From ff8c1df71db70a3d4ed8c3bb14b164671e944bab Mon Sep 17 00:00:00 2001
From: Nikita Revenco <154856872+NikitaRevenco@users.noreply.github.com>
Date: Fri, 20 Dec 2024 09:00:56 +0000
Subject: [PATCH] feat: correct implementations for kebab, snake and title case

---
 helix-core/src/case_conversion.rs | 96 ++++++++++++++++---------------
 1 file changed, 51 insertions(+), 45 deletions(-)

diff --git a/helix-core/src/case_conversion.rs b/helix-core/src/case_conversion.rs
index 67bf17180..35287d5be 100644
--- a/helix-core/src/case_conversion.rs
+++ b/helix-core/src/case_conversion.rs
@@ -88,60 +88,66 @@ pub fn to_pascal_case_with(text: impl Iterator<Item = char>, buf: &mut Tendril)
     }
 }
 
-pub fn to_snake_case_with(text: impl Iterator<Item = char>, buf: &mut Tendril) {
-    let mut at_word_start = true;
+pub fn to_title_case_with(text: impl Iterator<Item = char>, buf: &mut Tendril) {
+    let mut capitalize_next = true;
+    let mut prev_is_lowercase = false;
+
     for c in text {
-        // we don't count _ as a word char here so case conversions work well
-        if !c.is_alphanumeric() {
-            at_word_start = true;
-            continue;
-        }
-        if at_word_start {
-            at_word_start = false;
-            buf.push('_');
-            buf.push(c);
+        if c.is_alphanumeric() {
+            if capitalize_next || (prev_is_lowercase && c.is_uppercase()) {
+                buf.extend(c.to_uppercase());
+                capitalize_next = false;
+            } else {
+                buf.extend(c.to_lowercase());
+            }
+            prev_is_lowercase = c.is_lowercase();
         } else {
-            buf.push(c)
+            capitalize_next = true;
+            prev_is_lowercase = false;
+            buf.push(' ');
         }
     }
+
+    *buf = buf.trim().into();
+}
+
+pub fn to_case_with_separator(
+    text: impl Iterator<Item = char>,
+    buf: &mut Tendril,
+    separator: char,
+) {
+    let mut prev_is_lowercase = false; // Tracks if the previous character was lowercase
+    let mut prev_is_alphanumeric = false; // Tracks if the previous character was alphanumeric
+
+    for c in text {
+        if c.is_alphanumeric() {
+            if prev_is_lowercase && c.is_uppercase() {
+                buf.push(separator);
+            }
+            if !prev_is_alphanumeric && !buf.is_empty() {
+                buf.push(separator);
+            }
+
+            buf.push(c.to_ascii_lowercase());
+            prev_is_lowercase = c.is_lowercase();
+            prev_is_alphanumeric = true;
+        } else {
+            prev_is_lowercase = false;
+            prev_is_alphanumeric = false;
+        }
+    }
+
+    if buf.ends_with(separator) {
+        buf.pop();
+    }
 }
 
 pub fn to_kebab_case_with(text: impl Iterator<Item = char>, buf: &mut Tendril) {
-    let mut at_word_start = false;
-    for c in text {
-        // we don't count _ as a word char here so case conversions work well
-        if !c.is_alphanumeric() {
-            at_word_start = true;
-            continue;
-        }
-        if at_word_start {
-            at_word_start = false;
-            buf.push('-');
-            buf.push(c);
-        } else {
-            buf.push(c)
-        }
-    }
+    to_case_with_separator(text, buf, '-');
 }
 
-pub fn to_title_case_with(text: impl Iterator<Item = char>, buf: &mut Tendril) {
-    let mut at_word_start = true;
-    for (i, c) in text.enumerate() {
-        // we don't count _ as a word char here so case conversions work well
-        if !c.is_alphanumeric() {
-            at_word_start = true;
-            continue;
-        }
-        if at_word_start {
-            at_word_start = false;
-            if i != 0 {
-                buf.push(' ');
-            }
-            buf.extend(c.to_uppercase());
-        } else {
-            buf.push(c)
-        }
-    }
+pub fn to_snake_case_with(text: impl Iterator<Item = char>, buf: &mut Tendril) {
+    to_case_with_separator(text, buf, '_');
 }
 
 pub fn to_camel_case_with(mut text: impl Iterator<Item = char>, buf: &mut Tendril) {