Split `Rule::update` in several functions

Also optimization with a static Regex

Cargo.toml

@@ -15,4 +15,5 @@ serde = {version = "1.0", features = ["derive"]}
 serde_yaml = "0.7"
 serde_json = "1.0"
 # Regex support
-regex = "1.3"
+regex = "1.3"
+lazy_static = "1.4.0"

src/lib.rs

@@ -12,6 +12,9 @@
 //! [original software](https://github.com/ceronyon/LangEvolve) which applies
 //! user-defined sound changes to words and texts based on regex expressions.
 
+#[macro_use]
+extern crate lazy_static;
+
 use std::fs::File;
 extern crate log;
 extern crate simplelog;

src/settings/rule/mod.rs

@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+
 extern crate serde;
 extern crate serde_json;
 extern crate serde_yaml;
@@ -31,28 +33,54 @@ impl Rule {
         }
     }
 
+    fn detect_categories(&self) -> (u8, u8) {
+        lazy_static! {
+            static ref RE : Regex = Regex::new("%([A-Z])");
+        }
+        let captures_from = match RE.captures(self.from.as_str()) {
+            None => 0 as u8,
+            Some(c) => c.len() as u8,
+        };
+        let captures_to = match RE.captures(&self.to) {
+            None => 0 as u8,
+            Some(c) => c.len() as u8,
+        };
+        (captures_from, captures_to)
+    }
+
+    fn simple_rewrite(&self, categories: &HashMap<String, String>) -> Self {
+        let mut rule = self.clone();
+        for (category, content) in categories {
+            rule.from = Regex::new(
+                rule.from
+                    .to_string()
+                    .replace(
+                        format!("%{}", category).as_str(),
+                        format!("[{}]", content).as_str(),
+                    )
+                    .as_str()
+            );
+        }
+        rule
+    }
+
     // TODO break categories in different rules
     pub fn update(
         &self,
-        categories: &std::collections::HashMap<String, String>,
+        categories: &HashMap<String, String>,
     ) -> std::result::Result<Rule, String> {
         let mut rule = self.clone();
-        let re = Regex::new("%\\D");
-        let from_match = re.is_match(&self.from.as_str());
-        let to_match = re.is_match(&self.to.as_str());
-        if from_match && !to_match {
-            for (category, content) in categories {
-                rule.from = Regex::new(
-                    rule.from
-                        .to_string()
-                        .replace(
-                            format!("%{}", category).as_str(),
-                            format!("[{}]", content).as_str(),
-                        )
-                        .as_str(),
-                );
-            }
+        let (from_match, to_match) = self.detect_categories();
+        // If there are only simple rewrites to make in the from String
+        if from_match > 0 && to_match == 0 {
+            rule = self.simple_rewrite(&categories);
         }
+
+        // If there are equivalences between from and to
+        if from_match > 0 && to_match <= from_match && to_match > 0 {
+
+        }
+
         Ok(rule)
     }