replaced split_line with a multibyte aware version

src/generator/ical.rs

@@ -19,13 +19,14 @@ fn get_value(value: &Option<String>) -> String {
 }
 
 pub(crate) fn split_line<T: Into<String>>(str: T) -> String {
-    let mut str = str.into();
-    let mut x = 75;
-    while x < str.len() {
-        str.insert_str(x, "\r\n ");
-        x += 77;
-    }
-    str
+    let str = str.into();
+    let mut chars = str.chars();
+    let mut first = true;
+    let sub_string = (0..)
+        .map(|_| chars.by_ref().take(if first { first = false; 75 } else { 74 }).collect::<String>())
+        .take_while(|s| !s.is_empty())
+        .collect::<Vec<_>>();
+    sub_string.join("\r\n ")
 }
 
 //
@@ -85,6 +86,17 @@ mod should {
         assert_eq!(text, split_line(text.replace("\r\n ", "")));
     }
 
+    #[test]
+    fn split_long_line_multibyte() {
+        // the following text includes multibyte characters (UTF-8) at strategic places to ensure
+        // split_line would panic if not multibyte aware
+        let text = "DESCRIPTION:ABCDEFGHIJ\\n\\nKLMNOPQRSTUVWXYZ123456789üABCDEFGHIJKLMNOPQRS\\n\\n\r\n \
+                     TUVWXYZ123456ä7890ABCDEFGHIJKLM\\n\\nNOPQRSTUVWXYZ1234567890ABCDEFGHIJKLMNOP\r\n \
+                     QRSTUVWXöYZ1234567890ABCDEFGHIJKLMNOPQRSTUVWX\\n\\nYZ1234567890abcdefghiÜjkl\r\n \
+                     m\\nnopqrstuvwx";
+        assert_eq!(text, split_line(text.replace("\r\n ", "")));
+    }
+
     #[test]
     fn protect_chars_in_params() {
         assert_eq!(