jam-std-common 0.1.16

use super::hashing::keccak_concat;
use jam_types::{Hash, MmrPeakHash};
use scale::{Decode, Encode};

#[derive(Debug, Encode, Decode, Eq, PartialEq, Clone, Default)]
pub struct Mmr {
	pub peaks: Vec<Option<Hash>>,
}

impl Mmr {
	/// Construct an empty MMR.
	pub fn new() -> Self {
		Default::default()
	}

	/// Append a new peak to the MMR.
	pub fn append(&mut self, mut peak: Hash) {
		for height in 0..usize::MAX {
			match self.peaks.get_mut(height) {
				None => {
					self.peaks.push(Some(peak));
					break
				},
				Some(p) => match p.take() {
					None => {
						*p = Some(peak);
						break
					},
					Some(left) => peak = keccak_concat([&left[..], &peak[..]]),
				},
			}
		}
	}

	/// MMR root.
	pub fn root(&self) -> MmrPeakHash {
		let mut iter = self.peaks.iter().filter_map(Option::as_ref);
		let mut root = iter.next().cloned().unwrap_or_default();
		for node in iter {
			root = keccak_concat([b"peak", &root[..], &node[..]]);
		}
		root.into()
	}
}