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use rand::Rng;

const CHACHA_KEY_SIZE: usize = 32;
const CHACHA_IV_SIZE: usize = 8;

extern "C" {
  fn chacha8(data: *const u8, length: usize, key: *const u8, iv: *const u8, cipher: *mut u8);
  fn cn_slow_hash(data: *const u8, length: usize, hash: *mut u8, variant: usize, prehashed: usize);
  fn cn_fast_hash(data: *const u8, length: usize, hash: *mut u8);
  fn secret_key_to_public_key(secret_key: *const u8, public_key: *mut u8) -> bool;
  fn random_scalar(secret_key: *mut u8);
}

pub struct ChachaKey {
  pub data: [u8; CHACHA_KEY_SIZE],
}

pub type Hash = ChachaKey;

pub struct ChachaIV {
  pub data: [u8; CHACHA_IV_SIZE],
}

pub struct Chacha {
  pub key: ChachaKey,
  pub iv: ChachaIV,
}

impl ChachaIV {
  pub fn new() -> ChachaIV {
    let mut rng = rand::thread_rng();
    let mut data: [u8; CHACHA_IV_SIZE] = [0; CHACHA_IV_SIZE];
    for x in &mut data {
      *x = rng.gen();
    }
    ChachaIV { data }
  }
  pub fn from(data: [u8; CHACHA_IV_SIZE]) -> ChachaIV {
    ChachaIV { data }
  }
}

impl Chacha {
  pub fn new(key: ChachaKey, iv: ChachaIV) -> Chacha {
    Chacha { key, iv }
  }
  pub fn encrypt(&self, plain: &[u8]) -> Vec<u8> {
    let mut cipher = vec![0; plain.len()];
    unsafe {
      chacha8(
        plain.as_ptr(),
        plain.len(),
        self.key.data.as_ptr(),
        self.iv.data.as_ptr(),
        cipher.as_mut_ptr(),
      );
    }
    cipher
  }
}

impl ChachaKey {
  pub fn generate(password: String) -> ChachaKey {
    let input = password.as_bytes();
    let mut data: [u8; CHACHA_KEY_SIZE] = [0; CHACHA_KEY_SIZE];
    unsafe {
      cn_slow_hash(input.as_ptr(), input.len(), data.as_mut_ptr(), 0, 0);
    }
    ChachaKey { data }
  }
}

pub fn generate_secret_key() -> [u8; 32] {
  let mut secrete_key: [u8; 32] = [0; 32];
  unsafe {
    random_scalar(secrete_key.as_mut_ptr());
  }
  secrete_key
}

pub fn secret_to_public(secret_key: &[u8; 32]) -> [u8; 32] {
  let mut public_key: [u8; 32] = [0; 32];
  unsafe {
    if !secret_key_to_public_key(secret_key.as_ptr(), public_key.as_mut_ptr()) {
      panic!("Wrong secret key!");
    }
  }
  public_key
}

pub fn fast_hash(data: &[u8]) -> [u8; 32] {
  let mut hash: [u8; 32] = [0; 32];
  unsafe { cn_fast_hash(data.as_ptr(), data.len(), hash.as_mut_ptr()) }
  hash
}

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

  #[test]
  fn should_generate_key_and_cipher_contents() {
    let key = ChachaKey::generate(String::from(""));
    println!("key {:?}", key.data);
    assert!(
      key.data
        == [
          235, 20, 232, 168, 51, 250, 198, 254, 154, 67, 181, 123, 51, 103, 137, 196, 111, 254,
          147, 242, 134, 132, 82, 36, 7, 32, 96, 123, 20, 56, 126, 17
        ]
    );

    let key1 = ChachaKey::generate(String::from("This is a test"));
    println!("key {:?}", key1.data);

    // assert!(key1.data == [97, 48, 56, 52, 102, 48, 49, 100, 49, 52, 51, 55, 97, 48, 57, 99, 54, 57, 56, 53, 52, 48, 49, 98, 54, 48, 100, 52, 51, 53, 53, 52]);
    assert!(
      key1.data
        == [
          160, 132, 240, 29, 20, 55, 160, 156, 105, 133, 64, 27, 96, 212, 53, 84, 174, 16, 88, 2,
          197, 245, 216, 169, 179, 37, 54, 73, 192, 190, 102, 5
        ]
    );

    let _iv = ChachaIV::new();
    let iv = ChachaIV::from([0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18]);
    let chacha = Chacha::new(key, iv);
    let plain = *b"hello world!";
    let cipher = chacha.encrypt(&plain[..]);
    let cipher1 = chacha.encrypt(&cipher[..]);
    assert!(plain == cipher1.as_slice());
  }

  #[test]
  fn should_get_public_key_from_secret_key() {
    let secret_key = [
      50, 228, 229, 247, 39, 151, 194, 252, 14, 45, 218, 78, 128, 230, 27, 208, 9, 57, 52, 163, 5,
      175, 8, 201, 211, 185, 66, 113, 88, 68, 170, 8,
    ];
    let public_key = secret_to_public(&secret_key);
    println!("{:?}", public_key);
    println!("{:?}", public_key);
    assert!(
      public_key
        == [
          81, 76, 248, 201, 237, 192, 109, 39, 58, 159, 67, 13, 120, 203, 91, 70, 36, 216, 162,
          222, 0, 100, 243, 152, 32, 48, 89, 129, 252, 169, 180, 36
        ]
    );
  }

  #[test]
  fn should_get_fast_hash() {
    let input = [
      0x01, 0x3c, 0x01, 0xff, 0x00, 0x01, 0x01, 0x02, 0x9b, 0x2e, 0x4c, 0x02, 0x81, 0xc0, 0xb0,
      0x2e, 0x7c, 0x53, 0x29, 0x1a, 0x94, 0xd1, 0xd0, 0xcb, 0xff, 0x88, 0x83, 0xf8, 0x02, 0x4f,
      0x51, 0x42, 0xee, 0x49, 0x4f, 0xfb, 0xbd, 0x08, 0x80, 0x71, 0x21, 0x01, 0xa9, 0xa4, 0x56,
      0x9f, 0x7e, 0x10, 0x16, 0x4a, 0x32, 0x32, 0x4b, 0x2b, 0x87, 0x8a, 0xe3, 0x2d, 0x98, 0xbe,
      0x09, 0x49, 0xce, 0x6e, 0x01, 0x50, 0xba, 0x1d, 0x7e, 0x54, 0xd6, 0x09, 0x69, 0xe5,
    ];
    let hash = fast_hash(&input);
    assert!(
      hash
        == [
          81, 131, 30, 137, 17, 68, 149, 122, 23, 4, 105, 195, 35, 123, 221, 255, 230, 192, 96, 73,
          129, 38, 117, 210, 237, 178, 168, 52, 82, 247, 162, 80
        ]
    );
    let input = [
      50, 228, 229, 247, 39, 151, 194, 252, 14, 45, 218, 78, 128, 230, 27, 208, 9, 57, 52, 163, 5,
      175, 8, 201, 211, 185, 66, 113, 88, 68, 170, 8,
    ];
    let hash = fast_hash(&input);
    assert!(
      hash
        == [
          197, 173, 69, 56, 117, 95, 205, 188, 226, 116, 198, 205, 121, 235, 248, 74, 211, 46, 177,
          65, 72, 147, 115, 194, 212, 214, 163, 109, 121, 3, 36, 249
        ]
    );
    let input = [50];
    let hash = fast_hash(&input);
    assert!(
      hash
        == [
          173, 124, 91, 239, 2, 120, 22, 168, 0, 218, 23, 54, 68, 79, 181, 138, 128, 126, 244, 201,
          96, 59, 120, 72, 103, 63, 126, 58, 104, 235, 20, 165
        ]
    );
  }

  #[test]
  fn should_get_public_key_from_generated_secret_key() {
    let secret_key = generate_secret_key();
    let public_key = secret_to_public(&secret_key);
    println!("{:?}", secret_key);
    println!("{:?}", public_key);
    assert!(public_key.len() == 32);
  }
}