// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.5.0;

interface IOreoSwapBEP20 {
  event Approval(address indexed owner, address indexed spender, uint value);
  event Transfer(address indexed from, address indexed to, uint value);

  function name() external view returns (string memory);
  function symbol() external view returns (string memory);
  function decimals() external view returns (uint8);
  function totalSupply() external view returns (uint);
  function balanceOf(address owner) external view returns (uint);
  function allowance(address owner, address spender) external view returns (uint);

  function approve(address spender, uint value) external returns (bool);
  function transfer(address to, uint value) external returns (bool);
  function transferFrom(address from, address to, uint value) external returns (bool);
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.5.0;

interface IOreoSwapCallee {
  function OreoSwapCall(address sender, uint amount0, uint amount1, bytes calldata data) external;
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.5.0;

interface IOreoSwapFactory {
  event PairCreated(address indexed token0, address indexed token1, address pair, uint);

  function feeTo() external view returns (address);
  function feeToSetter() external view returns (address);

  function getPair(address tokenA, address tokenB) external view returns (address pair);
  function allPairs(uint) external view returns (address pair);
  function allPairsLength() external view returns (uint);

  function createPair(address tokenA, address tokenB) external returns (address pair);

  function setFeeTo(address) external;
  function setFeeToSetter(address) external;
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity =0.6.12;

import './libraries/OreoSwapSafeMath.sol';

contract OreoSwapLP {
  using OreoSwapSafeMath for uint;

  string public constant name = 'OreoSwap LP Token';
  string public constant symbol = 'Oreo-LP';
  uint8 public constant decimals = 18;
  uint  public totalSupply;
  mapping(address => uint) public balanceOf;
  mapping(address => mapping(address => uint)) public allowance;

  bytes32 public DOMAIN_SEPARATOR;
  // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
  bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
  mapping(address => uint) public nonces;

  event Approval(address indexed owner, address indexed spender, uint value);
  event Transfer(address indexed from, address indexed to, uint value);

  constructor() public {
    uint chainId;
    assembly {
      chainId := chainid()
    }
    DOMAIN_SEPARATOR = keccak256(
      abi.encode(
        keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
        keccak256(bytes(name)),
        keccak256(bytes('1')),
        chainId,
        address(this)
      )
    );
  }

  function _mint(address to, uint value) internal {
    totalSupply = totalSupply.add(value);
    balanceOf[to] = balanceOf[to].add(value);
    emit Transfer(address(0), to, value);
  }

  function _burn(address from, uint value) internal {
    balanceOf[from] = balanceOf[from].sub(value);
    totalSupply = totalSupply.sub(value);
    emit Transfer(from, address(0), value);
  }

  function _approve(address owner, address spender, uint value) private {
    allowance[owner][spender] = value;
    emit Approval(owner, spender, value);
  }

  function _transfer(address from, address to, uint value) private {
    balanceOf[from] = balanceOf[from].sub(value);
    balanceOf[to] = balanceOf[to].add(value);
    emit Transfer(from, to, value);
  }

  function approve(address spender, uint value) external returns (bool) {
    _approve(msg.sender, spender, value);
    return true;
  }

  function transfer(address to, uint value) external returns (bool) {
    _transfer(msg.sender, to, value);
    return true;
  }

  function transferFrom(address from, address to, uint value) external returns (bool) {
    if (allowance[from][msg.sender] != uint(-1)) {
      allowance[from][msg.sender] = allowance[from][msg.sender].sub(value);
    }
    _transfer(from, to, value);
    return true;
  }

  function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
    require(deadline >= block.timestamp, 'OreoSwapLP::permit::EXPIRED');
    bytes32 digest = keccak256(
      abi.encodePacked(
        '\x19\x01',
        DOMAIN_SEPARATOR,
        keccak256(abi.encode(PERMIT_TYPEHASH, owner, spender, value, nonces[owner]++, deadline))
      )
    );
    address recoveredAddress = ecrecover(digest, v, r, s);
    require(recoveredAddress != address(0) && recoveredAddress == owner, 'OreoSwapLP::permit::INVALID_SIGNATURE');
    _approve(owner, spender, value);
  }
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity =0.6.12;

// a library for performing various math operations
library OreoSwapMath {
  function min(uint x, uint y) internal pure returns (uint z) {
    z = x < y ? x : y;
  }

  // babylonian method (https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method)
  // reference: https://github.com/abdk-consulting/abdk-libraries-solidity/blob/master/ABDKMath64x64.sol#L687
  function sqrt(uint x) internal pure returns (uint z) {
    if (x == 0) return 0;
    uint xx = x;
    uint r = 1;

    if (xx >= 0x100000000000000000000000000000000) {
      xx >>= 128;
      r <<= 64;
    }

    if (xx >= 0x10000000000000000) {
      xx >>= 64;
      r <<= 32;
    }
    if (xx >= 0x100000000) {
      xx >>= 32;
      r <<= 16;
    }
    if (xx >= 0x10000) {
      xx >>= 16;
      r <<= 8;
    }
    if (xx >= 0x100) {
      xx >>= 8;
      r <<= 4;
    }
    if (xx >= 0x10) {
      xx >>= 4;
      r <<= 2;
    }
    if (xx >= 0x8) {
      r <<= 1;
    }

    r = (r + x / r) >> 1;
    r = (r + x / r) >> 1;
    r = (r + x / r) >> 1;
    r = (r + x / r) >> 1;
    r = (r + x / r) >> 1;
    r = (r + x / r) >> 1;
    r = (r + x / r) >> 1; // Seven iterations should be enough
    uint r1 = x / r;
    return (r < r1 ? r : r1);
  }
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity =0.6.12;

import './OreoSwapLP.sol';
import './libraries/OreoSwapMath.sol';
import './libraries/UQ112x112.sol';
import './interfaces/IOreoSwapBEP20.sol';
import './interfaces/IOreoSwapFactory.sol';
import './interfaces/IOreoSwapCallee.sol';

contract OreoSwapPair is OreoSwapLP {
  using OreoSwapSafeMath  for uint;
  using UQ112x112 for uint224;

  uint public constant MINIMUM_LIQUIDITY = 10**3;
  bytes4 private constant SELECTOR = bytes4(keccak256(bytes('transfer(address,uint256)')));

  address public factory;
  address public token0;
  address public token1;

  uint112 private reserve0;           // uses single storage slot, accessible via getReserves
  uint112 private reserve1;           // uses single storage slot, accessible via getReserves
  uint32  private blockTimestampLast; // uses single storage slot, accessible via getReserves

  uint public price0CumulativeLast;
  uint public price1CumulativeLast;
  uint public kLast; // reserve0 * reserve1, as of immediately after the most recent liquidity event

  uint private unlocked = 1;

  modifier lock() {
    require(unlocked == 1, 'OreoSwapPair::lock::LOCKED');
    unlocked = 0;
    _;
    unlocked = 1;
  }

  function getReserves() public view returns (uint112 _reserve0, uint112 _reserve1, uint32 _blockTimestampLast) {
    _reserve0 = reserve0;
    _reserve1 = reserve1;
    _blockTimestampLast = blockTimestampLast;
  }

  function _safeTransfer(address token, address to, uint value) private {
    (bool success, bytes memory data) = token.call(abi.encodeWithSelector(SELECTOR, to, value));
    require(success && (data.length == 0 || abi.decode(data, (bool))), 'OreoSwapPair::_safeTransfer::TRANSFER_FAILED');
  }

  event Mint(address indexed sender, uint amount0, uint amount1);
  event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
  event Swap(
    address indexed sender,
    uint amount0In,
    uint amount1In,
    uint amount0Out,
    uint amount1Out,
    address indexed to
  );
  event Sync(uint112 reserve0, uint112 reserve1);

  constructor() public {
    factory = msg.sender;
  }

  // called once by the factory at time of deployment
  function initialize(address _token0, address _token1) external {
    require(msg.sender == factory, 'OreoSwapPair::initialize::FORBIDDEN'); // sufficient check
    token0 = _token0;
    token1 = _token1;
  }

  // update reserves and, on the first call per block, price accumulators
  function _update(uint balance0, uint balance1, uint112 _reserve0, uint112 _reserve1) private {
    require(balance0 <= uint112(-1) && balance1 <= uint112(-1), 'OreoSwapPair::_update::OVERFLOW');
    uint32 blockTimestamp = uint32(block.timestamp % 2**32);
    uint32 timeElapsed = blockTimestamp - blockTimestampLast; // overflow is desired
    if (timeElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
      // * never overflows, and + overflow is desired
      price0CumulativeLast += uint(UQ112x112.encode(_reserve1).uqdiv(_reserve0)) * timeElapsed;
      price1CumulativeLast += uint(UQ112x112.encode(_reserve0).uqdiv(_reserve1)) * timeElapsed;
    }
    reserve0 = uint112(balance0);
    reserve1 = uint112(balance1);
    blockTimestampLast = blockTimestamp;
    emit Sync(reserve0, reserve1);
  }

  // if fee is on, mint liquidity equivalent to 8/25 of the growth in sqrt(k)
  function _mintFee(uint112 _reserve0, uint112 _reserve1) private returns (bool feeOn) {
    address feeTo = IOreoSwapFactory(factory).feeTo();
    feeOn = feeTo != address(0);
    uint _kLast = kLast; // gas savings
    if (feeOn) {
      if (_kLast != 0) {
        uint rootK = OreoSwapMath.sqrt(uint(_reserve0).mul(_reserve1));
        uint rootKLast = OreoSwapMath.sqrt(_kLast);
        if (rootK > rootKLast) {
          uint numerator = totalSupply.mul(rootK.sub(rootKLast)).mul(8);
          uint denominator = rootK.mul(17).add(rootKLast.mul(8));
          uint liquidity = numerator / denominator;
          if (liquidity > 0) _mint(feeTo, liquidity);
        }
      }
    } else if (_kLast != 0) {
      kLast = 0;
    }
  }

  // this low-level function should be called from a contract which performs important safety checks
  function mint(address to) external lock returns (uint liquidity) {
    (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
    uint balance0 = IOreoSwapBEP20(token0).balanceOf(address(this));
    uint balance1 = IOreoSwapBEP20(token1).balanceOf(address(this));
    uint amount0 = balance0.sub(_reserve0);
    uint amount1 = balance1.sub(_reserve1);

    bool feeOn = _mintFee(_reserve0, _reserve1);
    uint _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
    if (_totalSupply == 0) {
      liquidity = OreoSwapMath.sqrt(amount0.mul(amount1)).sub(MINIMUM_LIQUIDITY);
      _mint(address(0), MINIMUM_LIQUIDITY); // permanently lock the first MINIMUM_LIQUIDITY tokens
    } else {
      liquidity = OreoSwapMath.min(amount0.mul(_totalSupply) / _reserve0, amount1.mul(_totalSupply) / _reserve1);
    }
    require(liquidity > 0, 'OreoSwapPair::mint::INSUFFICIENT_LIQUIDITY_MINTED');
    _mint(to, liquidity);

    _update(balance0, balance1, _reserve0, _reserve1);
    if (feeOn) kLast = uint(reserve0).mul(reserve1); // reserve0 and reserve1 are up-to-date
    emit Mint(msg.sender, amount0, amount1);
  }

  // this low-level function should be called from a contract which performs important safety checks
  function burn(address to) external lock returns (uint amount0, uint amount1) {
    (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
    address _token0 = token0;                                // gas savings
    address _token1 = token1;                                // gas savings
    uint balance0 = IOreoSwapBEP20(_token0).balanceOf(address(this));
    uint balance1 = IOreoSwapBEP20(_token1).balanceOf(address(this));
    uint liquidity = balanceOf[address(this)];

    bool feeOn = _mintFee(_reserve0, _reserve1);
    uint _totalSupply = totalSupply; // gas savings, must be defined here since totalSupply can update in _mintFee
    amount0 = liquidity.mul(balance0) / _totalSupply; // using balances ensures pro-rata distribution
    amount1 = liquidity.mul(balance1) / _totalSupply; // using balances ensures pro-rata distribution
    require(amount0 > 0 && amount1 > 0, 'OreoSwapPair::burn::INSUFFICIENT_LIQUIDITY_BURNED');
    _burn(address(this), liquidity);
    _safeTransfer(_token0, to, amount0);
    _safeTransfer(_token1, to, amount1);
    balance0 = IOreoSwapBEP20(_token0).balanceOf(address(this));
    balance1 = IOreoSwapBEP20(_token1).balanceOf(address(this));

    _update(balance0, balance1, _reserve0, _reserve1);
    if (feeOn) kLast = uint(reserve0).mul(reserve1); // reserve0 and reserve1 are up-to-date
    emit Burn(msg.sender, amount0, amount1, to);
  }

  // this low-level function should be called from a contract which performs important safety checks
  function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external lock {
      require(amount0Out > 0 || amount1Out > 0, 'OreoSwapPair::swap::INSUFFICIENT_OUTPUT_AMOUNT');
      (uint112 _reserve0, uint112 _reserve1,) = getReserves(); // gas savings
      require(amount0Out < _reserve0 && amount1Out < _reserve1, 'OreoSwapPair::swap::INSUFFICIENT_LIQUIDITY');

      uint balance0;
      uint balance1;
      { // scope for _token{0,1}, avoids stack too deep errors
      address _token0 = token0;
      address _token1 = token1;
      require(to != _token0 && to != _token1, 'OreoSwapPair::swap::INVALID_TO');
      if (amount0Out > 0) _safeTransfer(_token0, to, amount0Out); // optimistically transfer tokens
      if (amount1Out > 0) _safeTransfer(_token1, to, amount1Out); // optimistically transfer tokens
      if (data.length > 0) IOreoSwapCallee(to).OreoSwapCall(msg.sender, amount0Out, amount1Out, data);
      balance0 = IOreoSwapBEP20(_token0).balanceOf(address(this));
      balance1 = IOreoSwapBEP20(_token1).balanceOf(address(this));
      }
      uint amount0In = balance0 > _reserve0 - amount0Out ? balance0 - (_reserve0 - amount0Out) : 0;
      uint amount1In = balance1 > _reserve1 - amount1Out ? balance1 - (_reserve1 - amount1Out) : 0;
      require(amount0In > 0 || amount1In > 0, 'OreoSwapPair::swap::INSUFFICIENT_INPUT_AMOUNT');
      { // scope for reserve{0,1}Adjusted, avoids stack too deep errors
      uint balance0Adjusted = balance0.mul(10000).sub(amount0In.mul(25));
      uint balance1Adjusted = balance1.mul(10000).sub(amount1In.mul(25));
      require(balance0Adjusted.mul(balance1Adjusted) >= uint(_reserve0).mul(_reserve1).mul(10000**2), 'OreoSwapPair::swap::K');
      }

      _update(balance0, balance1, _reserve0, _reserve1);
      emit Swap(msg.sender, amount0In, amount1In, amount0Out, amount1Out, to);
  }

  // force balances to match reserves
  function skim(address to) external lock {
      address _token0 = token0; // gas savings
      address _token1 = token1; // gas savings
      _safeTransfer(_token0, to, IOreoSwapBEP20(_token0).balanceOf(address(this)).sub(reserve0));
      _safeTransfer(_token1, to, IOreoSwapBEP20(_token1).balanceOf(address(this)).sub(reserve1));
  }

  // force reserves to match balances
  function sync() external lock {
      _update(IOreoSwapBEP20(token0).balanceOf(address(this)), IOreoSwapBEP20(token1).balanceOf(address(this)), reserve0, reserve1);
  }
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity =0.6.12;

// a library for performing overflow-safe math, courtesy of DappHub (https://github.com/dapphub/ds-math)

library OreoSwapSafeMath {
  function add(uint x, uint y) internal pure returns (uint z) {
    require((z = x + y) >= x, 'OreoSwapSafeMath::add::ds-math-add-overflow');
  }

  function sub(uint x, uint y) internal pure returns (uint z) {
    require((z = x - y) <= x, 'OreoSwapSafeMath::sub::ds-math-sub-underflow');
  }

  function mul(uint x, uint y) internal pure returns (uint z) {
    require(y == 0 || (z = x * y) / y == x, 'OreoSwapSafeMath::mul::ds-math-mul-overflow');
  }
}

// SPDX-License-Identifier: GPL-3.0

pragma solidity =0.6.12;

// a library for handling binary fixed point numbers (https://en.wikipedia.org/wiki/Q_(number_format))

// range: [0, 2**112 - 1]
// resolution: 1 / 2**112

library UQ112x112 {
  uint224 constant Q112 = 2**112;

  // encode a uint112 as a UQ112x112
  function encode(uint112 y) internal pure returns (uint224 z) {
    z = uint224(y) * Q112; // never overflows
  }

  // divide a UQ112x112 by a uint112, returning a UQ112x112
  function uqdiv(uint224 x, uint112 y) internal pure returns (uint224 z) {
    z = x / uint224(y);
  }
}

{
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    "contracts/swap/OreoSwapPair.sol": "OreoSwapPair"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs",
    "useLiteralContent": true
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}