import os
import signal
import sys
import textwrap
import time
from pathlib import Path

PID_FILE = Path("pid.txt")
MAIN_SCRIPT = "main.py"
START_DELAY = 0.3


def display_help():
    print(
        textwrap.dedent("""\
        Usage: python service.py <option>

        Options:
          status  - Get status of main script.
          start   - Start main script.
          stop    - Stop main script.
          restart - Restart main script.""")
    )


def get_pid() -> int | None:
    try:
        content = PID_FILE.read_text().strip()
        pid = int(content)
        # Verify the process actually exists
        os.kill(pid, 0)
        return pid
    except (FileNotFoundError, ValueError, ProcessLookupError, PermissionError):
        return None


def clear_pid():
    PID_FILE.write_text("")


def start_process():
    os.system(f"nohup python {MAIN_SCRIPT} &")
    time.sleep(START_DELAY)
    return get_pid()


def cmd_status():
    pid = get_pid()
    if pid:
        print(f"[Running] PID: {pid}")
        return 0
    print("[Stopped]")
    return 1


def cmd_start():
    if pid := get_pid():
        print(f"Already running with PID: {pid}")
        return 2
    if pid := start_process():
        print(f"Started with PID: {pid}")
        return 0
    print(f"Can't get PID... Crash? | CWD: {os.getcwd()}")
    return 1


def cmd_stop():
    pid = get_pid()
    clear_pid()
    if not pid:
        print(f"Process already stopped. | CWD: {os.getcwd()}")
        return 2
    try:
        os.kill(pid, signal.SIGTERM)  # Graceful shutdown vs SIGKILL
        print("Process successfully stopped.")
        return 0
    except ProcessLookupError:
        print(f"Process already stopped. | CWD: {os.getcwd()}")
        return 2


def cmd_restart():
    pid = get_pid()
    if pid:
        try:
            os.kill(pid, signal.SIGTERM)
        except ProcessLookupError:
            pass
    clear_pid()
    if pid := start_process():
        print(f"Restarted with PID: {pid}")
        return 0
    print(f"Can't get PID... Crash? | CWD: {os.getcwd()}")
    return 1


COMMANDS = {
    "status": cmd_status,
    "start": cmd_start,
    "stop": cmd_stop,
    "restart": cmd_restart,
}

if __name__ == "__main__":
    if len(sys.argv) < 2 or sys.argv[1] not in COMMANDS:
        display_help()
        sys.exit(0)

    exit_code = COMMANDS[sys.argv[1]]()
    sys.exit(exit_code)