vector-core 0.2.0

Core library for Vector — the single source of truth for all Vector clients, SDKs, and interfaces.
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//! WebXDC Mini App helpers shared across transports (DM + Community).
//!
//! The realtime-channel topic for a Mini App is minted ONCE at send time and
//! carried on the file event as a `webxdc-topic` tag, so every participant
//! joins the SAME gossip topic. Locally-derived topics are asymmetric in DMs
//! (each side's chat_id is the other party's npub), which silently splits the
//! players onto disjoint topics — the tag is the single source of truth.

/// Mint a fresh realtime-channel topic id for an outbound `.xdc` attachment.
///
/// 32 bytes of SHA-256 over a domain separator + file hash + sender + send-time
/// nanos, encoded base32 (RFC 4648, no padding) — the same codec the miniapp
/// realtime layer's `decode_topic_id` expects, so the tag value round-trips
/// into an iroh `TopicId`. The nanos input makes re-sends of the same file
/// distinct sessions.
pub fn mint_topic_id(file_hash: &str, sender_hex: &str) -> String {
    use sha2::{Digest, Sha256};
    let nanos = std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_nanos())
        .unwrap_or(0);
    let mut hasher = Sha256::new();
    hasher.update(b"webxdc-realtime-v1:");
    hasher.update(file_hash.as_bytes());
    hasher.update(b":");
    hasher.update(sender_hex.as_bytes());
    hasher.update(b":");
    hasher.update(nanos.to_le_bytes());
    base32_nopad_encode(&hasher.finalize())
}

/// BASE32 no-pad encoding (RFC 4648). Mirrors the miniapp realtime layer's
/// codec exactly — the two must agree for topic tags to decode.
pub fn base32_nopad_encode(bytes: &[u8]) -> String {
    const ALPHABET: &[u8; 32] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
    let mut out = String::with_capacity((bytes.len() * 8 + 4) / 5);
    let mut buf: u64 = 0;
    let mut bits: u32 = 0;
    for &b in bytes {
        buf = (buf << 8) | b as u64;
        bits += 8;
        while bits >= 5 {
            bits -= 5;
            out.push(ALPHABET[((buf >> bits) & 0x1F) as usize] as char);
        }
    }
    if bits > 0 {
        out.push(ALPHABET[((buf << (5 - bits)) & 0x1F) as usize] as char);
    }
    out
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn minted_topic_is_32_bytes_base32() {
        let t = mint_topic_id("abc123", "deadbeef");
        // 32 bytes → ceil(256/5) = 52 base32 chars
        assert_eq!(t.len(), 52);
        assert!(t.chars().all(|c| c.is_ascii_uppercase() || ('2'..='7').contains(&c)));
    }

    #[test]
    fn resends_mint_distinct_topics() {
        let a = mint_topic_id("abc123", "deadbeef");
        let b = mint_topic_id("abc123", "deadbeef");
        assert_ne!(a, b, "same file re-sent must start a fresh session topic");
    }

    #[test]
    fn base32_matches_rfc4648_vectors() {
        // RFC 4648 §10 test vectors (padding stripped)
        assert_eq!(base32_nopad_encode(b""), "");
        assert_eq!(base32_nopad_encode(b"f"), "MY");
        assert_eq!(base32_nopad_encode(b"fo"), "MZXQ");
        assert_eq!(base32_nopad_encode(b"foo"), "MZXW6");
        assert_eq!(base32_nopad_encode(b"foob"), "MZXW6YQ");
        assert_eq!(base32_nopad_encode(b"fooba"), "MZXW6YTB");
        assert_eq!(base32_nopad_encode(b"foobar"), "MZXW6YTBOI");
    }
}