1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128

use alloc::string::ToString;

use super::{
    AccountId, ByteReader, ByteWriter, Deserializable, DeserializationError, Felt, NoteError,
    NoteTag, NoteType, Serializable, Word,
};

// NOTE METADATA
// ================================================================================================

/// Metadata associated with a note.
///
/// Note type and tag must be internally consistent according to the following rules:
///
/// - For off-chain notes, the most significant bit of the tag must be 0.
/// - For public notes, the second most significant bit of the tag must be 0.
/// - For encrypted notes, two most significant bits of the tag must be 00.
///
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct NoteMetadata {
    /// The ID of the account which created the note.
    sender: AccountId,

    /// Defines how the note is to be stored (e.g., on-chain or off-chain).
    note_type: NoteType,

    /// A value which can be used by the recipient(s) to identify notes intended for them.
    tag: NoteTag,

    /// An arbitrary user-defined value.
    aux: Felt,
}

impl NoteMetadata {
    /// Returns a new [NoteMetadata] instantiated with the specified parameters.
    ///
    /// # Errors
    /// Returns an error if the note type and note tag are inconsistent.
    pub fn new(
        sender: AccountId,
        note_type: NoteType,
        tag: NoteTag,
        aux: Felt,
    ) -> Result<Self, NoteError> {
        let tag = tag.validate(note_type)?;
        Ok(Self { sender, note_type, tag, aux })
    }

    /// Returns the account which created the note.
    pub fn sender(&self) -> AccountId {
        self.sender
    }

    /// Returns the note's type.
    pub fn note_type(&self) -> NoteType {
        self.note_type
    }

    /// Returns the tag associated with the note.
    pub fn tag(&self) -> NoteTag {
        self.tag
    }

    /// Returns the note's aux field.
    pub fn aux(&self) -> Felt {
        self.aux
    }

    /// Returns `true` if the note is off-chain.
    pub fn is_offchain(&self) -> bool {
        self.note_type == NoteType::OffChain
    }
}

impl From<NoteMetadata> for Word {
    fn from(metadata: NoteMetadata) -> Self {
        (&metadata).into()
    }
}

impl From<&NoteMetadata> for Word {
    fn from(metadata: &NoteMetadata) -> Self {
        let mut elements = Word::default();
        elements[0] = metadata.tag.inner().into();
        elements[1] = metadata.sender.into();
        elements[2] = metadata.note_type.into();
        elements[3] = metadata.aux;
        elements
    }
}

impl TryFrom<Word> for NoteMetadata {
    type Error = NoteError;

    fn try_from(elements: Word) -> Result<Self, Self::Error> {
        let sender = elements[1].try_into().map_err(NoteError::InvalidNoteSender)?;
        let note_type = elements[2].try_into()?;
        let tag: u64 = elements[0].into();
        let tag: u32 =
            tag.try_into().map_err(|_| NoteError::InconsistentNoteTag(note_type, tag))?;
        Self::new(sender, note_type, tag.into(), elements[3])
    }
}

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

impl Serializable for NoteMetadata {
    fn write_into<W: ByteWriter>(&self, target: &mut W) {
        self.sender.write_into(target);
        self.note_type.write_into(target);
        self.tag.write_into(target);
        self.aux.write_into(target);
    }
}

impl Deserializable for NoteMetadata {
    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
        let sender = AccountId::read_from(source)?;
        let note_type = NoteType::read_from(source)?;
        let tag = NoteTag::read_from(source)?;
        let aux = Felt::read_from(source)?;

        Self::new(sender, note_type, tag, aux)
            .map_err(|err| DeserializationError::InvalidValue(err.to_string()))
    }
}