// SPDX-License-Identifier: MIT
/**
  ∩~~~~∩ 
  ξ ･×･ ξ 
  ξ　~　ξ 
  ξ　　 ξ 
  ξ　　 “~～~～〇 
  ξ　　　　　　 ξ 
  ξ ξ ξ~～~ξ ξ ξ 
　 ξ_ξξ_ξ　ξ_ξξ_ξ
Alpaca Fin Corporation
*/

pragma solidity 0.6.12;

interface ERC20Interface {
  function balanceOf(address user) external view returns (uint256);
}

library SafeToken {
  function myBalance(address token) internal view returns (uint256) {
    return ERC20Interface(token).balanceOf(address(this));
  }

  function balanceOf(address token, address user) internal view returns (uint256) {
    return ERC20Interface(token).balanceOf(user);
  }

  function safeApprove(
    address token,
    address to,
    uint256 value
  ) internal {
    // bytes4(keccak256(bytes('approve(address,uint256)')));
    (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x095ea7b3, to, value));
    require(success && (data.length == 0 || abi.decode(data, (bool))), "!safeApprove");
  }

  function safeTransfer(
    address token,
    address to,
    uint256 value
  ) internal {
    // bytes4(keccak256(bytes('transfer(address,uint256)')));
    (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0xa9059cbb, to, value));
    require(success && (data.length == 0 || abi.decode(data, (bool))), "!safeTransfer");
  }

  function safeTransferFrom(
    address token,
    address from,
    address to,
    uint256 value
  ) internal {
    // bytes4(keccak256(bytes('transferFrom(address,address,uint256)')));
    (bool success, bytes memory data) = token.call(abi.encodeWithSelector(0x23b872dd, from, to, value));
    require(success && (data.length == 0 || abi.decode(data, (bool))), "!safeTransferFrom");
  }

  function safeTransferETH(address to, uint256 value) internal {
    // solhint-disable-next-line no-call-value
    (bool success, ) = to.call{ value: value }(new bytes(0));
    require(success, "!safeTransferETH");
  }
}