Merge pull request #44 from moia-oss/tw_shrink

src/lib.rs

@@ -548,6 +548,75 @@ impl TimeWindow {
         }
     }
 
+    /// Postpones the time window start so that the new duration matches the
+    /// given value. Is a No-Op if the new duration is smaller than the
+    /// current one. Negative durations set the result time window size to
+    /// zero.
+    ///
+    /// # Examples
+    /// ```
+    /// # use tinytime::Duration;
+    /// # use tinytime::TimeWindow;
+    /// let x = TimeWindow::from_seconds(1, 3);
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(3, 3),
+    ///     x.shrink_towards_end_to(Duration::seconds(-1))
+    /// );
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(3, 3),
+    ///     x.shrink_towards_end_to(Duration::seconds(0))
+    /// );
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(2, 3),
+    ///     x.shrink_towards_end_to(Duration::seconds(1))
+    /// );
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(1, 3),
+    ///     x.shrink_towards_end_to(Duration::seconds(5))
+    /// );
+    /// ```
+    pub fn shrink_towards_end_to(self, new_duration: Duration) -> TimeWindow {
+        let duration = new_duration
+            .min(self.duration()) // Resize only if new duration is smaller than the current one
+            .max(Duration::ZERO); // Make sure the new duration is non-negative
+
+        TimeWindow::from_end(duration, self.end)
+    }
+
+    /// Prepones the time window end so that the new duration matches the given
+    /// value. Is a No-Op if the new duration is smaller than the current
+    /// one. Negative durations set the result time window size to zero.
+    ///
+    /// # Examples
+    /// ```
+    /// # use tinytime::Duration;
+    /// # use tinytime::TimeWindow;
+    /// let x = TimeWindow::from_seconds(1, 3);
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(1, 1),
+    ///     x.shrink_towards_start_to(Duration::seconds(-1))
+    /// );
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(1, 1),
+    ///     x.shrink_towards_start_to(Duration::seconds(0))
+    /// );
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(1, 2),
+    ///     x.shrink_towards_start_to(Duration::seconds(1))
+    /// );
+    /// assert_eq!(
+    ///     TimeWindow::from_seconds(1, 3),
+    ///     x.shrink_towards_start_to(Duration::seconds(5))
+    /// );
+    /// ```
+    pub fn shrink_towards_start_to(self, new_duration: Duration) -> TimeWindow {
+        let duration = new_duration
+            .min(self.duration()) // Resize only if new duration is smaller than the current one
+            .max(Duration::ZERO); // Make sure the new duration is non-negative
+
+        TimeWindow::from_duration(self.start, duration)
+    }
+
     /// Returns true if this time window contains the given time.
     /// # Examples
     ///