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use std::collections::BTreeMap;
use bitcoin::hashes::{sha256, Hash, HashEngine};
use bitcoin::secp256k1::rand::{thread_rng, Rng};
use bitcoin::util::uint::Uint256;
use crate::commit_verify::TryCommitVerify;
pub type MultiMsg = BTreeMap<sha256::Hash, sha256::Hash>;
pub type Lnpbp4Hash = sha256::Hash;
#[derive(Copy, Clone, Error, Debug, Display)]
#[display(Debug)]
pub struct TooManyMessagesError;
#[derive(
Clone,
PartialEq,
Eq,
PartialOrd,
Ord,
Debug,
Display,
StrictEncode,
StrictDecode,
)]
#[lnpbp_crate(crate)]
#[display(Debug)]
pub struct MultimsgCommitmentItem {
pub protocol: Option<sha256::Hash>,
pub commitment: Lnpbp4Hash,
}
impl MultimsgCommitmentItem {
pub fn new(protocol: Option<sha256::Hash>, commitment: Lnpbp4Hash) -> Self {
Self {
protocol,
commitment,
}
}
}
#[derive(
Clone,
PartialEq,
Eq,
PartialOrd,
Ord,
Debug,
Display,
Default,
StrictEncode,
StrictDecode,
)]
#[lnpbp_crate(crate)]
#[display(Debug)]
pub struct MultimsgCommitment {
pub commitments: Vec<MultimsgCommitmentItem>,
pub entropy: Option<u64>,
}
impl TryCommitVerify<MultiMsg> for MultimsgCommitment {
type Error = TooManyMessagesError;
fn try_commit(multimsg: &MultiMsg) -> 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, (sha256::Hash, sha256::Hash)>::new();
if multimsg.into_iter().all(|(protocol, digest)| {
let rem = Uint256::from_be_bytes(protocol.into_inner())
% Uint256::from_u64(n as u64)
.expect("Bitcoin U256 struct is broken");
ordered
.insert(
rem.low_u64() as usize,
(protocol.clone(), digest.clone()),
)
.is_none()
}) {
break ordered;
}
n += 1;
if n > SORT_LIMIT {
return Err(TooManyMessagesError);
}
};
let entropy = {
let mut rng = thread_rng();
rng.gen::<u64>()
};
let entropy_digest = {
let mut engine = sha256::Hash::engine();
engine.input(&entropy.to_le_bytes());
sha256::Hash::from_engine(engine)
};
let mut commitments = Vec::<_>::with_capacity(n);
for i in 0..n {
match ordered.get(&i) {
None => {
let mut engine = sha256::Hash::engine();
engine.input(&i.to_le_bytes());
engine.input(&entropy_digest[..]);
commitments.push(MultimsgCommitmentItem::new(
None,
sha256::Hash::from_engine(engine),
))
}
Some((contract_id, commitment)) => {
commitments.push(MultimsgCommitmentItem::new(
Some(*contract_id),
*commitment,
))
}
}
}
Ok(Self {
commitments,
entropy: Some(entropy),
})
}
}