Optimized rule rewriting

I didn't have to do it in two `replace` calls

Now I have to check if the rule has a or several corresponding
categories in the initial and final regex, find whether they have the
same amount of elements, and if so create rules that allow elements from
each category to be mapped 1:1

src/settings/mod.rs

@@ -284,30 +284,36 @@ impl Settings {
         RULESET_CURRENT_VERSION.to_string()
     }
 
-    fn update_rules(&self) -> Vec<(Regex, String)> {
+    fn update_rules(&self) -> std::result::Result<Vec<(Regex, String)>, String> {
         let mut rules = self.rules.clone();
 
+        // TODO break categories in different rules
+        for (from, to) in rules.iter_mut() {
+            let re = Regex::new("%\\D");
+            let from_match = re.is_match(from.as_str());
+            let to_match = re.is_match(to);
+            if from_match || to_match {
                 for (category, content) in &self.categories {
-            let mut temp_rules: Vec<(Regex, String)> = Vec::new();
-            for (from, to) in &rules {
-                let from = Regex::new(
+                    if from_match {
+                        *from = Regex::new(
                             from.to_string()
                                 .replace(
-                            category.as_str(),
+                                    format!("%{}", category).as_str(),
                                     format!("[{}]", content).as_str(),
                                 )
-                        .replace("%", "")
-                        .as_str(),
+                                .as_str()
                         );
-                let to = to.to_string().replace(
-                    category,
-                    format!("[{}]", content).replace("%", "").as_str(),
+                    }
+                    if to_match {
+                        *to = to.to_string().replace(
+                            format!("%{}", category).as_str(),
+                            format!("[{}]", content).as_str()
                         );
-                temp_rules.push((from, to));
                     }
-            rules = temp_rules.clone();
                 }
-        rules
+            }
+        }
+        Ok(rules)
     }
 
     /// Apply list of rules to input
@@ -334,9 +340,9 @@ impl Settings {
     /// // set some input
     /// let _output = settings.apply(input);
     /// ```
-    pub fn apply(&self, s: String) -> String {
-        // Replace all `%C`s by their equivalent
-        let rules = self.update_rules();
+    pub fn apply(&self, s: String) -> std::result::Result<String, String> {
+        // TODO Add Error handling
+        let rules = self.update_rules().unwrap();
         let mut s = s.clone();
         debug!("===============================================");
         for (from, to) in rules {
@@ -345,7 +351,7 @@ impl Settings {
             s = from.replace_all(&s, to.as_str()).to_string();
             debug!("new: {}", s);
         }
-        s
+        Ok(s)
     }
 }