Initial commit

src/post_queue.rs

@@ -0,0 +1,105 @@
+use std::{
+    cmp::{Ordering, Reverse},
+    ops::Deref,
+};
+
+use serde::Serialize;
+
+#[derive(Debug, Clone, Serialize)]
+pub struct Item {
+    pub novel: String,
+    pub post_at: jiff::Zoned,
+}
+
+pub struct Closest<'a> {
+    queue: &'a mut Queue,
+}
+
+impl<'a> Closest<'a> {
+    pub fn try_pop(self, now: &jiff::Zoned) -> Option<Item> {
+        let last = self.queue.entries.pop().unwrap();
+
+        if now >= &last.post_at {
+            Some(last)
+        } else {
+            self.queue.entries.push(last);
+            None
+        }
+    }
+}
+
+impl<'a> Deref for Closest<'a> {
+    type Target = Item;
+
+    fn deref(&self) -> &Self::Target {
+        let len = self.queue.entries.len() - 1;
+        &self.queue.entries[len]
+    }
+}
+
+fn cmp_items(lhs: &Item, rhs: &Item) -> Ordering {
+    Reverse(&lhs.post_at).cmp(&Reverse(&rhs.post_at))
+}
+
+#[derive(Debug, Default)]
+pub struct Queue {
+    entries: Vec<Item>,
+}
+
+impl FromIterator<Item> for Queue {
+    fn from_iter<T: IntoIterator<Item = Item>>(iter: T) -> Self {
+        let mut entries: Vec<Item> = iter.into_iter().collect();
+        entries.sort_unstable_by(cmp_items);
+
+        #[cfg(debug_assertions)]
+        if entries.len() >= 2 {
+            let first = &entries[0].post_at;
+            let second = &entries[1].post_at;
+
+            assert!(first >= second);
+        }
+
+        Self { entries }
+    }
+}
+
+impl Queue {
+    pub fn len(&self) -> usize {
+        self.entries.len()
+    }
+
+    pub fn closest(&self) -> Option<&Item> {
+        self.entries.last()
+    }
+
+    pub fn closest_mut(&mut self) -> Option<Closest<'_>> {
+        if self.entries.is_empty() {
+            None
+        } else {
+            Some(Closest { queue: self })
+        }
+    }
+
+    pub fn add(&mut self, item: Item) {
+        // This could be:
+        // let Ok(idx) | Err(idx) = ..;
+        // But fuck rust, it's not allowed.
+        let res = self
+            .entries
+            .binary_search_by(|probe| cmp_items(probe, &item));
+
+        // The why блядь?
+        let idx = match res {
+            Ok(i) => i,
+            Err(i) => i,
+        };
+
+        self.entries.insert(idx, item);
+    }
+
+    pub const fn new() -> Self {
+        Self {
+            entries: Vec::new(),
+        }
+    }
+}