1use super::{vec, NodeIndex, Rpo256, Vec, Word};
  2use core::ops::{Deref, DerefMut};
  3
  4// MERKLE PATH
  5// ================================================================================================
  6
  7/// A merkle path container, composed of a sequence of nodes of a Merkle tree.
  8#[derive(Clone, Debug, Default, PartialEq, Eq)]
  9pub struct MerklePath {
 10    nodes: Vec<Word>,
 11}
 12
 13impl MerklePath {
 14    // CONSTRUCTORS
 15    // --------------------------------------------------------------------------------------------
 16
 17    /// Creates a new Merkle path from a list of nodes.
 18    pub fn new(nodes: Vec<Word>) -> Self {
 19        Self { nodes }
 20    }
 21
 22    // PROVIDERS
 23    // --------------------------------------------------------------------------------------------
 24
 25    /// Computes the merkle root for this opening.
 26    pub fn compute_root(&self, index_value: u64, node: Word) -> Word {
 27        let mut index = NodeIndex::new(self.depth(), index_value);
 28        self.nodes.iter().copied().fold(node, |node, sibling| {
 29            // compute the node and move to the next iteration.
 30            let input = index.build_node(node.into(), sibling.into());
 31            index.move_up();
 32            Rpo256::merge(&input).into()
 33        })
 34    }
 35
 36    /// Returns the depth in which this Merkle path proof is valid.
 37    pub fn depth(&self) -> u8 {
 38        self.nodes.len() as u8
 39    }
 40
 41    /// Verifies the Merkle opening proof towards the provided root.
 42    ///
 43    /// Returns `true` if `node` exists at `index` in a Merkle tree with `root`.
 44    pub fn verify(&self, index: u64, node: Word, root: &Word) -> bool {
 45        root == &self.compute_root(index, node)
 46    }
 47}
 48
 49impl From<Vec<Word>> for MerklePath {
 50    fn from(path: Vec<Word>) -> Self {
 51        Self::new(path)
 52    }
 53}
 54
 55impl Deref for MerklePath {
 56    // we use `Vec` here instead of slice so we can call vector mutation methods directly from the
 57    // merkle path (example: `Vec::remove`).
 58    type Target = Vec<Word>;
 59
 60    fn deref(&self) -> &Self::Target {
 61        &self.nodes
 62    }
 63}
 64
 65impl DerefMut for MerklePath {
 66    fn deref_mut(&mut self) -> &mut Self::Target {
 67        &mut self.nodes
 68    }
 69}
 70
 71impl FromIterator<Word> for MerklePath {
 72    fn from_iter<T: IntoIterator<Item = Word>>(iter: T) -> Self {
 73        Self::new(iter.into_iter().collect())
 74    }
 75}
 76
 77impl IntoIterator for MerklePath {
 78    type Item = Word;
 79    type IntoIter = vec::IntoIter<Word>;
 80
 81    fn into_iter(self) -> Self::IntoIter {
 82        self.nodes.into_iter()
 83    }
 84}
 85
 86// MERKLE PATH CONTAINERS
 87// ================================================================================================
 88
 89/// A container for a [Word] value and its [MerklePath] opening.
 90#[derive(Clone, Debug, Default, PartialEq, Eq)]
 91pub struct ValuePath {
 92    /// The node value opening for `path`.
 93    pub value: Word,
 94    /// The path from `value` to `root` (exclusive).
 95    pub path: MerklePath,
 96}
 97
 98/// A container for a [MerklePath] and its [Word] root.
 99///
100/// This structure does not provide any guarantees regarding the correctness of the path to the
101/// root. For more information, check [MerklePath::verify].
102#[derive(Clone, Debug, Default, PartialEq, Eq)]
103pub struct RootPath {
104    /// The node value opening for `path`.
105    pub root: Word,
106    /// The path from `value` to `root` (exclusive).
107    pub path: MerklePath,
108}