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use std::ops::Deref;
use bincode::Encode;
use sha2::{Digest, Sha256};
pub struct HashChain<T: Encode> {
data: Vec<(Vec<u8>, T)>, // Vector of (hash, value) pairs
}
impl<T: Encode> HashChain<T> {
fn push(&mut self, data: T) {
let prev_hash = self
.data
.last()
.map(|p| {
p.0.clone()
})
.unwrap_or_default();
self.data
.push((Self::hash(&prev_hash, &data), data));
}
fn insert(&mut self, data: T, base_hash: &[u8]) {
let pos = self
.data
.iter()
.position(|x| x.0 == base_hash)
.unwrap();
self.data
.insert(pos, (Self::hash(base_hash, &data), data));
}
fn verify(&self, from_hash: &[u8]) -> bool {
let start_idx = self
.data
.iter()
.position(|x| x.0 == from_hash)
.unwrap();
(start_idx
..self
.data
.len())
.all(|i| {
Self::hash(
if i == 0 {
&Vec::default()
} else {
&self.data[i - 1].0
},
&self.data[i].1,
) == self.data[i].0
})
}
fn hash(prev_hash: &[u8], data: &T) -> Vec<u8> {
let mut hasher = Sha256::new();
hasher.update(prev_hash);
hasher.update(bincode::encode_to_vec(data, bincode::config::standard()).unwrap());
hasher
.finalize()
.to_vec()
}
}
impl<T: Encode> Deref for HashChain<T> {
type Target = Vec<(Vec<u8>, T)>;
fn deref(&self) -> &Self::Target {
&self.data
}
}
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