Add tests for ordering, conversion and formatting `DateTime` struct

src/datetime.rs

@@ -48,6 +48,7 @@ impl DateTime {
         // days plus some remainder. So we use self.days - 1 for our calculations
         seconds += i64::from(self.day - 1) * SECONDS_PER_DAY;
         seconds += i64::from(self.hour) * SECONDS_PER_HOUR;
+        seconds += i64::from(self.minute) * SECONDS_PER_MINUTE;
         seconds += i64::from(self.second);
         seconds += self.zone.as_seconds();
         seconds
@@ -138,6 +139,29 @@ impl DateTime {
             }
         }
     }
+
+    pub fn weekday(&self) -> Weekday {
+        let ts = self.timestamp();
+        let days = ts / SECONDS_PER_DAY;
+        let rem = days % 7;
+        rem.try_into().unwrap()
+    }
+}
+
+impl fmt::Display for DateTime {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}-{:0>2}-{:0>2}T{:0>2}:{:0>2}:{:0>2}{}",
+            self.year.get(),
+            self.month as u8,
+            self.day,
+            self.hour,
+            self.minute,
+            self.second,
+            self.zone,
+        )
+    }
 }
 
 impl Ord for DateTime {
@@ -153,3 +177,87 @@ impl PartialOrd for DateTime {
         Some(self.cmp(other))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn weekday() {
+        let mut dt = DateTime {
+            year: Year::new(2024),
+            month: Month::Janurary,
+            day: 29,
+            hour: 18,
+            minute: 14,
+            second: 42,
+            zone: TimeZone::Utc,
+        };
+        assert_eq!(dt.weekday(), Weekday::Monday);
+        dt = DateTime {
+            year: Year::new(2024),
+            month: Month::Janurary,
+            day: 27,
+            hour: 12,
+            minute: 42,
+            second: 14,
+            zone: TimeZone::Offset {
+                sign: crate::zone::Sign::Positive,
+                hours: 3,
+                minutes: 15,
+            },
+        };
+        assert_eq!(dt.weekday(), Weekday::Saturday);
+    }
+
+    #[test]
+    fn ord() {
+        let a = DateTime {
+            year: Year::new(2024),
+            month: Month::Janurary,
+            day: 29,
+            hour: 18,
+            minute: 28,
+            second: 42,
+            zone: TimeZone::new(Some(4), None).unwrap(),
+        };
+        let b = DateTime {
+            year: Year::new(2024),
+            month: Month::Janurary,
+            day: 29,
+            hour: 18,
+            minute: 05,
+            second: 42,
+            zone: TimeZone::new(Some(5), None).unwrap(),
+        };
+        assert!(a < b);
+    }
+
+    #[test]
+    fn ts() {
+        let ts: i64 = 1706571482;
+        let dt = DateTime {
+            year: Year::new(2024),
+            month: Month::Janurary,
+            day: 29,
+            hour: 23,
+            minute: 38,
+            second: 02,
+            zone: TimeZone::Utc,
+        };
+        assert_eq!(dt.timestamp(), ts);
+        assert_eq!(dt, DateTime::from_timestamp(ts));
+    }
+
+    #[test]
+    fn fmt() {
+        let mut dt = DateTime::from_timestamp(1706571482);
+        assert_eq!(dt.to_string(), "2024-01-29T23:38:02Z");
+        dt.zone = TimeZone::Offset {
+            sign: crate::zone::Sign::Positive,
+            hours: 4,
+            minutes: 15,
+        };
+        assert_eq!(dt.to_string(), "2024-01-29T23:38:02+04:15")
+    }
+}

src/weekday.rs

@@ -11,3 +11,23 @@ pub enum Weekday {
     Tuesday,
     Wednesday,
 }
+
+impl TryFrom<i64> for Weekday {
+    type Error = ParseWeekdayError;
+
+    fn try_from(value: i64) -> Result<Self, Self::Error> {
+        match value {
+            0 => Ok(Self::Thursday),
+            1 => Ok(Self::Friday),
+            2 => Ok(Self::Saturday),
+            3 => Ok(Self::Sunday),
+            4 => Ok(Self::Monday),
+            5 => Ok(Self::Tuesday),
+            6 => Ok(Self::Wednesday),
+            _ => Err(ParseWeekdayError),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct ParseWeekdayError;

src/zone.rs

@@ -105,7 +105,7 @@ impl fmt::Display for TimeZone {
                 hours,
                 minutes,
             } => {
-                write!(f, "{sign}{hours}:{minutes}")
+                write!(f, "{sign}{hours:0>2}:{minutes:0>2}")
             }
         }
     }