fix: utf8 replacements (#26)

* fix: utf8 replacements

* fix

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "zeditor"
-version = "0.1.0-very-well-done"
+version = "0.1.0-walemoji"
 edition = "2021"
 
 [dependencies]

src/replace.rs

@@ -123,14 +123,19 @@ fn replace_text(text: &str, replacements: &[Replacement]) -> String {
 
     let mut out = String::new();
     let mut last: usize = 0;
+
+    // we need to take care not to split unicode characters in the
+    // middle of their sequences
+    // see https://stackoverflow.com/a/51983601/9935916
+    let utf8 = text.chars().collect::<Vec<_>>();
     for r in rs {
-        out.push_str(&text[last..r.start]);
+        out.push_str(&utf8[last..r.start].iter().cloned().collect::<String>());
         out.push_str(&r.term);
 
         last = r.end;
     }
 
-    out.push_str(&text[last..]);
+    out.push_str(&utf8[last..].iter().cloned().collect::<String>());
 
     out
 }
@@ -163,4 +168,17 @@ mod tests {
         let expected = "a quick brown dog jumped over a tiny turtle";
         assert_eq!(replace_text(input, &replacements), expected.to_string());
     }
+
+    #[test]
+    fn utf8_test() {
+        let input = "🌎🍌🐶🐮💘";
+        let replacements = vec![Replacement {
+            term: "foo".to_string(),
+            start: 1,
+            end: 2,
+        }];
+
+        let expected = "🌎foo🐶🐮💘";
+        assert_eq!(replace_text(input, &replacements), expected.to_string());
+    }
 }