block19.ruby

Transaction = Struct.new :version, :inputs, :outputs, :locktime do
  def serialize
    inputs_hex = inputs.map(&:serialize).join
    outputs_hex = outputs.map(&:serialize).join
    int_to_hex(version) + byte_to_hex(inputs.size) + inputs_hex +
      byte_to_hex(outputs.size) + outputs_hex + int_to_hex(locktime)
  end
  def hash
    hash_to_hex sha256(sha256(serialize))
  end
  def signature_hash(lock_script = nil, sighash_type = 0x1)
    inputs.first.unlock_script = lock_script if lock_script
    hash = sha256(sha256(serialize + int_to_hex(sighash_type)))
    [hash].pack('H*')
  end
  def sign(private_key, public_key, lock_script, sighash_type = 0x01)
    bytes_string = signature_hash lock_script, sighash_type
    r, s = ecdsa_sign private_key, bytes_string
    der = Der.new r: r, s: s
    inputs.first.unlock_script = "#{der.serialize} #{public_key}"
    serialize
  end
end
transaction = Transaction.new 1, [input], [output, change], 0