1 files changed, 40 insertions, 16 deletions

diff --git a/src/datetime.rs b/src/datetime.rs
index df4e637..9a43a4b 100644
--- a/src/datetime.rs
+++ b/src/datetime.rs
@@ -1,6 +1,6 @@
 use crate::{
 	timezone::{Utc, UtcOffset},
-	Date, Month, Time, TimeZone, Year,
+	Date, Month, Time, TimeZone, UnixTimestamp, Year,
 };
 
 use core::{cmp::Ordering, fmt::Display, hash::Hash};
@@ -45,72 +45,82 @@ impl<Tz: TimeZone> DateTime<Tz> {
 impl NaiveDateTime {
 	// TODO docs
 
+	#[must_use]
 	pub const fn new(date: Date, time: Time) -> Self {
 		Self { date, time }
 	}
 
+	#[must_use]
 	pub const fn date(self) -> Date {
 		self.date
 	}
 
+	#[must_use]
 	pub const fn time(self) -> Time {
 		self.time
 	}
 
+	#[must_use]
 	pub const fn year(self) -> Year {
 		self.date.year()
 	}
 
+	#[must_use]
 	pub const fn month(self) -> Month {
 		self.date.month()
 	}
 
+	#[must_use]
 	pub const fn day(self) -> u8 {
 		self.date.day()
 	}
 
+	#[must_use]
 	pub const fn hour(self) -> u8 {
 		self.time.hour()
 	}
 
+	#[must_use]
 	pub const fn minute(self) -> u8 {
 		self.time.minute()
 	}
 
+	#[must_use]
 	pub const fn second(self) -> u8 {
 		self.time.second()
 	}
 
+	#[must_use]
 	pub const fn millisecond(self) -> u16 {
 		self.time.millisecond()
 	}
 
+	#[must_use]
 	pub const fn microsecond(self) -> u32 {
 		self.time.microsecond()
 	}
 
+	#[must_use]
 	pub const fn nanosecond(self) -> u32 {
 		self.time.nanosecond()
 	}
 
 	#[must_use]
-	pub fn add_seconds(self, seconds: isize) -> Self {
-		let time = self.time.add_seconds(seconds);
+	pub fn add_seconds_overflowing(self, seconds: i64) -> (Self, bool) {
+		let timestamp: UnixTimestamp = self.into();
+		let (timestamp, overflow) = timestamp.add_seconds_overflowing(seconds);
+		let datetime: NaiveDateTime = timestamp.into();
 
-		Self {
-			date: self.date,
-			time,
-		}
+		(datetime, overflow)
 	}
 
 	#[must_use]
-	pub fn add_nanoseconds(self, nanoseconds: isize) -> Self {
-		let time = self.time.add_nanoseconds(nanoseconds);
+	pub fn add_nanoseconds_overflowing(self, nanoseconds: i64) -> (Self, bool) {
+		let timestamp: UnixTimestamp = self.into();
+		let (timestamp, overflow) = timestamp.add_nanoseconds_overflowing(nanoseconds);
+		let datetime: NaiveDateTime = timestamp.into();
 
-		Self {
-			date: self.date,
-			time,
-		}
+		(datetime, overflow)
 	}
 }
 
@@ -153,7 +163,7 @@ impl<Tz: TimeZone, Other: TimeZone> PartialEq<DateTime<Other>> for DateTime<Tz>
 
 impl<Tz: TimeZone> Hash for DateTime<Tz> {
 	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-		self.utc_datetime.hash(state)
+		self.utc_datetime.hash(state);
 	}
 }
 
@@ -169,8 +179,6 @@ impl<Tz: TimeZone> Ord for DateTime<Tz> {
 	}
 }
 
-// TODO addition
-
 impl Display for NaiveDateTime {
 	fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
 		write!(f, "{} {}", self.date, self.time)
@@ -182,3 +190,19 @@ impl<Tz: TimeZone> Display for DateTime<Tz> {
 		write!(f, "{} {}", self.utc_datetime, self.timezone)
 	}
 }
+
+impl From<UnixTimestamp> for NaiveDateTime {
+	fn from(timestamp: UnixTimestamp) -> Self {
+		const UNIX_EPOCH_DAYS_AFTER_CE: i64 = Date::UNIX_EPOCH.days_after_common_era();
+		let days_after_unix_epoch = timestamp.seconds_since_unix_epoch() / 86_400;
+		let days_after_ce = days_after_unix_epoch + UNIX_EPOCH_DAYS_AFTER_CE as i64;
+		let date = Date::from_days_after_common_era(days_after_ce);
+		let seconds_after_midnight = timestamp.seconds_since_unix_epoch() % 86_400;
+		let nanoseconds = timestamp.nanosecond();
+		let time = Time::MIDNIGHT
+			.add_seconds(seconds_after_midnight as isize)
+			.add_nanoseconds(nanoseconds as isize);
+
+		Self::new(date, time)
+	}
+}