From 2bf74ecbabb9c4ce89c24d42562837f5764b6305 Mon Sep 17 00:00:00 2001
From: Nathan Fisher <jeang3nie@hitchhiker-linux.org>
Date: Sat, 10 Jun 2023 01:13:52 -0400
Subject: [PATCH] impl PartialOrd for DateTime

---
 src/time/mod.rs | 57 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 52 insertions(+), 5 deletions(-)

diff --git a/src/time/mod.rs b/src/time/mod.rs
index 04ce077..2b5cda8 100644
--- a/src/time/mod.rs
+++ b/src/time/mod.rs
@@ -1,5 +1,5 @@
 //! A container representing a moment in ISO-8601 format Time
-use std::{fmt, str::FromStr};
+use std::{cmp::Ordering, fmt, str::FromStr};
 
 mod error;
 mod parser;
@@ -7,8 +7,9 @@ pub use {error::Error, parser::Parser};
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+use x509_parser::der_parser::ber::ber_read_element_header;
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
 pub enum Sign {
     Positive,
@@ -36,7 +37,7 @@ impl TryFrom<char> for Sign {
     }
 }
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
 pub struct Offset {
     pub sign: Sign,
@@ -54,7 +55,7 @@ impl fmt::Display for Offset {
     }
 }
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
 pub enum TimeZone {
     UTC,
@@ -70,7 +71,7 @@ impl fmt::Display for TimeZone {
     }
 }
 
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(Deserialize, Serialize))]
 pub struct DateTime {
     pub year: u32,
@@ -110,6 +111,52 @@ impl fmt::Display for DateTime {
     }
 }
 
+impl PartialOrd for DateTime {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        let a = self.normalize()?;
+        let b = other.normalize()?;
+        (a.year, a.month, a.day, a.hour, a.minute, a.second)
+            .partial_cmp(&(b.year, b.month, b.day, b.hour, b.minute, b.second))
+    }
+}
+
+impl DateTime {
+    pub fn normalize(&self) -> Option<Self> {
+        if self.tz == Some(TimeZone::UTC) {
+            Some(*self)
+        } else {
+            if let Some(TimeZone::Offset(tz)) = self.tz {
+                let hour = if let Some(hour) = self.hour {
+                    match tz.sign {
+                        Sign::Positive => Some(hour + tz.hours),
+                        Sign::Negative => Some(hour - tz.hours),
+                    }
+                } else {
+                    None
+                };
+                let minute = 'blk: {
+                    if let Some(minutes) = self.minute {
+                        if let Some(o) = tz.minutes {
+                            match tz.sign {
+                                Sign::Positive => break 'blk Some(minutes + o),
+                                Sign::Negative => break 'blk Some(minutes - o),
+                            }
+                        }
+                    }
+                    None
+                };
+                Some(DateTime {
+                    hour,
+                    minute,
+                    ..*self
+                })
+            } else {
+                None
+            }
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;