From 646145dd10b3a9549f82b237ee46726d728d3631 Mon Sep 17 00:00:00 2001
From: Josh Kingsley <josh@joshkingsley.me>
Date: Mon, 1 Dec 2025 14:57:26 +0200
Subject: Add day1 with Rotation struct and tests

---
 day1/src/main.rs | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 day1/src/main.rs

(limited to 'day1/src')

diff --git a/day1/src/main.rs b/day1/src/main.rs
new file mode 100644
index 0000000..778fc6d
--- /dev/null
+++ b/day1/src/main.rs
@@ -0,0 +1,52 @@
+use std::str::FromStr;
+
+#[derive(Debug, PartialEq, Eq)]
+enum Rotation {
+    Left(u16),
+    Right(u16),
+}
+
+struct ParseRotationError(String);
+
+impl FromStr for Rotation {
+    type Err = ParseRotationError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut chars = s.chars();
+        let lr = chars.next().ok_or_else(|| ParseRotationError(s.into()))?;
+        let n: u16 = chars
+            .collect::<String>()
+            .parse()
+            .map_err(|_| ParseRotationError(s.into()))?;
+
+        match lr {
+            'L' => Ok(Self::Left(n)),
+            'R' => Ok(Self::Right(n)),
+            _ => Err(ParseRotationError(s.into())),
+        }
+    }
+}
+
+fn main() {
+    println!("Hello, world!");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_rotation() {
+        assert!("L2"
+            .parse::<Rotation>()
+            .is_ok_and(|rot| rot == Rotation::Left(2)));
+
+        assert!("R929"
+            .parse::<Rotation>()
+            .is_ok_and(|rot| rot == Rotation::Right(929)));
+
+        assert!("M1".parse::<Rotation>().is_err());
+        assert!("L".parse::<Rotation>().is_err());
+        assert!("2".parse::<Rotation>().is_err());
+    }
+}
-- 
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