1use proc_macro::TokenStream;
 2use quote::quote;
 3use syn::{parse_macro_input, parse_quote, DeriveInput};
 4
 5pub fn derive_component(input: TokenStream) -> TokenStream {
 6    let ast = parse_macro_input!(input as DeriveInput);
 7    let name = &ast.ident;
 8
 9    let mut trait_generics = ast.generics.clone();
10    let view_type = if let Some(view_type) = specified_view_type(&ast) {
11        quote! { #view_type }
12    } else {
13        if let Some(first_type_param) = ast.generics.params.iter().find_map(|param| {
14            if let syn::GenericParam::Type(type_param) = param {
15                Some(type_param.ident.clone())
16            } else {
17                None
18            }
19        }) {
20            quote! { #first_type_param }
21        } else {
22            trait_generics.params.push(parse_quote! { V: 'static });
23            quote! { V }
24        }
25    };
26
27    let (impl_generics, _, where_clause) = trait_generics.split_for_impl();
28    let (_, ty_generics, _) = ast.generics.split_for_impl();
29
30    let expanded = quote! {
31        impl #impl_generics gpui::Component<#view_type> for #name #ty_generics #where_clause {
32            fn render(self) -> gpui::AnyElement<#view_type> {
33                (move |view_state: &mut #view_type, cx: &mut gpui::ViewContext<'_, #view_type>| self.render(view_state, cx))
34                    .render()
35            }
36        }
37    };
38
39    TokenStream::from(expanded)
40}
41
42fn specified_view_type(ast: &DeriveInput) -> Option<proc_macro2::Ident> {
43    let component_attr = ast
44        .attrs
45        .iter()
46        .find(|attr| attr.path.is_ident("component"))?;
47
48    if let Ok(syn::Meta::List(meta_list)) = component_attr.parse_meta() {
49        meta_list.nested.iter().find_map(|nested| {
50            if let syn::NestedMeta::Meta(syn::Meta::NameValue(nv)) = nested {
51                if nv.path.is_ident("view_type") {
52                    if let syn::Lit::Str(lit_str) = &nv.lit {
53                        return Some(
54                            lit_str
55                                .parse::<syn::Ident>()
56                                .expect("Failed to parse view_type"),
57                        );
58                    }
59                }
60            }
61            None
62        })
63    } else {
64        None
65    }
66}