import os
import subprocess
import logging
import time
import psutil

logger = logging.getLogger(__name__)

def get_os_type():
    """
    Simple check to distinguish Alpine from others.
    """
    if os.path.exists("/etc/alpine-release"):
        return "alpine"
    return "debian" # default fallback to systemctl

def control_service(action: str):
    """
    Action: start, stop, restart
    """
    if action not in ["start", "stop", "restart"]:
        raise ValueError("Invalid action")

    os_type = get_os_type()
    
    cmd = []
    if os_type == "alpine":
        cmd = ["rc-service", "openvpn", action]
    else:
        cmd = ["systemctl", action, "openvpn"]

    try:
        # Capture output to return it or log it
        result = subprocess.run(cmd, capture_output=True, text=True, check=True)
        return {
            "status": "success",
            "message": f"Service {action} executed successfully",
            "stdout": result.stdout
        }
    except subprocess.CalledProcessError as e:
        logger.error(f"Service control failed: {e.stderr}")
        return {
            "status": "error",
            "message": f"Failed to {action} service",
            "stderr": e.stderr
        }
    except FileNotFoundError:
        # Happens if rc-service or systemctl is missing (e.g. dev env)
        return {
            "status": "error",
            "message": f"Command not found found for OS type {os_type}"
        }

def get_process_stats():
    """
    Returns dict with pid, cpu_percent, memory_mb, uptime.
    Uses psutil for robust telemetry.
    """
    pid = None
    process = None

    # Find the process
    try:
        # Iterate over all running processes
        for proc in psutil.process_iter(['pid', 'name']):
            try:
                if proc.info['name'] == 'openvpn':
                    pid = proc.info['pid']
                    process = proc
                    break
            except (psutil.NoSuchProcess, psutil.AccessDenied, psutil.ZombieProcess):
                pass
    except Exception as e:
        logger.error(f"Failed to find process via psutil: {e}")

    if not pid or not process:
        return {
            "status": "stopped",
            "pid": None,
            "cpu_percent": 0.0,
            "memory_mb": 0.0,
            "uptime": None
        }

    # Get Stats
    try:
        # CPU Percent
        # Increasing interval to 1.0s to ensure we capture enough ticks for accurate reading
        # especially on systems with low clock resolution (e.g. 100Hz = 10ms ticks)
        cpu = process.cpu_percent(interval=1.0)
        
        # Memory (RSS)
        mem_info = process.memory_info()
        rss_mb = round(mem_info.rss / 1024 / 1024, 2)
        
        # Uptime
        create_time = process.create_time()
        uptime_seconds = time.time() - create_time
        uptime_str = format_seconds(uptime_seconds)

        return {
            "status": "running",
            "pid": pid,
            "cpu_percent": cpu,
            "memory_mb": rss_mb,
            "uptime": uptime_str
        }

    except (psutil.NoSuchProcess, psutil.AccessDenied):
        # Process might have died between discovery and stats
        return {
            "status": "stopped",
            "pid": None,
            "cpu_percent": 0.0,
            "memory_mb": 0.0,
            "uptime": None
        }
    except Exception as e:
        logger.error(f"Failed to get process stats: {e}")
        return {
            "status": "running",
            "pid": pid,
            "cpu_percent": 0.0,
            "memory_mb": 0.0,
            "uptime": None
        }

def format_seconds(seconds: float) -> str:
    seconds = int(seconds)
    days, seconds = divmod(seconds, 86400)
    hours, seconds = divmod(seconds, 3600)
    minutes, seconds = divmod(seconds, 60)
    
    parts = []
    if days > 0: parts.append(f"{days}d")
    if hours > 0: parts.append(f"{hours}h")
    if minutes > 0: parts.append(f"{minutes}m")
    parts.append(f"{seconds}s")
    
    return " ".join(parts)