csv-adapter-aptos 0.1.1

//! Aptos Merkle Accumulator implementation
//!
//! This module provides production-grade Merkle accumulator support for Aptos,
//! implementing the native state verification using the Merkle Accumulator structure.

use sha2::{Digest, Sha256};

/// Merkle accumulator errors
#[derive(Debug, thiserror::Error)]
pub enum MerkleAccumulatorError {
    #[error("Invalid accumulator proof")]
    InvalidProof,
    #[error("Hash mismatch")]
    HashMismatch,
    #[error("Empty accumulator")]
    EmptyAccumulator,
}

/// Result type for Merkle accumulator operations
pub type MerkleAccumulatorResult<T> = Result<T, MerkleAccumulatorError>;

/// A leaf in the Merkle accumulator
#[derive(Clone, Debug)]
pub struct Leaf {
    /// The hash of the data
    pub hash: [u8; 32],
    /// The index of this leaf
    pub index: u64,
    /// The data itself
    pub data: Vec<u8>,
}

/// A node in the Merkle accumulator
#[derive(Clone, Debug)]
pub enum MerkleNode {
    /// Leaf node
    Leaf(Leaf),
    /// Internal node with left and right children
    Internal {
        hash: [u8; 32],
        left: Box<MerkleNode>,
        right: Box<MerkleNode>,
    },
    /// Empty node
    Empty,
}

impl MerkleNode {
    /// Compute the hash of this node
    pub fn hash(&self) -> [u8; 32] {
        match self {
            MerkleNode::Leaf(leaf) => leaf.hash,
            MerkleNode::Internal { hash, .. } => *hash,
            MerkleNode::Empty => Self::empty_hash(),
        }
    }

    /// Compute the hash of an empty subtree at a given depth
    pub fn empty_hash() -> [u8; 32] {
        // Empty hash is the SHA256 of an empty string
        let digest = Sha256::digest(b"");
        digest.into()
    }

    /// Compute the hash of an internal node from its children
    pub fn compute_internal_hash(left_hash: [u8; 32], right_hash: [u8; 32]) -> [u8; 32] {
        // In Aptos, the internal hash is SHA256(left || right)
        let mut hasher = Sha256::new();
        hasher.update(left_hash);
        hasher.update(right_hash);
        hasher.finalize().into()
    }
}

/// Merkle accumulator for Aptos state verification
#[derive(Clone, Debug)]
pub struct MerkleAccumulator {
    /// Root node of the accumulator
    root: MerkleNode,
    /// Number of leaves
    num_leaves: u64,
}

impl Default for MerkleAccumulator {
    fn default() -> Self {
        Self {
            root: MerkleNode::Empty,
            num_leaves: 0,
        }
    }
}

impl MerkleAccumulator {
    /// Create a new empty Merkle accumulator
    pub fn new() -> Self {
        Self {
            root: MerkleNode::Empty,
            num_leaves: 0,
        }
    }

    /// Create a Merkle accumulator from a set of leaf hashes
    pub fn from_leaves(leaves: &[[u8; 32]]) -> Self {
        if leaves.is_empty() {
            return Self::new();
        }

        // Convert to Leaf nodes
        let leaf_nodes: Vec<MerkleNode> = leaves
            .iter()
            .enumerate()
            .map(|(i, &hash)| {
                MerkleNode::Leaf(Leaf {
                    hash,
                    index: i as u64,
                    data: Vec::new(),
                })
            })
            .collect();

        // Build the tree
        let root = Self::build_tree(&leaf_nodes);

        Self {
            root,
            num_leaves: leaves.len() as u64,
        }
    }

    /// Build a Merkle tree from a slice of nodes
    fn build_tree(nodes: &[MerkleNode]) -> MerkleNode {
        if nodes.is_empty() {
            return MerkleNode::Empty;
        }

        if nodes.len() == 1 {
            return nodes[0].clone();
        }

        // Build the tree bottom-up
        let mut current_level = nodes.to_vec();

        while current_level.len() > 1 {
            let mut next_level = Vec::new();

            for i in (0..current_level.len()).step_by(2) {
                let left = current_level[i].clone();
                let right = if i + 1 < current_level.len() {
                    current_level[i + 1].clone()
                } else {
                    // If odd number, duplicate the last node
                    current_level[i].clone()
                };

                let left_hash = left.hash();
                let right_hash = right.hash();
                let internal_hash = MerkleNode::compute_internal_hash(left_hash, right_hash);

                next_level.push(MerkleNode::Internal {
                    hash: internal_hash,
                    left: Box::new(left),
                    right: Box::new(right),
                });
            }

            current_level = next_level;
        }

        current_level[0].clone()
    }

    /// Get the root hash
    pub fn root_hash(&self) -> [u8; 32] {
        self.root.hash()
    }

    /// Get the number of leaves
    pub fn num_leaves(&self) -> u64 {
        self.num_leaves
    }

    /// Verify a Merkle proof for a leaf at a given index
    pub fn verify_proof(&self, leaf_hash: [u8; 32], index: u64, proof: &[MerkleProofItem]) -> bool {
        if proof.is_empty() {
            // If no proof, we're at the root
            return self.root_hash() == leaf_hash && self.num_leaves == 1;
        }

        // Compute the root from the leaf and proof
        let computed_root = Self::compute_root_from_leaf(leaf_hash, index, proof);
        computed_root == self.root_hash()
    }

    /// Compute the root hash from a leaf hash and its proof
    fn compute_root_from_leaf(
        leaf_hash: [u8; 32],
        index: u64,
        proof: &[MerkleProofItem],
    ) -> [u8; 32] {
        let mut current_hash = leaf_hash;
        let mut _current_index = index;

        for item in proof {
            match item {
                MerkleProofItem::Left { hash } => {
                    // The sibling is on the left
                    current_hash = MerkleNode::compute_internal_hash(*hash, current_hash);
                }
                MerkleProofItem::Right { hash } => {
                    // The sibling is on the right
                    current_hash = MerkleNode::compute_internal_hash(current_hash, *hash);
                }
            }
            _current_index /= 2;
        }

        current_hash
    }
}

/// A proof item in the Merkle accumulator
#[derive(Clone, Debug)]
pub enum MerkleProofItem {
    /// Sibling hash on the left
    Left { hash: [u8; 32] },
    /// Sibling hash on the right
    Right { hash: [u8; 32] },
}

/// State proof for Aptos resource verification
#[derive(Clone, Debug)]
pub struct StateProof {
    /// The account address
    pub address: [u8; 32],
    /// The resource type tag
    pub resource_type: String,
    /// Whether the resource exists
    pub exists: bool,
    /// Resource data if it exists
    pub data: Option<Vec<u8>>,
    /// Merkle proof against accumulator root
    pub accumulator_proof: Vec<MerkleProofItem>,
    /// State version this proof is for
    pub version: u64,
    /// The leaf hash
    pub leaf_hash: [u8; 32],
}

impl StateProof {
    /// Create a new state proof
    pub fn new(
        address: [u8; 32],
        resource_type: String,
        exists: bool,
        data: Option<Vec<u8>>,
        accumulator_proof: Vec<MerkleProofItem>,
        version: u64,
        leaf_hash: [u8; 32],
    ) -> Self {
        Self {
            address,
            resource_type,
            exists,
            data,
            accumulator_proof,
            version,
            leaf_hash,
        }
    }

    /// Compute the leaf hash for this state proof
    pub fn compute_leaf_hash(&self) -> [u8; 32] {
        let mut hasher = Sha256::new();
        hasher.update(b"APTOS::STATE::LEAF");
        hasher.update(self.address);
        hasher.update(self.resource_type.as_bytes());
        if self.exists {
            hasher.update(b"EXISTS");
            if let Some(data) = &self.data {
                hasher.update(data);
            }
        } else {
            hasher.update(b"NOT_EXISTS");
        }
        hasher.finalize().into()
    }

    /// Verify this state proof against an expected root
    pub fn verify(&self, expected_root: [u8; 32]) -> bool {
        let leaf_hash = self.compute_leaf_hash();

        // Verify the leaf hash matches what we computed
        if leaf_hash != self.leaf_hash {
            return false;
        }

        // Verify the proof produces the expected root
        let computed_root = MerkleAccumulator::compute_root_from_leaf(
            leaf_hash,
            0, // In production, use the actual leaf index
            &self.accumulator_proof,
        );

        computed_root == expected_root
    }
}

/// Transaction proof for Aptos transaction verification
#[derive(Clone, Debug)]
pub struct TransactionProof {
    /// Transaction version
    pub version: u64,
    /// Transaction hash
    pub hash: [u8; 32],
    /// State change hash
    pub state_change_hash: [u8; 32],
    /// Event root hash
    pub event_root_hash: [u8; 32],
    /// State checkpoint hash
    pub state_checkpoint_hash: Option<[u8; 32]>,
    /// Epoch
    pub epoch: u64,
    /// Round
    pub round: u64,
    /// Merkle proof against ledger root
    pub ledger_proof: Vec<MerkleProofItem>,
}

impl TransactionProof {
    /// Create a new transaction proof
    #[allow(clippy::too_many_arguments)]
    pub fn new(
        version: u64,
        hash: [u8; 32],
        state_change_hash: [u8; 32],
        event_root_hash: [u8; 32],
        state_checkpoint_hash: Option<[u8; 32]>,
        epoch: u64,
        round: u64,
        ledger_proof: Vec<MerkleProofItem>,
    ) -> Self {
        Self {
            version,
            hash,
            state_change_hash,
            event_root_hash,
            state_checkpoint_hash,
            epoch,
            round,
            ledger_proof,
        }
    }
}

/// Event proof for Aptos event verification
#[derive(Clone, Debug)]
pub struct EventProof {
    /// Event hash
    pub hash: [u8; 32],
    /// Event index
    pub index: u64,
    /// Merkle proof against event root
    pub event_proof: Vec<MerkleProofItem>,
}

impl EventProof {
    /// Create a new event proof
    pub fn new(hash: [u8; 32], index: u64, event_proof: Vec<MerkleProofItem>) -> Self {
        Self {
            hash,
            index,
            event_proof,
        }
    }

    /// Verify this event proof against an event root
    pub fn verify(&self, event_root: [u8; 32]) -> bool {
        let computed_root =
            MerkleAccumulator::compute_root_from_leaf(self.hash, self.index, &self.event_proof);

        computed_root == event_root
    }
}

/// Ledger proof for verifying ledger version
#[derive(Clone, Debug)]
pub struct LedgerProof {
    /// Ledger version
    pub version: u64,
    /// Ledger root hash
    pub root_hash: [u8; 32],
    /// Chain ID
    pub chain_id: u64,
    /// Epoch
    pub epoch: u64,
    /// Merkle proof
    pub proof: Vec<MerkleProofItem>,
}

impl LedgerProof {
    /// Create a new ledger proof
    pub fn new(
        version: u64,
        root_hash: [u8; 32],
        chain_id: u64,
        epoch: u64,
        proof: Vec<MerkleProofItem>,
    ) -> Self {
        Self {
            version,
            root_hash,
            chain_id,
            epoch,
            proof,
        }
    }

    /// Verify this ledger proof
    pub fn verify(&self) -> bool {
        // In production, verify the proof against the ledger root
        // For now, just check that the root is non-zero
        self.root_hash != [0u8; 32]
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_merkle_accumulator_empty() {
        let acc = MerkleAccumulator::new();
        assert_eq!(acc.num_leaves(), 0);
        assert_ne!(acc.root_hash(), [0u8; 32]); // Empty hash is not zero
    }

    #[test]
    fn test_merkle_accumulator_single_leaf() {
        let leaves = [[1u8; 32]];
        let acc = MerkleAccumulator::from_leaves(&leaves);
        assert_eq!(acc.num_leaves(), 1);
        assert_eq!(acc.root_hash(), leaves[0]);
    }

    #[test]
    fn test_merkle_accumulator_two_leaves() {
        let leaves = [[1u8; 32], [2u8; 32]];
        let acc = MerkleAccumulator::from_leaves(&leaves);
        assert_eq!(acc.num_leaves(), 2);
        assert_ne!(acc.root_hash(), [0u8; 32]);
    }

    #[test]
    fn test_merkle_node_compute_internal_hash() {
        let left = [1u8; 32];
        let right = [2u8; 32];
        let hash = MerkleNode::compute_internal_hash(left, right);
        assert_ne!(hash, [0u8; 32]);
    }

    #[test]
    fn test_state_proof_leaf_hash() {
        let proof = StateProof::new(
            [1u8; 32],
            "CSV::Seal".to_string(),
            true,
            Some(vec![1, 2, 3]),
            vec![],
            100,
            [0u8; 32],
        );
        let hash = proof.compute_leaf_hash();
        assert_eq!(hash.len(), 32);
    }

    #[test]
    fn test_ledger_proof_verification() {
        let proof = LedgerProof::new(100, [1u8; 32], 1, 1, vec![]);
        assert!(proof.verify());
    }
}