miden_objects/notes/
note_id.rs

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use alloc::string::String;
use core::fmt::Display;

use super::{Digest, Felt, Hasher, NoteDetails, Word};
use crate::utils::{
    serde::{ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable},
    HexParseError,
};

// NOTE ID
// ================================================================================================

/// Returns a unique identifier of a note, which is simultaneously a commitment to the note.
///
/// Note ID is computed as:
///
/// > hash(recipient, asset_hash),
///
/// where `recipient` is defined as:
///
/// > hash(hash(hash(serial_num, ZERO), script_hash), input_hash)
///
/// This achieves the following properties:
/// - Every note can be reduced to a single unique ID.
/// - To compute a note ID, we do not need to know the note's serial_num. Knowing the hash of the
///   serial_num (as well as script hash, input hash, and note assets) is sufficient.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct NoteId(Digest);

impl NoteId {
    /// Returns a new [NoteId] instantiated from the provided note components.
    pub fn new(recipient: Digest, asset_commitment: Digest) -> Self {
        Self(Hasher::merge(&[recipient, asset_commitment]))
    }

    /// Returns the elements representation of this note ID.
    pub fn as_elements(&self) -> &[Felt] {
        self.0.as_elements()
    }

    /// Returns the byte representation of this note ID.
    pub fn as_bytes(&self) -> [u8; 32] {
        self.0.as_bytes()
    }

    /// Returns a big-endian, hex-encoded string.
    pub fn to_hex(&self) -> String {
        self.0.to_hex()
    }

    /// Returns the digest defining this note ID.
    pub fn inner(&self) -> Digest {
        self.0
    }
}

impl Display for NoteId {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "{}", self.to_hex())
    }
}

// CONVERSIONS INTO NOTE ID
// ================================================================================================

impl From<&NoteDetails> for NoteId {
    fn from(note: &NoteDetails) -> Self {
        Self::new(note.recipient().digest(), note.assets().commitment())
    }
}

impl From<Word> for NoteId {
    fn from(value: Word) -> Self {
        Self(value.into())
    }
}

impl From<Digest> for NoteId {
    fn from(value: Digest) -> Self {
        Self(value)
    }
}

impl NoteId {
    /// Attempts to convert from a hexadecimal string to [NoteId].
    pub fn try_from_hex(hex_value: &str) -> Result<NoteId, HexParseError> {
        Digest::try_from(hex_value).map(NoteId::from)
    }
}

// CONVERSIONS FROM NOTE ID
// ================================================================================================

impl From<NoteId> for Digest {
    fn from(id: NoteId) -> Self {
        id.inner()
    }
}

impl From<NoteId> for Word {
    fn from(id: NoteId) -> Self {
        id.0.into()
    }
}

impl From<NoteId> for [u8; 32] {
    fn from(id: NoteId) -> Self {
        id.0.into()
    }
}

impl From<&NoteId> for Word {
    fn from(id: &NoteId) -> Self {
        id.0.into()
    }
}

impl From<&NoteId> for [u8; 32] {
    fn from(id: &NoteId) -> Self {
        id.0.into()
    }
}

// SERIALIZATION
// ================================================================================================

impl Serializable for NoteId {
    fn write_into<W: ByteWriter>(&self, target: &mut W) {
        target.write_bytes(&self.0.to_bytes());
    }
}

impl Deserializable for NoteId {
    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
        let id = Digest::read_from(source)?;
        Ok(Self(id))
    }
}

#[cfg(test)]
mod tests {
    use alloc::string::ToString;

    use super::NoteId;

    #[test]
    fn note_id_try_from_hex() {
        let note_id_hex = "0xc9d31c82c098e060c9b6e3af2710b3fc5009a1a6f82ef9465f8f35d1f5ba4a80";
        let note_id = NoteId::try_from_hex(note_id_hex).unwrap();

        assert_eq!(note_id.inner().to_string(), note_id_hex)
    }
}