pragma experimental ABIEncoderV2;
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.0;

import { SliceLib } from "./SliceLib.sol";

library RevertCaptureLib {
  using SliceLib for *;
  uint32 constant REVERT_WITH_REASON_MAGIC = 0x08c379a0; // keccak256("Error(string)")
  function decodeString(bytes memory input) internal pure returns (string memory retval) {
    (retval) = abi.decode(input, (string));
  }
  function decodeError(bytes memory buffer) internal pure returns (string memory) {
    if (buffer.length == 0) return "captured empty revert buffer";
    if (uint32(uint256(bytes32(buffer.toSlice(0, 4).asWord()))) != REVERT_WITH_REASON_MAGIC) return "captured a revert error, but it doesn't conform to the standard";
    bytes memory revertMessageEncoded = buffer.toSlice(4).copy();
    if (revertMessageEncoded.length == 0) return "captured empty revert message";
    (string memory revertMessage) = decodeString(revertMessageEncoded);
    return revertMessage;
  }
}