import readline # GNU readline (ie allows input() history buffer)
from itertools import chain

from bcrypter.cli.builtins import *
from bcrypter.cli.commands import *
from bcrypter.lib.result import Result
from bcrypter.exceptions import CmdDeclarationError

class REPL:
    _PROMPT = '>> '
    _DEFAULT_HISTORY_FILE = '.bcrypter_history'

    _BUILTINS = [
        BuiltinHelp(),
    ]
    _COMMANDS = [
    ]
    
    def __init__(self, history_file: str = _DEFAULT_HISTORY_FILE) -> None:
        for cmd in chain(REPL._BUILTINS, REPL._COMMANDS):
            result = cmd._is_consistent():
            if result.is_err():
                raise CmdDeclarationError(result.message)
        self._history_file = history_file
        readline.read_history_file(self._history_file)

    def __del__(self) -> None:
        readline.write_history_file(self._history_file)

    def prompt(self) -> str:
        return input(REPL._PROMPT)

    '''
    Parse and execute a string command
    '''
    def exec(self, cmd: str) -> Result[Command]:
        cmd = cmd.strip().split()
        if not len(cmd):
            return Result.warn('No command given')