wip: history independant treap

mast/src/lib.rs

@@ -1,18 +1,232 @@
 #![allow(unused)]
 
-mod node;
-mod storage;
-mod tree;
-
-use crate::node::Node;
-
-// // TODO: maybe add nonce for encrypted  trees.
-// // TODO: why add header in each node? or in the Mast commit?
-// //  Would we need to read a node without traversing down from the Mast commit?
-// pub struct Mast {
-//     /// The name of this Mast to be used as a prefix for all nodes
-//     /// in the storage, seperating different Masts.
-//     name: String,
-//     root: Option<Hash>,
-//     storage: MastStorage,
-// }
+use blake3::{Hash, Hasher};
+
+use std::cmp::Ordering;
+use std::mem;
+
+type Key = Box<[u8]>;
+type Value = Box<[u8]>;
+
+const KEY: [u8; 32] = [1_u8; 32];
+
+#[derive(Debug, Clone)]
+pub struct Node {
+    key: Key,
+    value: Value,
+
+    priority: Hash,
+
+    left: Option<Box<Node>>,
+    right: Option<Box<Node>>,
+}
+
+enum RemovalCases {
+    RemoveNode,
+    RotateLeft,
+    RotateRight,
+}
+
+impl Node {
+    pub fn new(key: &[u8], value: &[u8]) -> Node {
+        let priority = Hasher::new().update(&key).finalize();
+
+        Node {
+            key: key.into(),
+            value: value.into(),
+            priority,
+            left: None,
+            right: None,
+        }
+    }
+
+    pub fn get(&self, key: &[u8]) -> Option<&[u8]> {
+        match key.cmp(&self.key) {
+            Ordering::Equal => Some(&self.value),
+            Ordering::Less => self.left.as_ref().and_then(|n| n.get(key)),
+            Ordering::Greater => self.right.as_ref().and_then(|n| n.get(key)),
+        }
+    }
+
+    // pub fn get_mut(&mut self, key: &K) -> Option<&mut V> {
+    //     match key.cmp(&self.key) {
+    //         Ordering::Equal => Some(&mut self.value),
+    //         Ordering::Less => self.left.as_mut().and_then(|n| n.get_mut(key)),
+    //         Ordering::Greater => self.right.as_mut().and_then(|n| n.get_mut(key)),
+    //     }
+    // }
+
+    pub fn insert_or_replace(subtree: &mut Option<Box<Node>>, new: Node) -> Option<Value> {
+        match *subtree {
+            None => {
+                mem::replace(subtree, Some(Box::new(new)));
+                None
+            }
+            Some(ref mut node) => node.insert(new),
+        }
+    }
+
+    pub fn insert(&mut self, node: Node) -> Option<Value> {
+        match node.key.cmp(&self.key) {
+            Ordering::Equal => {
+                if self.priority.as_bytes() < node.priority.as_bytes() {
+                    self.priority = node.priority;
+                }
+                Some(mem::replace(&mut self.value, node.value))
+            }
+            Ordering::Less => {
+                let old_value = Node::insert_or_replace(&mut self.left, node);
+                if self.is_heap_property_violated(&self.left) {
+                    self.right_rotate();
+                }
+                old_value
+            }
+            Ordering::Greater => {
+                let old_value = Node::insert_or_replace(&mut self.right, node);
+                if self.is_heap_property_violated(&self.right) {
+                    self.left_rotate();
+                }
+                old_value
+            }
+        }
+    }
+
+    // pub fn remove(subtree: &mut Option<Box<Node<K, V>>>, key: &K) -> Option<V> {
+    //     {
+    //         let node = match *subtree {
+    //             None => return None,
+    //             Some(ref mut n) => n,
+    //         };
+    //         match key.cmp(&node.key) {
+    //             Ordering::Less => return Node::remove(&mut node.left, key),
+    //             Ordering::Greater => return Node::remove(&mut node.right, key),
+    //             Ordering::Equal => {}
+    //         }
+    //     }
+    //     Node::rotate_down(subtree)
+    // }
+    //
+    // fn rotate_down(subtree: &mut Option<Box<Node<K, V>>>) -> Option<V> {
+    //     let case = match *subtree {
+    //         None => return None,
+    //         Some(ref root) => match (&root.left, &root.right) {
+    //             (&None, &None) => RemovalCases::RemoveNode,
+    //             (&Some(ref left), &Some(ref right)) => {
+    //                 if left.priority >= right.priority {
+    //                     RemovalCases::RotateRight
+    //                 } else {
+    //                     RemovalCases::RotateLeft
+    //                 }
+    //             }
+    //             (&Some(_), &None) => RemovalCases::RotateRight,
+    //             (&None, &Some(_)) => RemovalCases::RotateLeft,
+    //         },
+    //     };
+    //     match case {
+    //         RemovalCases::RemoveNode => subtree.take().map(|n| n.value),
+    //         RemovalCases::RotateLeft => subtree.as_mut().and_then(|n| {
+    //             n.left_rotate();
+    //             Node::rotate_down(&mut n.left)
+    //         }),
+    //         RemovalCases::RotateRight => subtree.as_mut().and_then(|n| {
+    //             n.right_rotate();
+    //             Node::rotate_down(&mut n.right)
+    //         }),
+    //     }
+    // }
+
+    // #[inline]
+    fn is_heap_property_violated(&self, subtree: &Option<Box<Node>>) -> bool {
+        match *subtree {
+            None => false,
+            Some(ref b) => self.priority.as_bytes() < b.priority.as_bytes(),
+        }
+    }
+
+    //       q               p
+    //      / \             / \
+    //     p  C   --->     A  q
+    //    / \                / \
+    //   A  B               B  C
+    fn right_rotate(&mut self) {
+        // Cut left subtree of q
+        let left = mem::replace(&mut self.left, None);
+        if let Some(mut node) = left {
+            // Let subtree p be root and `node` point to q
+            mem::swap(self, &mut *node);
+            // Move subtree B from p to left subtree of q
+            mem::swap(&mut self.right, &mut node.left);
+            // Let q be right child of p
+            mem::replace(&mut self.right, Some(node));
+        }
+    }
+
+    //     p               q
+    //    / \             / \
+    //   A  q   --->     p  C
+    //     / \          / \
+    //    B  C         A  B
+    fn left_rotate(&mut self) {
+        // Cut right subtree of p
+        let right = mem::replace(&mut self.right, None);
+        if let Some(mut node) = right {
+            // Let subtree q be root and `node` point to p
+            mem::swap(self, &mut *node);
+            // Move subtree B from q to right subtree of p
+            mem::swap(&mut self.left, &mut node.right);
+            // Let p be left child of q
+            mem::replace(&mut self.left, Some(node));
+        }
+    }
+
+    pub fn as_mermaid_graph(&self) -> String {
+        let mut graph = String::from("graph TD;\n"); // Start of the Mermaid graph
+        build_graph_string(&Some(self.clone().into()), &mut graph);
+        graph
+    }
+}
+
+fn build_graph_string(node: &Option<Box<Node>>, graph: &mut String) {
+    if let Some(ref n) = node {
+        let key = bytes_to_string(&n.key);
+        let node_label = format!("{}({}:)", key, key);
+
+        graph.push_str(&format!("    {};\n", node_label));
+
+        if n.left.is_some() {
+            let key = bytes_to_string(&n.left.as_ref().unwrap().key);
+            let left_label = format!("{}({})", key, key);
+
+            graph.push_str(&format!("    {} --> {};\n", node_label, left_label));
+            build_graph_string(&n.left, graph);
+        }
+
+        if n.right.is_some() {
+            let key = bytes_to_string(&n.right.as_ref().unwrap().key);
+            let right_label = format!("{}({})", key, key);
+
+            graph.push_str(&format!("    {} --> {};\n", node_label, right_label));
+            build_graph_string(&n.right, graph);
+        }
+    }
+}
+
+fn bytes_to_string(bytes: &[u8]) -> String {
+    bytes.iter().map(|&b| b.to_string()).collect()
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn basic() {
+        let mut tree = Node::new(b"a", b"0");
+
+        for i in 0..254 {
+            tree.insert(Node::new(&[i], b"0"));
+        }
+
+        println!("{}", tree.as_mermaid_graph())
+    }
+}