refactor Assignments::next

day04/common.rs

@@ -31,21 +31,7 @@ impl Iterator for Assignments {
         if let Some(line) = io::stdin().lines().next() {
             let line = line.unwrap();
             if line.len() > 0 {
-                if let Some((left, right)) = line.split_once(',') {
+                return Some(Assignment::from_str(&line));
-                    if let (Some((s1, e1)), Some((s2, e2))) =
-                        (left.split_once('-'), right.split_once('-'))
-                    {
-                        if let (Ok(s1), Ok(e1), Ok(s2), Ok(e2)) = (
-                            s1.parse::<u8>(),
-                            e1.parse::<u8>(),
-                            s2.parse::<u8>(),
-                            e2.parse::<u8>(),
-                        ) {
-                            return Some(Ok(Assignment::new(s1..=e1, s2..=e2)));
-                        }
-                    }
-                }
-                return Some(Err("input file contains invalid line"));
             }
         }
         None
@@ -60,6 +46,25 @@ impl Assignment {
         }
     }
 
+    fn parse_range(input: &str) -> Result<RangeInclusive<u8>, &'static str> {
+        if let Some((start, end)) = input.split_once('-') {
+            if let (Ok(start), Ok(end)) = (start.parse::<u8>(), end.parse::<u8>()) {
+                return Ok(start..=end);
+            }
+        }
+        Err("invalid range string")
+    }
+
+    pub fn from_str(input: &str) -> Result<Self, &'static str> {
+        if let Some((left, right)) = input.split_once(',') {
+            return Ok(Assignment::new(
+                Self::parse_range(left)?,
+                Self::parse_range(right)?,
+            ));
+        }
+        Err("invalid assignment string")
+    }
+
     pub fn has_obsolete_range(&self) -> bool {
         self.range1.contains(self.range2.start()) && self.range1.contains(self.range2.end())
             || self.range2.contains(self.range1.start()) && self.range2.contains(self.range1.end())