From b58312c19684d91fe9df94c13fb4f89e717bd938 Mon Sep 17 00:00:00 2001
From: Nilstrieb <nilstrieb@gmail.com>
Date: Fri, 6 Aug 2021 22:45:04 +0200
Subject: [PATCH] get

---
 src/linked_list.rs | 86 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 77 insertions(+), 9 deletions(-)

diff --git a/src/linked_list.rs b/src/linked_list.rs
index 914a58a..dd3295e 100644
--- a/src/linked_list.rs
+++ b/src/linked_list.rs
@@ -1,5 +1,9 @@
+use std::fmt::Debug;
 use std::ptr::NonNull;
 
+type NodePtr<T> = Option<NonNull<Node<T>>>;
+
+/// A doubly linked list with unsafe :O, except it's kind of shit compared to the std one
 #[derive(Debug)]
 pub struct LinkedList<T> {
     start: Option<NonNull<Node<T>>>,
@@ -15,19 +19,66 @@ where
     }
 }
 
+#[derive(Debug)]
 pub struct Node<T> {
     value: T,
-    next: Option<NonNull<Node<T>>>,
-    prev: Option<NonNull<Node<T>>>,
+    next: NodePtr<T>,
+    prev: NodePtr<T>,
 }
 
 impl<T> LinkedList<T> {
-    pub fn new() -> Self<T> {
+    /// Creates a new empty Linked List
+    pub fn new() -> LinkedList<T> {
         Self {
             start: None,
             end: None,
         }
     }
+
+    /// Prepend an element to the start of the list
+    pub fn prepend(&mut self, element: T) {
+        match self.start {
+            None => {
+                let node = allocate_nonnull(Node {
+                    value: element,
+                    next: None,
+                    prev: None,
+                });
+                self.start = Some(node);
+                self.end = Some(node);
+            }
+            Some(mut node) => {
+                let new = allocate_nonnull(Node {
+                    value: element,
+                    next: Some(node),
+                    prev: None,
+                });
+                unsafe { node.as_mut() }.prev = Some(new);
+            }
+        }
+    }
+
+    /// Random access over the list
+    pub fn get(&self, index: usize) -> Option<&T> {
+        dbg!(self);
+        Self::get_inner(self.start.as_ref(), index).map(|n| &n.value)
+    }
+
+    fn get_inner(node: Option<&NonNull<Node<T>>>, index: usize) -> Option<&Node<T>> {
+        if let Some(ptr) = node {
+            match index {
+                0 => unsafe { Some(ptr.as_ref()) },
+                n => LinkedList::get_inner(Some(ptr), n - 1),
+            }
+        } else {
+            None
+        }
+    }
+}
+
+fn allocate_nonnull<T>(element: T) -> NonNull<T> {
+    let mut boxed = Box::new(element);
+    NonNull::new(boxed.as_mut()).expect("Allocation returned null pointer")
 }
 
 impl<T> IntoIterator for LinkedList<T> {
@@ -40,7 +91,7 @@ impl<T> IntoIterator for LinkedList<T> {
 }
 
 pub struct IntoIter<T> {
-    item: Option<NonNull<Node<T>>>,
+    item: NodePtr<T>,
 }
 
 impl<T> IntoIter<T> {
@@ -53,12 +104,29 @@ impl<T> Iterator for IntoIter<T> {
     type Item = T;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let next = self.item.take();
-        let ptr = match next {
-            None => return None,
-            Some(mut ptr) => unsafe { ptr.as_mut() },
-        };
+        //let next = self.item.take();
+        //let ptr = match next {
+        //    None => return None,
+        //    Some(mut ptr) => unsafe { ptr.as_mut() },
+        //};
 
         todo!()
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn random_access() {
+        let mut list = LinkedList::new();
+        list.prepend("hallo");
+        list.prepend("test");
+        list.prepend("nice");
+        assert_eq!(list.get(0), Some(&"nice"));
+        assert_eq!(list.get(1), Some(&"test"));
+        assert_eq!(list.get(2), Some(&"hallo"));
+        assert_eq!(list.get(3), None);
+    }
+}