feat: add method max to Outcome

01.workspace/oxidice_lib/src/imp/mod.rs

@@ -2,4 +2,5 @@ pub mod die_new;
 pub mod die_roll;
 pub mod handful_grab;
 pub mod handful_roll;
+pub mod outcome_max;
 pub mod outcome_sum;

01.workspace/oxidice_lib/src/imp/outcome_max.rs

@@ -0,0 +1,41 @@
+use crate::*;
+
+fn max_of(values: Vec<u16>) -> Result<Outcome, FailedTo> {
+    if values.is_empty() {
+        return Err(FailedTo::ProcessInput);
+    }
+    let ret = Ok(Outcome::Scalar(u16::MAX));
+    ret.and_then(|_| {
+        values
+            .iter()
+            .max()
+            .ok_or(FailedTo::FindMin)
+            .map(|min| Outcome::Scalar(*min))
+    })
+}
+
+impl Outcome {
+    pub fn max(self) -> Result<Outcome, FailedTo> {
+        match self {
+            Outcome::Scalar(value) => Ok(Outcome::Scalar(value)),
+            Outcome::List(values) => max_of(values),
+        }
+    }
+}
+
+#[cfg(test)]
+mod unit_tests {
+    use super::*;
+    #[test]
+    fn check_max() {
+        let outcome = Handful::grab(2, 20).roll();
+        let max = outcome.clone().max().unwrap();
+        match outcome {
+            Outcome::List(values) => {
+                let expected_max = values.iter().max().unwrap();
+                assert_eq!(max, Outcome::Scalar(*expected_max));
+            }
+            _ => panic!("outcome is not a list"),
+        }
+    }
+}