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use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::quote;
use syn::parse::{Parse, ParseStream};
use syn::{parse_macro_input, Ident, Result, Token, Type};
mod kw {
syn::custom_keyword!(to);
syn::custom_keyword!(with);
}
#[proc_macro]
pub fn attach(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as OpenInput);
let instantiation_expr;
let pass_object_expr;
let tag_str;
let tag_type;
match input.tag {
Tag::Ident(tag) => {
instantiation_expr = quote! {
let mut new_node = #tag::default();
};
pass_object_expr = quote! {
new_tag = Some(MathNode::#tag(new_node));
};
tag_str = tag.to_string();
tag_type = tag;
}
Tag::Enum(enum_name, enum_type) => {
let enum_str = enum_name.to_string().to_lowercase();
let fn_str = format!("new_{}", enum_str);
let fn_ident = Ident::new(&fn_str, Span::call_site());
instantiation_expr = quote! {};
pass_object_expr = quote! {
new_tag = Some(MathNode::#fn_ident(#enum_name::#enum_type));
};
tag_str = format!("{}::{}", enum_name.to_string(), enum_type.to_string());
tag_type = enum_name;
}
}
let attr_idents = input.attr_idents;
let attr_types = input.attr_types;
let mut attr_str = Vec::new();
for ident in &attr_idents {
let mut ident_str = ident.to_string();
if ident_str.starts_with("r#") {
ident_str = ident_str.trim_start_matches("r#").to_string()
}
attr_str.push(ident_str);
}
let store_attr = quote! {
let attributes = e.attributes().map(|a| a.unwrap()).collect::<Vec<_>>();
for attribute in attributes {
let key = std::str::from_utf8(attribute.key).unwrap();
let value = attribute.unescape_and_decode_value(&reader).unwrap();
match key {
#(#attr_str => {
new_node.#attr_idents =
Some(value.parse::<#attr_types>().expect("Incorrect type"));
})*
_ => {
panic!("Attribute {} not parsed for {}", key, #tag_str);
}
}
}
};
let index_expr = quote! {
parent.index(MathNodeType::#tag_type, current.clone());
};
let parents = &input.parents;
let mut parent_strs: Vec<String> = Vec::new();
let mut index_exprs: Vec<proc_macro2::TokenStream> = Vec::new();
let parents_to_index: Vec<String> = vec!["Apply", "Lambda", "Piecewise", "Piece", "Otherwise"]
.iter()
.map(|&a| a.into())
.collect();
for parent in parents {
let parent_str = parent.to_string();
if parents_to_index.contains(&parent_str) {
index_exprs.push(index_expr.clone());
} else {
index_exprs.push(quote! {})
}
parent_strs.push(parent_str);
}
let tokens = quote! {
{
#instantiation_expr
#store_attr
match container[current] {
#(MathNode::#parents (ref mut parent) => {
#pass_object_expr
current = container_len;
parent.children.push(current.clone());
#index_exprs
stack.push(current.clone());
})*
_ => {
panic!("Tag {:?} not parsed under parent {:?}", #tag_str, container[current]);
}
}
}
};
tokens.into()
}
#[derive(Debug)]
struct OpenInput {
tag: Tag,
parents: Vec<Ident>,
attr_idents: Vec<Ident>,
attr_types: Vec<Type>,
}
#[derive(Debug)]
enum Tag {
Ident(Ident),
Enum(Ident, Ident),
}
impl Parse for OpenInput {
fn parse(input: ParseStream) -> Result<Self> {
let tag_ident = syn::Ident::parse(input)?;
let tag: Tag;
let mut lookahead = input.lookahead1();
if lookahead.peek(Token![:]) {
input.parse::<Token![:]>()?;
input.parse::<Token![:]>()?;
let enum_type = syn::Ident::parse(input)?;
tag = Tag::Enum(tag_ident, enum_type);
} else {
tag = Tag::Ident(tag_ident);
}
let mut attr_idents = Vec::new();
let mut attr_types = Vec::new();
lookahead = input.lookahead1();
if lookahead.peek(kw::with) {
let _with = input.parse::<kw::with>()?;
loop {
let ident = syn::Ident::parse(input)?;
attr_idents.push(ident);
let _as = input.parse::<Token![as]>();
let ty = syn::Type::parse(input)?;
attr_types.push(ty);
if input.peek(Token![,]) {
input.parse::<Token![,]>()?;
}
lookahead = input.lookahead1();
if lookahead.peek(kw::to) {
break;
}
}
}
let _to = input.parse::<kw::to>()?;
let mut parents = vec![syn::Ident::parse(input)?];
loop {
lookahead = input.lookahead1();
if lookahead.peek(Token![|]) {
input.parse::<Token![|]>()?;
} else {
break;
}
lookahead = input.lookahead1();
if lookahead.peek(Ident) {
parents.push(syn::Ident::parse(input)?);
}
}
Ok(OpenInput {
tag,
parents,
attr_idents,
attr_types,
})
}
}
#[proc_macro]
pub fn close(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as CloseInput);
let tag = &input.tag;
let tag_str = input.tag.to_string();
let tokens = quote! {
match container[current] {
MathNode::#tag (ref mut tag_field) => {
stack.pop();
current = stack.last().unwrap().to_owned();
tag_field.parent = Some(current.clone());
}
_ => {
panic!("Trying to close {} but currently in {:?}", #tag_str, container[current]);
}
}
};
tokens.into()
}
#[derive(Debug)]
struct CloseInput {
tag: Ident,
}
impl Parse for CloseInput {
fn parse(input: ParseStream) -> Result<Self> {
let tag = syn::Ident::parse(input)?;
Ok(CloseInput { tag })
}
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
}