use base64::{decode, encode};
use basex_rs::{BaseX, Decode, Encode, BITCOIN};
use bitcoin::consensus::encode::{serialize, VarInt};
use ripemd::Ripemd160;
use secp256k1::Secp256k1;
use sha2::{Digest, Sha256};

pub mod error;
pub use error::CryptError as Error;

fn sha256d(input: &[u8]) -> Vec<u8> {
  let mut hasher1 = Sha256::default();
  hasher1.update(input);
  let mut hasher2 = Sha256::default();
  hasher2.update(hasher1.finalize());
  return hasher2.finalize().into_iter().collect();
}

fn hash160(input: &[u8]) -> Vec<u8> {
  let mut hasher1 = Sha256::default();
  hasher1.update(input);
  let mut hasher2 = Ripemd160::default();
  hasher2.update(hasher1.finalize());
  return hasher2.finalize().into_iter().collect();
}

fn serialize_address(public_key: secp256k1::PublicKey) -> String {
  let serialized = public_key.serialize_uncompressed();

  let hashed = hash160(&serialized);
  let version = [0u8];
  let hashed2 = sha256d(&[&version, hashed.as_slice()].concat());
  let out = &[&version, hashed.as_slice(), hashed2.get(0..4).unwrap()].concat();

  BaseX::new(BITCOIN).encode(out)
}

static MSG_SIGN_PREFIX: &'static [u8] = b"\x18Bitcoin Signed Message:\n";

pub fn msg_hash(msg: &[u8]) -> Vec<u8> {
  let bytes;
  bytes = serialize(&VarInt(msg.len() as u64));
  sha256d(&[MSG_SIGN_PREFIX, bytes.as_slice(), msg].concat())
}

/// Verifies that sign is a valid sign for given data and address
/// ```
/// use zeronet_cryptography::verify;
///
/// let data = "Testmessage";
/// let address = "1HZwkjkeaoZfTSaJxDw6aKkxp45agDiEzN";
/// let signature = "G+Hnv6dXxOAmtCj8MwQrOh5m5bV9QrmQi7DSGKiRGm9TWqWP3c5uYxUI/C/c+m9+LtYO26GbVnvuwu7hVPpUdow=";
///
/// match verify(data, address, signature) {
/// 	Ok(_) => println!("Signature is valid."),
/// 	Err(_) => println!("Signature is invalid."),
/// }
/// ```
pub fn verify<T: Into<Vec<u8>>>(data: T, valid_address: &str, sign: &str) -> Result<(), Error> {
  let sig = decode(sign)?;
  let hash = msg_hash(&data.into());

  let (sig_first, sig_r) = match sig.split_first() {
    Some(t) => t,
    None => return Err(Error::DecodeSignatureFailure),
  };

  let rec_id_v = (sig_first - 27) & 3;
  // This is not necessary for ZeroNet's cryptography
  // I've commented it out in case it is needed later.
  // // let rec_compact = (sig_first - 27) & 4 != 0;
  let rec_id = secp256k1::recovery::RecoveryId::from_i32(rec_id_v as i32)?;
  let signature = secp256k1::recovery::RecoverableSignature::from_compact(&sig_r, rec_id)?;
  let message = secp256k1::Message::from_slice(hash.as_slice())?;
  let secp = Secp256k1::new();
  let recovered: secp256k1::PublicKey = secp.recover(&message, &signature)?;
  let address = serialize_address(recovered);

  if address == valid_address {
    return Ok(());
  }
  return Err(Error::AddressMismatch(address));
}

/// Generate a valid signature for given data and private key
/// ```
/// use zeronet_cryptography::sign;
///
/// let data = "Testmessage";
/// let private_key = "5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss";
///
/// match sign(data, private_key) {
/// 	Ok(signature) => println!("The signature is {}", signature),
/// 	Err(_) => println!("An error occured during the signing process"),
/// }
/// ```
pub fn sign<T: Into<Vec<u8>>>(data: T, privkey: &str) -> Result<String, Error> {
  let hex = match BaseX::new(BITCOIN).decode(String::from(privkey)) {
    Some(h) => h,
    None => return Err(Error::PrivateKeyFailure),
  };
  let privkey = secp256k1::SecretKey::from_slice(&hex[1..33])?;
  let hash = msg_hash(&data.into());
  let message = secp256k1::Message::from_slice(hash.as_slice())?;
  let secp = Secp256k1::new();
  let sig = secp.sign_recoverable(&message, &privkey);
  let (rec_id, ser_c) = sig.serialize_compact();
  let ser_c_v: [&[u8]; 2] = [&[(rec_id.to_i32() + 27) as u8], &ser_c];

  let s = encode(&ser_c_v.concat());
  return Ok(s);
}

/// Create a valid key pair
/// ```
/// use zeronet_cryptography::create;
///
/// let (priv_key, pub_key) = create();
/// ```
pub fn create() -> (String, String) {
  let secp = secp256k1::Secp256k1::new();
  let mut rng = secp256k1::rand::thread_rng();
  let (priv_key, address) = secp.generate_keypair(&mut rng);

  let address = serialize_address(address);

  let slice: &[u8] = &priv_key[..];
  let mut bytes = vec![128];
  bytes.extend_from_slice(slice);
  bytes.extend_from_slice(&[92, 91, 187, 38]);
  let priv_key = BaseX::new(BITCOIN).encode(&bytes);

  (priv_key, address)
}

#[cfg(test)]
#[cfg_attr(tarpaulin, ignore)]
mod tests {
  use super::*;

  const PUBKEY: &str = "1HZwkjkeaoZfTSaJxDw6aKkxp45agDiEzN";
  const PRIVKEY: &str = "5KYZdUEo39z3FPrtuX2QbbwGnNP5zTd7yyr2SC1j299sBCnWjss";
  const MESSAGE: &str = "Testmessage";
  const SIGNATURE: &str =
    "G+Hnv6dXxOAmtCj8MwQrOh5m5bV9QrmQi7DSGKiRGm9TWqWP3c5uYxUI/C/c+m9+LtYO26GbVnvuwu7hVPpUdow=";
  const MSG_HASH: &[u8] = &[
    250, 76, 36, 63, 188, 246, 57, 82, 210, 190, 131, 30, 80, 21, 194, 116, 202, 29, 102, 133, 20,
    205, 34, 11, 215, 177, 255, 148, 166, 130, 107, 161,
  ];

  #[test]
  fn test_msg_hash() {
    let result = msg_hash(MESSAGE.as_bytes());
    assert_eq!(result, MSG_HASH);
  }

  #[test]
  fn test_verification() {
    let result = verify(MESSAGE, PUBKEY, SIGNATURE);
    assert_eq!(result.is_ok(), true);

    let result = verify(MESSAGE.as_bytes(), PUBKEY, "i");
    assert_eq!(result.unwrap_err(), Error::DecodeSignatureFailure);
  }

  #[test]
  fn test_signing() {
    let result = super::sign(MESSAGE, PRIVKEY);
    assert_eq!(result.is_ok(), true);
    let result2 = super::verify(MESSAGE, PUBKEY, &result.unwrap());
    assert_eq!(result2.is_ok(), true);
  }

  #[test]
  fn test_creating() {
    let (priv_key, address) = super::create();
    let signature = super::sign(MESSAGE, &priv_key).unwrap();
    let result = super::verify(MESSAGE, &address, &signature);
    assert_eq!(result.is_ok(), true);
  }
}