Simple die roller

1 files changed, 41 insertions, 0 deletions

diff --git a/src/dice.rs b/src/dice.rs
new file mode 100644
index 0000000..b238a0b
--- /dev/null
+++ b/src/dice.rs
@@ -0,0 +1,41 @@
+use rand::Rng;
+
+/// Roll a single die with the specified number of sides.
+pub fn roll_die(sides: u32) -> u32 {
+    let mut rng = rand::thread_rng();
+    rng.gen_range(1..=sides)
+}
+
+/// Parse and roll dice from a dice formula (e.g. "4d6+2" or "d12*3").
+// TODO: Have rolls return a RollResult or something.
+pub fn roll_formula(formula: &str) -> Option<u32> {
+    let delimiters = ['d', '+', '-', '*', '/']; // Only d implemented right now.
+    let parts: Vec<&str> = formula.split(|c| delimiters.contains(&c)).collect();
+
+    if parts.len() < 2 {
+        return None;
+    }
+
+    let num_dice = if parts[0].is_empty() {
+        1
+    } else {
+        match parts[0].parse::<u32>() {
+            Ok(num) => num,
+            Err(_) => return None,
+        }
+    };
+
+    let sides = match parts[1].parse::<u32>() {
+        Ok(num) => num,
+        Err(_) => return None,
+    };
+
+    let mut total = 0;
+
+    for _ in 0..num_dice {
+        let roll = roll_die(sides);
+        total += roll;
+    }
+
+    Some(total)
+}