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use std::collections::BTreeMap;
use bitcoin::hashes::{sha256d, Hash, HashEngine};
use bitcoin::secp256k1::rand::{thread_rng, Rng};
use bitcoin::util::uint::Uint256;
use client_side_validation::commit_verify::TryCommitVerify;
pub type ProtocolId = [u8; 32];
pub type Commitment = sha256d::Hash;
pub type MessageMap = BTreeMap<ProtocolId, Commitment>;
#[derive(Copy, Clone, Error, Debug, Display)]
#[display(Debug)]
pub struct TooManyMessagesError;
#[derive(
Clone,
PartialEq,
Eq,
PartialOrd,
Ord,
Debug,
Display,
StrictEncode,
StrictDecode,
)]
#[display(Debug)]
pub struct MultimsgCommitmentItem {
pub protocol: Option<ProtocolId>,
pub commitment: Commitment,
}
impl MultimsgCommitmentItem {
pub fn new(protocol: Option<ProtocolId>, commitment: Commitment) -> Self {
Self {
protocol,
commitment,
}
}
}
#[derive(
Clone,
PartialEq,
Eq,
PartialOrd,
Ord,
Debug,
Display,
Default,
StrictEncode,
StrictDecode,
)]
#[display(Debug)]
pub struct MultimsgCommitment {
pub commitments: Vec<MultimsgCommitmentItem>,
pub entropy: Option<u64>,
}
impl TryCommitVerify<MessageMap> for MultimsgCommitment {
type Error = TooManyMessagesError;
fn try_commit(multimsg: &MessageMap) -> Result<Self, TooManyMessagesError> {
const SORT_LIMIT: usize = 2 << 16;
let mut n = multimsg.len();
n = n.max(3);
let ordered = loop {
let mut ordered =
BTreeMap::<usize, (ProtocolId, Commitment)>::new();
if multimsg.into_iter().all(|(protocol, digest)| {
let rem = Uint256::from_be_bytes(*protocol)
% Uint256::from_u64(n as u64)
.expect("Bitcoin U256 struct is broken");
ordered
.insert(rem.low_u64() as usize, (*protocol, *digest))
.is_none()
}) {
break ordered;
}
n += 1;
if n > SORT_LIMIT {
return Err(TooManyMessagesError);
}
};
let entropy = {
let mut rng = thread_rng();
rng.gen::<u64>()
};
let mut commitments = Vec::<_>::with_capacity(n);
for i in 0..n {
match ordered.get(&i) {
None => {
let mut engine = Commitment::engine();
for _ in 0..4 {
engine.input(&entropy.to_le_bytes());
engine.input(&i.to_le_bytes());
}
commitments.push(MultimsgCommitmentItem::new(
None,
Commitment::from_engine(engine),
))
}
Some((contract_id, commitment)) => {
commitments.push(MultimsgCommitmentItem::new(
Some(*contract_id),
*commitment,
))
}
}
}
Ok(Self {
commitments,
entropy: Some(entropy),
})
}
}