refactor: share token count utilities

server/src/model/token_count.rs

@@ -0,0 +1,39 @@
+pub(crate) fn parse_token_count(value: &str) -> Option<u64> {
+    let value = value.trim().to_ascii_lowercase();
+    let (number, multiplier) = match value.chars().last()? {
+        'k' => (&value[..value.len() - 1], 1_000),
+        'm' => (&value[..value.len() - 1], 1_000_000),
+        _ => (value.as_str(), 1),
+    };
+    number.parse::<u64>().ok()?.checked_mul(multiplier)
+}
+
+pub(crate) fn format_token_count(tokens: u64) -> String {
+    if tokens >= 1_000_000 && tokens.is_multiple_of(1_000_000) {
+        format!("{}M", tokens / 1_000_000)
+    } else if tokens >= 1_000 && tokens.is_multiple_of(1_000) {
+        format!("{}K", tokens / 1_000)
+    } else {
+        tokens.to_string()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn token_counts_parse_plain_and_abbreviated_values() {
+        assert_eq!(parse_token_count("272000"), Some(272_000));
+        assert_eq!(parse_token_count("272K"), Some(272_000));
+        assert_eq!(parse_token_count("1m"), Some(1_000_000));
+        assert_eq!(parse_token_count("invalid"), None);
+    }
+
+    #[test]
+    fn token_counts_format_exact_thousands_and_millions() {
+        assert_eq!(format_token_count(272_000), "272K");
+        assert_eq!(format_token_count(1_000_000), "1M");
+        assert_eq!(format_token_count(272_001), "272001");
+    }
+}