Major refactoring and cleanup

src/line_range.rs

@@ -0,0 +1,73 @@
+use errors::*;
+
+pub struct LineRange {
+    pub lower: usize,
+    pub upper: usize,
+}
+
+impl LineRange {
+    pub fn from(range_raw: &str) -> Result<LineRange> {
+        LineRange::parse_range(range_raw)
+    }
+
+    pub fn new() -> LineRange {
+        LineRange {
+            lower: usize::min_value(),
+            upper: usize::max_value(),
+        }
+    }
+
+    pub fn parse_range(range_raw: &str) -> Result<LineRange> {
+        let mut new_range = LineRange::new();
+
+        if range_raw.bytes().nth(0).ok_or("Empty line range")? == b':' {
+            new_range.upper = range_raw[1..].parse()?;
+            return Ok(new_range);
+        } else if range_raw.bytes().last().ok_or("Empty line range")? == b':' {
+            new_range.lower = range_raw[..range_raw.len() - 1].parse()?;
+            return Ok(new_range);
+        }
+
+        let line_numbers: Vec<&str> = range_raw.split(':').collect();
+        if line_numbers.len() == 2 {
+            new_range.lower = line_numbers[0].parse()?;
+            new_range.upper = line_numbers[1].parse()?;
+            return Ok(new_range);
+        }
+
+        Err("expected single ':' character".into())
+    }
+}
+
+#[test]
+fn test_parse_full() {
+    let range = LineRange::from("40:50").expect("Shouldn't fail on test!");
+    assert_eq!(40, range.lower);
+    assert_eq!(50, range.upper);
+}
+
+#[test]
+fn test_parse_partial_min() {
+    let range = LineRange::from(":50").expect("Shouldn't fail on test!");
+    assert_eq!(usize::min_value(), range.lower);
+    assert_eq!(50, range.upper);
+}
+
+#[test]
+fn test_parse_partial_max() {
+    let range = LineRange::from("40:").expect("Shouldn't fail on test!");
+    assert_eq!(40, range.lower);
+    assert_eq!(usize::max_value(), range.upper);
+}
+
+#[test]
+fn test_parse_fail() {
+    let range = LineRange::from("40:50:80");
+    assert!(range.is_err());
+    let range = LineRange::from("40::80");
+    assert!(range.is_err());
+    let range = LineRange::from(":40:");
+    assert!(range.is_err());
+    let range = LineRange::from("40");
+    assert!(range.is_err());
+}