use super::{Key, PrivateParts, PublicParts};
use crate::error::{Error, ErrorKind, OsshResult};
use crate::format::ossh_pubkey::*;
use openssl::bn::BigNum;
use openssl::hash::MessageDigest;
use openssl::pkey::{PKey, Private, Public};
use openssl::rsa::{Rsa, RsaRef};
use openssl::sign::{Signer, Verifier};
use std::fmt;

const RSA_DEF_SIZE: usize = 2048;
const RSA_MIN_SIZE: usize = 1024;
const RSA_MAX_SIZE: usize = 16384;
/// The default name of RSA key returned by [`Key::keyname()`](../trait.Key.html#method.keyname)
pub const RSA_NAME: &str = "ssh-rsa";
/// The sha2-256 algorithm name of RSA key returned by [`Key::keyname()`](../trait.Key.html#method.keyname)
pub const RSA_SHA256_NAME: &str = "rsa-sha2-256";
/// The sha2-512 algorithm name of RSA key returned by [`Key::keyname()`](../trait.Key.html#method.keyname)
pub const RSA_SHA512_NAME: &str = "rsa-sha2-512";
/// The short name of the of RSA key returned by [`Key::short_keyname()`](../trait.Key.html#method.short_keyname)
pub const RSA_SHORT_NAME: &str = "RSA";

/// An enum determining the hash function which used to sign or verify
#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
pub enum RsaSignature {
    SHA1,
    SHA2_256,
    #[default]
    SHA2_512,
}

impl RsaSignature {
    /// Parse from key name
    pub fn from_name(s: &str) -> Option<Self> {
        match s {
            RSA_NAME => Some(RsaSignature::SHA1),
            RSA_SHA256_NAME => Some(RsaSignature::SHA2_256),
            RSA_SHA512_NAME => Some(RsaSignature::SHA2_512),
            _ => None,
        }
    }

    /// The name of the algorithm
    pub fn name(self) -> &'static str {
        match self {
            RsaSignature::SHA1 => RSA_NAME,
            RsaSignature::SHA2_256 => RSA_SHA256_NAME,
            RsaSignature::SHA2_512 => RSA_SHA512_NAME,
        }
    }

    fn get_digest(self) -> MessageDigest {
        use RsaSignature::*;
        match self {
            SHA1 => MessageDigest::sha1(),
            SHA2_256 => MessageDigest::sha256(),
            SHA2_512 => MessageDigest::sha512(),
        }
    }
}

/// Represent the RSA public key
#[derive(Debug, Clone)]
pub struct RsaPublicKey {
    rsa: Rsa<Public>,
    signhash: RsaSignature,
}

impl RsaPublicKey {
    /// Create the RSA public key from public components
    pub fn new(n: BigNum, e: BigNum) -> Result<RsaPublicKey, openssl::error::ErrorStack> {
        let rsa = Rsa::from_public_components(n, e)?;
        Ok(RsaPublicKey {
            rsa,
            signhash: RsaSignature::default(),
        })
    }

    /// Create the RSA public key from public components and set the signature hash
    pub fn new_with_signhash(
        n: BigNum,
        e: BigNum,
        sig_hash: RsaSignature,
    ) -> Result<RsaPublicKey, Error> {
        let rsa = Rsa::from_public_components(n, e)?;
        Ok(RsaPublicKey {
            rsa,
            signhash: sig_hash,
        })
    }

    pub(crate) fn from_ossl_rsa(key: Rsa<Public>, signhash: RsaSignature) -> OsshResult<Self> {
        let rsa = Self { rsa: key, signhash };
        if rsa.size() >= RSA_MIN_SIZE && rsa.size() <= RSA_MAX_SIZE {
            Ok(rsa)
        } else {
            Err(ErrorKind::InvalidKeySize.into())
        }
    }

    /// Get the signature hash type
    pub fn sign_type(&self) -> RsaSignature {
        self.signhash
    }

    /// Set the signature hash type
    pub fn set_sign_type(&mut self, sig: RsaSignature) {
        self.signhash = sig;
    }

    pub(crate) fn ossl_rsa(&self) -> &RsaRef<Public> {
        &self.rsa
    }
}

impl Key for RsaPublicKey {
    fn size(&self) -> usize {
        self.rsa.n().num_bits() as usize
    }

    fn keyname(&self) -> &'static str {
        self.signhash.name()
    }

    fn short_keyname(&self) -> &'static str {
        RSA_SHORT_NAME
    }
}

impl PublicParts for RsaPublicKey {
    fn blob(&self) -> Result<Vec<u8>, Error> {
        encode_rsa_pubkey(&self.rsa)
    }

    fn verify(&self, data: &[u8], sig: &[u8]) -> Result<bool, Error> {
        if self.size() < RSA_MIN_SIZE {
            return Err(ErrorKind::InvalidKeySize.into());
        }
        let pkey = PKey::from_rsa(self.rsa.clone())?;
        let mut veri = Verifier::new(self.signhash.get_digest(), &pkey)?;
        veri.update(data)?;
        Ok(veri.verify(sig)?)
    }
}

impl PartialEq for RsaPublicKey {
    fn eq(&self, other: &RsaPublicKey) -> bool {
        self.rsa.e() == other.rsa.e() && self.rsa.n() == other.rsa.n()
    }
}

impl fmt::Display for RsaPublicKey {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.write_str(&serialize_ossh_pubkey(self, "").unwrap())
    }
}

/// Represent the RSA key pair
pub struct RsaKeyPair {
    rsa: Rsa<Private>,
    signhash: RsaSignature,
}

impl RsaKeyPair {
    pub(crate) fn from_ossl_rsa(key: Rsa<Private>, signhash: RsaSignature) -> OsshResult<Self> {
        let rsa = Self { rsa: key, signhash };
        if rsa.size() >= RSA_MIN_SIZE && rsa.size() <= RSA_MAX_SIZE {
            Ok(rsa)
        } else {
            Err(ErrorKind::InvalidKeySize.into())
        }
    }

    pub(crate) fn ossl_rsa(&self) -> &RsaRef<Private> {
        &self.rsa
    }

    /// Generate RSA key pair
    ///
    /// The bits parameter should be within 1024 ~ 16384 bits or `0` to use default length (2048 bits).
    pub fn generate(mut bits: usize) -> OsshResult<Self> {
        if bits == 0 {
            bits = RSA_DEF_SIZE;
        }
        if !(RSA_MIN_SIZE..=RSA_MAX_SIZE).contains(&bits) {
            return Err(Error::from_kind(ErrorKind::InvalidKeySize));
        }
        Ok(RsaKeyPair {
            rsa: Rsa::generate(bits as u32)?,
            signhash: RsaSignature::default(),
        })
    }

    /// Get the signature hash type
    pub fn sign_type(&self) -> RsaSignature {
        self.signhash
    }

    /// Set the signature hash type
    pub fn set_sign_type(&mut self, sig: RsaSignature) {
        self.signhash = sig;
    }

    /// Clone the public parts to generate public key
    pub fn clone_public_key(&self) -> Result<RsaPublicKey, Error> {
        let n = self.rsa.n().to_owned()?;
        let e = self.rsa.e().to_owned()?;
        RsaPublicKey::new_with_signhash(n, e, self.signhash)
    }
}

impl Key for RsaKeyPair {
    fn size(&self) -> usize {
        self.rsa.n().num_bits() as usize
    }

    fn keyname(&self) -> &'static str {
        self.signhash.name()
    }

    fn short_keyname(&self) -> &'static str {
        RSA_SHORT_NAME
    }
}

impl PublicParts for RsaKeyPair {
    fn blob(&self) -> Result<Vec<u8>, Error> {
        encode_rsa_pubkey(&self.rsa)
    }

    fn verify(&self, data: &[u8], sig: &[u8]) -> Result<bool, Error> {
        self.clone_public_key()?.verify(data, sig)
    }
}

impl PrivateParts for RsaKeyPair {
    fn sign(&self, data: &[u8]) -> Result<Vec<u8>, Error> {
        if self.size() < RSA_MIN_SIZE {
            return Err(ErrorKind::InvalidKeySize.into());
        }
        let pkey = PKey::from_rsa(self.rsa.clone())?;
        let mut sign = Signer::new(self.signhash.get_digest(), &pkey)?;
        sign.update(data)?;
        Ok(sign.sign_to_vec()?)
    }
}

#[allow(non_upper_case_globals)]
#[cfg(test)]
mod test {
    use super::*;
    use openssl::bn::BigNum;

    const pub_str: &str = "rsa-sha2-512 AAAAB3NzaC1yc2EAAAADAQABAAABAQC9NCtKoC/4Gk+zS8XGtA5aGC9BeFfcOCg/9C14ph4oHVXzWlR5t3HdHJK6EJGLlC6fj5vI+6cviX7NUbXJXQ/hJe4m4c5AGzubX/jfzNTjBa+hB+5CEqSztA20aHgEWzBwoakhkOd0knT6IvHV/vqTzHVbtfWIiof2SenyHv7yD9RbS9SCmkjISi4wQWzJ1Yu0O1CbH/U1c18WnP46/HBiaJcmV9hk/L3vjSoI7kpjXfSq4d3KLnwsUdrFdhh3eN7K4/ZdnrZC8n1liDXyMAWiaAL8cu8K5wmBmnHTcqIwxYu7g+k46OzcaZxVy0i9hFBM2bzvGvsCJOF3Hh6zF15p";
    const e: [u8; 3] = [0x01, 0x00, 0x01];
    const n: [u8; 0x101] = [
        0x00, 0xbd, 0x34, 0x2b, 0x4a, 0xa0, 0x2f, 0xf8, 0x1a, 0x4f, 0xb3, 0x4b, 0xc5, 0xc6, 0xb4,
        0x0e, 0x5a, 0x18, 0x2f, 0x41, 0x78, 0x57, 0xdc, 0x38, 0x28, 0x3f, 0xf4, 0x2d, 0x78, 0xa6,
        0x1e, 0x28, 0x1d, 0x55, 0xf3, 0x5a, 0x54, 0x79, 0xb7, 0x71, 0xdd, 0x1c, 0x92, 0xba, 0x10,
        0x91, 0x8b, 0x94, 0x2e, 0x9f, 0x8f, 0x9b, 0xc8, 0xfb, 0xa7, 0x2f, 0x89, 0x7e, 0xcd, 0x51,
        0xb5, 0xc9, 0x5d, 0x0f, 0xe1, 0x25, 0xee, 0x26, 0xe1, 0xce, 0x40, 0x1b, 0x3b, 0x9b, 0x5f,
        0xf8, 0xdf, 0xcc, 0xd4, 0xe3, 0x05, 0xaf, 0xa1, 0x07, 0xee, 0x42, 0x12, 0xa4, 0xb3, 0xb4,
        0x0d, 0xb4, 0x68, 0x78, 0x04, 0x5b, 0x30, 0x70, 0xa1, 0xa9, 0x21, 0x90, 0xe7, 0x74, 0x92,
        0x74, 0xfa, 0x22, 0xf1, 0xd5, 0xfe, 0xfa, 0x93, 0xcc, 0x75, 0x5b, 0xb5, 0xf5, 0x88, 0x8a,
        0x87, 0xf6, 0x49, 0xe9, 0xf2, 0x1e, 0xfe, 0xf2, 0x0f, 0xd4, 0x5b, 0x4b, 0xd4, 0x82, 0x9a,
        0x48, 0xc8, 0x4a, 0x2e, 0x30, 0x41, 0x6c, 0xc9, 0xd5, 0x8b, 0xb4, 0x3b, 0x50, 0x9b, 0x1f,
        0xf5, 0x35, 0x73, 0x5f, 0x16, 0x9c, 0xfe, 0x3a, 0xfc, 0x70, 0x62, 0x68, 0x97, 0x26, 0x57,
        0xd8, 0x64, 0xfc, 0xbd, 0xef, 0x8d, 0x2a, 0x08, 0xee, 0x4a, 0x63, 0x5d, 0xf4, 0xaa, 0xe1,
        0xdd, 0xca, 0x2e, 0x7c, 0x2c, 0x51, 0xda, 0xc5, 0x76, 0x18, 0x77, 0x78, 0xde, 0xca, 0xe3,
        0xf6, 0x5d, 0x9e, 0xb6, 0x42, 0xf2, 0x7d, 0x65, 0x88, 0x35, 0xf2, 0x30, 0x05, 0xa2, 0x68,
        0x02, 0xfc, 0x72, 0xef, 0x0a, 0xe7, 0x09, 0x81, 0x9a, 0x71, 0xd3, 0x72, 0xa2, 0x30, 0xc5,
        0x8b, 0xbb, 0x83, 0xe9, 0x38, 0xe8, 0xec, 0xdc, 0x69, 0x9c, 0x55, 0xcb, 0x48, 0xbd, 0x84,
        0x50, 0x4c, 0xd9, 0xbc, 0xef, 0x1a, 0xfb, 0x02, 0x24, 0xe1, 0x77, 0x1e, 0x1e, 0xb3, 0x17,
        0x5e, 0x69,
    ];

    fn get_test_pubkey() -> Result<RsaPublicKey, Error> {
        let rsa_e = BigNum::from_slice(&e)?;
        let rsa_n = BigNum::from_slice(&n)?;
        Ok(RsaPublicKey::new(rsa_n, rsa_e)?)
    }

    #[test]
    fn rsa_publickey_serialize() {
        let key = get_test_pubkey().unwrap();
        assert_eq!(key.to_string(), String::from(pub_str));
    }

    #[test]
    fn rsa_publickey_size() {
        let key = get_test_pubkey().unwrap();
        assert_eq!(key.size(), 2048);
    }
}