From f251c7cce50df75195b8c21858e44d4ae8c0ebc3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Matou=C5=A1=20Volf?=
 <66163112+matous-volf@users.noreply.github.com>
Date: Mon, 9 Sep 2024 18:48:10 +0200
Subject: [PATCH] feat: create a utility struct for reversing `Option` ordering

---
 src/main.rs                     |  1 +
 src/utils/mod.rs                |  1 +
 src/utils/reverse_ord_option.rs | 31 +++++++++++++++++++++++++++++++
 3 files changed, 33 insertions(+)
 create mode 100644 src/utils/mod.rs
 create mode 100644 src/utils/reverse_ord_option.rs

diff --git a/src/main.rs b/src/main.rs
index a7a75b6..31ce965 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,7 @@ mod route;
 mod schema;
 mod server;
 mod query;
+mod utils;
 
 use components::app::App;
 use dioxus::prelude::*;
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
new file mode 100644
index 0000000..84f597f
--- /dev/null
+++ b/src/utils/mod.rs
@@ -0,0 +1 @@
+pub(crate) mod reverse_ord_option;
diff --git a/src/utils/reverse_ord_option.rs b/src/utils/reverse_ord_option.rs
new file mode 100644
index 0000000..fa5f9f3
--- /dev/null
+++ b/src/utils/reverse_ord_option.rs
@@ -0,0 +1,31 @@
+use std::cmp::Ordering;
+
+/* The default ordering of `Option`s is `None` being less than `Some`. The purpose of this struct is
+   to reverse that. */
+#[derive(PartialEq)]
+pub(crate) struct ReverseOrdOption<'a, T>(&'a Option<T>);
+
+impl<'a, T: Ord> Eq for ReverseOrdOption<'a, T> {}
+
+impl<'a, T: Ord> PartialOrd<Self> for ReverseOrdOption<'a, T> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl<'a, T: Ord> Ord for ReverseOrdOption<'a, T> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self.0.as_ref(), other.0.as_ref()) {
+            (None, None) => Ordering::Equal,
+            (None, Some(_)) => Ordering::Greater,
+            (Some(_), None) => Ordering::Less,
+            (Some(self_time), Some(other_time)) => self_time.cmp(other_time)
+        }
+    }
+}
+
+impl<'a, T> From<&'a Option<T>> for ReverseOrdOption<'a, T> {
+    fn from(value: &'a Option<T>) -> Self {
+        ReverseOrdOption(value)
+    }
+}