#!/usr/bin/env python3

import subprocess
import argparse
from http.server import HTTPServer, BaseHTTPRequestHandler

class HealthCheckHandler(BaseHTTPRequestHandler):
    """
    HTTP server that returns 200 if a network device is up, 
    and 503 if it is down or missing.
    """

    def check_device(self):
        device = self.server.device
        try:
            # -run command: ip link show <device> up
            # -check=True ensures we can catch errors easily
            # -capture_output=True keeps the terminal clean
            result = subprocess.run(
                ["ip", "link", "show", device, "up"],
                capture_output=True,
                text=True,
                check=False
            )
            # Return True only if exit code is 0 and output is not empty
            return result.returncode == 0 and len(result.stdout.strip()) > 0
        except FileNotFoundError:
            print("Error: 'ip' command not found. Are you on Linux?")
            return False

    def do_GET(self):
        if self.check_device():
            self.send_response(200)
            self.send_header("Content-Type", "text/plain")
            self.end_headers()
            self.wfile.write(b"healthy\n")
        else:
            self.send_response(503)
            self.send_header("Content-Type", "text/plain")
            self.end_headers()
            self.wfile.write(b"unhealthy\n")

    def do_HEAD(self):
        self.do_GET()

    # Suppress standard logging to keep console clean, optional
    def log_message(self, format, *args):
        return

def main():
    parser = argparse.ArgumentParser(
        description="Modern HTTP health check for network devices."
    )
    parser.add_argument("-d", "--device", default="wg0",
                        help="Device name to check (e.g., eth0, wg0). Default: wg0")
    parser.add_argument("-p", "--port", type=int, default=8080,
                        help="Port to listen on. Default: 8080")
    parser.add_argument("-t", "--test", action="store_true",
                        help="Check status once and exit.")

    args = parser.parse_args()

    # logic for --test flag
    if args.test:
        # Temporary mock-up of the check logic for CLI test
        cmd = ["ip", "link", "show", args.device, "up"]
        res = subprocess.run(cmd, capture_output=True, text=True)
        if res.returncode == 0 and res.stdout:
            print(f"Device {args.device}: UP")
            exit(0)
        else:
            print(f"Device {args.device}: DOWN")
            exit(1)

    # Start the Server
    server = HTTPServer(('', args.port), HealthCheckHandler)
    server.device = args.device
    print(f"Starting health check server for {args.device} on port {args.port}...")
    
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        print("\nShutting down server.")
        server.server_close()

if __name__ == "__main__":
    main()