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use bincode::Encode;
use sha2::{Digest, Sha256, digest::DynDigest};
use std::{
hash::{Hash, Hasher},
ops::Deref,
};
use serde::{Deserialize, Serialize};
use crate::{ZERO_PREFIX_AMOUNT, transaction::Transaction};
pub trait CryptoDigest {
fn digest(&self, state: &mut impl DynDigest);
}
#[derive(Deserialize, Serialize, Clone, PartialEq, Encode)]
pub struct Block {
pub prev_hash: Vec<u8>,
pub trans: Transaction,
pub pow: Option<u64>,
}
impl Block {
fn new(prev_hash: Option<&[u8]>, trans: Transaction) -> Self {
Self {
prev_hash: prev_hash
.unwrap_or(&[])
.to_vec(), // special blocks
trans,
pow: None,
}
}
fn pref_zeros(hashed: &[u8]) -> Result<usize, usize> {
hashed
.iter()
.try_fold(0, |nonce, x| {
if nonce >= ZERO_PREFIX_AMOUNT {
Ok(nonce)
} else if *x == 0 {
Ok(nonce + 1)
} else {
Err(nonce)
}
})
}
fn calc_pow(&self) -> u64 {
for i in 0.. {
// reset every loop
let mut hasher = Sha256::new();
self.digest(&mut hasher);
let hashed = hasher.finalize();
if Self::pref_zeros(&hashed).is_ok() {
return i;
}
}
unreachable!()
}
pub fn verify_pow(&self) -> bool {
if let Some(nonce) = self.pow {
let mut hasher = Sha256::new();
Digest::update(&mut hasher, bincode::encode_to_vec((&self.prev_hash, &self.trans, nonce), bincode::config::standard()).unwrap());
Self::pref_zeros(&hasher.finalize()).is_ok()
} else {
false
}
}
pub fn calc_set_pow(&mut self) {
self.pow = Some(self.calc_pow());
}
}
impl CryptoDigest for Block {
fn digest(&self, state: &mut impl DynDigest) {
state.update(&bincode::encode_to_vec((&self.prev_hash, &self.trans, &self.pow), bincode::config::standard()).unwrap());
}
}
#[derive(Default, Deserialize, Serialize, Clone, PartialEq)]
pub struct BlockChain {
pub blocks: Vec<Block>,
}
impl BlockChain {
pub fn new(blocks: Vec<Block>) -> Self {
Self {
blocks,
}
}
pub fn new_block(&self, trans: Transaction) -> Block {
let mut hasher = Sha256::new();
let prev = self
.blocks
.last();
let prev_hash = if let Some(b) = prev {
b.digest(&mut hasher);
Some(&*hasher.finalize())
} else {
None
};
Block::new(prev_hash, trans)
}
pub fn store(&mut self, block: Block) {
// TODO: verify blocks
self.blocks
.push(block)
}
}
impl Deref for BlockChain {
type Target = Vec<Block>;
fn deref(&self) -> &Self::Target {
&self.blocks
}
}
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