eatgel/eatgel-proc-macro/src/lib.rs

extern crate proc_macro;

use proc_macro::{Literal, TokenStream, TokenTree};
use proc_macro_roids::{DeriveInputStructExt, FieldExt};
use quote::quote;
use std::str::FromStr;

use proc_macro2::TokenStream as TokenStream2;
use syn::{parse_macro_input, parse_quote, DeriveInput};

#[proc_macro_derive(ShaderData, attributes(skip))]
pub fn derive_shader_data(token_stream: TokenStream) -> TokenStream {
    let mut iter = token_stream.into_iter();
    let empty = TokenStream::new();

    if let Some(TokenTree::Ident(ident)) = iter.next() {
        if ident.to_string() != "struct" {
            return empty;
        }
    } else {
        return empty;
    }

    let struct_name = if let Some(TokenTree::Ident(ident)) = iter.next() {
        ident.to_string()
    } else {
        return empty;
    };

    let mut group = if let Some(TokenTree::Group(group)) = iter.next() {
        group
    } else {
        return empty;
    }
    .stream()
    .into_iter();

    let mut keys = vec![];

    loop {
        let item = group.next();
        if item.is_none() {
            break;
        }

        let item = item.unwrap();

        if item.to_string() == "#" {
            if let Some(TokenTree::Group(tag)) = group.next() {
                if tag.to_string() == "[skip]" {
                    while let Some(x) = group.next() {
                        if x.to_string() == "," {
                            break;
                        }
                    }
                }
                continue;
            } else {
                break;
            }
        }

        let name = match item {
            TokenTree::Ident(ident) => ident.to_string(),
            _ => break,
        };

        // :
        group.next();
        let mut stream = vec![];
        while let Some(x) = group.next() {
            if x.to_string() == "," {
                break;
            }

            stream.push(x);
        }

        keys.push(name);
    }

    let init = keys
        .iter()
        .map(|name| Literal::string(&name).to_string())
        .collect::<Vec<String>>()
        .join(", ");

    let mut index = -1;

    let apply = keys
        .iter()
        .map(|name| {
            index += 1;

            format!(
                "(gl as &dyn UpdateUniform<_>).update_uniform_by_index(gl, program_id, {}, &self.{});",
                index,
                name
            )
        })
        .collect::<Vec<String>>()
        .join("\n");

    let gen_source = format!(
        r#"
impl ::eatgel::ShaderData for {} {{
    fn init(&mut self, gl: &mut ::eatgel::GlContext, program_id: u32) {{
        gl.register_uniforms(program_id, &[{}]);
    }}
    fn apply(&self, gl: &::eatgel::GlContext, program_id: u32) {{
        {}
    }}
}}
"#,
        struct_name, init, apply,
    );

    TokenStream::from_str(&gen_source).unwrap()
}

#[proc_macro_derive(VertexData, attributes(skip))]
pub fn derive_vertex_data(token_stream: TokenStream) -> TokenStream {
    let ast = parse_macro_input!(token_stream as DeriveInput);
    let name = &ast.ident;

    let mut index = -1;
    let fields = ast
        .fields()
        .iter()
        .map(move |field| {
            index += 1;
            let name = index;
            (name, field)
        })
        .filter(|(_, field)| !field.is_phantom_data())
        .filter(|(_, field)| !field.contains_tag(&parse_quote!(vertex_data), &parse_quote!(skip)));

    let sizes = fields
        .clone()
        .map(|(_, field)| {
            let type_name = field.type_name();

            quote!(
                ::std::mem::size_of::<#type_name>()
            )
        })
        .collect::<Vec<_>>();

    let types = fields
        .clone()
        .map(|(_, field)| {
            let type_name = field.type_name();

            quote!(
                ::eatgel::type_descriptor_of::<#type_name>()
            )
        })
        .collect::<Vec<_>>();

    let pointers = fields
        .map(|(index, field)| {
            if let Some(name) = field.ident.as_ref() {
                quote!(
                    self.#name.as_ptr() as *const ::std::ffi::c_void
                )
            } else {
                quote!(
                    self.#index.as_ptr() as *const ::std::ffi::c_void
                )
            }
        })
        .collect::<Vec<_>>();

    let token_stream2: TokenStream2 = quote!(
        impl ::eatgel::VertexData for #name {
            fn get_sizes() -> Box<[usize]> {
                return vec![#(#sizes,)*].into_boxed_slice()
            }

            fn get_types() -> Box<[::eatgel::TypeDescriptor]> {
                return vec![#(#types,)*].into_boxed_slice()
            }

            fn get_pointers(&self) -> Box<[*const ::std::ffi::c_void]> {
                return vec![#(#pointers,)*].into_boxed_slice()
            }
        }
    );

    token_stream2.into()
}