// Copyright 2018 MaidSafe.net limited.
//
// This SAFE Network Software is licensed to you under The General Public License (GPL), version 3.
// Unless required by applicable law or agreed to in writing, the SAFE Network Software distributed
// under the GPL Licence is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. Please review the Licences for the specific language governing
// permissions and limitations relating to use of the SAFE Network Software.

use crate::client::id::SafeKey;
use crate::client::MDataInfo;
use crate::crypto::{shared_box, shared_secretbox};
use crate::errors::CoreError;
use crate::utils::{SymEncKey, SymEncNonce, SYM_ENC_KEY_LEN, SYM_ENC_NONCE_LEN};
use crate::DIR_TAG;
use bincode::{deserialize, serialize};
use hmac::Hmac;
use miscreant::aead::Aead;
use miscreant::aead::Aes128SivAead;
use pbkdf2;
use rand::{thread_rng, CryptoRng, Rng};
use safe_nd::{ClientFullId, MDataKind, PublicKey, XorName, XOR_NAME_LEN};
use serde::{Deserialize, Serialize};
use sha3::Sha3_256;
use std::convert::TryInto;
use threshold_crypto;
use tiny_keccak::sha3_256;
use unwrap::unwrap;

const ITERATIONS: usize = 10000;

/// Object representing the User Account information on the network.
#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
pub struct Account {
    /// The User Account Keys.
    pub maid_keys: ClientKeys,
    /// The user's access container.
    pub access_container: MDataInfo,
    /// The user's configuration directory.
    pub config_root: MDataInfo,
    /// Set to `true` when all root and standard containers
    /// have been created successfully. `false` signifies that
    /// previous attempt might have failed - check on login.
    pub root_dirs_created: bool,
}

impl Account {
    /// Creates new Account with a provided set of keys.
    pub fn new(maid_keys: ClientKeys) -> Result<Self, CoreError> {
        Ok(Self {
            maid_keys,
            access_container: MDataInfo::random_private(MDataKind::Seq, DIR_TAG)?,
            config_root: MDataInfo::random_private(MDataKind::Seq, DIR_TAG)?,
            root_dirs_created: false,
        })
    }

    /// Symmetrically encrypts Account using User's credentials.
    ///
    /// Credentials are passed through key-derivation-function first.
    pub fn encrypt(&self, password: &[u8], pin: &[u8]) -> Result<Vec<u8>, CoreError> {
        let serialised_self = serialize(self)?;
        let (key, nonce) = Self::generate_crypto_keys(password, pin)?;
        let mut cipher = Aes128SivAead::new(&key);

        Ok(cipher.seal(&nonce, &[], &serialised_self))
    }

    /// Symmetrically decrypts Account using User's credentials.
    ///
    /// Credentials are passed through key-derivation-function first.
    pub fn decrypt(encrypted_self: &[u8], password: &[u8], pin: &[u8]) -> Result<Self, CoreError> {
        let (key, nonce) = Self::generate_crypto_keys(password, pin)?;
        let mut cipher = Aes128SivAead::new(&key);

        let decrypted_self = cipher
            .open(&nonce, &[], &encrypted_self)
            .map_err(|_| CoreError::SymmetricDecipherFailure)?;

        Ok(deserialize(&decrypted_self)?)
    }

    /// Generates User's Identity for the network using supplied credentials in
    /// a deterministic way.  This is similar to the username in various places.
    pub fn generate_network_id(keyword: &[u8], pin: &[u8]) -> Result<XorName, CoreError> {
        let mut id = XorName([0; XOR_NAME_LEN]);
        Self::derive_key(&mut id.0[..], keyword, pin);

        Ok(id)
    }

    fn generate_crypto_keys(
        password: &[u8],
        pin: &[u8],
    ) -> Result<(SymEncKey, SymEncNonce), CoreError> {
        let mut output = [0; SYM_ENC_KEY_LEN + SYM_ENC_NONCE_LEN];
        Self::derive_key(&mut output[..], password, pin);

        // OK to unwrap here, as we guaranteed the slices have the correct length.
        let key: SymEncKey = unwrap!(output[..SYM_ENC_KEY_LEN].try_into());
        let nonce: SymEncNonce = unwrap!(output[SYM_ENC_KEY_LEN..].try_into());

        Ok((key, nonce))
    }

    fn derive_key(output: &mut [u8], input: &[u8], user_salt: &[u8]) {
        let salt = sha3_256(user_salt);
        pbkdf2::pbkdf2::<Hmac<Sha3_256>>(input, &salt, ITERATIONS, output)
    }
}

/// Client signing and encryption keypairs.
#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
pub struct ClientKeys {
    /// This is the identity of the Client in the Network.
    pub client_id: ClientFullId,
    /// Symmetric encryption key.
    pub enc_key: shared_secretbox::Key,
    /// Encryption public key.
    pub enc_public_key: threshold_crypto::PublicKey,
    /// Encryption private key.
    pub enc_secret_key: shared_box::SecretKey,
}

impl ClientKeys {
    /// Generates random client keys, with an optional seed.
    ///
    /// Only signing keys are generated from the seed.
    pub fn new<T: CryptoRng + Rng>(rng: &mut T) -> Self {
        let (enc_public_key, enc_secret_key) = shared_box::gen_keypair();
        let enc_key = shared_secretbox::gen_key();
        let client_id = ClientFullId::new_bls(rng);

        Self {
            enc_public_key,
            enc_secret_key,
            enc_key,
            client_id,
        }
    }

    /// Converts `ClientKeys` into a Client `SafeKey`.
    pub fn client_safe_key(&self) -> SafeKey {
        SafeKey::client(self.client_id.clone())
    }

    /// Returns the associated public key.
    pub fn public_key(&self) -> PublicKey {
        *self.client_id.public_id().public_key()
    }
}

impl Default for ClientKeys {
    fn default() -> Self {
        Self::new(&mut thread_rng())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use bincode::{deserialize, serialize};
    use std::u32;

    // Test deterministically generating User's Identity for the network using supplied credentials.
    #[test]
    fn generate_network_id() {
        let keyword1 = b"user1";

        let user1_id1 = unwrap!(Account::generate_network_id(keyword1, b"0"));
        let user1_id2 = unwrap!(Account::generate_network_id(keyword1, b"1234"));
        let user1_id3 = unwrap!(Account::generate_network_id(
            keyword1,
            u32::MAX.to_string().as_bytes(),
        ));

        assert_ne!(user1_id1, user1_id2);
        assert_ne!(user1_id1, user1_id3);
        assert_ne!(user1_id2, user1_id3);

        assert_eq!(
            user1_id1,
            unwrap!(Account::generate_network_id(keyword1, b"0"))
        );
        assert_eq!(
            user1_id2,
            unwrap!(Account::generate_network_id(keyword1, b"1234"))
        );
        assert_eq!(
            user1_id3,
            unwrap!(Account::generate_network_id(
                keyword1,
                u32::MAX.to_string().as_bytes(),
            ))
        );

        let keyword2 = b"user2";
        let user1_id = unwrap!(Account::generate_network_id(keyword1, b"248"));
        let user2_id = unwrap!(Account::generate_network_id(keyword2, b"248"));

        assert_ne!(user1_id, user2_id);
    }

    // Test deterministically generating cryptographic keys.
    #[test]
    fn generate_crypto_keys() {
        let password1 = b"super great password";
        let password2 = b"even better password";

        let keys1 = unwrap!(Account::generate_crypto_keys(password1, b"0"));
        let keys2 = unwrap!(Account::generate_crypto_keys(password1, b"1234"));
        let keys3 = unwrap!(Account::generate_crypto_keys(
            password1,
            u32::MAX.to_string().as_bytes(),
        ));
        assert_ne!(keys1, keys2);
        assert_ne!(keys1, keys3);
        assert_ne!(keys2, keys3);

        let keys1 = unwrap!(Account::generate_crypto_keys(password1, b"0"));
        let keys2 = unwrap!(Account::generate_crypto_keys(password2, b"0"));
        assert_ne!(keys1, keys2);

        let keys1 = unwrap!(Account::generate_crypto_keys(password1, b"0"));
        let keys2 = unwrap!(Account::generate_crypto_keys(password1, b"0"));
        assert_eq!(keys1, keys2);
    }

    // Test serialising and deserialising accounts.
    #[test]
    fn serialisation() {
        let account = unwrap!(Account::new(ClientKeys::default()));
        let encoded = unwrap!(serialize(&account));
        let decoded: Account = unwrap!(deserialize(&encoded));

        assert_eq!(decoded, account);
    }

    // Test encryption and decryption of accounts.
    #[test]
    fn encryption() {
        let account = unwrap!(Account::new(ClientKeys::default()));

        let password = b"impossible to guess";
        let pin = b"1000";

        let encrypted = unwrap!(account.encrypt(password, pin));
        let encoded = unwrap!(serialize(&account));
        assert!(!encrypted.is_empty());
        assert_ne!(encrypted, encoded);

        let decrypted = unwrap!(Account::decrypt(&encrypted, password, pin));
        assert_eq!(account, decrypted);
    }
}