#!/usr/bin/env python3
import os
import shlex
from pathlib import Path
from typing import List, Optional
import argparse
import json

class EfxSession:
    def __init__(self, cfg):
        self.cmd = cfg.get('cmd', '/bin/bash --login')
        self.title = cfg.get('title', 'System Shell')

    def execute(self):
        cmd_val = shlex.split(self.cmd)
        os.execvp(cmd_val[0], cmd_val)

class EfxConfig:
    def __init__(self, cfg):
        self._sessions = _attr_sessions(cfg)

    def get_session(self, num: int) -> Optional[EfxSession]:
        return self._sessions[num] if 0 <= num < len(self._sessions) else None

def _load_config() -> EfxConfig:
    json_site = (Path.home() / '.efx_site.json')
    if not json_site.exists():
        raise RuntimeError('No available configuration')
    cfg = json.loads(json_site.read_text())
    return EfxConfig(cfg)

def _attr_sessions(cfg) -> List[EfxSession]:
    return [EfxSession(x) for x in cfg.get('sessions', [])]

def main():
    parser = argparse.ArgumentParser(description='Site Information[Session]')
    parser.add_argument('id', type=int, help='Session identifier')
    args = parser.parse_args()
    
    cfg = _load_config()
    session = cfg.get_session(args.id)
    if not session:
        raise RuntimeError('Invalid session id')
    session.execute()

    
if __name__ == "__main__":
    main()