code: def main(option, problem):
      
      # No problem given (or given option ignores the problem argument)
      if problem == 0 or option in {skip, verify_all}:
          # Determine the highest problem number in the current directory
          files = problem_glob()
          problem = max(file.num for file in files) if files else 0
  
          # No Project Euler files in current directory (no glob results)
          if problem == 0:
              # Generate the first problem file if option is appropriate
              if option not in {cheat, preview, verify_all}:
                  msg = "No Project Euler files found in the current directory."
                  click.echo(msg)
                  option = generate
  
              # Set problem number to 1
              problem = 1
  
          # --preview and no problem; preview the next problem
          elif option is preview:
              problem += 1
  
          # No option and no problem; generate next file if answer is
          # correct (verify() will exit if the solution is incorrect)
          if option is None:
              verify(problem)
              problem += 1
              option = generate
  
      # Problem given but no option; decide between generate and verify
      elif option is None:
          option = verify if Problem(problem).glob else generate
  
      # Execute function based on option
      option(problem)
      sys.exit(0)
docs: Python-based Project Euler command line tool.