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extern crate proc_macro;
mod component_field;
use syn::{
DeriveInput,
Data,
DataStruct,
DataEnum,
DataUnion,
Fields,
Ident,
Generics,
FieldsNamed,
Field,
parse_macro_input,
token::{Struct, Enum, Union},
};
use proc_macro2::{TokenStream, Span};
use quote::quote;
use crate::component_field::ComponentField;
#[proc_macro_derive(ComponentGroup)]
pub fn derive_component_group(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let DeriveInput {ident, generics, data, ..} = parse_macro_input!(input as DeriveInput);
match data {
Data::Struct(DataStruct {
struct_token: Struct {span},
fields: Fields::Named(FieldsNamed {named: fields, ..}),
..
}) => {
if fields.is_empty() {
error(span, "struct must have at least one field to derive ComponentGroup")
} else {
impl_component_group(ident, &generics, fields.iter())
}.into()
},
Data::Struct(DataStruct {struct_token: Struct {span}, ..}) |
Data::Enum(DataEnum {enum_token: Enum {span}, ..}) |
Data::Union(DataUnion {union_token: Union {span}, ..}) => {
error(span, "Only structs with named fields are supported").into()
},
}
}
fn error(span: Span, message: &str) -> TokenStream {
syn::Error::new(span, message).to_compile_error()
}
fn impl_component_group<'a>(
ident: Ident,
generics: &'a Generics,
fields: impl Iterator<Item=&'a Field>,
) -> TokenStream {
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let fields: Vec<_> = fields.map(ComponentField::from).collect();
let field_names: Vec<_> = fields.iter().map(|f| f.ident).collect();
let first_from_world = first_from_world_method(&field_names, &fields);
let from_world = from_world_method(&field_names, &fields);
let create = create_method(&fields);
let update = update_method(&field_names, &fields);
let remove = remove_method(&field_names, &fields);
quote! {
impl #impl_generics component_group::ComponentGroup for #ident #ty_generics #where_clause {
#first_from_world
#from_world
#create
#update
#remove
}
}
}
fn first_from_world_method(field_names: &[&Ident], fields: &[ComponentField]) -> TokenStream {
let joinables = fields.into_iter().map(|&ComponentField {ident: field_name, is_optional, ..}| {
if is_optional {
quote! {#field_name.maybe()}
} else {
quote! {&#field_name}
}
});
let clones = fields.into_iter().map(|&ComponentField {ident: field_name, is_optional, ..}| {
if is_optional {
quote! {#field_name.cloned()}
} else {
quote! {Clone::clone(#field_name)}
}
});
let tys = fields.into_iter().map(|f| f.ty);
quote! {
fn first_from_world(world: &specs::World) -> Option<(specs::Entity, Self)> {
use specs::{Join, Entities};
let ( __entities, #(#field_names),* ) = world.system_data::<( Entities, #(specs::ReadStorage<#tys>),* )>();
( &__entities, #(#joinables),* ).join().next().map(|( __entity, #(#field_names),* )| (__entity, Self {
#(#field_names : #clones),*
}))
}
}
}
fn from_world_method(field_names: &[&Ident], fields: &[ComponentField]) -> TokenStream {
let tys = fields.into_iter().map(|f| f.ty);
let reads = fields.into_iter().map(|&ComponentField {ident: field_name, ty, is_optional}| {
if is_optional {
quote! {#field_name.get(entity).cloned()}
} else {
let err = format!("expected a {} component to be present", quote!(#ty));
quote! {#field_name.get(entity).cloned().expect(#err)}
}
});
quote! {
fn from_world(world: &specs::World, entity: specs::Entity) -> Self {
let ( #(#field_names),* ) = world.system_data::<( #(specs::ReadStorage<#tys>),* )>();
Self {
#( #field_names : #reads ),*
}
}
}
}
fn create_method(fields: &[ComponentField]) -> TokenStream {
let with_comp = fields.into_iter().map(|&ComponentField {ident: field_name, is_optional, ..}| {
if is_optional {
quote! {
if let Some(#field_name) = self.#field_name {
builder = builder.with(#field_name);
}
}
} else {
quote! { builder = builder.with(self.#field_name); }
}
});
quote! {
fn create(self, world: &mut specs::World) -> specs::Entity {
use specs::{Builder, WorldExt};
#[allow(unused_mut)]
let mut builder = world.create_entity();
#( #with_comp )*
builder.build()
}
}
}
fn update_method(field_names: &[&Ident], fields: &[ComponentField]) -> TokenStream {
let tys = fields.into_iter().map(|f| f.ty);
let updates = fields.into_iter().map(|&ComponentField {ident: field_name, is_optional, ..}| {
if is_optional {
quote! {
match self.#field_name {
Some(value) => #field_name.insert(entity, value)?,
None => #field_name.remove(entity),
};
}
} else {
quote! { #field_name.insert(entity, self.#field_name)?; }
}
});
quote! {
type UpdateError = specs::error::Error;
fn update(self, world: &mut specs::World, entity: specs::Entity) -> Result<(), Self::UpdateError> {
let ( #(mut #field_names),* ) = world.system_data::<( #( specs::WriteStorage<#tys> ),* )>();
#( #updates )*
Ok(())
}
}
}
fn remove_method(field_names: &[&Ident], fields: &[ComponentField]) -> TokenStream {
let tys = fields.into_iter().map(|f| f.ty);
let reads = fields.into_iter().map(|&ComponentField {ident: field_name, ty, is_optional}| {
if is_optional {
quote! {#field_name.remove(entity)}
} else {
let err = format!("expected a {} component to be present", quote!(#ty));
quote! {#field_name.remove(entity).expect(#err)}
}
});
quote! {
fn remove(world: &mut specs::World, entity: specs::Entity) -> Self {
let ( #(mut #field_names),* ) = world.system_data::<( #(specs::WriteStorage<#tys>),* )>();
Self {
#( #field_names : #reads ),*
}
}
}
}