templating code

src/main.rs

@@ -37,6 +37,7 @@ mod key_value;
 use key_value::KeyValueStore as KV;
 mod config_spec;
 use config_spec::{CfgField, CfgGroup, CfgSpec};
+mod template;
 
 pub mod variables_and_settings;
 

src/template.rs

@@ -0,0 +1,20 @@
+use regex::{Captures, Regex};
+
+pub fn replace<F>( text: &str, replacer: F ) -> String where F: Fn(&Captures) -> String {
+    let regex = Regex::new( r"\{\{([\w_-]+)\}\}" ).unwrap();
+    regex.replace_all(text, replacer).into_owned()
+}
+
+pub fn config_replacer<'a>( config: &'a crate::KV, blacklist_substrings : &'a [&'a str] ) -> impl Fn(&Captures) -> String + 'a {
+    move |caps: &Captures| {
+        let key = &caps[1];
+        if blacklist_substrings.iter().any(|&substr| key.contains(substr)) {
+            caps[0].to_string()
+        } else {
+            match config.get(key).ok() {
+                Some(value) => value,
+                None => caps[0].to_string(),
+            }
+        }
+    }
+}