use crate::error::*;
use crate::{crypto, DigestAlgorithm};
/// A utility for hashing payloads. Feed your entity body to this, then pass the `finish`
/// result to a request or response.
pub struct PayloadHasher(Box<dyn crypto::Hasher>);

impl PayloadHasher {
    /// Create a new PayloadHasher. The `content_type` should be lower-case and should
    /// not include parameters. The digest is assumed to be the same as the digest used
    /// for the credentials in the request.
    pub fn new<B>(content_type: B, algorithm: DigestAlgorithm) -> Result<Self>
    where
        B: AsRef<[u8]>,
    {
        let mut hasher = PayloadHasher(crypto::new_hasher(algorithm)?);
        hasher.update(b"hawk.1.payload\n")?;
        hasher.update(content_type.as_ref())?;
        hasher.update(b"\n")?;
        Ok(hasher)
    }

    /// Hash a single value and return it
    pub fn hash<B1, B2>(
        content_type: B1,
        algorithm: DigestAlgorithm,
        payload: B2,
    ) -> Result<Vec<u8>>
    where
        B1: AsRef<[u8]>,
        B2: AsRef<[u8]>,
    {
        let mut hasher = PayloadHasher::new(content_type, algorithm)?;
        hasher.update(payload)?;
        hasher.finish()
    }

    /// Update the hash with new data.
    pub fn update<B>(&mut self, data: B) -> Result<()>
    where
        B: AsRef<[u8]>,
    {
        self.0.update(data.as_ref())?;
        Ok(())
    }

    /// Finish hashing and return the result
    ///
    /// Note that this appends a newline to the payload, as does the JS Hawk implementaiton.
    pub fn finish(mut self) -> Result<Vec<u8>> {
        self.update(b"\n")?;
        Ok(self.0.finish()?)
    }
}

#[cfg(all(test, any(feature = "use_ring", feature = "use_openssl")))]
mod tests {
    use super::PayloadHasher;

    #[test]
    fn hash_consistency() -> super::Result<()> {
        let mut hasher1 = PayloadHasher::new("text/plain", crate::SHA256)?;
        hasher1.update("pày")?;
        hasher1.update("load")?;
        let hash1 = hasher1.finish()?;

        let mut hasher2 = PayloadHasher::new("text/plain", crate::SHA256)?;
        hasher2.update("pàyload")?;
        let hash2 = hasher2.finish()?;

        let hash3 = PayloadHasher::hash("text/plain", crate::SHA256, "pàyload")?;

        let hash4 = // "pàyload" as utf-8 bytes
            PayloadHasher::hash("text/plain", crate::SHA256, vec![112, 195, 160, 121, 108, 111, 97, 100])?;

        assert_eq!(
            hash1,
            vec![
                228, 238, 241, 224, 235, 114, 158, 112, 211, 254, 118, 89, 25, 236, 87, 176, 181,
                54, 61, 135, 42, 223, 188, 103, 194, 59, 83, 36, 136, 31, 198, 50
            ]
        );
        assert_eq!(hash2, hash1);
        assert_eq!(hash3, hash1);
        assert_eq!(hash4, hash1);
        Ok(())
    }
}