[Database] Add 'creation_datetime' to User + some little things

backend/src/utils.rs

@@ -39,3 +39,44 @@ pub fn get_url_from_host(host: &str) -> String {
         host
     )
 }
+
+pub fn substitute(str: &str, pattern: &str, replacements: &[&str]) -> String {
+    let mut result = String::with_capacity(
+        (str.len() + replacements.iter().map(|s| s.len()).sum::<usize>())
+            .saturating_sub(pattern.len() * replacements.len()),
+    );
+
+    let mut i = 0;
+    for s in str.split(pattern) {
+        result.push_str(s);
+        if i < replacements.len() {
+            result.push_str(replacements[i]);
+        }
+        i += 1;
+    }
+
+    if i == 1 {
+        return str.to_string();
+    }
+
+    result
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_substitute() {
+        assert_eq!(substitute("", "", &[]), "");
+        assert_eq!(substitute("", "", &[""]), "");
+        assert_eq!(substitute("", "{}", &["a"]), "");
+        assert_eq!(substitute("a", "{}", &["b"]), "a");
+        assert_eq!(substitute("a{}", "{}", &["b"]), "ab");
+        assert_eq!(substitute("{}c", "{}", &["b"]), "bc");
+        assert_eq!(substitute("a{}c", "{}", &["b"]), "abc");
+        assert_eq!(substitute("{}b{}", "{}", &["a", "c"]), "abc");
+        assert_eq!(substitute("{}{}{}", "{}", &["a", "bc", "def"]), "abcdef");
+        assert_eq!(substitute("{}{}{}", "{}", &["a"]), "a");
+    }
+}