CryptoRandomBlockheader

CryptoRandomBlockheader.sol

pragma solidity >=0.4.0 <0.7.0;

abstract contract IBlockHeaderPrecompiledContract {
    function getBitcoinHeader(int256 indexBlock) public virtual view returns (bytes memory coinbase);
}

contract CryptoRandomBlockheader  {
  IBlockHeaderPrecompiledContract blockHeader =
  IBlockHeaderPrecompiledContract(0x0000000000000000000000000000000001000010);

  bool public waitForRandom;
  uint public deadline;
  
  function debug_queryLastMergeMiningHeaderHash() public  returns (bytes32) {
    return bitcoiMergeMiningnHeaderHash(block.number - 1);
  }
  
  function getBlockNumber() public view returns (uint) {
      return block.number;
  }
  
  function isRandomSeedReady() public view returns (bool) {
      if (!waitForRandom)
        return false;
      
      require(block.number<deadline+4000);
      
      // Assure the deadline block has been mined, and it has 60
      // confirmations (30 minutes)
      return block.number>=deadline+6;
  }
  
  function getRandomSeed() public returns (bytes32) {
      require(isRandomSeedReady());
      waitForRandom = false;
      return bitcoiMergeMiningnHeaderHash(deadline);
  }
  
  function startWaitForRandomValue() public {
    // Wait approximately one hour 
    deadline =  block.number+12;
    waitForRandom = true;
  }
  
  function bitcoiMergeMiningnHeaderHash (uint index) public view returns (bytes32) {
    bytes memory header = blockHeader.getBitcoinHeader(int256(block.number-1-index));
    bytes32 x = sha256(header);
    bytes32 y = sha256(abi.encodePacked(x));
    return y;
  }
  
  function bytesToBytes32(bytes memory source) private pure returns (bytes32 result) {
    if (source.length == 0) {
        return 0x0;
    }
    assembly {
        result := mload(add(source, 32))
    }
  }
}