Write score calculation code

cli/src/datasets.rs

@@ -24,3 +24,32 @@ pub fn new_dataset(dataset: &Path) -> sqlite::Result<Connection> {
     connection.execute(query)?;
     Ok(connection)
 }
+
+// Score calculation
+
+/// Calculate the collective expected score for each team.
+fn expected_scores(ratings: &Teams<&mut f64>) -> Vec<f64> {
+    let qs: Vec<f64> = ratings
+        .into_iter()
+        .map(|es| 10_f64.powf(es.iter().map(|x| **x).sum::<f64>() / es.len() as f64 / 400.0))
+        .collect();
+    let sumq: f64 = qs.iter().sum();
+    qs.into_iter().map(|q| q / sumq).collect()
+}
+
+/// Adjust the ratings of each player based on who won.
+fn adjust_ratings(ratings: Teams<&mut f64>, winner: usize) {
+    let exp_scores = expected_scores(&ratings);
+
+    ratings
+        .into_iter()
+        .zip(exp_scores.into_iter())
+        .enumerate()
+        .for_each(|(i, (es, exp_sc))| {
+            let len = es.len() as f64;
+            let score = f64::from(winner == i);
+            es.into_iter()
+                .for_each(|e| *e += 40.0 * (score - exp_sc) / len);
+        })
+}
+