light-hasher 5.0.0

use crate::{Hasher, HasherError, Poseidon};

/// Creates a hash chain from an array of [u8;32] arrays.
///
/// # Parameters
/// - `inputs`: An array of [u8;32] arrays to be hashed.
///
/// # Returns
/// - `Result<[u8; 32], HasherError>`: The resulting hash chain or an error.
pub fn create_hash_chain_from_array<const T: usize>(
    inputs: [[u8; 32]; T],
) -> Result<[u8; 32], HasherError> {
    create_hash_chain_from_slice(&inputs)
}

/// Creates a hash chain from a slice of [u8;32] arrays.
///
/// # Parameters
/// - `inputs`: A slice of [u8;32] array to be hashed.
///
/// # Returns
/// - `Result<[u8; 32], HasherError>`: The resulting hash chain or an error.
pub fn create_hash_chain_from_slice(inputs: &[[u8; 32]]) -> Result<[u8; 32], HasherError> {
    if inputs.is_empty() {
        return Ok([0u8; 32]);
    }
    let mut hash_chain = inputs[0];
    for input in inputs.iter().skip(1) {
        hash_chain = Poseidon::hashv(&[&hash_chain, input])?;
    }
    Ok(hash_chain)
}

/// Creates a two inputs hash chain from two slices of [u8;32] arrays.
/// The two slices must have the same length.
/// Hashes are hashed in pairs, with the first hash from
/// the first slice and the second hash from the second slice.
/// H(i) = H(H(i-1), hashes_first[i], hashes_second[i])
///
/// # Parameters
/// - `hashes_first`: A slice of [u8;32] arrays to be hashed first.
/// - `hashes_second`: A slice of [u8;32] arrays to be hashed second.
///
/// # Returns
/// - `Result<[u8; 32], HasherError>`: The resulting hash chain or an error.
pub fn create_two_inputs_hash_chain(
    hashes_first: &[[u8; 32]],
    hashes_second: &[[u8; 32]],
) -> Result<[u8; 32], HasherError> {
    let first_len = hashes_first.len();
    if first_len != hashes_second.len() {
        return Err(HasherError::InvalidInputLength(
            first_len,
            hashes_second.len(),
        ));
    }
    if hashes_first.is_empty() {
        return Ok([0u8; 32]);
    }
    let mut hash_chain = Poseidon::hashv(&[&hashes_first[0], &hashes_second[0]])?;

    if first_len == 1 {
        return Ok(hash_chain);
    }

    for i in 1..first_len {
        hash_chain = Poseidon::hashv(&[&hash_chain, &hashes_first[i], &hashes_second[i]])?;
    }
    Ok(hash_chain)
}