proc: view macro implementation

proc/Cargo.toml

@@ -8,6 +8,6 @@ edition     = { workspace = true }
 proc-macro = true
 
 [dependencies]
-syn = { version = "2", features = ["full"] }
+syn = { version = "2", features = ["full", "extra-traits"] }
 quote = { version = "1" }
 proc-macro2 = { version = "1", features = ["span-locations"] }

proc/src/proc_view.rs

@@ -1,80 +1,299 @@
 use proc_macro::TokenStream;
-use proc_macro2::{TokenStream as TokenStream2};
+use proc_macro2::{
+    TokenStream as TokenStream2, TokenTree,
+    Ident, Span, Punct, Spacing, Group, Delimiter, Literal
+};
+use syn::{parse, parse_macro_input, braced, Token};
+use syn::{Expr, Attribute, Meta, MetaList, Path, PathSegment, PathArguments, ImplItem, LitStr};
+use syn::parse::{Parse, ParseStream, Result};
+use syn::token::{PathSep, Brace};
+use syn::punctuated::Punctuated;
+use quote::{quote, TokenStreamExt, ToTokens};
 
-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);
-    quote::quote! {
-        #attrs
+pub(crate) fn view_impl (meta: TokenStream, data: TokenStream) -> TokenStream {
+    let mut out = TokenStream2::new();
+    ViewDefinition {
+        meta: parse_macro_input!(meta as ViewMeta),
+        data: parse_macro_input!(data as ViewImpl),
+    }.to_tokens(&mut out);
+    out.into()
+}
+
+#[derive(Debug, Clone)]
+struct ViewDefinition {
+    meta: ViewMeta,
+    data: ViewImpl,
+}
+
+#[derive(Debug, Clone)]
+struct ViewMeta {
+    output: Ident,
+    //attrs:  Vec<Attribute>,
+}
+
+#[derive(Debug, Clone)]
+struct ViewImpl {
+    target: Ident,
+    items:  Vec<ViewItem>,
+    syms:   Vec<ViewSym>,
+}
+
+#[derive(Debug, Clone)]
+struct ViewItem {
+    item:   ImplItem,
+    expose: Option<Literal>,
+}
+
+#[derive(Debug, Clone)]
+struct ViewSym {
+    symbol: Literal,
+    name:   Ident,
+}
+
+impl Parse for ViewDefinition {
+    fn parse (input: ParseStream) -> Result<Self> {
+        Ok(Self {
+            meta: input.parse::<ViewMeta>()?,
+            data: input.parse::<ViewImpl>()?,
+        })
+    }
+}
+
+impl Parse for ViewMeta {
+    fn parse (input: ParseStream) -> Result<Self> {
+        Ok(Self {
+            output: input.parse::<Ident>()?,
+        })
+    }
+}
+
+impl Parse for ViewImpl {
+    fn parse (input: ParseStream) -> Result<Self> {
+        let _ = input.parse::<Token![impl]>()?;
+        let mut syms  = vec![];
+        Ok(Self {
+            target: input.parse::<Ident>()?,
+            items: {
+                let group;
+                let brace = braced!(group in input);
+                let mut items = vec![];
+                while !group.is_empty() {
+                    let item = group.parse::<ViewItem>()?;
+                    if let Some(expose) = &item.expose {
+                        if let ImplItem::Fn(ref item) = item.item {
+                            let symbol = expose.clone();
+                            let name   = item.sig.ident.clone();
+                            syms.push(ViewSym { symbol, name })
+                        } else {
+                            return Err(
+                                input.error("only fn items can be exposed to #[tengri::view]")
+                            )
+                        }
+                    }
+                    items.push(item);
+                }
+                items
+            },
+            syms,
+        })
+    }
+}
+
+
+impl Parse for ViewItem {
+    fn parse (input: ParseStream) -> Result<Self> {
+        let mut expose = None;
+        Ok(Self {
+            item: {
+                let mut item = input.parse::<ImplItem>()?;
+                if let ImplItem::Fn(ref mut item) = item {
+                    item.attrs = item.attrs.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::Literal(name)) = tokens.clone().into_iter().next()
+                        {
+                            expose = Some(name);
+                            return false
+                        }
+                        true
+                    }).map(|x|x.clone()).collect();
+                };
+                item
+            },
+            expose,
+        })
+    }
+}
+
+impl ToTokens for ViewSym {
+    fn to_tokens (&self, out: &mut TokenStream2) {
+        use Spacing::*;
+        out.append(Punct::new(':', Joint));
+        out.append(Punct::new(':', Alone));
+        out.append(Ident::new("tengri", Span::call_site()));
+        out.append(Punct::new(':', Joint));
+        out.append(Punct::new(':', Alone));
+        out.append(Ident::new("dsl", Span::call_site()));
+        out.append(Punct::new(':', Joint));
+        out.append(Punct::new(':', Alone));
+        out.append(Ident::new("Value", Span::call_site()));
+        out.append(Punct::new(':', Joint));
+        out.append(Punct::new(':', Alone));
+        out.append(Ident::new("Sym", Span::call_site()));
+        out.append(Group::new(Delimiter::Parenthesis, {
+            let mut out = TokenStream2::new();
+            out.append(self.symbol.clone());
+            out
+        }));
+        out.append(Punct::new('=', Joint));
+        out.append(Punct::new('>', Alone));
+        out.append(Ident::new("Some", Span::call_site()));
+        out.append(Group::new(Delimiter::Parenthesis, {
+            let mut out = TokenStream2::new();
+            out.append(Ident::new("self", Span::call_site()));
+            out.append(Punct::new('.', Alone));
+            out.append(self.name.clone());
+            out.append(Group::new(Delimiter::Parenthesis, TokenStream2::new()));
+            out.append(Punct::new('.', Alone));
+            out.append(Ident::new("boxed", Span::call_site()));
+            out.append(Group::new(Delimiter::Parenthesis, TokenStream2::new()));
+            out
+        }));
+        out.append(Punct::new(',', Alone));
+    }
+}
+
+impl ToTokens for ViewItem {
+    fn to_tokens (&self, out: &mut TokenStream2) {
+        self.item.to_tokens(out)
+    }
+}
+
+impl ToTokens for ViewDefinition {
+    fn to_tokens (&self, out: &mut TokenStream2) {
+        let Self {
+            meta: ViewMeta { output },
+            data: ViewImpl { target, syms, items },
+        } = self;
+        for token in quote! {
+            /// Augmented by [tengri_proc].
             impl #target {
-            #items
+                #(#items)*
             }
-        impl ::tengri::Content<#output> for #target {
+            /// Generated by [tengri_proc].
+            impl ::tengri::output::Content<#output> for #target {
                 fn content (&self) -> impl Render<#output> {
-                self.size.of(::tengri::View(self, #define))
+                    self.size.of(::tengri::output::View(self, self.config.view))
                 }
             }
-        impl<'a> ::tengri::ViewContext<'a, #output> for #target {
+            /// Generated by [tengri_proc].
+            impl<'a> ::tengri::output::ViewContext<'a, #output> for #target {
                 fn get_content_sym (&'a self, value: &Value<'a>) -> Option<RenderBox<'a, #output>> {
                     match value {
-                    #mapped
+                        #(#syms)*
                         _ => panic!("expected Sym(content), got: {value:?}")
                     }
-                //if let Value::Sym(s) = value {
-                    //match *s {
-                        //$($sym => Some($body.boxed()),)*
-                        //_ => None
-                    //}
-                //} else {
-                    //panic!("expected Sym(content), got: {value:?}")
-                //}
                 }
             }
-    }.into()
-}
-
-struct ViewMeta {
-    attrs:  &'static str,
-    output: &'static str,
-    define: &'static str,
-}
-
-impl syn::parse::Parse for ViewMeta {
-    fn parse (input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
-        Ok(Self {
-            attrs:  "",
-            output: "",
-            define: "",
-        })
+        } {
+            out.append(token)
+        }
     }
 }
 
-struct ViewItem {
-    items:  &'static str,
-    target: &'static str,
-    mapped: &'static str,
+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
 }
 
-impl syn::parse::Parse for ViewItem {
-    fn parse (input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
-        Ok(Self {
-            items:  "",
-            target: "",
-            mapped: "",
-        })
+impl std::cmp::PartialEq for ViewItem {
+    fn eq (&self, other: &Self) -> bool {
+        self.item == other.item && (format!("{:?}", self.expose) == format!("{:?}", other.expose))
     }
 }
 
-#[cfg(test)] #[test] fn test_view () {
-
-    let _: syn::ItemImpl = syn::parse_quote! {
-        #[tengri::view(Tui)]
-        impl SomeView {
-            #[tengri::view(":view")]
-            fn view (&self) -> impl Content<TuiOut> + use<'_> {
-                "view"
+impl std::cmp::PartialEq for ViewSym {
+    fn eq (&self, other: &Self) -> bool {
+        self.name == other.name && (format!("{}", self.symbol) == format!("{}", other.symbol))
     }
+}
+
+#[cfg(test)] use syn::{ItemImpl, parse_quote as pq};
+
+#[cfg(test)] #[test] fn test_view_meta () {
+    let x: ViewMeta   = pq! { SomeOutput };
+    let output: Ident = pq! { SomeOutput };
+    assert_eq!(x.output, output);
+}
+
+#[cfg(test)] #[test] fn test_view_impl () {
+    let x: ViewImpl = pq! {
+        impl Foo {
+            /// docstring1
+            #[tengri::view(":view1")] #[bar] fn a_view () {}
+
+            #[baz]
+            /// docstring2
+            #[baz] fn is_not_view () {}
         }
     };
-
+    let expected_target: Ident = pq! { Foo };
+    assert_eq!(x.target, expected_target);
+    assert_eq!(x.items.len(), 2);
+    assert_eq!(x.items[0].item, pq! {
+        /// docstring1
+        #[bar] fn a_view () {}
+    });
+    assert_eq!(x.items[1].item, pq! {
+        #[baz]
+        /// docstring2
+        #[baz] fn is_not_view () {}
+    });
+    assert_eq!(x.syms, vec![
+        ViewSym { symbol: pq! { ":view1" }, name: pq! { a_view }, },
+    ]);
+}
+
+#[cfg(test)] #[test] fn test_view_definition () {
+    // FIXME
+    //let parsed: ViewDefinition = pq! {
+        //#[tengri_proc::view(SomeOutput)]
+        //impl SomeView {
+            //#[tengri::view(":view-1")]
+            //fn view_1 (&self) -> impl Content<SomeOutput> + use<'_> {
+                //"view-1"
+            //}
+        //}
+    //};
+    //let written = quote! { #parsed };
+    //assert_eq!(format!("{written}"), format!("{}", quote! {
+        //impl SomeView {
+            //fn view_1 (&self) -> impl Content<SomeOutput> + use<'_> {
+                //"view-1"
+            //}
+        //}
+        ///// Generated by [tengri_proc].
+        //impl ::tengri::output::Content<SomeOutput> for SomeView {
+            //fn content (&self) -> impl Render<SomeOutput> {
+                //self.size.of(::tengri::output::View(self, self.config.view))
+            //}
+        //}
+        ///// Generated by [tengri_proc].
+        //impl<'a> ::tengri::dsl::ViewContext<'a, SomeOutput> for SomeView {
+            //fn get_content_sym (&'a self, value: &Value<'a>) -> Option<RenderBox<'a, SomeOutput>> {
+                //match value {
+                    //::tengri::dsl::Value::Sym(":view-1") => self.view_1().boxed(),
+                    //_ => panic!("expected Sym(content), got: {value:?}")
+                //}
+            //}
+        //}
+    //}));
 }