// SPDX-License-Identifier: MIT
pragma solidity ^0.6.8;
pragma experimental ABIEncoderV2;

import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Pausable.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";

import { DSMath } from "../libs/safeMath.sol";

interface AccountInterface {
  function isAuth(address) external view returns(bool);
  function cast(address[] calldata _targets, bytes[] calldata _datas, address _origin) external payable;
}

interface IndexInterface {
  function master() external view returns (address);
  function build(address _owner, uint accountVersion, address _origin) external returns (address _account);
}

interface RegistryInterface {
  function chief(address) external view returns (bool);
  function poolLogic(address) external returns (address);
  function insureFee(address) external view returns (uint);
  function withdrawalFee(address) external view returns (uint);
  function isDsa(address, address) external view returns (bool);
}

interface RateInterface {
  function getTotalToken() external returns (uint totalUnderlyingTkn);
}

contract PoolToken is ReentrancyGuard, DSMath, ERC20Pausable {
    using SafeERC20 for IERC20;

    event LogDeploy(address token, uint amount);
    event LogExchangeRate(uint exchangeRate, uint tokenBalance, uint insuranceAmt);
    event LogSettle(uint settleBlock);
    event LogDeposit(uint depositAmt, uint poolMintAmt);
    event LogWithdraw(uint withdrawAmt, uint poolBurnAmt, uint feeAmt);
    event LogAddInsurance(uint amount);
    event LogWithdrawInsurance(uint amount);
    event LogPausePool(bool);

    IERC20 public immutable baseToken; // Base token. Eg:- DAI, USDC, etc.
    RegistryInterface public immutable registry; // Pool Registry
    IndexInterface public constant instaIndex = IndexInterface(0x2971AdFa57b20E5a416aE5a708A8655A9c74f723); // Main Index

    uint private tokenBalance; // total token balance since last rebalancing
    uint public exchangeRate; // initial 1 token = 1
    uint public insuranceAmt; // insurance amount to keep pool safe

    constructor(
        address _registry,
        string memory _name,
        string memory _symbol,
        address _baseToken
    ) public ERC20(_name, _symbol) {
        baseToken = IERC20(_baseToken);
        registry = RegistryInterface(_registry);
        exchangeRate = 10 ** uint(36 - ERC20(_baseToken).decimals());
    }

    modifier isChief() {
        require(registry.chief(msg.sender) || msg.sender == instaIndex.master(), "not-chief");
        _;
    }

    function deploy(address _dsa, address token, uint amount) public isChief {
      require(registry.isDsa(address(this), _dsa), "not-autheticated-dsa");
      require(AccountInterface(_dsa).isAuth(address(this)), "token-pool-not-auth");  
      if (token == address(0)) { // pool base token
        baseToken.safeTransfer(_dsa, amount);
      } else if (token == 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE){ // non-pool ethereum
        payable(_dsa).transfer(amount);
      } else { // non-pool other tokens
        IERC20(token).safeTransfer(_dsa, amount);
      }
      emit LogDeploy(token, amount);
    }

    /**
      * @dev get pool token rate
      * @param tokenAmt total token amount
      */
    function getCurrentRate(uint tokenAmt) public returns (uint) {
      return wdiv(totalSupply(), tokenAmt);
    }

    /**
      * @dev sets exchange rates
      */
    function setExchangeRate() public isChief {
      uint _previousRate = exchangeRate;
      uint _totalToken = RateInterface(registry.poolLogic(address(this))).getTotalToken();
      _totalToken = sub(_totalToken, insuranceAmt);
      uint _currentRate = getCurrentRate(_totalToken);
      require(_currentRate != 0, "current-rate-is-zero");
      if (_currentRate > _previousRate) { // loss => deduct partially/fully from insurance amount
        uint _loss = sub(tokenBalance, _totalToken);
        if (_loss <= insuranceAmt) {
          insuranceAmt = sub(insuranceAmt, _loss);
          _currentRate = _previousRate;
        } else {
          tokenBalance = add(_totalToken, insuranceAmt);
          insuranceAmt = 0;
          _currentRate = getCurrentRate(tokenBalance);
        }
      } else { // profit => add to insurance amount
        uint insureFeeAmt = wmul(sub(_totalToken, tokenBalance), registry.insureFee(address(this)));
        insuranceAmt = add(insuranceAmt, insureFeeAmt);
        tokenBalance = sub(_totalToken, insureFeeAmt);
        _currentRate = getCurrentRate(tokenBalance);
      }
      exchangeRate = _currentRate;
      emit LogExchangeRate(exchangeRate, tokenBalance, insuranceAmt);
    }

    function settle(address _dsa, address[] calldata _targets, bytes[] calldata _datas, address _origin) external isChief {
      require(registry.isDsa(address(this), _dsa), "not-autheticated-dsa");
      AccountInterface dsaWallet = AccountInterface(_dsa);
      if (_targets.length > 0 && _datas.length > 0) {
        dsaWallet.cast(_targets, _datas, _origin);
      }
      require(dsaWallet.isAuth(address(this)), "token-pool-not-auth"); 
      setExchangeRate();
      emit LogSettle(block.number);
    }

    function deposit(uint tknAmt) external whenNotPaused payable returns (uint _mintAmt) {
      require(msg.value == 0, "non-eth-pool");
      tokenBalance = add(tokenBalance, tknAmt);

      baseToken.safeTransferFrom(msg.sender, address(this), tknAmt);
      _mintAmt = wmul(tknAmt, exchangeRate);
      _mint(msg.sender, _mintAmt);

      emit LogDeposit(tknAmt, _mintAmt);
    }

    function withdraw(uint tknAmt, address to) external nonReentrant whenNotPaused returns (uint _tknAmt) {
      uint poolBal = baseToken.balanceOf(address(this));
      require(tknAmt <= poolBal, "not-enough-liquidity-available");
      uint _bal = balanceOf(msg.sender);
      uint _tknBal = wdiv(_bal, exchangeRate);
      uint _burnAmt;
      if (tknAmt == uint(-1)) {
        _burnAmt = _bal;
        _tknAmt = _tknBal;
      } else {
        require(tknAmt <= _tknBal, "balance-exceeded");
        _burnAmt = wmul(tknAmt, exchangeRate);
        _tknAmt = tknAmt;
      }

      tokenBalance = sub(tokenBalance, _tknAmt);

      _burn(msg.sender, _burnAmt);

      uint _withdrawalFee = registry.withdrawalFee(address(this));
      uint _feeAmt;
      if (_withdrawalFee > 0) {
        _feeAmt = wmul(_tknAmt, _withdrawalFee);
        insuranceAmt = add(insuranceAmt, _feeAmt);
        _tknAmt = sub(_tknAmt, _feeAmt);
      }

      baseToken.safeTransfer(to, _tknAmt);

      emit LogWithdraw(tknAmt, _burnAmt, _feeAmt);
    }

    function addInsurance(uint tknAmt) external {
      baseToken.safeTransferFrom(msg.sender, address(this), tknAmt);
      insuranceAmt = add(insuranceAmt, tknAmt);
      emit LogAddInsurance(tknAmt);
    }

    function withdrawInsurance(uint tknAmt) external {
      require(msg.sender == instaIndex.master(), "not-master");
      require(tknAmt <= insuranceAmt, "not-enough-insurance");
      baseToken.safeTransfer(msg.sender, tknAmt);
      insuranceAmt = sub(insuranceAmt, tknAmt);
      emit LogWithdrawInsurance(tknAmt);
    }

    function shutdown() external {
      require(msg.sender == instaIndex.master(), "not-master");
      paused() ? _unpause() : _pause();
    }

    receive() external payable {}
}