started derive macro to parse configuration

derive_config_parser/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "derive_config_parser"
+version = "0.1.0"
+autotests = false
+edition = "2021"
+publish = false
+
+[lib]
+proc-macro = true
+
+[dependencies]
+quote = "1.0.38"
+syn = { version = "2.0.92", features = ["extra-traits"] }
+

derive_config_parser/src/lib.rs

@@ -0,0 +1,45 @@
+
+use core::panic;
+use proc_macro::TokenStream;
+
+/// **for structs only**
+/// - implements `parse_config(&mut self, input: &String) -> Result<()>`
+/// which parses a string and fills the fills recognised values into the struct
+/// - implements `write_default_config() -> Result<String>`
+/// which write a default configuration, in case the documentation is lacking
+#[proc_macro_derive(ConfigParser)]
+pub fn derive(input: TokenStream) -> TokenStream {
+    let ast = syn::parse_macro_input!(input as syn::DeriveInput);
+    let name = &ast.ident;
+    let fields = if let syn::Data::Struct(syn::DataStruct{ fields: syn::Fields::Named(syn::FieldsNamed{ ref named, .. }), .. }) = ast.data {
+        named
+    } else {
+        panic!("failed to parse struct fields");
+    };
+
+    println!("{:#?}", ast);
+//    let string = format!("{:#?}", ast);
+//    _ = std::fs::write("test.txt", string);
+
+    let expanded_stream: TokenStream = quote::quote! {
+        impl #name {
+            pub fn parse_config(&mut self, input: &String) -> std::io::Result<()> {
+                let mut setting_names = std::collections::HashMap::new();
+                let lines = input.lines();
+                for line in lines {
+                    let mut tokens: Vec<&str> = line.split('=').map(|entry| entry.trim()).collect();
+                    tokens.retain(|entry| !entry.is_empty());
+                    if tokens.len() != 2 {
+                        // println!("error in line'", line);
+                        continue;
+                    }
+                    setting_names.insert(tokens[0], tokens[1]);
+                }
+                //println!("{:#?}", setting_names);
+                Ok(())
+            }
+        }
+    }.into();
+    expanded_stream
+//    TokenStream::new()
+}