kdk_entropy/
error.rs

1use core::fmt;
2
3/// Errors returned by [`crate::dice_to_entropy`] and friends.
4///
5/// Manual `Display` (no `thiserror`) so the error messages stay auditable
6/// and don't accidentally inherit upstream formatting that could leak
7/// secret bytes.
8#[derive(Debug, PartialEq, Eq)]
9pub enum EntropyError {
10    /// Caller supplied fewer rolls than `min_rolls::<FACES, N>()` requires.
11    /// Fields: `(required, given)`.
12    TooFewRolls(usize, usize),
13
14    /// Caller supplied more rolls than `max_rolls::<FACES, N>()` permits.
15    /// Fields: `(allowed, given)`.
16    TooManyRolls(usize, usize),
17
18    /// A roll byte was outside the valid range `1..=FACES`.
19    /// Fields: `(value, index)`.
20    RollOutOfRange(u8, usize),
21
22    /// The `(FACES, N)` generic combination is not one of the supported
23    /// dice configurations (d6/d20 × 16/32 bytes). Fields: `(FACES, N)`.
24    UnsupportedConfig(u8, usize),
25
26    /// A card byte appeared twice in the input — only relevant to
27    /// `deck_to_entropy`. Fields: `(value, second_index)`.
28    DuplicateCard(u8, usize),
29}
30
31impl fmt::Display for EntropyError {
32    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
33        match self {
34            EntropyError::TooFewRolls(required, given) => {
35                write!(f, "too few rolls: required {required}, got {given}")
36            }
37            EntropyError::TooManyRolls(allowed, given) => {
38                write!(
39                    f,
40                    "too many rolls: at most {allowed} permitted, got {given}"
41                )
42            }
43            EntropyError::RollOutOfRange(value, index) => {
44                write!(
45                    f,
46                    "roll at index {index} has value {value}: out of valid range"
47                )
48            }
49            EntropyError::UnsupportedConfig(faces, n) => {
50                write!(
51                    f,
52                    "unsupported (FACES, N) configuration: ({faces}, {n}) — supported: d6/d20 x 16/32 bytes"
53                )
54            }
55            EntropyError::DuplicateCard(value, index) => {
56                write!(f, "card value {value} at index {index} was already drawn")
57            }
58        }
59    }
60}
61
62impl core::error::Error for EntropyError {}
kdk_entropy/error.rs

kdk_entropy/
error.rs
