Initial commit

src/template/day.rs

@@ -0,0 +1,181 @@
+use std::error::Error;
+use std::fmt::Display;
+use std::str::FromStr;
+
+#[cfg(feature = "today")]
+use chrono::{Datelike, FixedOffset, Utc};
+
+#[cfg(feature = "today")]
+const SERVER_UTC_OFFSET: i32 = -5;
+
+/// A valid day number of advent (i.e. an integer in range 1 to 25).
+///
+/// # Display
+/// This value displays as a two digit number.
+///
+/// ```
+/// # use advent_of_code::Day;
+/// let day = Day::new(8).unwrap();
+/// assert_eq!(day.to_string(), "08")
+/// ```
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Day(u8);
+
+impl Day {
+    /// Creates a [`Day`] from the provided value if it's in the valid range,
+    /// returns [`None`] otherwise.
+    pub const fn new(day: u8) -> Option<Self> {
+        if day == 0 || day > 25 {
+            return None;
+        }
+        Some(Self(day))
+    }
+
+    /// Converts the [`Day`] into an [`u8`].
+    pub fn into_inner(self) -> u8 {
+        self.0
+    }
+}
+
+#[cfg(feature = "today")]
+impl Day {
+    /// Returns the current day if it's between the 1st and the 25th of december, `None` otherwise.
+    pub fn today() -> Option<Self> {
+        let offset = FixedOffset::east_opt(SERVER_UTC_OFFSET * 3600)?;
+        let today = Utc::now().with_timezone(&offset);
+        if today.month() == 12 && today.day() <= 25 {
+            Self::new(u8::try_from(today.day()).ok()?)
+        } else {
+            None
+        }
+    }
+}
+
+impl Display for Day {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:02}", self.0)
+    }
+}
+
+impl PartialEq<u8> for Day {
+    fn eq(&self, other: &u8) -> bool {
+        self.0.eq(other)
+    }
+}
+
+impl PartialOrd<u8> for Day {
+    fn partial_cmp(&self, other: &u8) -> Option<std::cmp::Ordering> {
+        self.0.partial_cmp(other)
+    }
+}
+
+/* -------------------------------------------------------------------------- */
+
+impl FromStr for Day {
+    type Err = DayFromStrError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let day = s.parse().map_err(|_| DayFromStrError)?;
+        Self::new(day).ok_or(DayFromStrError)
+    }
+}
+
+/// An error which can be returned when parsing a [`Day`].
+#[derive(Debug)]
+pub struct DayFromStrError;
+
+impl Error for DayFromStrError {}
+
+impl Display for DayFromStrError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("expecting a day number between 1 and 25")
+    }
+}
+
+/* -------------------------------------------------------------------------- */
+
+/// An iterator that yields every day of advent from the 1st to the 25th.
+pub fn all_days() -> AllDays {
+    AllDays::new()
+}
+
+/// An iterator that yields every day of advent from the 1st to the 25th.
+pub struct AllDays {
+    current: u8,
+}
+
+impl AllDays {
+    #[allow(clippy::new_without_default)]
+    pub fn new() -> Self {
+        Self { current: 1 }
+    }
+}
+
+impl Iterator for AllDays {
+    type Item = Day;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current > 25 {
+            return None;
+        }
+        // NOTE: the iterator starts at 1 and we have verified that the value is not above 25.
+        let day = Day(self.current);
+        self.current += 1;
+
+        Some(day)
+    }
+}
+
+/* -------------------------------------------------------------------------- */
+
+/// Creates a [`Day`] value in a const context.
+#[macro_export]
+macro_rules! day {
+    ($day:expr) => {
+        const {
+            $crate::template::Day::new($day)
+                .expect("invalid day number, expecting a value between 1 and 25")
+        }
+    };
+}
+
+/* -------------------------------------------------------------------------- */
+
+#[cfg(feature = "test_lib")]
+mod tests {
+    use super::{Day, all_days};
+
+    #[test]
+    fn all_days_iterator() {
+        let mut iter = all_days();
+
+        assert_eq!(iter.next(), Some(Day(1)));
+        assert_eq!(iter.next(), Some(Day(2)));
+        assert_eq!(iter.next(), Some(Day(3)));
+        assert_eq!(iter.next(), Some(Day(4)));
+        assert_eq!(iter.next(), Some(Day(5)));
+        assert_eq!(iter.next(), Some(Day(6)));
+        assert_eq!(iter.next(), Some(Day(7)));
+        assert_eq!(iter.next(), Some(Day(8)));
+        assert_eq!(iter.next(), Some(Day(9)));
+        assert_eq!(iter.next(), Some(Day(10)));
+        assert_eq!(iter.next(), Some(Day(11)));
+        assert_eq!(iter.next(), Some(Day(12)));
+        assert_eq!(iter.next(), Some(Day(13)));
+        assert_eq!(iter.next(), Some(Day(14)));
+        assert_eq!(iter.next(), Some(Day(15)));
+        assert_eq!(iter.next(), Some(Day(16)));
+        assert_eq!(iter.next(), Some(Day(17)));
+        assert_eq!(iter.next(), Some(Day(18)));
+        assert_eq!(iter.next(), Some(Day(19)));
+        assert_eq!(iter.next(), Some(Day(20)));
+        assert_eq!(iter.next(), Some(Day(21)));
+        assert_eq!(iter.next(), Some(Day(22)));
+        assert_eq!(iter.next(), Some(Day(23)));
+        assert_eq!(iter.next(), Some(Day(24)));
+        assert_eq!(iter.next(), Some(Day(25)));
+        assert_eq!(iter.next(), None);
+    }
+}
+
+/* -------------------------------------------------------------------------- */