_builder.clone();
    let name_builder3 = name_builder.clone();
    let elements = match &input.data {
        ::syn::Data::Struct(s) => match &s.fields {
            syn::Fields::Named(n) => n.named.clone(),
            _ => panic!("only named supported"),
        },
        _ => panic!("only struct allowed"),
    };
    let all_fields = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() != "version"
                && id.to_string() != "_bok_base"
                && id.to_string() != "_bok_repo"
            {
                return Some(&field.ident);
            }
        }
        None
    });
    let all_fields2 = all_fields.clone();
    let all_fields3 = all_fields.clone();
    let all_fields_mut = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() != "version"
                && id.to_string() != "_bok_base"
                && id.to_string() != "_bok_repo"
            {
                return Some(quote::format_ident!("{}_mut", id.to_string()));
            }
        }
        None
    });
    let all_types = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() != "version"
                && id.to_string() != "_bok_base"
                && id.to_string() != "_bok_repo"
            {
                return Some(&field.ty);
            }
        }
        None
    });
    let all_types2 = all_types.clone();
    let non_opt_fields = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() == "version"
                || id.to_string() == "_bok_base"
                || id.to_string() == "_bok_repo"
            {
                return None;
            }
        }
        match &field.ty {
            syn::Type::Path(pth) => {
                let first_path = pth.path.segments.first().unwrap();
                if first_path.ident == "Option" {
                    None
                } else {
                    let id = &field.ident;
                    Some(quote! {#id})
                }
            }
            t => Some(quote! {#t}),
        }
    });
    let opt_fields = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() == "version"
                || id.to_string() == "_bok_base"
                || id.to_string() == "_bok_repo"
            {
                return None;
            }
        }
        match &field.ty {
            syn::Type::Path(pth) => {
                let first_path = pth.path.segments.first().unwrap();
                if first_path.ident == "Option" {
                    let id = &field.ident;
                    Some(quote! {#id})
                } else {
                    None
                }
            }
            _ => None,
        }
    });
    let non_opt_types = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() == "version"
                || id.to_string() == "_bok_base"
                || id.to_string() == "_bok_repo"
            {
                return None;
            }
        }
        match &field.ty {
            syn::Type::Path(pth) => {
                let first_path = pth.path.segments.first().unwrap();
                if first_path.ident == "Option" {
                    None
                } else {
                    let t = &field.ty;
                    Some(quote! {#t})
                }
            }
            _ => None,
        }
    });
    let opt_types = elements.iter().filter_map(|field| {
        if let Some(id) = field.ident.clone() {
            if id.to_string() == "version"
                || id.to_string() == "_bok_base"
                || id.to_string() == "_bok_repo"
            {
                return None;
            }
        }
        if let ::syn::Type::Path(pth) = &field.ty {
            let first_path = pth.path.segments.first().unwrap();
            if first_path.ident == "Option" {
                if let syn::PathArguments::AngleBracketed(
                    syn::AngleBracketedGenericArguments { args, .. },
                ) = &first_path.arguments
                {
                    if let Some(syn::GenericArgument::Type(syn::Type::Path(
                        p,
                    ))) = args.first()
                    {
                        let id = &p.path.segments.first().unwrap().ident;
                        return Some(quote! {#id});
                    }
                }
            }
        }
        None
    });
    let non_opt_fields2 = non_opt_fields.clone();
    let non_opt_fields3 = non_opt_fields.clone();
    let non_opt_fields4 = non_opt_fields.clone();
    let non_opt_fields5 = non_opt_fields.clone();
    let opt_fields2 = opt_fields.clone();
    let opt_fields3 = opt_fields.clone();
    let opt_types2 = opt_types.clone();
    let non_opt_types2 = non_opt_types.clone();

    {
        let ::syn::Data::Struct(ref mut ds) = input.data else {
            panic!("::bok::package expected a struct");
        };
        let ::syn::Fields::Named(ref mut _old_nf) = ds.fields else {
            panic!("::bok::package expected a named field");
        };
    }
    let pkg_struct = quote! {
        #input
    };
    let mut pkg_struct_str = String::new();
    {
        use ::core::fmt::Write;
        write!(&mut pkg_struct_str, "{}", pkg_struct)
            .expect("can't write package struct into string");
    }

    let trait_deps = ::quote::format_ident!("BokDeps{}", name);

    let expanded = quote! {
        impl<R> ::core::fmt::Display for #name<R>
        where
            R: ::bok::Repository + #trait_deps,
        {
            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>)
                ->::core::fmt::Result
            {
                <#name<R> as ::bok::PkgCode>::fmt(self, f)
            }
        }
        impl<R> ::bok::PkgCode for #name<R>
        where
            R: ::bok::Repository + 'static + #trait_deps,
        {
            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>)
                ->::core::fmt::Result
            {
                // FIXME: this sounds convoluted.
                // first we turn everything into a string, then we
                // parse the string into tokenstream again to format it
                // reason: the `prettyplease` works on `::syn::File`
                // and I can't find an easy translation
                //   `TokenStream2 -> TokenStream`
                use ::bok::Pkg;

                // don't add a method if it is just the base Trait implementation
                fn maybe_add_fn(out: &mut String, name: &str, fn_str: &str) -> ::core::fmt::Result {

                    //FIXME: check with the code exported from macro_magic base
                    let str_base = "self . base () . unwrap () . ".to_owned() + name + " ()";

                    if fn_str.trim() != str_base {
                        use ::core::fmt::Write;

                        write!(out,
                            "\
                            fn {}(&self) -> Result<(), ()> {{\n\
                            {}\n\
                            }}\n",
                            name,
                            fn_str,
                            )

                    } else {
                        ::core::fmt::Result::Ok(())
                    }
                };

                use ::core::fmt::Write;

                let pkg_empty = ::bok::PkgEmpty::default();
                let mut pkg_string = String::new();
                // FIXME: filter out the things added from base pkg
                write!(&mut pkg_string,
                    "#[::bok::package(::bok::PkgEmpty)]\n\
                    {}",
                    #pkg_struct_str)?;
                write!(&mut pkg_string,
                    "#[::bok::package_impl]\n\
                    impl ::bok::Pkg for {} {{\n",
                    ::std::stringify!(#name)
                )?;
                maybe_add_fn(&mut pkg_string, "prepare", &self.prepare_code().to_string())?;
                maybe_add_fn(&mut pkg_string, "configure", &self.configure_code().to_string())?;
                maybe_add_fn(&mut pkg_string, "build", &self.build_code().to_string())?;
                maybe_add_fn(&mut pkg_string, "check", &self.check_code().to_string())?;
                maybe_add_fn(&mut pkg_string, "install", &self.install_code().to_string())?;
                write!(&mut pkg_string, "}}\n")?;
                let re_parsed = ::syn::parse_file(&pkg_string).unwrap();
                let formatted = prettyplease::unparse(&re_parsed);
                f.write_str(&formatted)
            }
        }
        impl<R> #name<R>
        where
            R: ::bok::Repository + 'static + #trait_deps + ::core::default::Default,
        {
            pub fn as_pkg(&self) -> &dyn ::bok::Pkg {
                self
            }
            pub fn as_pkg_mut(&mut self) -> &mut dyn ::bok::Pkg {
                self
            }
            pub fn builder() -> #name_builder<R> {
                #name_builder::<R>::default()
            }
            #(pub fn #all_fields2(&self) -> &#all_types {
                &self.#all_fields2
            })*
            #(pub fn #all_fields_mut(&mut self) -> &#all_types2 {
                &mut self.#all_fields3
            })*
        }
        #[derive(::std::default::Default, ::std::fmt::Debug)]
        pub struct #name_builder<R>
        where
            R: ::bok::Repository + 'static + #trait_deps,
        {
            _bok_repo: ::std::marker::PhantomData<R>,
            #(#non_opt_fields: ::std::option::Option<#non_opt_types>,)*
            #(#opt_fields: ::std::option::Option<#opt_types>,)*
        }
        impl<R> ::bok::PkgBuilder for #name_builder2<R>
        where
            R: ::bok::Repository + 'static + #trait_deps,
        {
            fn name(&self) -> ::bok::PkgName {
                use ::bok::Pkg;
                #name::<R>::default().name()
            }
            fn path(&self) -> ::bok::Path<::bok::PkgName> {
                use ::bok::Pkg;
                #name::<R>::default().path()
            }
            fn version(&self) -> ::bok::Version {
                use ::bok::Pkg;
                #name::<R>::default().version()
            }
            fn default_unused(&mut self) -> &mut dyn ::bok::PkgBuilder {
                let def = #name::<R>::default();
                #(if self.#non_opt_fields5.is_none() {
                    self.#non_opt_fields5 = Some(def.#non_opt_fields5);
                })*

                self
            }
            fn build(&mut self) -> Result<Box<dyn ::bok::Pkg>, ::std::boxed::Box<dyn ::std::error::Error>> {
                #(if self.#non_opt_fields2.is_none() {
                    return ::std::result::Result::Err("unset field".into());
                })*
                Ok(
                    Box::new(#name::<R> {
                        _bok_base: ::std::marker::PhantomData::default(),
                        _bok_repo: ::std::marker::PhantomData::default(),
                        version: #name::<R>::default().version,
                        #(#non_opt_fields3 : self.#non_opt_fields3.clone().unwrap(),)*
                        #(#opt_fields2 : self.#opt_fields2.clone(),)*
                    })
                )
            }
        }
        impl<R> #name_builder3<R>
        where
            R: ::bok::Repository +'static + #trait_deps,
        {
            pub fn as_any(&self) -> &dyn ::std::any::Any {
                self
            }
            pub fn as_any_mut(&mut self) -> &mut dyn ::std::any::Any {
                self
            }
            pub fn as_builder(&self) -> &dyn ::bok::PkgBuilder {
                self
            }
            pub fn as_builder_mut(&mut self) -> &mut dyn ::bok::PkgBuilder {
                self
            }
            #(pub fn #non_opt_fields4 (&mut self, val : #non_opt_types2) -> &mut Self {
                if self.#non_opt_fields4 != None &&
                    self.#non_opt_fields4 != Some(val) {
                    panic!("Package \"{}\": mandatory attribute set multiple times: \"{}\"",
                        ::std::stringify!(#name),
                        ::std::stringify!(#non_opt_fields4));
                }
                self.#non_opt_fields4 = Some(val);
                self
            })*
            #(pub fn #opt_fields3 (&mut self, val : #opt_types2) -> &mut Self {
                if self.#opt_fields3 != None &&
                    self.#opt_fields3 != Some(val) {
                    panic!("Package \"{}\": optional attribute set multiple times: \"{}\"",
                        ::std::stringify!(#name),
                        ::std::stringify!(#opt_fields3));
                }
                self.#opt_fields3 = Some(val);
                self
            })*
        }
    };

    TokenStream::from(expanded)
}