Move Cafeteria code into new MultiInterval struct, add FromStr implementation for Interval

src/common/interval.rs

@@ -1,12 +1,21 @@
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone)]
+use std::collections::BTreeSet;
+use std::str::FromStr;
+
+#[derive(PartialEq, Eq, PartialOrd, Ord, Copy, Clone)]
 pub struct Interval {
     pub start: u64,
     pub end: u64,
 }
 
 impl Interval {
-    pub fn new(start: u64, end: u64) -> Interval {
-        Interval { start, end }
+    const INTERVAL_SPLIT_CHAR: char = '-';
+
+    pub fn new(start: u64, end: u64) -> Result<Interval, IntervalError> {
+        if start <= end {
+            Ok(Interval { start, end })
+        } else {
+            Err(IntervalError::InvalidBoundaries)
+        }
     }
 
     pub fn contains(&self, value: u64) -> bool {
@@ -17,3 +26,86 @@ impl Interval {
         self.end - self.start + 1
     }
 }
+
+impl FromStr for Interval {
+    type Err = IntervalError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let (x_str, y_str) = s
+            .split_once(Self::INTERVAL_SPLIT_CHAR)
+            .ok_or(IntervalError::ParseError)?;
+        let x = x_str
+            .parse::<u64>()
+            .map_err(|_| IntervalError::ParseError)?;
+        let y = y_str
+            .parse::<u64>()
+            .map_err(|_| IntervalError::ParseError)?;
+        Interval::new(x, y)
+    }
+}
+
+pub struct MultiInterval {
+    intervals: BTreeSet<Interval>,
+}
+
+impl MultiInterval {
+    pub fn new() -> MultiInterval {
+        MultiInterval {
+            intervals: BTreeSet::new(),
+        }
+    }
+
+    pub fn add(&mut self, mut interval: Interval) {
+        let mut to_delete = Vec::new();
+        for next in self.intervals.range(&interval..) {
+            if interval.contains(next.start) || interval.end + 1 == next.start {
+                // New interval overlaps with the "next" interval already in the collection.
+                if interval.end < next.end {
+                    interval.end = next.end;
+                }
+                to_delete.push(*next);
+            } else {
+                break;
+            }
+        }
+
+        let mut do_insert = true;
+        if let Some(prev) = self.intervals.range(..=&interval).next_back() {
+            if interval.contains(prev.end) || prev.end + 1 == interval.start {
+                // Enlarges new interval to replace the "previous" interval already in the collection.
+                interval.start = prev.start;
+                to_delete.push(*prev);
+            } else if interval.end <= prev.end {
+                do_insert = false;
+            }
+        }
+
+        for del in to_delete {
+            self.intervals.remove(&del);
+        }
+
+        if do_insert {
+            self.intervals.insert(interval);
+        }
+    }
+
+    pub fn contains(&self, value: u64) -> bool {
+        let interval = Interval::new(value, value).unwrap();
+
+        if let Some(prev) = self.intervals.range(..=&interval).next_back() {
+            prev.contains(value)
+        } else {
+            false
+        }
+    }
+
+    pub fn len(&self) -> u64 {
+        self.intervals.iter().map(|x| x.len()).sum()
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum IntervalError {
+    ParseError,
+    InvalidBoundaries,
+}