postgress

imphnen-macros/src/lib.rs

@@ -0,0 +1,96 @@
+use proc_macro::TokenStream;
+use quote::{quote, format_ident};
+use syn::{parse_macro_input, Data, DeriveInput, Fields, Type, PathArguments, GenericArgument};
+
+#[proc_macro_derive(Builder)]
+pub fn derive_builder(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    let name = &input.ident;
+    let builder_name = format_ident!("{}Builder", name);
+
+    let fields = match &input.data {
+        Data::Struct(data) => match &data.fields {
+            Fields::Named(fields) => &fields.named,
+            _ => panic!("Builder derive only supports structs with named fields"),
+        },
+        _ => panic!("Builder derive only supports structs"),
+    };
+
+    let builder_fields = fields.iter().map(|f| {
+        let name = &f.ident;
+        let ty = &f.ty;
+        if is_option(ty) {
+            let inner_ty = extract_option_inner(ty);
+            quote! {
+                #name: Option<#inner_ty>
+            }
+        } else {
+            quote! {
+                #name: Option<#ty>
+            }
+        }
+    });
+
+    let builder_methods = fields.iter().map(|f| {
+        let name = &f.ident;
+        let ty = &f.ty;
+        if is_option(ty) {
+            let inner_ty = extract_option_inner(ty);
+            quote! {
+                #[must_use]
+                pub fn #name(mut self, #name: #inner_ty) -> Self {
+                    self.#name = Some(#name);
+                    self
+                }
+            }
+        } else {
+            quote! {
+                #[must_use]
+                pub fn #name(mut self, #name: #ty) -> Self {
+                    self.#name = Some(#name);
+                    self
+                }
+            }
+        }
+    });
+
+    let expanded = quote! {
+        #[derive(Default, serde::Serialize, serde::Deserialize)]
+        pub struct #builder_name {
+            #(#builder_fields,)*
+        }
+
+        impl #builder_name {
+            #[must_use]
+            pub fn new() -> Self {
+                Self::default()
+            }
+
+            #(#builder_methods)*
+        }
+    };
+
+    TokenStream::from(expanded)
+}
+
+fn is_option(ty: &Type) -> bool {
+    if let Type::Path(type_path) = ty {
+        if let Some(segment) = type_path.path.segments.last() {
+            return segment.ident == "Option";
+        }
+    }
+    false
+}
+
+fn extract_option_inner(ty: &Type) -> &Type {
+    if let Type::Path(type_path) = ty {
+        if let Some(segment) = type_path.path.segments.last() {
+            if let PathArguments::AngleBracketed(args) = &segment.arguments {
+                if let Some(GenericArgument::Type(inner_ty)) = args.args.first() {
+                    return inner_ty;
+                }
+            }
+        }
+    }
+    panic!("Expected Option<T>");
+}