// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;
pragma experimental ABIEncoderV2;

import { Initializable } from "@openzeppelin/contracts-v3/proxy/Initializable.sol";
import { IERC20 } from "@openzeppelin/contracts-v3/token/ERC20/IERC20.sol";
import { SafeERC20 } from "@openzeppelin/contracts-v3/token/ERC20/SafeERC20.sol";
import { ITornadoInstance } from "./interfaces/ITornadoInstance.sol";

interface ITornadoRouter {
  function approveExactToken(IERC20 _token, address _spender, uint256 _amount) external;
}

contract InstanceRegistry is Initializable {
  using SafeERC20 for IERC20;

  enum InstanceState {
    DISABLED,
    ENABLED
  }

  struct Instance {
    bool isERC20;
    IERC20 token;
    InstanceState state;
    // the fee of the uniswap pool which will be used to get a TWAP
    uint24 uniswapPoolSwappingFee;
    // the fee the protocol takes from relayer, it should be multiplied by PROTOCOL_FEE_DIVIDER from FeeManager.sol
    uint32 protocolFeePercentage;
  }

  struct Tornado {
    ITornadoInstance addr;
    Instance instance;
  }

  address public immutable governance;
  ITornadoRouter public router;

  mapping(ITornadoInstance => Instance) public instances;
  ITornadoInstance[] public instanceIds;

  event InstanceStateUpdated(ITornadoInstance indexed instance, InstanceState state);
  event RouterRegistered(address tornadoRouter);

  modifier onlyGovernance() {
    require(msg.sender == governance, "Not authorized");
    _;
  }

  constructor(address _governance) public {
    governance = _governance;
  }

  function initialize(Tornado[] memory _instances, address _router) external initializer {
    router = ITornadoRouter(_router);
    for (uint256 i = 0; i < _instances.length; i++) {
      _updateInstance(_instances[i]);
      instanceIds.push(_instances[i].addr);
    }
  }

  /**
   * @dev Add or update an instance.
   */
  function updateInstance(Tornado calldata _tornado) external virtual onlyGovernance {
    require(_tornado.instance.state != InstanceState.DISABLED, "Use removeInstance() for remove");
    if (instances[_tornado.addr].state == InstanceState.DISABLED) {
      instanceIds.push(_tornado.addr);
    }
    _updateInstance(_tornado);
  }

  /**
   * @dev Remove an instance.
   * @param _instanceId The instance id in `instanceIds` mapping to remove.
   */
  function removeInstance(uint256 _instanceId) external virtual onlyGovernance {
    ITornadoInstance _instance = instanceIds[_instanceId];
    (bool isERC20, IERC20 token) = (instances[_instance].isERC20, instances[_instance].token);

    if (isERC20) {
      uint256 allowance = token.allowance(address(router), address(_instance));
      if (allowance != 0) {
        router.approveExactToken(token, address(_instance), 0);
      }
    }

    delete instances[_instance];
    instanceIds[_instanceId] = instanceIds[instanceIds.length - 1];
    instanceIds.pop();
    emit InstanceStateUpdated(_instance, InstanceState.DISABLED);
  }

  /**
   * @notice This function should allow governance to set a new protocol fee for relayers
   * @param instance the to update
   * @param newFee the new fee to use
   * */
  function setProtocolFee(ITornadoInstance instance, uint32 newFee) external onlyGovernance {
    instances[instance].protocolFeePercentage = newFee;
  }

  /**
   * @notice This function should allow governance to set a new tornado proxy address
   * @param routerAddress address of the new proxy
   * */
  function setTornadoRouter(address routerAddress) external onlyGovernance {
    router = ITornadoRouter(routerAddress);
    emit RouterRegistered(routerAddress);
  }

  function _updateInstance(Tornado memory _tornado) internal virtual {
    instances[_tornado.addr] = _tornado.instance;
    if (_tornado.instance.isERC20) {
      IERC20 token = IERC20(_tornado.addr.token());
      require(token == _tornado.instance.token, "Incorrect token");
      uint256 allowance = token.allowance(address(router), address(_tornado.addr));

      if (allowance == 0) {
        router.approveExactToken(token, address(_tornado.addr), type(uint256).max);
      }
    }
    emit InstanceStateUpdated(_tornado.addr, _tornado.instance.state);
  }

  /**
   * @dev Returns all instance configs
   */
  function getAllInstances() public view returns (Tornado[] memory result) {
    result = new Tornado[](instanceIds.length);
    for (uint256 i = 0; i < instanceIds.length; i++) {
      ITornadoInstance _instance = instanceIds[i];
      result[i] = Tornado({ addr: _instance, instance: instances[_instance] });
    }
  }

  /**
   * @dev Returns all instance addresses
   */
  function getAllInstanceAddresses() public view returns (ITornadoInstance[] memory result) {
    result = new ITornadoInstance[](instanceIds.length);
    for (uint256 i = 0; i < instanceIds.length; i++) {
      result[i] = instanceIds[i];
    }
  }

  /// @notice get erc20 tornado instance token
  /// @param instance the interface (contract) key to the instance data
  function getPoolToken(ITornadoInstance instance) external view returns (address) {
    return address(instances[instance].token);
  }
}