//! All structures related to Noise parameter definitions (cryptographic primitive choices, protocol
//! patterns/names)

#[allow(unused_imports)]
#[cfg(feature = "nightly")]
use std::convert::TryFrom;

#[allow(unused_imports)]
#[cfg(not(feature = "nightly"))]
use utils::TryFrom;

use std::str::FromStr;
mod patterns;

pub use self::patterns::*;

/// I recommend you choose `Noise`.
#[derive(PartialEq, Copy, Clone, Debug)]
pub enum BaseChoice {
    Noise,
}

impl FromStr for BaseChoice {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        use self::BaseChoice::*;
        match s {
            "Noise"    => Ok(Noise),
            _          => Err("base type unsupported"),
        }
    }
}

/// One of `25519` or `448`, per the spec.
#[derive(PartialEq, Copy, Clone, Debug)]
pub enum DHChoice {
    Curve25519,
    Ed448,
}

impl FromStr for DHChoice {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        use self::DHChoice::*;
        match s {
            "25519" => Ok(Curve25519),
            "448"   => Ok(Ed448),
            _       => Err("DH type unsupported")
        }
    }
}

/// One of `ChaChaPoly` or `AESGCM`, per the spec.
#[derive(PartialEq, Copy, Clone, Debug)]
pub enum CipherChoice {
    ChaChaPoly,
    AESGCM,
}

impl FromStr for CipherChoice {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        use self::CipherChoice::*;
        match s {
            "ChaChaPoly" => Ok(ChaChaPoly),
            "AESGCM"     => Ok(AESGCM),
            _            => Err("cipher type unsupported")
        }
    }
}

/// One of the supported SHA-family or BLAKE-family hash choices, per the spec.
#[derive(PartialEq, Copy, Clone, Debug)]
pub enum HashChoice {
    SHA256,
    SHA512,
    Blake2s,
    Blake2b,
}

impl FromStr for HashChoice {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        use self::HashChoice::*;
        match s {
            "SHA256"  => Ok(SHA256),
            "SHA512"  => Ok(SHA512),
            "BLAKE2s" => Ok(Blake2s),
            "BLAKE2b" => Ok(Blake2b),
            _         => Err("hash type unsupported")
        }
    }
}

/// The set of choices (as specified in the Noise spec) that constitute a full protocol definition.
///
/// See: [Chapter 11: Protocol Names](http://noiseprotocol.org/noise.html#protocol-names).
///
/// # Examples
///
/// From a string definition:
///
/// ```
/// # use snow::params::*;
///
/// let params: NoiseParams = "Noise_XX_25519_AESGCM_SHA256".parse().unwrap();
/// ```
#[derive(PartialEq, Clone, Debug)]
pub struct NoiseParams {
    pub name: String,
    pub base: BaseChoice,
    pub handshake: HandshakeChoice,
    pub dh: DHChoice,
    pub cipher: CipherChoice,
    pub hash: HashChoice,
}

impl NoiseParams {

    /// Construct a new NoiseParams via specifying enums directly.
    pub fn new(name: String,
               base: BaseChoice,
               handshake: HandshakeChoice,
               dh: DHChoice,
               cipher: CipherChoice,
               hash: HashChoice) -> Self
    {
        NoiseParams { name, base, handshake, dh, cipher, hash }
    }
}

impl FromStr for NoiseParams {
    type Err = &'static str;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut split = s.split('_');
        static TOO_FEW: &'static str = "too few parameters";
        Ok(NoiseParams::new(s.to_owned(),
                            split.next().ok_or(TOO_FEW)?.parse()?,
                            split.next().ok_or(TOO_FEW)?.parse()?,
                            split.next().ok_or(TOO_FEW)?.parse()?,
                            split.next().ok_or(TOO_FEW)?.parse()?,
                            split.next().ok_or(TOO_FEW)?.parse()?))
    }
}

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

    #[test]
    fn test_simple_handshake() {
        let _: HandshakePattern = "XX".parse().unwrap();
    }

    #[test]
    fn test_basic() {
        let p: NoiseParams = "Noise_XX_25519_AESGCM_SHA256".parse().unwrap();
        assert!(p.handshake.modifiers.list.is_empty());
    }

    #[test]
    fn test_fallback_mod() {
        let p: NoiseParams = "Noise_XXfallback_25519_AESGCM_SHA256".parse().unwrap();
        assert!(p.handshake.modifiers.list[0] == HandshakeModifier::Fallback);
    }

    #[test]
    fn test_psk_fallback_mod() {
        let p: NoiseParams = "Noise_XXfallback+psk0_25519_AESGCM_SHA256".parse().unwrap();
        assert!(p.handshake.modifiers.list.len() == 2);
    }

    #[test]
    fn test_single_psk_mod() {
        let p: NoiseParams = "Noise_XXpsk0_25519_AESGCM_SHA256".parse().unwrap();
        match p.handshake.modifiers.list[0] {
            HandshakeModifier::Psk(0) => {},
            _ => panic!("modifier isn't as expected!")
        }
    }

    #[test]
    fn test_multi_psk_mod() {
        use self::HandshakeModifier::*;

        let p: NoiseParams = "Noise_XXpsk0+psk1+psk2_25519_AESGCM_SHA256".parse().unwrap();
        let mods = p.handshake.modifiers.list;
        match (mods[0], mods[1], mods[2]) {
            (Psk(0), Psk(1), Psk(2)) => {},
            _ => panic!("modifiers weren't as expected! actual: {:?}", mods)
        }
    }

    #[test]
    fn test_modified_psk_handshake() {
        let p: NoiseParams = "Noise_XXpsk0_25519_AESGCM_SHA256".parse().unwrap();
        let tokens = HandshakeTokens::try_from(p.handshake).unwrap();
        match tokens.msg_patterns[0][0] {
            Token::Psk(_) => {},
            _ => panic!("missing token!")
        }
    }

    #[test]
    fn test_modified_multi_psk_handshake() {
        let p: NoiseParams = "Noise_XXpsk0+psk2_25519_AESGCM_SHA256".parse().unwrap();

        let tokens = HandshakeTokens::try_from(p.handshake).unwrap();

        match tokens.msg_patterns[0][0] {
            Token::Psk(_) => {},
            _ => panic!("missing token!")
        }

        let second = &tokens.msg_patterns[1];
        match second[second.len()-1] {
            Token::Psk(_) => {},
            _ => panic!("missing token!")
        }
    }
}