wip: proc: view macro implementation

proc/src/proc_view.rs

@@ -1,19 +1,26 @@
 use proc_macro::TokenStream;
-use proc_macro2::{TokenStream as TokenStream2};
+use proc_macro2::{TokenStream as TokenStream2, TokenTree, Ident};
+use syn::parse_macro_input;
+use syn::{Expr, Attribute, Meta, MetaList, Path, PathSegment, PathArguments, ImplItem};
+use syn::parse::{Parse, ParseStream, Result};
+use syn::token::PathSep;
+use syn::punctuated::Punctuated;
 
 pub(crate) fn view_impl (meta: TokenStream, item: TokenStream) -> TokenStream {
-    let ViewMeta { output, define, attrs } = syn::parse_macro_input!(meta as ViewMeta);
-    let ViewItem { target, mapped, items } = syn::parse_macro_input!(item as ViewItem);
+    let ViewMeta { output, define, attrs, .. } = parse_macro_input!(meta as ViewMeta);
+    let ViewItem { target, mapped, items, .. } = parse_macro_input!(item as ViewItem);
     quote::quote! {
-        #attrs
+        #(#attrs)*
         impl #target {
-            #items
+            #(#items)*
         }
+        /// Generated by [tengri_proc].
         impl ::tengri::Content<#output> for #target {
             fn content (&self) -> impl Render<#output> {
                 self.size.of(::tengri::View(self, #define))
             }
         }
+        /// Generated by [tengri_proc].
         impl<'a> ::tengri::ViewContext<'a, #output> for #target {
             fn get_content_sym (&'a self, value: &Value<'a>) -> Option<RenderBox<'a, #output>> {
                 match value {
@@ -34,31 +41,57 @@ pub(crate) fn view_impl (meta: TokenStream, item: TokenStream) -> TokenStream {
 }
 
 struct ViewMeta {
-    attrs:  &'static str,
-    output: &'static str,
-    define: &'static str,
+    attrs:  Vec<Attribute>,
+    output: Option<Ident>,
+    define: Expr,
 }
 
-impl syn::parse::Parse for ViewMeta {
-    fn parse (input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
-        Ok(Self {
-            attrs:  "",
-            output: "",
-            define: "",
-        })
+impl Parse for ViewMeta {
+    fn parse (input: ParseStream) -> Result<Self> {
+        let mut output = None;
+        let mut define = None;
+        let mut attrs  = input.call(Attribute::parse_outer)?.into_iter().filter(|attr| {
+            if let Attribute { meta: Meta::List(MetaList { path, tokens, .. }), .. } = attr
+                && path.segments.len() == 2
+                && nth_segment_is(&path.segments, 0, "tengri")
+                && nth_segment_is(&path.segments, 1, "view")
+                && let Some(TokenTree::Group(group)) = tokens.clone().into_iter().next()
+                && let Some(TokenTree::Ident(ident)) = group.stream().into_iter().next()
+            {
+                output = Some(ident);
+                return false
+            }
+            true
+        }).collect();
+
+        if let Some(define) = define {
+            Ok(Self { attrs, output, define })
+        } else {
+            Err(input.error("Missing view definition."))
+        }
     }
 }
 
+fn nth_segment_is (segments: &Punctuated<PathSegment, PathSep>, n: usize, x: &str) -> bool {
+    if let Some(PathSegment { arguments: PathArguments::None, ident, .. }) = segments.get(n) {
+        if format!("{ident}") != x {
+            return true
+        }
+    }
+    return false
+}
+
 struct ViewItem {
-    items:  &'static str,
+    items:  Vec<ImplItem>,
     target: &'static str,
     mapped: &'static str,
 }
 
-impl syn::parse::Parse for ViewItem {
-    fn parse (input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
+impl Parse for ViewItem {
+    fn parse (input: ParseStream) -> Result<Self> {
+        let items = vec![];
         Ok(Self {
-            items:  "",
+            items,
             target: "",
             mapped: "",
         })
@@ -67,12 +100,19 @@ impl syn::parse::Parse for ViewItem {
 
 #[cfg(test)] #[test] fn test_view () {
 
-    let _: syn::ItemImpl = syn::parse_quote! {
+    use syn::{ItemImpl, parse_quote};
+
+    let _: ItemImpl = parse_quote! {
         #[tengri::view(Tui)]
         impl SomeView {
-            #[tengri::view(":view")]
+            #[tengri::view]
             fn view (&self) -> impl Content<TuiOut> + use<'_> {
-                "view"
+                "view-1"
+            }
+
+            #[tengri::view(":view-1")]
+            fn view_1 (&self) -> impl Content<TuiOut> + use<'_> {
+                "view-1"
             }
         }
     };