// SPDX-License-Identifier: MIT
pragma solidity ^0.6.12;

/**
 * @title Block library
 *
 * @author Stanisław Głogowski <stan@pillarproject.io>
 */
library BlockLib {
  struct BlockRelated {
    bool added;
    uint256 removedAtBlockNumber;
  }

  /**
   * @notice Verifies self struct at current block
   * @param self self struct
   * @return true on correct self struct
   */
  function verifyAtCurrentBlock(
    BlockRelated memory self
  )
    internal
    view
    returns (bool)
  {
    return verifyAtBlock(self, block.number);
  }

  /**
   * @notice Verifies self struct at any block
   * @param self self struct
   * @return true on correct self struct
   */
  function verifyAtAnyBlock(
    BlockRelated memory self
  )
    internal
    pure
    returns (bool)
  {
    return verifyAtBlock(self, 0);
  }

  /**
   * @notice Verifies self struct at specific block
   * @param self self struct
   * @param blockNumber block number to verify
   * @return true on correct self struct
   */
  function verifyAtBlock(
    BlockRelated memory self,
    uint256 blockNumber
  )
    internal
    pure
    returns (bool)
  {
    bool result = false;

    if (self.added) {
      if (self.removedAtBlockNumber == 0) {
        result = true;
      } else if (blockNumber == 0) {
        result = true;
      } else {
        result = self.removedAtBlockNumber > blockNumber;
      }
    }

    return result;
  }
}