use salsa20::{

   cipher::{generic_array::GenericArray, NewCipher, StreamCipher},

   Salsa20, XSalsa20,

 };

 const KEY_BYTES: usize = 32;

 const IV_BYTES: usize = 8;

 const IV_BYTES_XSALSA20: usize = 24;

 const IV_XSALSA20: [u8; IV_BYTES_XSALSA20] = *b"24-byte nonce for xsalsa";

 const KEY_XSALSA20: [u8; KEY_BYTES] = *b"this is 32-byte key for xsalsa20";

 const IV0: [u8; IV_BYTES] = [0; IV_BYTES];

 const IV1: [u8; IV_BYTES] = [0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00];

 const IVHI: [u8; IV_BYTES] = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01];

 const KEY0: [u8; KEY_BYTES] = [

   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

   0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

 ];

 const KEY1: [u8; KEY_BYTES] = [

   0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

   0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

 ];

 const EXPECTED_KEY1_IV0: [u8; 64] = [

   0xe3, 0xbe, 0x8f, 0xdd, 0x8b, 0xec, 0xa2, 0xe3, 0xea, 0x8e, 0xf9, 0x47, 0x5b,

   0x29, 0xa6, 0xe7, 0x00, 0x39, 0x51, 0xe1, 0x09, 0x7a, 0x5c, 0x38, 0xd2, 0x3b,

   0x7a, 0x5f, 0xad, 0x9f, 0x68, 0x44, 0xb2, 0x2c, 0x97, 0x55, 0x9e, 0x27, 0x23,

   0xc7, 0xcb, 0xbd, 0x3f, 0xe4, 0xfc, 0x8d, 0x9a, 0x07, 0x44, 0x65, 0x2a, 0x83,

   0xe7, 0x2a, 0x9c, 0x46, 0x18, 0x76, 0xaf, 0x4d, 0x7e, 0xf1, 0xa1, 0x17,

 ];

 const EXPECTED_KEY0_IV1: [u8; 64] = [

   0x2a, 0xba, 0x3d, 0xc4, 0x5b, 0x49, 0x47, 0x00, 0x7b, 0x14, 0xc8, 0x51, 0xcd,

   0x69, 0x44, 0x56, 0xb3, 0x03, 0xad, 0x59, 0xa4, 0x65, 0x66, 0x28, 0x03, 0x00,

   0x67, 0x05, 0x67, 0x3d, 0x6c, 0x3e, 0x29, 0xf1, 0xd3, 0x51, 0x0d, 0xfc, 0x04,

   0x05, 0x46, 0x3c, 0x03, 0x41, 0x4e, 0x0e, 0x07, 0xe3, 0x59, 0xf1, 0xf1, 0x81,

   0x6c, 0x68, 0xb2, 0x43, 0x4a, 0x19, 0xd3, 0xee, 0xe0, 0x46, 0x48, 0x73,

 ];

 const EXPECTED_KEY0_IVHI: [u8; 64] = [

   0xb4, 0x7f, 0x96, 0xaa, 0x96, 0x78, 0x61, 0x35, 0x29, 0x7a, 0x3c, 0x4e, 0xc5,

   0x6a, 0x61, 0x3d, 0x0b, 0x80, 0x09, 0x53, 0x24, 0xff, 0x43, 0x23, 0x9d, 0x68,

   0x4c, 0x57, 0xff, 0xe4, 0x2e, 0x1c, 0x44, 0xf3, 0xcc, 0x01, 0x16, 0x13, 0xdb,

   0x6c, 0xdc, 0x88, 0x09, 0x99, 0xa1, 0xe6, 0x5a, 0xed, 0x12, 0x87, 0xfc, 0xb1,

   0x1c, 0x83, 0x9c, 0x37, 0x12, 0x07, 0x65, 0xaf, 0xa7, 0x3e, 0x50, 0x75,

 ];

 const EXPECTED_XSALSA20_ZEROS: [u8; 64] = [

   0x48, 0x48, 0x29, 0x7f, 0xeb, 0x1f, 0xb5, 0x2f, 0xb6, 0x6d, 0x81, 0x60, 0x9b,

   0xd5, 0x47, 0xfa, 0xbc, 0xbe, 0x70, 0x26, 0xed, 0xc8, 0xb5, 0xe5, 0xe4, 0x49,

   0xd0, 0x88, 0xbf, 0xa6, 0x9c, 0x08, 0x8f, 0x5d, 0x8d, 0xa1, 0xd7, 0x91, 0x26,

   0x7c, 0x2c, 0x19, 0x5a, 0x7f, 0x8c, 0xae, 0x9c, 0x4b, 0x40, 0x50, 0xd0, 0x8c,

   0xe6, 0xd3, 0xa1, 0x51, 0xec, 0x26, 0x5f, 0x3a, 0x58, 0xe4, 0x76, 0x48,

 ];

 const EXPECTED_XSALSA20_HELLO_WORLD: [u8; 12] = [

   0x00, 0x2d, 0x45, 0x13, 0x84, 0x3f, 0xc2, 0x40, 0xc4, 0x01, 0xe5, 0x41,

 ];

 #[test]

 fn salsa20_key1_iv0() {

   let mut cipher =

     Salsa20::new(&GenericArray::from(KEY1), &GenericArray::from(IV0));

   let mut buf = [0; 64];

   cipher.apply_keystream(&mut buf);

   for i in 0..64 {

     assert_eq!(buf[i], EXPECTED_KEY1_IV0[i])

   }

 }

 #[test]

 fn salsa20_key0_iv1() {

   let mut cipher =

     Salsa20::new(&GenericArray::from(KEY0), &GenericArray::from(IV1));

   let mut buf = [0; 64];

   cipher.apply_keystream(&mut buf);

   for i in 0..64 {

     assert_eq!(buf[i], EXPECTED_KEY0_IV1[i])

   }

 }

 #[test]

 fn salsa20_key0_ivhi() {

   let mut cipher =

     Salsa20::new(&GenericArray::from(KEY0), &GenericArray::from(IVHI));

   let mut buf = [0; 64];

   cipher.apply_keystream(&mut buf);

   for i in 0..64 {

     assert_eq!(buf[i], EXPECTED_KEY0_IVHI[i])

   }

 }

 #[test]

 fn xsalsa20_encrypt_zeros() {

   let key = GenericArray::from(KEY_XSALSA20);

   let iv = GenericArray::from(IV_XSALSA20);

   let mut cipher = XSalsa20::new(&key, &iv);

   let mut buf = [0; 64];

   cipher.apply_keystream(&mut buf);

   for i in 0..64 {

     assert_eq!(buf[i], EXPECTED_XSALSA20_ZEROS[i]);

   }

 }

 #[test]

 fn xsalsa20_encrypt_hello_world() {

   let key = GenericArray::from(KEY_XSALSA20);

   let iv = GenericArray::from(IV_XSALSA20);

   let mut cipher = XSalsa20::new(&key, &iv);

   let mut buf = *b"Hello world!";

   cipher.apply_keystream(&mut buf);

   assert_eq!(buf, EXPECTED_XSALSA20_HELLO_WORLD);

 }

 /// ed-25519 test gen_keypair

 #[test]

 fn gen_keypair() {

   use crate::{PUBLIC_KEY_LENGTH, SECRET_KEY_LENGTH};

   // use ed25519::signature::Signature;

   use ed25519_dalek::*;

   use hex::FromHex;

   let secret_key: &[u8] =

     b"833fe62409237b9d62ec77587520911e9a759cec1d19755b7da901b96dca3d42";

   let public_key: &[u8] =

     b"ec172b93ad5e563bf4932c70e1245034c35467ef2efd4d64ebf819683467e2bf";

   let message: &[u8] = b"616263";

   let signature: &[u8] = b"98a70222f0b8121aa9d30f813d683f809e462b469c7ff87639499bb94e6dae4131f85042463c2a355a2003d062adf5aaa10b8c61e636062aaad11c2a26083406";

   let sec_bytes: Vec<u8> = FromHex::from_hex(secret_key).unwrap();

   let pub_bytes: Vec<u8> = FromHex::from_hex(public_key).unwrap();

   let msg_bytes: Vec<u8> = FromHex::from_hex(message).unwrap();

   let sig_bytes: Vec<u8> = FromHex::from_hex(signature).unwrap();

   let secret: SecretKey =

     SecretKey::from_bytes(&sec_bytes[..SECRET_KEY_LENGTH]).unwrap();

   let public: PublicKey =

     PublicKey::from_bytes(&pub_bytes[..PUBLIC_KEY_LENGTH]).unwrap();

   let keypair: Keypair = Keypair { secret, public };

   let sig1: Signature = Signature::from_bytes(&sig_bytes[..]).unwrap();

   let mut prehash_for_signing: Sha512 = Sha512::default();

   let mut prehash_for_verifying: Sha512 = Sha512::default();

   prehash_for_signing.update(&msg_bytes[..]);

   prehash_for_verifying.update(&msg_bytes[..]);

   let sig2: Signature =

     keypair.sign_prehashed(prehash_for_signing, None).unwrap();

   assert!(

     sig1 == sig2,

     "Original signature from test vectors doesn't equal signature produced:\

                 \noriginal:\n{:?}\nproduced:\n{:?}",

     sig1,

     sig2

   );

   assert!(

     keypair

       .verify_prehashed(prehash_for_verifying, None, &sig2)

       .is_ok(),

     "Could not verify ed25519ph signature!"

   );

 }