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use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use solana_sdk::bs58;
use std::{convert::TryFrom, fmt};

pub const HASH_BYTES: usize = 32;

#[derive(Serialize, Deserialize, Clone, Copy, Default, Eq, PartialEq, Ord, PartialOrd, Hash)]
#[repr(transparent)]
pub struct Hash(pub [u8; HASH_BYTES]);

#[derive(Clone, Default)]
pub struct Hasher {
    hasher: Sha256,
}

impl Hasher {
    pub fn hash(&mut self, val: &[u8]) {
        self.hasher.update(val);
    }
    pub fn hashv(&mut self, vals: &[&[u8]]) {
        for val in vals {
            self.hash(val);
        }
    }
    pub fn result(self) -> Hash {
        // At the time of this writing, the sha2 library is stuck on an old version
        // of generic_array (0.9.0). Decouple ourselves with a clone to our version.
        Hash(<[u8; HASH_BYTES]>::try_from(self.hasher.finalize().as_slice()).unwrap())
    }
}

impl AsRef<[u8]> for Hash {
    fn as_ref(&self) -> &[u8] {
        &self.0[..]
    }
}

impl fmt::Debug for Hash {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", bs58::encode(self.0).into_string())
    }
}

impl fmt::Display for Hash {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", bs58::encode(self.0).into_string())
    }
}

impl Hash {
    pub fn new(hash_slice: &[u8]) -> Self {
        Hash(<[u8; HASH_BYTES]>::try_from(hash_slice).unwrap())
    }

    pub fn to_bytes(self) -> [u8; HASH_BYTES] {
        self.0
    }
}

/// Return a Sha256 hash for the given data.
pub fn hashv(vals: &[&[u8]]) -> Hash {
    // Perform the calculation inline, calling this from within a program is
    // not supported
    #[cfg(not(target_arch = "bpf"))]
    {
        let mut hasher = Hasher::default();
        hasher.hashv(vals);
        hasher.result()
    }
}

/// Return a Sha256 hash for the given data.
pub fn hash(val: &[u8]) -> Hash {
    hashv(&[val])
}

pub fn sighash(namespace: &str, name: &str) -> [u8; 8] {
    let preimage = format!("{}:{}", namespace, name);

    let mut sighash = [0u8; 8];
    sighash.copy_from_slice(&hash(preimage.as_bytes()).to_bytes()[..8]);
    sighash
}