monoprotocol 0.2.0

use serde::{Deserialize, Serialize};

/// Content-addressed blob reference (BLAKE3).
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct ContentHash(pub [u8; 32]);

impl ContentHash {
    pub fn hash(data: &[u8]) -> Self {
        Self(*blake3::hash(data).as_bytes())
    }

    pub fn hex(&self) -> String {
        self.0.iter().map(|b| format!("{b:02x}")).collect()
    }

    pub fn from_hex(s: &str) -> Option<Self> {
        let s = s.trim();
        if s.len() != 64 {
            return None;
        }
        let mut arr = [0u8; 32];
        for (i, chunk) in s.as_bytes().chunks(2).enumerate() {
            let hi = hex_nibble(chunk.first()?)?;
            let lo = hex_nibble(chunk.get(1)?)?;
            arr[i] = (hi << 4) | lo;
        }
        Some(Self(arr))
    }
}

fn hex_nibble(b: &u8) -> Option<u8> {
    match b {
        b'0'..=b'9' => Some(b - b'0'),
        b'a'..=b'f' => Some(b - b'a' + 10),
        b'A'..=b'F' => Some(b - b'A' + 10),
        _ => None,
    }
}

impl std::fmt::Display for ContentHash {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.hex())
    }
}