SwapHoodPair

[
  {
    "inputs": [],
    "stateMutability": "nonpayable",
    "type": "constructor"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "owner",
        "type": "address"
      },
      {
        "indexed": true,
        "internalType": "address",
        "name": "spender",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "value",
        "type": "uint256"
      }
    ],
    "name": "Approval",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "sender",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount0",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount1",
        "type": "uint256"
      },
      {
        "indexed": true,
        "internalType": "address",
        "name": "to",
        "type": "address"
      }
    ],
    "name": "Burn",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "sender",
        "type": "address"
      },
      {
        "indexed": true,
        "internalType": "address",
        "name": "recipient",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount0",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount1",
        "type": "uint256"
      }
    ],
    "name": "Claim",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "sender",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount0",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount1",
        "type": "uint256"
      }
    ],
    "name": "Fees",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "sender",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount0",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount1",
        "type": "uint256"
      }
    ],
    "name": "Mint",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "sender",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount0In",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount1In",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount0Out",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "amount1Out",
        "type": "uint256"
      },
      {
        "indexed": true,
        "internalType": "address",
        "name": "to",
        "type": "address"
      }
    ],
    "name": "Swap",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "reserve0",
        "type": "uint256"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "reserve1",
        "type": "uint256"
      }
    ],
    "name": "Sync",
    "type": "event"
  },
  {
    "anonymous": false,
    "inputs": [
      {
        "indexed": true,
        "internalType": "address",
        "name": "from",
        "type": "address"
      },
      {
        "indexed": true,
        "internalType": "address",
        "name": "to",
        "type": "address"
      },
      {
        "indexed": false,
        "internalType": "uint256",
        "name": "value",
        "type": "uint256"
      }
    ],
    "name": "Transfer",
    "type": "event"
  },
  {
    "inputs": [],
    "name": "DOMAIN_SEPARATOR",
    "outputs": [
      {
        "internalType": "bytes32",
        "name": "",
        "type": "bytes32"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "PERMIT_TYPEHASH",
    "outputs": [
      {
        "internalType": "bytes32",
        "name": "",
        "type": "bytes32"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      },
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "allowance",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "spender",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amount",
        "type": "uint256"
      }
    ],
    "name": "approve",
    "outputs": [
      {
        "internalType": "bool",
        "name": "",
        "type": "bool"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "balanceOf",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "blockTimestampLast",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "to",
        "type": "address"
      }
    ],
    "name": "burn",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "amount0",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "amount1",
        "type": "uint256"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "chainId",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "claimFees",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "claimed0",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "claimed1",
        "type": "uint256"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "claimable0",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "claimable1",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "tokenIn",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amountIn",
        "type": "uint256"
      }
    ],
    "name": "current",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "amountOut",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "currentCumulativePrices",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "reserve0Cumulative",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "reserve1Cumulative",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "blockTimestamp",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "decimals",
    "outputs": [
      {
        "internalType": "uint8",
        "name": "",
        "type": "uint8"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "factory",
    "outputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "fees",
    "outputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "uint256",
        "name": "amountIn",
        "type": "uint256"
      },
      {
        "internalType": "address",
        "name": "tokenIn",
        "type": "address"
      }
    ],
    "name": "getAmountOut",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "getFee",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "getReserves",
    "outputs": [
      {
        "internalType": "uint112",
        "name": "_reserve0",
        "type": "uint112"
      },
      {
        "internalType": "uint112",
        "name": "_reserve1",
        "type": "uint112"
      },
      {
        "internalType": "uint32",
        "name": "_blockTimestampLast",
        "type": "uint32"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "index0",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "index1",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "lastObservation",
    "outputs": [
      {
        "components": [
          {
            "internalType": "uint256",
            "name": "timestamp",
            "type": "uint256"
          },
          {
            "internalType": "uint256",
            "name": "reserve0Cumulative",
            "type": "uint256"
          },
          {
            "internalType": "uint256",
            "name": "reserve1Cumulative",
            "type": "uint256"
          }
        ],
        "internalType": "struct IPair.Observation",
        "name": "",
        "type": "tuple"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "metadata",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "dec0",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "dec1",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "r0",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "r1",
        "type": "uint256"
      },
      {
        "internalType": "address",
        "name": "t0",
        "type": "address"
      },
      {
        "internalType": "address",
        "name": "t1",
        "type": "address"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "to",
        "type": "address"
      }
    ],
    "name": "mint",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "liquidity",
        "type": "uint256"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "name",
    "outputs": [
      {
        "internalType": "string",
        "name": "",
        "type": "string"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "nonces",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "observationLength",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "name": "observations",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "timestamp",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "reserve0Cumulative",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "reserve1Cumulative",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "owner",
        "type": "address"
      },
      {
        "internalType": "address",
        "name": "spender",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "value",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "deadline",
        "type": "uint256"
      },
      {
        "internalType": "uint8",
        "name": "v",
        "type": "uint8"
      },
      {
        "internalType": "bytes32",
        "name": "r",
        "type": "bytes32"
      },
      {
        "internalType": "bytes32",
        "name": "s",
        "type": "bytes32"
      }
    ],
    "name": "permit",
    "outputs": [],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "tokenIn",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amountIn",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "points",
        "type": "uint256"
      }
    ],
    "name": "prices",
    "outputs": [
      {
        "internalType": "uint256[]",
        "name": "",
        "type": "uint256[]"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "tokenIn",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amountIn",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "granularity",
        "type": "uint256"
      }
    ],
    "name": "quote",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "amountOut",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "reserve0",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "reserve0CumulativeLast",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "reserve1",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "reserve1CumulativeLast",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "tokenIn",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amountIn",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "points",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "window",
        "type": "uint256"
      }
    ],
    "name": "sample",
    "outputs": [
      {
        "internalType": "uint256[]",
        "name": "",
        "type": "uint256[]"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "uint256",
        "name": "_fee",
        "type": "uint256"
      }
    ],
    "name": "setSwapFee",
    "outputs": [],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "to",
        "type": "address"
      }
    ],
    "name": "skim",
    "outputs": [],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "supplyIndex0",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "name": "supplyIndex1",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "uint256",
        "name": "amount0Out",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "amount1Out",
        "type": "uint256"
      },
      {
        "internalType": "address",
        "name": "to",
        "type": "address"
      },
      {
        "internalType": "bytes",
        "name": "data",
        "type": "bytes"
      }
    ],
    "name": "swap",
    "outputs": [],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "swapFee",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "symbol",
    "outputs": [
      {
        "internalType": "string",
        "name": "",
        "type": "string"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "sync",
    "outputs": [],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "token0",
    "outputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "token1",
    "outputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "tokens",
    "outputs": [
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      },
      {
        "internalType": "address",
        "name": "",
        "type": "address"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [],
    "name": "totalSupply",
    "outputs": [
      {
        "internalType": "uint256",
        "name": "",
        "type": "uint256"
      }
    ],
    "stateMutability": "view",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "dst",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amount",
        "type": "uint256"
      }
    ],
    "name": "transfer",
    "outputs": [
      {
        "internalType": "bool",
        "name": "",
        "type": "bool"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  },
  {
    "inputs": [
      {
        "internalType": "address",
        "name": "src",
        "type": "address"
      },
      {
        "internalType": "address",
        "name": "dst",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "amount",
        "type": "uint256"
      }
    ],
    "name": "transferFrom",
    "outputs": [
      {
        "internalType": "bool",
        "name": "",
        "type": "bool"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  }
]

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.13;

import "./interface/IERC20.sol";
import "./interface/IERC721Metadata.sol";
import "./interface/IPair.sol";
import "./interface/IFactory.sol";
import "./interface/ICallee.sol";
import "./interface/IUnderlying.sol";
import "./PairFees.sol";
import "./lib/Math.sol";
import "./lib/SafeERC20.sol";
import "./Reentrancy.sol";

// The base pair of pools
contract SwapHoodPair is IERC20, IPair, Reentrancy {
    using SafeERC20 for IERC20;

    string public name;
    string public symbol;
    uint8 public constant decimals = 18;

    uint public override totalSupply = 0;

    mapping(address => mapping(address => uint)) public override allowance;
    mapping(address => uint) public override balanceOf;

    bytes32 public immutable DOMAIN_SEPARATOR;
    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH =
        0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    uint internal constant _FEE_PRECISION = 1e32;
    mapping(address => uint) public nonces;
    uint public immutable chainId;

    uint internal constant MINIMUM_LIQUIDITY = 10 ** 3;
    /// @dev Capture oracle reading every 30 minutes
    uint internal constant PERIOD_SIZE = 1800;

    address public immutable override token0;
    address public immutable override token1;
    address public immutable fees;
    uint public swapFee;
    address public immutable factory;

    Observation[] public observations;

    uint internal immutable decimals0;
    uint internal immutable decimals1;

    uint public reserve0;
    uint public reserve1;
    uint public blockTimestampLast;

    uint public reserve0CumulativeLast;
    uint public reserve1CumulativeLast;

    // index0 and index1 are used to accumulate fees,
    // this is split out from normal trades to keep the swap "clean"
    // this further allows LP holders to easily claim fees for tokens they have/staked
    uint public index0 = 0;
    uint public index1 = 0;

    // position assigned to each LP to track their current index0 & index1 vs the global position
    mapping(address => uint) public supplyIndex0;
    mapping(address => uint) public supplyIndex1;

    // tracks the amount of unclaimed, but claimable tokens off of fees for token0 and token1
    mapping(address => uint) public claimable0;
    mapping(address => uint) public claimable1;

    event Fees(address indexed sender, uint amount0, uint amount1);
    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(uint reserve0, uint reserve1);
    event Claim(
        address indexed sender,
        address indexed recipient,
        uint amount0,
        uint amount1
    );

    constructor() {
        factory = msg.sender;
        (address _token0, address _token1) = IFactory(msg.sender)
            .getInitializable();
        (token0, token1) = (_token0, _token1);
        fees = address(new PairFees(_token0, _token1));
        name = string(
            abi.encodePacked(
                "Volatile AMM - ",
                IERC721Metadata(_token0).symbol(),
                "/",
                IERC721Metadata(_token1).symbol()
            )
        );
        symbol = string(
            abi.encodePacked(
                "vAMM-",
                IERC721Metadata(_token0).symbol(),
                "/",
                IERC721Metadata(_token1).symbol()
            )
        );
        swapFee = IFactory(msg.sender).getFee();

        decimals0 = 10 ** IUnderlying(_token0).decimals();
        decimals1 = 10 ** IUnderlying(_token1).decimals();

        observations.push(Observation(block.timestamp, 0, 0));

        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256(
                    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
                ),
                keccak256(bytes(name)),
                keccak256("1"),
                block.chainid,
                address(this)
            )
        );
        chainId = block.chainid;
    }

    function getFee() public view returns(uint256) {
      return swapFee;
    }

    function setSwapFee(uint256 _fee) external {
        require(msg.sender == factory, "not factory");
        require(_fee <= 500, "fee too high");
        require(_fee != 0, "fee must be nonzero");
        swapFee = _fee;
    }

    function observationLength() external view returns (uint) {
        return observations.length;
    }

    function lastObservation() public view returns (Observation memory) {
        return observations[observations.length - 1];
    }

    function metadata()
        external
        view
        returns (
            uint dec0,
            uint dec1,
            uint r0,
            uint r1,
            address t0,
            address t1
        )
    {
        return (
            decimals0,
            decimals1,
            reserve0,
            reserve1,
            token0,
            token1
        );
    }

    function tokens() external view override returns (address, address) {
        return (token0, token1);
    }

    /// @dev Claim accumulated but unclaimed fees (viewable via claimable0 and claimable1)
    function claimFees()
        external
        override
        returns (uint claimed0, uint claimed1)
    {
        _updateFor(msg.sender);

        claimed0 = claimable0[msg.sender];
        claimed1 = claimable1[msg.sender];

        if (claimed0 > 0 || claimed1 > 0) {
            claimable0[msg.sender] = 0;
            claimable1[msg.sender] = 0;

            PairFees(fees).claimFeesFor(msg.sender, claimed0, claimed1);

            emit Claim(msg.sender, msg.sender, claimed0, claimed1);
        }
    }

    /// @dev Accrue fees on token0
    function _update0(uint amount) internal {
        uint toFees = amount;

        // transfer the fees out to PairFees and Treasury
        IERC20(token0).safeTransfer(fees, toFees);
        // 1e32 adjustment is removed during claim
        uint _ratio = (toFees * _FEE_PRECISION) / totalSupply;
        if (_ratio > 0) {
            index0 += _ratio;
        }
        // keep the same structure of events for compatability
        emit Fees(msg.sender, toFees, 0);
    }

    /// @dev Accrue fees on token1
    function _update1(uint amount) internal {
        uint toFees = amount;

        IERC20(token1).safeTransfer(fees, toFees);
        uint _ratio = (toFees * _FEE_PRECISION) / totalSupply;
        if (_ratio > 0) {
            index1 += _ratio;
        }
        // keep the same structure of events for compatability
        emit Fees(msg.sender, 0, toFees);
    }

    /// @dev This function MUST be called on any balance changes,
    ///      otherwise can be used to infinitely claim fees
    //       Fees are segregated from core funds, so fees can never put liquidity at risk
    function _updateFor(address recipient) internal {
        uint _supplied = balanceOf[recipient];
        // get LP balance of `recipient`
        if (_supplied > 0) {
            uint _supplyIndex0 = supplyIndex0[recipient];
            // get last adjusted index0 for recipient
            uint _supplyIndex1 = supplyIndex1[recipient];
            uint _index0 = index0;
            // get global index0 for accumulated fees
            uint _index1 = index1;
            supplyIndex0[recipient] = _index0;
            // update user current position to global position
            supplyIndex1[recipient] = _index1;
            uint _delta0 = _index0 - _supplyIndex0;
            // see if there is any difference that need to be accrued
            uint _delta1 = _index1 - _supplyIndex1;
            if (_delta0 > 0) {
                uint _share = (_supplied * _delta0) / _FEE_PRECISION;
                // add accrued difference for each supplied token
                claimable0[recipient] += _share;
            }
            if (_delta1 > 0) {
                uint _share = (_supplied * _delta1) / _FEE_PRECISION;
                claimable1[recipient] += _share;
            }
        } else {
            supplyIndex0[recipient] = index0;
            // new users are set to the default global state
            supplyIndex1[recipient] = index1;
        }
    }

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

    /// @dev Update reserves and, on the first call per block, price accumulators
    function _update(
        uint balance0,
        uint balance1,
        uint _reserve0,
        uint _reserve1
    ) internal {
        uint blockTimestamp = block.timestamp;
        uint timeElapsed = blockTimestamp - blockTimestampLast;
        // overflow is desired
        if (timeElapsed > 0 && _reserve0 != 0 && _reserve1 != 0) {
            unchecked {
                reserve0CumulativeLast += _reserve0 * timeElapsed;
                reserve1CumulativeLast += _reserve1 * timeElapsed;
            }
        }

        Observation memory _point = lastObservation();
        timeElapsed = blockTimestamp - _point.timestamp;
        // compare the last observation with current timestamp,
        // if greater than 30 minutes, record a new event
        if (timeElapsed > PERIOD_SIZE) {
            observations.push(
                Observation(
                    blockTimestamp,
                    reserve0CumulativeLast,
                    reserve1CumulativeLast
                )
            );
        }
        reserve0 = balance0;
        reserve1 = balance1;
        blockTimestampLast = blockTimestamp;
        emit Sync(reserve0, reserve1);
    }

    /// @dev Produces the cumulative price using counterfactuals to save gas and avoid a call to sync.
    function currentCumulativePrices()
        public
        view
        returns (
            uint reserve0Cumulative,
            uint reserve1Cumulative,
            uint blockTimestamp
        )
    {
        blockTimestamp = block.timestamp;
        reserve0Cumulative = reserve0CumulativeLast;
        reserve1Cumulative = reserve1CumulativeLast;

        // if time has elapsed since the last update on the pair, mock the accumulated price values
        (
            uint _reserve0,
            uint _reserve1,
            uint _blockTimestampLast
        ) = getReserves();
        if (_blockTimestampLast != blockTimestamp) {
            // subtraction overflow is desired
            uint timeElapsed = blockTimestamp - _blockTimestampLast;
            unchecked {
                reserve0Cumulative += _reserve0 * timeElapsed;
                reserve1Cumulative += _reserve1 * timeElapsed;
            }
        }
    }

    /// @dev Gives the current twap price measured from amountIn * tokenIn gives amountOut
    function current(
        address tokenIn,
        uint amountIn
    ) external view returns (uint amountOut) {
        Observation memory _observation = lastObservation();
        (
            uint reserve0Cumulative,
            uint reserve1Cumulative,

        ) = currentCumulativePrices();
        if (block.timestamp == _observation.timestamp) {
            _observation = observations[observations.length - 2];
        }

        uint timeElapsed = block.timestamp - _observation.timestamp;
        uint _reserve0 = (reserve0Cumulative -
            _observation.reserve0Cumulative) / timeElapsed;
        uint _reserve1 = (reserve1Cumulative -
            _observation.reserve1Cumulative) / timeElapsed;
        amountOut = _getAmountOut(amountIn, tokenIn, _reserve0, _reserve1);
    }

    /// @dev As per `current`, however allows user configured granularity, up to the full window size
    function quote(
        address tokenIn,
        uint amountIn,
        uint granularity
    ) external view returns (uint amountOut) {
        uint[] memory _prices = sample(tokenIn, amountIn, granularity, 1);
        uint priceAverageCumulative;
        for (uint i = 0; i < _prices.length; i++) {
            priceAverageCumulative += _prices[i];
        }
        return priceAverageCumulative / granularity;
    }

    /// @dev Returns a memory set of twap prices
    function prices(
        address tokenIn,
        uint amountIn,
        uint points
    ) external view returns (uint[] memory) {
        return sample(tokenIn, amountIn, points, 1);
    }

    function sample(
        address tokenIn,
        uint amountIn,
        uint points,
        uint window
    ) public view returns (uint[] memory) {
        uint[] memory _prices = new uint[](points);

        uint length = observations.length - 1;
        uint i = length - (points * window);
        uint nextIndex = 0;
        uint index = 0;

        for (; i < length; i += window) {
            nextIndex = i + window;
            uint timeElapsed = observations[nextIndex].timestamp -
                observations[i].timestamp;
            uint _reserve0 = (observations[nextIndex].reserve0Cumulative -
                observations[i].reserve0Cumulative) / timeElapsed;
            uint _reserve1 = (observations[nextIndex].reserve1Cumulative -
                observations[i].reserve1Cumulative) / timeElapsed;
            _prices[index] = _getAmountOut(
                amountIn,
                tokenIn,
                _reserve0,
                _reserve1
            );
            index = index + 1;
        }
        return _prices;
    }

    /// @dev This low-level function should be called from a contract which performs important safety checks
    ///      standard uniswap v2 implementation
    function mint(address to) external override lock returns (uint liquidity) {
        (uint _reserve0, uint _reserve1) = (reserve0, reserve1);
        uint _balance0 = IERC20(token0).balanceOf(address(this));
        uint _balance1 = IERC20(token1).balanceOf(address(this));
        uint _amount0 = _balance0 - _reserve0;
        uint _amount1 = _balance1 - _reserve1;

        uint _totalSupply = totalSupply;
        // gas savings, must be defined here since totalSupply can update in _mintFee
        if (_totalSupply == 0) {
            liquidity = Math.sqrt(_amount0 * _amount1) - MINIMUM_LIQUIDITY;
            // permanently lock the first MINIMUM_LIQUIDITY tokens
            _mint(address(0), MINIMUM_LIQUIDITY);
        } else {
            liquidity = Math.min(
                (_amount0 * _totalSupply) / _reserve0,
                (_amount1 * _totalSupply) / _reserve1
            );
        }
        require(liquidity > 0, "SwapHoodPair: INSUFFICIENT_LIQUIDITY_MINTED");
        _mint(to, liquidity);

        _update(_balance0, _balance1, _reserve0, _reserve1);
        emit Mint(msg.sender, _amount0, _amount1);
    }

    /// @dev This low-level function should be called from a contract which performs important safety checks
    ///      standard uniswap v2 implementation
    function burn(
        address to
    ) external override lock returns (uint amount0, uint amount1) {
        (uint _reserve0, uint _reserve1) = (reserve0, reserve1);
        (address _token0, address _token1) = (token0, token1);
        uint _balance0 = IERC20(_token0).balanceOf(address(this));
        uint _balance1 = IERC20(_token1).balanceOf(address(this));
        uint _liquidity = balanceOf[address(this)];

        // gas savings, must be defined here since totalSupply can update in _mintFee
        uint _totalSupply = totalSupply;
        // using balances ensures pro-rata distribution
        amount0 = (_liquidity * _balance0) / _totalSupply;
        // using balances ensures pro-rata distribution
        amount1 = (_liquidity * _balance1) / _totalSupply;
        require(
            amount0 > 0 && amount1 > 0,
            "SwapHoodPair: INSUFFICIENT_LIQUIDITY_BURNED"
        );
        _burn(address(this), _liquidity);
        IERC20(_token0).safeTransfer(to, amount0);
        IERC20(_token1).safeTransfer(to, amount1);
        _balance0 = IERC20(_token0).balanceOf(address(this));
        _balance1 = IERC20(_token1).balanceOf(address(this));

        _update(_balance0, _balance1, _reserve0, _reserve1);
        emit Burn(msg.sender, amount0, amount1, to);
    }

    /// @dev 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 override lock {
        require(
            amount0Out > 0 || amount1Out > 0,
            "SwapHoodPair: INSUFFICIENT_OUTPUT_AMOUNT"
        );
        (uint _reserve0, uint _reserve1) = (reserve0, reserve1);
        require(
            amount0Out < _reserve0 && amount1Out < _reserve1,
            "SwapHoodPair: INSUFFICIENT_LIQUIDITY"
        );
        uint _balance0;
        uint _balance1;
        {
            // scope for _token{0,1}, avoids stack too deep errors
            (address _token0, address _token1) = (token0, token1);
            require(to != _token0 && to != _token1, "SwapHoodPair: INVALID_TO");
            // optimistically transfer tokens
            if (amount0Out > 0) IERC20(_token0).safeTransfer(to, amount0Out);
            // optimistically transfer tokens
            if (amount1Out > 0) IERC20(_token1).safeTransfer(to, amount1Out);
            // callback, used for flash loans
            if (data.length > 0)
                ICallee(to).hook(msg.sender, amount0Out, amount1Out, data);
            _balance0 = IERC20(_token0).balanceOf(address(this));
            _balance1 = IERC20(_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,
            "SwapHoodPair: INSUFFICIENT_INPUT_AMOUNT"
        );
        {
            // scope for reserve{0,1}Adjusted, avoids stack too deep errors
            (address _token0, address _token1) = (token0, token1);
            if (amount0In > 0)
                _update0(
                    (amount0In * swapFee) / 10000
                ); // accrue fees for token0 and move them out of pool
            if (amount1In > 0)
                _update1(
                    (amount1In * swapFee) / 10000
                ); // accrue fees for token1 and move them out of pool
            // since we removed tokens, we need to reconfirm balances,
            // but doing balanceOf again as safety check
            _balance0 = IERC20(_token0).balanceOf(address(this));
            _balance1 = IERC20(_token1).balanceOf(address(this));
            // The curve x*y for volatile pools
            require(
                _k(_balance0, _balance1) >= _k(_reserve0, _reserve1),
                "SwapHoodPair: K"
            );
        }

        _update(_balance0, _balance1, _reserve0, _reserve1);
        emit Swap(msg.sender, amount0In, amount1In, amount0Out, amount1Out, to);
    }

    /// @dev Force balances to match reserves
    function skim(address to) external lock {
        (address _token0, address _token1) = (token0, token1);
        IERC20(_token0).safeTransfer(
            to,
            IERC20(_token0).balanceOf(address(this)) - (reserve0)
        );
        IERC20(_token1).safeTransfer(
            to,
            IERC20(_token1).balanceOf(address(this)) - (reserve1)
        );
    }

    // force reserves to match balances
    function sync() external lock {
        _update(
            IERC20(token0).balanceOf(address(this)),
            IERC20(token1).balanceOf(address(this)),
            reserve0,
            reserve1
        );
    }

    function getAmountOut(
        uint amountIn,
        address tokenIn
    ) external view override returns (uint) {
        (uint _reserve0, uint _reserve1) = (reserve0, reserve1);
        amountIn -= (amountIn * swapFee) / 10000; // remove fee from amount received
        return _getAmountOut(amountIn, tokenIn, _reserve0, _reserve1);
    }

    function _getAmountOut(
        uint amountIn,
        address tokenIn,
        uint _reserve0,
        uint _reserve1
    ) internal view returns (uint) {
            (uint reserveA, uint reserveB) = tokenIn == token0
                ? (_reserve0, _reserve1)
                : (_reserve1, _reserve0);
            return (amountIn * reserveB) / (reserveA + amountIn);
    }

    function _k(uint x, uint y) internal view returns (uint) {
        return x * y;
    }

    //****************************************************************************
    //**************************** ERC20 *****************************************
    //****************************************************************************

    function _mint(address dst, uint amount) internal {
        // balances must be updated on mint/burn/transfer
        _updateFor(dst);
        totalSupply += amount;
        balanceOf[dst] += amount;
        emit Transfer(address(0), dst, amount);
    }

    function _burn(address dst, uint amount) internal {
        _updateFor(dst);
        totalSupply -= amount;
        balanceOf[dst] -= amount;
        emit Transfer(dst, address(0), amount);
    }

    function approve(
        address spender,
        uint amount
    ) external override returns (bool) {
        require(
            spender != address(0),
            "SwapHoodPair: Approve to the zero address"
        );
        allowance[msg.sender][spender] = amount;

        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function permit(
        address owner,
        address spender,
        uint value,
        uint deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external override {
        require(deadline >= block.timestamp, "SwapHoodPair: 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,
            "SwapHoodPair: INVALID_SIGNATURE"
        );
        allowance[owner][spender] = value;

        emit Approval(owner, spender, value);
    }

    function transfer(
        address dst,
        uint amount
    ) external override returns (bool) {
        _transferTokens(msg.sender, dst, amount);
        return true;
    }

    function transferFrom(
        address src,
        address dst,
        uint amount
    ) external override returns (bool) {
        address spender = msg.sender;
        uint spenderAllowance = allowance[src][spender];

        if (spender != src && spenderAllowance != type(uint).max) {
            require(
                spenderAllowance >= amount,
                "SwapHoodPair: Insufficient allowance"
            );
            unchecked {
                uint newAllowance = spenderAllowance - amount;
                allowance[src][spender] = newAllowance;
                emit Approval(src, spender, newAllowance);
            }
        }

        _transferTokens(src, dst, amount);
        return true;
    }

    function _transferTokens(address src, address dst, uint amount) internal {
        require(dst != address(0), "SwapHoodPair: Transfer to the zero address");

        // update fee position for src
        _updateFor(src);
        // update fee position for dst
        _updateFor(dst);

        uint srcBalance = balanceOf[src];
        require(
            srcBalance >= amount,
            "SwapHoodPair: Transfer amount exceeds balance"
        );
        unchecked {
            balanceOf[src] = srcBalance - amount;
        }

        balanceOf[dst] += amount;

        emit Transfer(src, dst, amount);
    }
}