closure like syntax v1

macros/src/lib.rs

@@ -1,57 +1,167 @@
-// macros/src/lib.rs
 use proc_macro::TokenStream;
-use quote::quote;
-use syn::{parse_macro_input, ItemFn, FnArg, Pat, Type, Ident, Attribute};
-
-/// Simple argument representation
-struct Arg {
-    attrs: Vec<Attribute>,
-    ident: Ident,
-    ty: Type,
-}
+use quote::{quote, ToTokens};
+use syn::{
+    parse_macro_input, AttributeArgs, FnArg, Ident, ItemFn, Pat, PatIdent, PatType, ReturnType,
+    Type, Expr, ExprClosure, token::Comma, spanned::Spanned,
+};
 
+/// The procedural macro
 #[proc_macro_attribute]
-pub fn builder(_attr: TokenStream, item: TokenStream) -> TokenStream {
+pub fn endpoint(attr: TokenStream, item: TokenStream) -> TokenStream {
     // Parse the input function
-    let input = parse_macro_input!(item as ItemFn);
+    let input_fn = parse_macro_input!(item as ItemFn);
 
-    let vis = &input.vis;
-    let name = &input.sig.ident;
-    let generics = &input.sig.generics;
+    // Parse the closure-like attribute: |x: u128, y: String| POST "/some/{x}/{y}"
+    let closure_expr: ExprClosure = match syn::parse(attr.clone()) {
+        Ok(c) => c,
+        Err(e) => return e.to_compile_error().into(),
+    };
 
-    // Collect arguments
-    let mut body_args: Vec<Arg> = Vec::new();
+    // Extract path parameters
+    let mut path_idents = Vec::new();
+    let mut path_types = Vec::new();
 
-    for arg in &input.sig.inputs {
-        if let FnArg::Typed(pat_type) = arg {
-            if let Pat::Ident(pat_ident) = &*pat_type.pat {
-                body_args.push(Arg {
-                    attrs: pat_type.attrs.clone(),
-                    ident: pat_ident.ident.clone(),
-                    ty: (*pat_type.ty).clone(),
-                });
+    for fnarg in closure_expr.inputs.iter() {
+        match fnarg {
+            FnArg::Typed(PatType { pat, ty, .. }) => {
+                if let Pat::Ident(PatIdent { ident, .. }) = **pat {
+                    path_idents.push(ident.clone());
+                    path_types.push(*ty.clone());
                 } else {
-                panic!("Only simple identifier patterns are supported");
+                    return syn::Error::new(pat.span(), "Unsupported pattern in path parameters")
+                        .to_compile_error()
+                        .into();
                 }
+            }
+            _ => {
+                return syn::Error::new(fnarg.span(), "Expected typed parameter")
+                    .to_compile_error()
+                    .into();
+            }
+        }
+    }
+
+    // Extract method and path literal from closure body
+    let (method, path_lit) = match *closure_expr.body {
+        Expr::Assign(ref assign) => {
+            return syn::Error::new(assign.span(), "Unexpected assignment in endpoint")
+                .to_compile_error()
+                .into();
+        }
+        Expr::Path(_) | Expr::Call(_) | Expr::Lit(_) => {
+            return syn::Error::new(closure_expr.body.span(), "Expected method + path string")
+                .to_compile_error()
+                .into();
+        }
+        Expr::Tuple(ref tup) => {
+            return syn::Error::new(closure_expr.body.span(), "Unexpected tuple in endpoint")
+                .to_compile_error()
+                .into();
+        }
+        Expr::Binary(ref _bin) => {
+            return syn::Error::new(closure_expr.body.span(), "Unexpected binary in endpoint")
+                .to_compile_error()
+                .into();
+        }
+        _ => {
+            // We will parse method & path using a simple hack: the closure body is `POST "/some/{x}"` etc
+            let ts = closure_expr.body.to_token_stream().to_string();
+            let ts = ts.trim();
+            let parts: Vec<&str> = ts.splitn(2, ' ').collect();
+            if parts.len() != 2 {
+                return syn::Error::new(closure_expr.body.span(), "Expected `METHOD \"/path\"`")
+                    .to_compile_error()
+                    .into();
+            }
+            let method = parts[0].trim().to_uppercase();
+            let path_lit = syn::LitStr::new(parts[1].trim_matches('"'), closure_expr.body.span());
+            (method, path_lit)
+        }
+    };
+
+    // Extract original function signature details
+    let vis = &input_fn.vis;
+    let orig_name = &input_fn.sig.ident;
+    let orig_generics = &input_fn.sig.generics;
+    let orig_inputs = &input_fn.sig.inputs;
+    let output = match &input_fn.sig.output {
+        ReturnType::Type(_, ty) => ty,
+        ReturnType::Default => {
+            return syn::Error::new(input_fn.sig.output.span(), "Function must have a return type")
+                .to_compile_error()
+                .into();
+        }
+    };
+
+    // Split query vs body params
+    let mut query_idents = Vec::new();
+    let mut query_types = Vec::new();
+    let mut body_idents = Vec::new();
+    let mut body_types = Vec::new();
+
+    for arg in orig_inputs.iter() {
+        match arg {
+            FnArg::Typed(PatType { pat, ty, attrs, .. }) => {
+                let is_query = attrs.iter().any(|a| a.path().is_ident("query"));
+                if let Pat::Ident(PatIdent { ident, .. }) = &**pat {
+                    if is_query {
+                        query_idents.push(ident.clone());
+                        query_types.push(*ty.clone());
                     } else {
-            panic!("&self / &mut self not supported");
+                        body_idents.push(ident.clone());
+                        body_types.push(*ty.clone());
+                    }
+                }
+            }
+            _ => {}
         }
     }
 
-    // Destructure the arguments for quote repetitions
-    let arg_idents: Vec<_> = body_args.iter().map(|a| &a.ident).collect();
-    let arg_tys: Vec<_> = body_args.iter().map(|a| &a.ty).collect();
-    let arg_attrs: Vec<_> = body_args.iter().map(|a| &a.attrs).collect();
-
-    // Generate the builder function
+    // Build the transformed function
     let expanded = quote! {
         #[bon::builder]
-        #vis fn #name #generics (
-            #(
-                #( #arg_attrs )* #arg_idents : #arg_tys
-            ),*
-        ) -> impl std::future::Future<Output = Result<(), restson::Error>> {
-            todo!()
+        #vis async fn #orig_name #orig_generics (
+            #( #[builder(finish_fn)] #path_idents: #path_types, )*
+            client: restson::RestClient,
+            #( #body_idents: #body_types ),*
+        ) -> Result<#output, restson::Error> {
+            // Query struct
+            #[derive(serde::Serialize)]
+            struct Query {
+                #( #query_idents: #query_types, )*
+            }
+            let query = Query { #( #query_idents ),* };
+            let query = query.to_vec::<(&str, &str)>();
+
+            // Body struct
+            #[derive(serde::Serialize)]
+            struct Body {
+                #( #body_idents: #body_types, )*
+            }
+            let body = Body { #( #body_idents ),* };
+
+            // RestPath impl for path parameters
+            impl restson::RestPath<( #( #path_types ),* )> for Body {
+                fn get_url(&self, #( #path_idents: #path_types ),* ) -> Result<String, restson::Error> {
+                    Ok(format!(#path_lit #(, #path_idents )* ))
+                }
+            }
+
+            // Response placeholder
+            #[derive(serde::de::DeserializeOwned)]
+            struct Response(Vec<serde_json::Value>);
+
+            // Make the REST call
+            let response: restson::Response<Response> = match #method {
+                ref m if m == "GET" => client.get_with(body, query).await?,
+                ref m if m == "POST" => client.post_capture_with(body, query).await?,
+                _ => panic!("Unsupported method"),
+            };
+
+            // Wrap the original todo!(response -> OutputType)
+            | #( #path_idents ),* | {
+                todo!(response -> #output)
+            } ( #( #path_idents ),* )
         }
     };