feat: one-to-many relation helper

Allow one to specify that a field of a model is a foreign key.
It will generate a bunch of helper methods to query related entities
from one entity.

lib/sqlxgentools_attrs/Cargo.toml

@@ -11,6 +11,8 @@ repository.workspace = true
 [dependencies]
 attribute-derive = "0.10.3"
 proc-macro2 = "1.0.92"
+quote = "1.0"
+syn = { version = "1.0" }
 
 [lib]
 proc-macro = true

lib/sqlxgentools_attrs/src/lib.rs

@@ -1,4 +1,6 @@
 use proc_macro::TokenStream;
+use quote::quote;
+use syn::{DeriveInput, Fields, parse_macro_input};
 
 #[proc_macro_attribute]
 pub fn sql_generator_model(_attr: TokenStream, item: TokenStream) -> TokenStream {
@@ -6,8 +8,34 @@ pub fn sql_generator_model(_attr: TokenStream, item: TokenStream) -> TokenStream
 }
 
 #[proc_macro_derive(SqlGeneratorDerive, attributes(sql_generator_field))]
-pub fn sql_generator_field(_item: TokenStream) -> TokenStream {
+pub fn derive_sql_generator_model(_input: TokenStream) -> TokenStream {
     TokenStream::new()
 }
 
+#[proc_macro_derive(SqlGeneratorModelWithId, attributes(sql_generator_field))]
+pub fn derive_sql_generator_model_with_id(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    let name = input.ident;
+
+    // Extract the fields of the struct
+    if let syn::Data::Struct(data) = input.data {
+        if let Fields::Named(fields) = data.fields {
+            for field in fields.named {
+                if field.ident.as_ref().map_or(false, |ident| ident == "id") {
+                    let expanded = quote! {
+                        impl DatabaseLine for #name {
+                            fn id(&self) -> String {
+                                self.id.clone()
+                            }
+                        }
+                    };
+                    return TokenStream::from(expanded);
+                }
+            }
+        }
+    }
+
+    // If `id` field is not found, return an error
+    panic!("Expected struct with a named field `id` of type String")
+}