pragma solidity ^0.6.1;

contract DSMath {

function add(uint x, uint y) internal pure returns (uint z) {

require((z = x + y) >= x, "ds-math-add-overflow");

}

function sub(uint x, uint y) internal pure returns (uint z) {

require((z = x - y) <= x, "ds-math-sub-underflow");

}

function mul(uint x, uint y) internal pure returns (uint z) {

require(y == 0 || (z = x * y) / y == x, "ds-math-mul-overflow");

}

function min(uint x, uint y) internal pure returns (uint z) {

return x <= y ? x : y;

}

function max(uint x, uint y) internal pure returns (uint z) {

return x >= y ? x : y;

}

function imin(int x, int y) internal pure returns (int z) {

return x <= y ? x : y;

}

function imax(int x, int y) internal pure returns (int z) {

return x >= y ? x : y;

}

uint constant WAD = 10 ** 18;

uint constant RAY = 10 ** 27;

function wmul(uint x, uint y) internal pure returns (uint z) {

z = add(mul(x, y), WAD / 2) / WAD;

}

function rmul(uint x, uint y) internal pure returns (uint z) {

z = add(mul(x, y), RAY / 2) / RAY;

}

function wdiv(uint x, uint y) internal pure returns (uint z) {

z = add(mul(x, WAD), y / 2) / y;

}

function rdiv(uint x, uint y) internal pure returns (uint z) {

z = add(mul(x, RAY), y / 2) / y;

}

// This famous algorithm is called "exponentiation by squaring"

// and calculates x^n with x as fixed-point and n as regular unsigned.

//

// It's O(log n), instead of O(n) for naive repeated multiplication.

//

// These facts are why it works:

//

// If n is even, then x^n = (x^2)^(n/2).

// If n is odd, then x^n = x * x^(n-1),

// and applying the equation for even x gives

// x^n = x * (x^2)^((n-1) / 2).

//

// Also, EVM division is flooring and

// floor[(n-1) / 2] = floor[n / 2].

//

function rpow(uint x, uint n) internal pure returns (uint z) {

z = n % 2 != 0 ? x : RAY;

for (n /= 2; n != 0; n /= 2) {

x = rmul(x, x);

if (n % 2 != 0) {

z = rmul(z, x);

}

}

}

}

contract ScenarioBondingCurve is DSMath {

address payable public beneficiary;

uint public currentSupply;

uint public totalContributed;

mapping (address => uint) public ledger;

mapping (address => uint) public contributions;

mapping (address => uint) public asks;

uint public exponent;

uint public coefficient;

uint public reserveRatio;

uint public constant precision = 1000000000000000000;

string internal constant INSUFFICIENT_ETH = 'Insufficient Ether';

string internal constant INSUFFICIENT_TOKENS = 'Request exceeds token balance';

string internal constant INVALID_ADDRESS = 'Wallet does not exist';

constructor()

public {

beneficiary = 0x4aB6A3307AEfcC05b9de8Dbf3B0a6DEcEBa320E6;

exponent = 2;

coefficient = 10000000000;

reserveRatio = wdiv(4, 5);

currentSupply = 1;

}

function buy(uint amount)

external payable {

uint price = calcMintPrice(amount);

require(msg.value >= price, INSUFFICIENT_ETH);

uint reserveValue = wmul(msg.value, reserveRatio);

uint contributionValue = sub(msg.value, reserveValue);

uint refund = msg.value - reserveValue - contributionValue;

if (refund > 0) {

msg.sender.transfer(refund);

}

ledger[msg.sender] = add(ledger[msg.sender], amount);

currentSupply = add(currentSupply, amount);

contribute(contributionValue, msg.sender);

}

function sell(uint amount)

external {

require(amount <= ledger[msg.sender], INSUFFICIENT_TOKENS);

uint exitValue = calcBurnReward(amount);

msg.sender.transfer(exitValue);

ledger[msg.sender] = sub(ledger[msg.sender], amount);

currentSupply = sub(currentSupply, amount);

}

function lovequit()

external {

require(ledger[msg.sender] > 0, INVALID_ADDRESS);

uint holdings = ledger[msg.sender];

uint exitValue = calcBurnReward(holdings);

currentSupply = sub(currentSupply, holdings);

contribute(exitValue, msg.sender);

ledger[msg.sender] = 0;

}

function contribute(uint amount, address sender)

internal {

beneficiary.transfer(amount);

contributions[sender] = add(contributions[sender], amount);

totalContributed = add(totalContributed, amount);

}

function setBuyPrice(uint amount)

public {

uint price = calcMintPrice(amount);

asks[msg.sender] = price;

}

function getPrice()

public view returns (uint) {

return asks[msg.sender];

}

function setSellPrice(uint amount)

public {

uint price = calcBurnReward(amount);

asks[msg.sender] = price;

}

function integrate(uint limitA, uint limitB, uint multiplier)

internal returns (uint) {

uint raiseExp = exponent + 1;

uint _coefficient = wmul(coefficient, multiplier);

uint upper = wdiv((limitB ** raiseExp), raiseExp);

uint lower = wdiv((limitA ** raiseExp), raiseExp);

return wmul(_coefficient, (sub(upper, lower)));

}

function calcMintPrice(uint amount)

internal returns (uint) {

uint newSupply = add(currentSupply, amount);

uint result = integrate(currentSupply, newSupply, precision);

return result;

}

function calcBurnReward(uint amount)

internal returns (uint) {

uint newSupply = sub(currentSupply, amount);

uint result = integrate(newSupply, currentSupply, reserveRatio);

return result;

}

}