Add weekdays

2 files changed, 178 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index c1bd251..fdfeb5c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,9 @@
 #![doc = include_str!("../README.md")]
 
 mod month;
+mod weekday;
 mod year;
 
 pub use month::Month;
+pub use weekday::Weekday;
 pub use year::Year;
diff --git a/src/weekday.rs b/src/weekday.rs
new file mode 100644
index 0000000..5679bc7
--- /dev/null
+++ b/src/weekday.rs
@@ -0,0 +1,176 @@
+use std::str::FromStr;
+
+use derive_more::Display;
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+use thiserror::Error;
+
+use self::Weekday::*;
+
+/// Day of the week
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Display)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[repr(u8)]
+pub enum Weekday {
+	Monday = 0,
+	Tuesday = 1,
+	Wednesday = 2,
+	Thursday = 3,
+	Friday = 4,
+	Saturday = 5,
+	Sunday = 6,
+}
+
+impl Weekday {
+	/// Get the weekday from its name. Returns `None` if an invalid name was given.
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(Weekday::Monday, Weekday::from_name("Monday").unwrap());
+	/// assert_eq!(None, Weekday::from_name("monday"));
+	/// ```
+	pub fn from_name(name: &str) -> Option<Self> {
+		match name {
+			"Monday" => Some(Monday),
+			"Tuesday" => Some(Tuesday),
+			"Wednesday" => Some(Wednesday),
+			"Thursday" => Some(Thursday),
+			"Friday" => Some(Friday),
+			"Saturday" => Some(Saturday),
+			"Sunday" => Some(Sunday),
+			_ => None,
+		}
+	}
+
+	/// Get the next weekday
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(Weekday::Tuesday, Weekday::Monday.next());
+	/// ```
+	pub const fn next(self) -> Self {
+		match self {
+			Monday => Tuesday,
+			Tuesday => Wednesday,
+			Wednesday => Thursday,
+			Thursday => Friday,
+			Friday => Saturday,
+			Saturday => Sunday,
+			Sunday => Monday,
+		}
+	}
+
+	/// Get the previous weekday
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(Weekday::Sunday, Weekday::Monday.previous());
+	/// ```
+	pub const fn previous(self) -> Self {
+		match self {
+			Monday => Sunday,
+			Tuesday => Monday,
+			Wednesday => Tuesday,
+			Thursday => Wednesday,
+			Friday => Thursday,
+			Saturday => Friday,
+			Sunday => Saturday,
+		}
+	}
+
+	/// Get the zero-indexed number of days from Monday.
+	/// In other words, the number representing the day of the week,
+	/// starting with Monday = 0
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(0, Weekday::Monday.number_days_from_monday());
+	/// assert_eq!(6, Weekday::Sunday.number_days_from_monday());
+	/// ```
+	pub const fn number_days_from_monday(self) -> u8 {
+		self as u8
+	}
+
+	/// Get the one-indexed number of days from Monday.
+	/// In other words, the number representing the day of the week,
+	/// starting with Monday = 1
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(1, Weekday::Monday.number_from_monday());
+	/// assert_eq!(7, Weekday::Sunday.number_from_monday());
+	/// ```
+	pub const fn number_from_monday(self) -> u8 {
+		self.number_days_from_monday() + 1
+	}
+
+	/// Get the zero-indexed number of days from Sunday.
+	/// In other words, the number representing the day of the week,
+	/// starting with Sunday = 0
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(0, Weekday::Sunday.number_days_from_sunday());
+	/// assert_eq!(1, Weekday::Monday.number_days_from_sunday());
+	/// ```
+	// TODO benchmark this
+	pub const fn number_days_from_sunday(self) -> u8 {
+		match self {
+			Sunday => 0,
+			_ => (self as u8) + 1,
+		}
+	}
+
+	/// Get the one-indexed number of days from Sunday.
+	/// In other words, the number representing the day of the week,
+	/// starting with Sunday = 1
+	///
+	/// # Example
+	///
+	/// ```
+	/// use botic::Weekday;
+	///
+	/// assert_eq!(1, Weekday::Sunday.number_from_sunday());
+	/// assert_eq!(2, Weekday::Monday.number_from_sunday());
+	/// ```
+	pub const fn number_from_sunday(self) -> u8 {
+		self.number_days_from_sunday() + 1
+	}
+}
+
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Error)]
+#[error("Failed to parse the month")]
+// TODO Consider trying to figure out what month the user meant to use
+pub struct ParseWeekdayError;
+
+// TODO make case-insensitive
+// TODO support short names
+impl FromStr for Weekday {
+	type Err = ParseWeekdayError;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		match Self::from_name(s) {
+			Some(weekday) => Ok(weekday),
+			None => Err(ParseWeekdayError),
+		}
+	}
+}