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use credentials::Key;
use base64;
use ring::constant_time;
use std::io::Write;
use std::ops::Deref;
use error::*;
use time;

/// The kind of MAC calcuation (corresponding to the first line of the message)
pub enum MacType {
    Header,
    Response,
    Bewit,
}

/// Mac represents a message authentication code, the signature in a Hawk transaction.
///
/// This class supports creating Macs using the Hawk specification, and comparing Macs
/// using a cosntant-time comparison (thus preventing timing side-channel attacks).
#[derive(Debug, Clone)]
pub struct Mac(Vec<u8>);

impl Mac {
    pub fn new(mac_type: MacType,
               key: &Key,
               ts: time::Timespec,
               nonce: &str,
               method: &str,
               host: &str,
               port: u16,
               path: &str,
               hash: Option<&[u8]>,
               ext: Option<&str>)
               -> Result<Mac> {
        let mut buffer: Vec<u8> = vec![];

        write!(buffer,
               "{}\n",
               match mac_type {
                   MacType::Header => "hawk.1.header",
                   MacType::Response => "hawk.1.response",
                   MacType::Bewit => "hawk.1.bewit",
               })?;
        write!(buffer, "{}\n", ts.sec)?;
        write!(buffer, "{}\n", nonce)?;
        write!(buffer, "{}\n", method)?;
        write!(buffer, "{}\n", path)?;
        write!(buffer, "{}\n", host)?;
        write!(buffer, "{}\n", port)?;

        if let Some(ref h) = hash {
            write!(buffer, "{}\n", base64::encode(h))?;
        } else {
            write!(buffer, "\n")?;
        }

        match ext {
            Some(ref e) => write!(buffer, "{}\n", e)?,
            None => write!(buffer, "\n")?,
        };

        return Ok(Mac(key.sign(buffer.as_ref())));
    }
}

impl AsRef<[u8]> for Mac {
    fn as_ref(&self) -> &[u8] {
        &self.0[..]
    }
}

impl From<Vec<u8>> for Mac {
    fn from(original: Vec<u8>) -> Self {
        Mac(original)
    }
}

impl Deref for Mac {
    type Target = Vec<u8>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl PartialEq for Mac {
    fn eq(&self, other: &Mac) -> bool {
        match constant_time::verify_slices_are_equal(&self.0[..], &other.0[..]) {
            Ok(_) => true,
            Err(_) => false,
        }
    }
}


#[cfg(test)]
mod test {
    use super::{Mac, MacType};
    use time::Timespec;
    use credentials::Key;
    use ring::digest;

    fn key() -> Key {
        Key::new(vec![11u8, 19, 228, 209, 79, 189, 200, 59, 166, 47, 86, 254, 235, 184, 120, 197,
                      75, 152, 201, 79, 115, 61, 111, 242, 219, 187, 173, 14, 227, 108, 60, 232],
                 &digest::SHA256)
    }

    #[test]
    fn test_make_mac() {
        let key = key();
        let mac = Mac::new(MacType::Header,
                           &key,
                           Timespec::new(1000, 100),
                           "nonny",
                           "POST",
                           "mysite.com",
                           443,
                           "/v1/api",
                           None,
                           None)
            .unwrap();
        println!("got {:?}", mac);
        assert!(mac.0 ==
                vec![192, 227, 235, 121, 157, 185, 197, 79, 189, 214, 235, 139, 9, 232, 99, 55,
                     67, 30, 68, 0, 150, 187, 192, 238, 21, 200, 209, 107, 245, 159, 243, 178]);
    }

    #[test]
    fn test_make_mac_hash() {
        let key = key();
        let hash = vec![1, 2, 3, 4, 5];
        let mac = Mac::new(MacType::Header,
                           &key,
                           Timespec::new(1000, 100),
                           "nonny",
                           "POST",
                           "mysite.com",
                           443,
                           "/v1/api",
                           Some(&hash),
                           None)
            .unwrap();
        println!("got {:?}", mac);
        assert!(mac.0 ==
                vec![61, 128, 208, 253, 88, 135, 190, 196, 1, 69, 153, 193, 124, 4, 195, 87, 38,
                     96, 181, 34, 65, 234, 58, 157, 175, 175, 145, 151, 61, 0, 57, 5]);
    }

    #[test]
    fn test_make_mac_ext() {
        let key = key();
        let ext = "ext-data".to_string();
        let mac = Mac::new(MacType::Header,
                           &key,
                           Timespec::new(1000, 100),
                           "nonny",
                           "POST",
                           "mysite.com",
                           443,
                           "/v1/api",
                           None,
                           Some(&ext))
            .unwrap();
        println!("got {:?}", mac);
        assert!(mac.0 ==
                vec![187, 104, 238, 100, 168, 112, 37, 68, 187, 141, 168, 155, 177, 193, 113, 0,
                     50, 105, 127, 36, 24, 117, 200, 251, 138, 199, 108, 14, 105, 123, 234, 119]);
    }
}