wot-network 0.0.6

Data structures for OpenPGP Web of Trust calculations
Documentation 
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use std::{cmp::Ordering, fmt};

/// The "trust depth" of a [Delegation](crate::Delegation).
///
/// See <https://www.rfc-editor.org/rfc/rfc9580.html#name-trust-signature>
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub enum TrustDepth {
    /// Encoded as 0 on the wire
    None,
    /// Can only be 1..=254
    Limited(u8),
    /// encoded as 255 on the wire
    Unlimited,
}

impl TrustDepth {
    /// Subtract `n` from this TrustDepth
    ///
    /// - `TrustDepth::Unlimited` always stays `TrustDepth::Unlimited`
    /// - `TrustDepth::None` always stays `TrustDepth::None`.
    /// - `TrustDepth::Limited(value)` will be set to `value - 1`.
    ///   If the result would be 0 or negative, `TrustDepth::None` is returned.
    pub fn minus(&self, n: u8) -> TrustDepth {
        match self {
            TrustDepth::Unlimited => TrustDepth::Unlimited,
            TrustDepth::Limited(val) => {
                if *val >= n {
                    TrustDepth::from(val - n)
                } else {
                    TrustDepth::None
                }
            }
            TrustDepth::None => TrustDepth::None,
        }
    }
}

impl From<u8> for TrustDepth {
    fn from(value: u8) -> Self {
        match value {
            0 => Self::None,
            u8::MAX => Self::Unlimited,
            i => Self::Limited(i),
        }
    }
}

impl PartialEq<u8> for TrustDepth {
    fn eq(&self, other: &u8) -> bool {
        match self {
            TrustDepth::None => *other == 0,
            TrustDepth::Limited(val) => val == other,
            TrustDepth::Unlimited => *other == u8::MAX,
        }
    }
}

impl PartialOrd<u8> for TrustDepth {
    fn partial_cmp(&self, other: &u8) -> Option<Ordering> {
        match self {
            TrustDepth::None => 0u8.partial_cmp(other),
            TrustDepth::Limited(val) => val.partial_cmp(other),
            TrustDepth::Unlimited => u8::MAX.partial_cmp(other),
        }
    }
}

impl TrustDepth {
    /// Check if the length of a path is acceptable relative to this TrustDepth.
    ///
    /// For limited trust depth, `path_len` must be below the depth limit.
    /// However, for [`TrustDepth::Unlimited`] any path length is acceptable.
    pub fn acceptable_path_len(&self, path_len: usize) -> bool {
        match self {
            Self::None => false,
            Self::Limited(limit) => (*limit as usize) > path_len,
            Self::Unlimited => true,
        }
    }
}

impl PartialOrd<Self> for TrustDepth {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for TrustDepth {
    fn cmp(&self, other: &TrustDepth) -> Ordering {
        match (*self, other) {
            (Self::Unlimited, Self::Unlimited) => Ordering::Equal,
            (Self::Unlimited, Self::Limited(_) | Self::None) => Ordering::Greater,
            (Self::Limited(_) | Self::None, Self::Unlimited) => Ordering::Less,
            (Self::None, Self::None) => Ordering::Equal,
            (Self::None, Self::Limited(_)) => Ordering::Less,
            (Self::Limited(_), Self::None) => Ordering::Greater,
            (Self::Limited(value), Self::Limited(other)) => value.cmp(other),
        }
    }
}

impl From<TrustDepth> for u8 {
    fn from(value: TrustDepth) -> Self {
        match value {
            TrustDepth::None => 0,
            TrustDepth::Limited(i) => i,
            TrustDepth::Unlimited => u8::MAX,
        }
    }
}

impl fmt::Display for TrustDepth {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            TrustDepth::None => write!(f, "None"),
            TrustDepth::Unlimited => write!(f, "Unlimited"),
            TrustDepth::Limited(val) => write!(f, "{}", val),
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::TrustDepth;

    #[test]
    fn trust_depth() {
        let depth1 = TrustDepth::Limited(0);
        let depth2 = TrustDepth::Limited(1);
        let depth3 = TrustDepth::Unlimited;

        assert!(depth1 < depth2);
        assert!(depth1 < depth3);
        assert!(depth2 < depth3);

        assert_eq!(depth1, depth1);
        assert_eq!(depth2, depth2);
        assert_eq!(depth3, depth3);
    }

    #[test]
    fn acceptable_path_len() {
        assert!(TrustDepth::Limited(10).acceptable_path_len(0));
        assert!(TrustDepth::Limited(10).acceptable_path_len(9));

        assert!(!TrustDepth::Limited(10).acceptable_path_len(10));
        assert!(!TrustDepth::Limited(10).acceptable_path_len(11));

        assert!(TrustDepth::Unlimited.acceptable_path_len(0));
        assert!(TrustDepth::Unlimited.acceptable_path_len(10));
        assert!(TrustDepth::Unlimited.acceptable_path_len(300));
    }
}