hashjunkie 0.5.2

use crate::{DigestValue, hashes::Hasher};

const PARALLEL_UPDATE_MIN: usize = 128 * 1024;
const PARALLEL_UPDATE_BATCH: usize = 16 * 1024 * 1024;

pub struct Blake3Hasher {
    inner: blake3::Hasher,
    pending: Vec<u8>,
}

impl Blake3Hasher {
    pub fn new() -> Self {
        Self {
            inner: blake3::Hasher::new(),
            pending: Vec::new(),
        }
    }

    fn flush_pending(&mut self) {
        if self.pending.is_empty() {
            return;
        }

        if self.pending.len() >= PARALLEL_UPDATE_MIN {
            self.inner.update_rayon(&self.pending);
        } else {
            self.inner.update(&self.pending);
        }
        self.pending.clear();
    }
}

impl Default for Blake3Hasher {
    fn default() -> Self {
        Self::new()
    }
}

impl Hasher for Blake3Hasher {
    fn update(&mut self, data: &[u8]) {
        if data.len() >= PARALLEL_UPDATE_BATCH {
            self.flush_pending();
            self.inner.update_rayon(data);
            return;
        }

        self.pending.extend_from_slice(data);
        if self.pending.len() >= PARALLEL_UPDATE_BATCH {
            self.flush_pending();
        }
    }

    fn finalize_hex(self: Box<Self>) -> String {
        self.finalize_digest().standard().to_string()
    }

    fn finalize_digest(mut self: Box<Self>) -> DigestValue {
        self.flush_pending();
        DigestValue::from_raw_hex(self.inner.finalize().as_bytes().to_vec())
    }
}

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

    fn hash(data: &[u8]) -> String {
        let mut h = Blake3Hasher::new();
        h.update(data);
        Box::new(h).finalize_hex()
    }

    // Official BLAKE3 test vectors from github.com/BLAKE3-team/BLAKE3
    #[test]
    fn blake3_empty() {
        assert_eq!(
            hash(b""),
            "af1349b9f5f9a1a6a0404dea36dcc9499bcb25c9adc112b7cc9a93cae41f3262"
        );
    }

    #[test]
    fn blake3_abc() {
        assert_eq!(
            hash(b"abc"),
            "6437b3ac38465133ffb63b75273a8db548c558465d79db03fd359c6cd5bd9d85"
        );
    }

    #[test]
    fn default_equals_new() {
        let mut h = Blake3Hasher::default();
        h.update(b"abc");
        assert_eq!(Box::new(h).finalize_hex(), hash(b"abc"));
    }

    #[test]
    fn chunked_matches_single() {
        let data = b"the quick brown fox jumps over the lazy dog";
        let single = hash(data);
        let mut h = Blake3Hasher::new();
        for chunk in data.chunks(5) {
            h.update(chunk);
        }
        assert_eq!(Box::new(h).finalize_hex(), single);
    }

    #[test]
    fn parallel_batches_match_single_update() {
        let data = (0..(PARALLEL_UPDATE_BATCH + PARALLEL_UPDATE_MIN + 17))
            .map(|i| (i % 251) as u8)
            .collect::<Vec<_>>();

        let single = hash(&data);

        let mut chunked = Blake3Hasher::new();
        for chunk in data.chunks(64 * 1024) {
            chunked.update(chunk);
        }

        assert_eq!(Box::new(chunked).finalize_hex(), single);
    }
}