From 1fc0371867b02127a5da63f01f03d264b382b552 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Mon, 25 Sep 2023 22:09:52 +0200
Subject: refactor: make camel cased text snake cased without regex

---
 macros/src/util/string.rs | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

(limited to 'macros/src/util')

diff --git a/macros/src/util/string.rs b/macros/src/util/string.rs
index a04a021..b29fe21 100644
--- a/macros/src/util/string.rs
+++ b/macros/src/util/string.rs
@@ -1,14 +1,28 @@
-use once_cell::sync::Lazy;
-use regex::Regex;
-
-static CAMELCASE_RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"([a-z])([A-Z])").unwrap());
-
 pub fn camelcase_to_snakecase(camelcased: &str) -> String
 {
-    CAMELCASE_RE
-        .replace(camelcased, "${1}_$2")
-        .to_string()
-        .to_lowercase()
+    let mut prev_char_was_lowercase = false;
+
+    camelcased
+        .chars()
+        .fold(String::new(), |mut acc, character| {
+            if character.is_lowercase() {
+                prev_char_was_lowercase = true;
+
+                acc.push(character);
+
+                return acc;
+            }
+
+            if character.is_uppercase() && prev_char_was_lowercase {
+                prev_char_was_lowercase = false;
+
+                acc.push('_');
+            }
+
+            acc.push(character.to_ascii_lowercase());
+
+            acc
+        })
 }
 
 #[cfg(test)]
@@ -21,6 +35,11 @@ mod tests
     {
         assert_eq!(camelcase_to_snakecase("LoginHandler"), "login_handler");
 
-        assert_eq!(camelcase_to_snakecase("Regex"), "regex");
+        assert_eq!(camelcase_to_snakecase("Transient"), "transient");
+
+        assert_eq!(
+            camelcase_to_snakecase("SystemInfoManager"),
+            "system_info_manager"
+        );
     }
 }
-- 
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