#![allow(unused)]

use std::fmt;

macro_rules! add_rust_log{
    (struct $struct_name:ident { $custom_field_name:ident: &'static str, $($field_name:ident: $field_type:ty),* }) => {
        struct $struct_name{
            $custom_field_name: &'static str,
            $($field_name: $field_type),*
        }

        impl $struct_name{
            fn set_rust_log(&self){
                let fields : String = [$(format!("{}={},", stringify!($field_name), self.$field_name)),*]
                    .iter()
                    .fold("".to_string(), |accumulator, current_field| format!("{}{}", accumulator, current_field));
                std::env::set_var("RUST_LOG", format!("{},{}", self.$custom_field_name, &fields[0 .. fields.len() - 1]));
            }
        }
    }
}

add_rust_log!{
    struct Coordinates{
        default_entry: &'static str,
        x: i32,
        y: i32
    }
}

#[test]
fn when_parsing_coordinates_then_rust_log_should_be_populated_correctly(){
    let a = Coordinates{ default_entry: "error", x: 2, y: 4 };
    a.set_rust_log();
    match std::env::var("RUST_LOG"){
        Ok(rust_log) => assert_eq!(rust_log, "error,x=2,y=4"),
        Err(_) => panic!("Something bad happened")
    }
}