ecs/update_macros/src/update.rs

use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use quote::{ToTokens, format_ident, quote};
use syn::Ident;

struct Query {
    components: Vec<Ident>,
    filter: Ident,
}

impl Query {
    pub fn new(components: impl Iterator<Item = Ident>, filter_id: usize) -> Self {
        Self {
            components: components.collect(),
            filter: format_ident!("Filter{filter_id}"),
        }
    }

    pub fn types(&self) -> proc_macro2::TokenStream {
        let component_list = self
            .components
            .iter()
            .map(|c| quote! { #c, })
            .collect::<Vec<_>>();

        let components = if component_list.len() == 1 {
            let component = &component_list[0];
            quote! { #component }
        } else {
            quote! { ( #(#component_list)* ) }
        };

        components
    }

    pub fn filter(&self) -> &Ident {
        &self.filter
    }
}

impl ToTokens for Query {
    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
        let component_list = self
            .components
            .iter()
            .map(|c| quote! { &mut #c, })
            .collect::<Vec<_>>();

        let components = if component_list.len() == 1 {
            let component = &component_list[0];
            quote! { #component }
        } else {
            quote! { ( #(#component_list)* ) }
        };

        let filter = self.filter.clone();

        proc_macro2::TokenStream::from(quote! {
            Query<#components, #filter>
        })
        .to_tokens(tokens);
    }
}

struct Update {
    queries: Vec<Query>,
    resources: Vec<Ident>,
}

impl Update {
    pub fn new(queries: impl Iterator<Item = usize>, resources: usize) -> Self {
        Self {
            queries: queries
                .enumerate()
                .map(|(query, component_count)| {
                    Query::new(
                        (1..component_count).map(|component| format_ident!("C{component}Q{query}")),
                        query,
                    )
                })
                .collect(),
            resources: (0..resources)
                .map(|resource| format_ident!("Res{resource}"))
                .collect(),
        }
    }

    pub fn query_types(&self)
}

pub fn update(max_components: usize, max_queries: usize) -> TokenStream {
    TokenStream::from(quote! {
        impl<Func, Filter, >



    })
}