commit_verify 0.10.4

// Client-side-validation foundation libraries.
//
// SPDX-License-Identifier: Apache-2.0
//
// Written in 2019-2023 by
//     Dr. Maxim Orlovsky <orlovsky@lnp-bp.org>
//
// Copyright (C) 2019-2023 LNP/BP Standards Association. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::io::Write;

use amplify::confinement::MediumOrdMap;
use amplify::num::u5;
use amplify::{Bytes32, Wrapper};

use crate::id::CommitmentId;
use crate::merkle::MerkleNode;
use crate::{strategies, CommitEncode, CommitStrategy};

/// Map from protocol ids to commitment messages.
pub type MessageMap = MediumOrdMap<ProtocolId, Message>;

/// Source data for creation of multi-message commitments according to [LNPBP-4]
/// procedure.
///
/// [LNPBP-4]: https://github.com/LNP-BP/LNPBPs/blob/master/lnpbp-0004.md
#[derive(Wrapper, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, From, Default)]
#[wrapper(Deref, BorrowSlice, Display, FromStr, Hex, Index, RangeOps)]
#[derive(StrictType, StrictEncode, StrictDecode)]
#[strict_type(lib = crate::LIB_NAME_COMMIT_VERIFY)]
#[cfg_attr(
    feature = "serde",
    derive(Serialize, Deserialize),
    serde(crate = "serde_crate", transparent)
)]
pub struct ProtocolId(
    #[from]
    #[from([u8; 32])]
    Bytes32,
);

impl CommitStrategy for ProtocolId {
    type Strategy = strategies::Strict;
}

impl ProtocolId {
    pub fn from_slice(slice: &[u8]) -> Option<Self> { Bytes32::from_slice(slice).map(Self) }
}

/// Original message participating in multi-message commitment.
///
/// The message must be represented by a 32-byte hash.
#[derive(Wrapper, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, From, Default)]
#[wrapper(Deref, BorrowSlice, Display, FromStr, Hex, Index, RangeOps)]
#[derive(StrictType, StrictEncode, StrictDecode)]
#[strict_type(lib = crate::LIB_NAME_COMMIT_VERIFY)]
#[derive(CommitEncode)]
#[commit_encode(crate = crate, strategy = strict)]
#[cfg_attr(
    feature = "serde",
    derive(Serialize, Deserialize),
    serde(crate = "serde_crate", transparent)
)]
pub struct Message(
    #[from]
    #[from([u8; 32])]
    Bytes32,
);

impl Message {
    pub fn from_slice(slice: &[u8]) -> Option<Self> { Bytes32::from_slice(slice).map(Self) }
}

#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, From)]
pub enum Leaf {
    Inhabited {
        protocol: ProtocolId,
        message: Message,
    },
    Entropy {
        entropy: u64,
        pos: u32,
    },
}

impl Leaf {
    pub fn entropy(entropy: u64, pos: u32) -> Self { Self::Entropy { entropy, pos } }

    pub fn inhabited(protocol: ProtocolId, message: Message) -> Self {
        Self::Inhabited { protocol, message }
    }
}

impl CommitEncode for Leaf {
    fn commit_encode(&self, e: &mut impl Write) {
        match self {
            Leaf::Inhabited { protocol, message } => {
                protocol.commit_encode(e);
                message.commit_encode(e);
            }
            Leaf::Entropy { entropy, pos } => {
                entropy.commit_encode(e);
                pos.commit_encode(e);
            }
        }
    }
}

impl CommitmentId for Leaf {
    const TAG: [u8; 32] = *b"urn:lnpbp:lnpbp0004:leaf:v01#23A";
    type Id = MerkleNode;
}

/// Final [LNPBP-4] commitment value.
///
/// Represents tagged hash of the merkle root of [`super::MerkleTree`] and
/// [`super::MerkleBlock`].
///
/// [LNPBP-4]: https://github.com/LNP-BP/LNPBPs/blob/master/lnpbp-0004.md
#[derive(Wrapper, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, From)]
#[wrapper(Deref, BorrowSlice, Display, FromStr, Hex, Index, RangeOps)]
#[derive(StrictType, StrictDumb, StrictEncode, StrictDecode)]
#[strict_type(lib = crate::LIB_NAME_COMMIT_VERIFY)]
#[cfg_attr(
    feature = "serde",
    derive(Serialize, Deserialize),
    serde(crate = "serde_crate", transparent)
)]
pub struct Commitment(
    #[from]
    #[from([u8; 32])]
    Bytes32,
);

impl CommitStrategy for Commitment {
    type Strategy = strategies::Strict;
}

impl Commitment {
    pub fn from_slice(slice: &[u8]) -> Option<Self> { Bytes32::from_slice(slice).map(Self) }
}

// TODO: Either this type or [`MerkleTree`] should remain
/// Structured source multi-message data for commitment creation
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
pub struct MultiSource {
    /// Minimal depth of the created LNPBP-4 commitment tree
    pub min_depth: u5,
    /// Map of the messages by their respective protocol ids
    pub messages: MessageMap,
}

impl Default for MultiSource {
    fn default() -> Self {
        MultiSource {
            min_depth: u5::with(3),
            messages: Default::default(),
        }
    }
}

/// Helper struct to track depth when merging two merkle blocks.
pub struct MerkleBuoy {
    buoy: u5,
    stack: Option<Box<MerkleBuoy>>,
}

impl MerkleBuoy {
    pub fn new(top: u5) -> Self {
        Self {
            buoy: top,
            stack: None,
        }
    }

    /// Measure the current buoy level.
    pub fn level(&self) -> u5 {
        self.stack
            .as_ref()
            .map(Box::as_ref)
            .map(MerkleBuoy::level)
            .unwrap_or(self.buoy)
    }

    /// Add new item to the buoy.
    ///
    /// Returns whether the buoy have surfaced in a result.
    ///
    /// The buoy surfaces each time the contents it has is reduced to two depth
    /// of the same level.
    pub fn push(&mut self, depth: u5) -> bool {
        if depth == u5::ZERO {
            return false;
        }
        match self
            .stack
            .as_mut()
            .map(|stack| (stack.push(depth), stack.level()))
        {
            None if depth == self.buoy => {
                self.buoy -= 1;
                true
            }
            None => {
                self.stack = Some(Box::new(MerkleBuoy::new(depth)));
                false
            }
            Some((true, level)) => {
                self.stack = None;
                self.push(level)
            }
            Some((false, _)) => false,
        }
    }
}