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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

use codec::{Decode, Encode, MaxEncodedLen};
use sp_runtime::traits::CheckedAdd;
use sp_std::fmt::Debug;

use crate::common::Types;

/// Wrapper for any kind of entity with a nonce.
/// Nonces are mostly used for replay protection.
/// Initial nonce will be equal to the current block number provided by the system.
#[derive(Encode, Decode, scale_info_derive::TypeInfo, Clone, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
#[cfg_attr(
    feature = "serde",
    serde(bound(
        serialize = "T: Sized, D: serde::Serialize",
        deserialize = "T: Sized, D: serde::Deserialize<'de>"
    ))
)]
#[scale_info(skip_type_params(T))]
#[scale_info(omit_prefix)]
#[codec(encode_bound(D: Encode))]
pub struct WithNonce<T: Types, D> {
    pub nonce: T::BlockNumber,
    #[cfg(test)]
    pub data: D,
    #[cfg(not(test))]
    data: D,
}

impl<T: Types, D: core::fmt::Debug> core::fmt::Debug for WithNonce<T, D> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("WithNonce")
            .field("nonce", &self.nonce)
            .field("data", &self.data)
            .finish()
    }
}

impl<T: Types, D: MaxEncodedLen> MaxEncodedLen for WithNonce<T, D> {
    fn max_encoded_len() -> usize {
        T::BlockNumber::max_encoded_len().saturating_add(D::max_encoded_len())
    }
}

/// A nonce handling-related error.
#[derive(Clone, Copy, Debug)]
pub enum NonceError {
    /// Provided nonce is incorrect, i.e. doesn't equal to the current plus 1.
    IncorrectNonce,
}

#[cfg(test)]
impl From<NonceError> for sp_runtime::DispatchError {
    fn from(_: NonceError) -> Self {
        sp_runtime::DispatchError::Other("Invalid nonce")
    }
}

impl<T: Types, D> WithNonce<T, D> {
    /// Adds a nonce to the given `data`.
    /// Nonce will be equal to the current block number provided by the system.
    pub fn new(data: D) -> Self
    where
        T: frame_system::Config<BlockNumber = <T as Types>::BlockNumber>,
    {
        Self::new_with_nonce(data, 0u8.into())
    }

    /// Adds supplied nonce to the given `data`.
    pub fn new_with_nonce(data: D, nonce: T::BlockNumber) -> Self {
        Self { nonce, data }
    }

    /// Returns read-only reference to the underlying data.
    pub fn data(&self) -> &D {
        &self.data
    }

    /// Takes underlying data. If you would like to update an entity, use `try_update` instead.
    pub fn into_data(self) -> D {
        self.data
    }

    /// Returns next nonce for the given entity.
    pub fn next_nonce(&self) -> Option<T::BlockNumber> {
        self.nonce.checked_add(&1u8.into())
    }

    /// Returns `true` if given nonce is the next nonce for the given entity, i.e. is equal to current nonce plus 1.
    pub fn is_next_nonce(&self, nonce: T::BlockNumber) -> bool {
        Some(nonce) == self.next_nonce()
    }

    /// Returns mutable reference to the underlying data if provided nonce is equal to current nonce plus 1,
    /// otherwise returns an error.
    pub fn try_update(&mut self, nonce: T::BlockNumber) -> Result<&mut D, NonceError> {
        if self.is_next_nonce(nonce) {
            self.nonce = nonce;

            Ok(&mut self.data)
        } else {
            Err(NonceError::IncorrectNonce)
        }
    }

    /// If supplied value is `Some(_)`, attempts to increase current nonce - succeeds if provided nonce is equal to
    /// current nonce plus 1, otherwise returns an error. If value is `None`, `None` will be returned.
    pub fn try_update_opt_with<F, E, R>(
        this_opt: &mut Option<Self>,
        nonce: T::BlockNumber,
        f: F,
    ) -> Option<Result<R, E>>
    where
        F: FnOnce(&mut Option<D>) -> Result<R, E>,
        E: From<NonceError>,
    {
        let mut mapped_opt = match this_opt.take().map(|mut this| {
            this.try_update(nonce)
                .map(drop)
                .map(|()| this)
                .map_err(E::from)
        })? {
            err @ Err(_) => return Some(err.map(|_| unreachable!())),
            Ok(this) => Some(this),
        };

        let res = Self::try_update_opt_without_increasing_nonce_with(&mut mapped_opt, f);
        *this_opt = mapped_opt;

        res
    }

    /// If supplied value is `Some(_)`, will update given entity without increasing nonce.
    pub fn try_update_opt_without_increasing_nonce_with<F, E, R>(
        this_opt: &mut Option<Self>,
        f: F,
    ) -> Option<Result<R, E>>
    where
        F: FnOnce(&mut Option<D>) -> Result<R, E>,
    {
        let this = this_opt.take()?;

        let Self { data, nonce } = this;
        let mut data_opt = Some(data);
        let res: Result<R, E> = (f)(&mut data_opt).map_err(Into::into);
        *this_opt = data_opt.map(|data| Self { data, nonce });

        Some(res)
    }
}