import cmd
from pathlib import Path


class History:
    def __init__(self):
        self.stack = []
        import readline
        readline.set_completer_delims(" ")

    def push(self, name):
        self.write()
        self.stack.append(name)
        self.read()

    def pop(self):
        self.write()
        self.stack.pop()
        self.read()

    def read(self):
        if self.stack:
            import readline
            readline.clear_history()
            readline.read_history_file(self.get_path())

    def write(self):
        if self.stack:
            import readline
            readline.write_history_file(self.get_path())

    def get_path(self):
        path = Path("_".join(self.stack))
        path.touch(exist_ok=True)
        return str(path)


g_history = History()


class HistoryShell(cmd.Cmd):
    """A version of the command shell with some context management of history."""
    def __init__(self, name):
        super().__init__()
        self.shell_name = name
        self.prompt = f"{name}> "

    def __enter__(self):
        g_history.push(self.shell_name)
        return self

    def __exit__(self, exc_type, exc_value, exc_traceback):
        g_history.pop()

    @staticmethod
    def do_exit(_dummy):
        return True


class MySubShell(HistoryShell):
    def __init__(self, name):
        super().__init__(name)

    def do_run(self, line):
        print(f"Executing 'run' from sub-shell with arguments '{line}'") 
        

class MyShell(HistoryShell):
    def __init__(self, name):
        super().__init__(name)

    def do_run(self, line):
        print(f"Executing 'run' from parent shell with arguments '{line}'") 
        
    def do_sub(self, line):
        """Launch sub-shell"""
        with MySubShell("subshell") as shell:
            shell.cmdloop()


if __name__ == "__main__":
    with MyShell("myshell") as shell:
        shell.cmdloop()