From d7e1f56e4dd8af5a993249ebb8d46d4461d8ddfc Mon Sep 17 00:00:00 2001
From: YK <yk@qcl.one>
Date: Sun, 8 Dec 2024 06:30:20 +0300
Subject: [PATCH] bad safe deque (chapter 4)

---
 src/bad_safe_deque.rs | 216 ++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs            |   1 +
 2 files changed, 217 insertions(+)
 create mode 100644 src/bad_safe_deque.rs

diff --git a/src/bad_safe_deque.rs b/src/bad_safe_deque.rs
new file mode 100644
index 0000000..8f90f77
--- /dev/null
+++ b/src/bad_safe_deque.rs
@@ -0,0 +1,216 @@
+use std::rc::Rc;
+use std::cell::{ Ref, RefCell, RefMut };
+
+pub struct List <T> {
+    head: Link<T>,
+    tail: Link<T>,
+}
+
+type Link <T> = Option<Rc<RefCell<Node<T>>>>;
+
+struct Node <T> {
+    value: T,
+    next: Link<T>,
+    prev: Link<T>,
+}
+
+
+impl <T> Node<T> {
+    fn new (value: T) -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self { value, next: None, prev: None, }))
+    }
+}
+
+pub struct IntoIter <T> (List<T>);
+
+
+impl <T> Iterator for IntoIter<T> {
+    type Item = T;
+    fn next (&mut self) -> Option<Self::Item> {
+        self.0.pop_front()
+    }
+}
+
+impl <T> DoubleEndedIterator for IntoIter<T> {
+    fn next_back (&mut self) -> Option<T> {
+        self.0.pop_back()
+    }
+}
+
+
+impl <T> List<T> {
+    pub fn new () -> Self {
+        Self { head: None, tail: None }
+    }
+
+    pub fn push_front (&mut self, value: T) {
+        let new = Node::new(value);
+        match self.head.take() {
+            Some(old) => {
+                old.borrow_mut().prev = Some(new.clone());
+                new.borrow_mut().next = Some(old);
+                self.head = Some(new);
+            },
+            None => {
+                self.tail = Some(new.clone());
+                self.head = Some(new);
+            }
+        }
+    }
+
+    pub fn push_back (&mut self, value: T) {
+        let new = Node::new(value);
+        match self.tail.take() {
+            Some(old) => {
+                old.borrow_mut().next = Some(new.clone());
+                new.borrow_mut().prev = Some(old);
+                self.tail = Some(new);
+            },
+            None => {
+                self.head = Some(new.clone());
+                self.tail = Some(new);
+            }
+        }
+    }
+
+    pub fn pop_front (&mut self) -> Option<T> {
+        self.head.take().map(|old| {
+            match old.borrow_mut().next.take() {
+                Some(new) => {
+                    new.borrow_mut().prev.take();
+                    self.head = Some(new);
+                },
+                None => {
+                    self.tail.take();
+                }
+            }
+
+            Rc::try_unwrap(old).ok().unwrap().into_inner().value
+        })
+    }
+
+
+    pub fn pop_back (&mut self) -> Option<T> {
+        self.tail.take().map(|old| {
+            match old.borrow_mut().prev.take() {
+                Some(new) => {
+                    new.borrow_mut().next.take();
+                    self.tail = Some(new);
+                },
+                None => {
+                    self.head.take();
+                }
+            }
+
+            Rc::try_unwrap(old).ok().unwrap().into_inner().value
+        })
+    }
+
+    pub fn peek_front (&self) -> Option<Ref<T>> {
+        self.head.as_ref().map(|node| Ref::map(node.borrow(), |node| &node.value))
+    }
+
+    pub fn peek_back (&self) -> Option<Ref<T>> {
+        self.tail.as_ref().map(|node| Ref::map(node.borrow(), |node| &node.value))
+    }
+
+    pub fn peek_front_mut (&self) -> Option<RefMut<T>> {
+        self.head.as_ref().map(|node| RefMut::map(node.borrow_mut(), |node| &mut node.value))
+    }
+
+    pub fn peek_back_mut (&self) -> Option<RefMut<T>> {
+        self.tail.as_ref().map(|node| RefMut::map(node.borrow_mut(), |node| &mut node.value))
+    }
+
+    pub fn into_iter (self) -> IntoIter<T> {
+        IntoIter(self)
+    }
+
+}
+
+impl <T> Drop for List<T> {
+    fn drop (&mut self) {
+        while self.pop_front().is_some() {}
+    }
+}
+
+
+
+#[cfg(test)]
+mod test {
+    use super::List;
+
+    #[test]
+    fn basics() {
+        let mut list = List::new();
+
+        // Check empty list behaves right
+        assert_eq!(list.pop_front(), None);
+
+        // Populate list
+        list.push_front(1);
+        list.push_front(2);
+        list.push_front(3);
+
+        // Check normal removal
+        assert_eq!(list.pop_front(), Some(3));
+        assert_eq!(list.pop_front(), Some(2));
+
+        // Push some more just to make sure nothing's corrupted
+        list.push_front(4);
+        list.push_front(5);
+
+        // Check normal removal
+        assert_eq!(list.pop_front(), Some(5));
+        assert_eq!(list.pop_front(), Some(4));
+
+        // Check exhaustion
+        assert_eq!(list.pop_front(), Some(1));
+        assert_eq!(list.pop_front(), None);
+
+        // ---- back -----
+
+        // Check empty list behaves right
+        assert_eq!(list.pop_back(), None);
+
+        // Populate list
+        list.push_back(1);
+        list.push_back(2);
+        list.push_back(3);
+
+        // Check normal removal
+        assert_eq!(list.pop_back(), Some(3));
+        assert_eq!(list.pop_back(), Some(2));
+
+        // Push some more just to make sure nothing's corrupted
+        list.push_back(4);
+        list.push_back(5);
+
+        // Check normal removal
+        assert_eq!(list.pop_back(), Some(5));
+        assert_eq!(list.pop_back(), Some(4));
+
+        // Check exhaustion
+        assert_eq!(list.pop_back(), Some(1));
+        assert_eq!(list.pop_back(), None);
+    }
+
+    #[test]
+    fn peek() {
+        let mut list = List::new();
+        assert!(list.peek_front().is_none());
+        assert!(list.peek_back().is_none());
+        assert!(list.peek_front_mut().is_none());
+        assert!(list.peek_back_mut().is_none());
+
+        list.push_front(1); list.push_front(2); list.push_front(3);
+
+        assert_eq!(&*list.peek_front().unwrap(), &3);
+        assert_eq!(&mut *list.peek_front_mut().unwrap(), &mut 3);
+        assert_eq!(&*list.peek_back().unwrap(), &1);
+        assert_eq!(&mut *list.peek_back_mut().unwrap(), &mut 1);
+    }
+
+
+
+}
diff --git a/src/lib.rs b/src/lib.rs
index ed55793..9964669 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
 pub mod bad;
 pub mod ok;
 pub mod persistent;
+pub mod bad_safe_deque;