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// Copyright (C) 2019-2021 Aleo Systems Inc.
// This file is part of the snarkVM library.

// The snarkVM library is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// The snarkVM library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with the snarkVM library. If not, see <https://www.gnu.org/licenses/>.

use snarkvm_algorithms::{crh::PedersenCompressedCRH, define_masked_merkle_tree_parameters, merkle_tree::prng};
use snarkvm_curves::{bls12_377::Fr, edwards_bls12::EdwardsProjective as EdwardsBls};
use snarkvm_utilities::{bytes::ToBytes, to_bytes};

use once_cell::sync::Lazy;
use serde::{Deserialize, Serialize};
use std::{
    fmt::{
        Display,
        Formatter,
        {self},
    },
    sync::Arc,
};

// Do not leak the type
mod window {
    use snarkvm_algorithms::crh::PedersenSize;

    #[derive(Clone, Debug, PartialEq, Eq, Hash)]
    pub struct TwoToOneWindow;

    impl PedersenSize for TwoToOneWindow {
        const NUM_WINDOWS: usize = 4;
        const WINDOW_SIZE: usize = 128;
    }
}

pub type MerkleTreeCRH = PedersenCompressedCRH<EdwardsBls, window::TwoToOneWindow>;

// We instantiate the tree here with depth = 2. This may change in the future.
pub const MASKED_TREE_DEPTH: usize = 2;

define_masked_merkle_tree_parameters!(MaskedMerkleTreeParameters, MerkleTreeCRH, MASKED_TREE_DEPTH);

/// A Merkle Tree instantiated with the Masked Pedersen hasher over BLS12-377
pub type EdwardsMaskedMerkleTree = MerkleTree<MaskedMerkleTreeParameters>;

/// Lazily evaluated parameters for the Masked Merkle tree
pub static PARAMS: Lazy<Arc<MaskedMerkleTreeParameters>> =
    Lazy::new(|| Arc::new(MaskedMerkleTreeParameters::setup(&mut prng())));

/// A Pedersen Merkle Root Hash
#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub struct PedersenMerkleRootHash(pub [u8; 32]);

impl PedersenMerkleRootHash {
    pub const fn size() -> usize {
        32
    }
}

impl Display for PedersenMerkleRootHash {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", hex::encode(self.0))
    }
}

/// Calculates the root of the Merkle tree using a Pedersen Hash instantiated with a PRNG
/// and returns it serialized
pub fn pedersen_merkle_root(hashes: &[[u8; 32]]) -> PedersenMerkleRootHash {
    pedersen_merkle_root_hash(hashes).into()
}

/// Calculates the root of the Merkle tree using a Pedersen Hash instantiated with a PRNG
pub fn pedersen_merkle_root_hash(hashes: &[[u8; 32]]) -> Fr {
    let tree = EdwardsMaskedMerkleTree::new(PARAMS.clone(), hashes.iter()).expect("could not create merkle tree");
    tree.root()
}

/// Calculates the root of the Merkle tree using a Pedersen Hash instantiated with a PRNG and the
/// base layer hashes leaved
pub fn pedersen_merkle_root_hash_with_leaves(hashes: &[[u8; 32]]) -> (Fr, Vec<Fr>) {
    let tree = EdwardsMaskedMerkleTree::new(PARAMS.clone(), hashes.iter()).expect("could not create merkle tree");
    (tree.root(), tree.hashed_leaves().to_vec())
}

impl From<Fr> for PedersenMerkleRootHash {
    fn from(src: Fr) -> PedersenMerkleRootHash {
        let root_bytes = to_bytes![src].expect("could not convert merkle root to bytes");
        let mut pedersen_merkle_root_bytes = [0u8; 32];
        pedersen_merkle_root_bytes[..].copy_from_slice(&root_bytes);
        PedersenMerkleRootHash(pedersen_merkle_root_bytes)
    }
}