// Unlock account before the login attempt
web3.personal.unlockAccount(req.body.address, req.body.password, function(error, unlocked) {
    console.log(`>>>>> Login - User is unlocked: ${unlocked}`);
    if (unlocked) {

        // Signing/ Encryption
        const addr = req.body.address;
        const msg = req.body.password;
        const hex_msg = '0x' + toHex(msg);
        let signature = web3.eth.sign(addr, hex_msg);

        console.log(`address -----> ${addr}`);
        console.log(`msg ---------> ${msg}`);
        console.log(`hex(msg) ----> ${hex_msg}`);
        console.log(`sig ---------> ${signature}`);

        const r = signature.slice(0, 66)
        const s = '0x' + signature.slice(66, 130)
        const v = '0x' + signature.slice(130, 132)
        const v_decimal = web3.toDecimal(v);

        console.log(`r -----------> ${r}`);
        console.log(`s -----------> ${s}`);
        console.log(`v -----------> ${v}`);
        console.log(`vd ----------> ${v_decimal}`);

        // Validation/Decryption
        const fixed_msg = `x19Ethereum Signed Message:n${msg.length}${msg}`
        const fixed_msg_sha = '0x' + web3.sha3(fixed_msg)

        loginContractInstance.isSigned.call(addr, fixed_msg_sha, v_decimal, r,s, function (err, signed) {
            console.log(`>>>>> Login - Signature: ${signed}`);

            if (signed) {
                // Saving login attempt
                loginContractInstance.successfulLogin.sendTransaction(req.body.address, req.body.password,
                    {from:'6ded1c5b448819a6cde4293e33fbe54583ef5c52', gas:200000},
                    function(err, transactionHash) {
                        if (!err) {
                            console.log(`>>>>> Login - login details (${addr}, ${msg}) successfully saved @ ${transactionHash}`);
                            console.log(`>>>>> Login - Successfully login`);

                        } else {
                            console.log(`>>>>> Login - login transaction failed: ${err}`);
                        }

                        // set primary account to mine
                        web3.eth.coinbase = req.body.address;

                        console.log(`>>>>> Login - Current User: ${web3.eth.coinbase} is logged in`);

                        var balanceWei = web3.eth.getBalance(req.body.address).toNumber();
                        var balance = web3.fromWei(balanceWei, 'ether');
                        res.json({
                            allowedLogin: true,
                            address: req.body.address,
                            balance: balance,
                            token: generateToken(addr)
                        });

                    });
            } else {
                loginContractInstance.recoverAddr.call(addr, fixed_msg_sha, v_decimal, r,s, function(err, actual) {
                    console.log(`>>>>> Login - Failed login: Signature not matched:${addr} = ${actual}`);
                    saveFailedLoginAttempts(loginContractInstance, req, res);
                });
            }
        });
    } else {
        console.log(`>>>>> Login - Failed login: User is locked`);
        saveFailedLoginAttempts(loginContractInstance, req, res);
    }

});

contract Login {

event LoginAttempt(address sender, string password);

address private sender;
string private password;

function successfulLogin (address _sender, string _password) public {
    LoginAttempt(_sender, _password);
    sender = _sender;
    password = _password;
}

function failedLogin (address _sender, string _password) public {
    LoginAttempt(_sender, _password);
}

function recoverAddr(bytes32 msgHash, uint8 v, bytes32 r, bytes32 s) public pure returns (address) {
    return ecrecover(msgHash, v, r, s);
}

function isSigned(address _addr, bytes32 msgHash, uint8 v, bytes32 r, bytes32 s) public pure returns (bool) {
    return ecrecover(msgHash, v, r, s) == _addr;
}