#!/usr/bin/env python3

import subprocess
import sys

############################################################################################
# CONFIGURATION
############################################################################################

HOSTS = {
    "Cloudflare DNS": "1.1.1.1",
    "Google DNS": "8.8.8.8",
    "Quad9 DNS": "9.9.9.9",
    "Office printer": "192.168.255.254",
}

IS_WINDOWS = sys.platform == "win32"

############################################################################################
# Functions
############################################################################################

def build_command(host):
    if IS_WINDOWS:
        return ["ping", "-n", "1", "-w", "1000", host]
    return ["ping", "-c", "1", "-w", "1", host]

def host_is_reachable(host):
    """
    Returns True if the host answers a single ping.
    """
    # Subprocess can be used to run a command on the host system.
    # Every argument that you would pass in the shell, becomes an element in the parameter of the subprocess function.

    # capture_output=True ensures that both stdout and stderr are captured by Python and do not clutter the terminal.
    # text=True converts the stdout and stderr to text, if set to True, the output is returned as bytes.
    result = subprocess.run(build_command(host), capture_output=True, text=True)

    # The returncode property contains the exit code: 0 for a successful reply, 1 for an unreachable host and 2 for a
    # hostname that doesn't exist.
    return result.returncode == 0

############################################################################################
# Main Program
############################################################################################

unreachable = 0

for name, host in HOSTS.items():
    if not host_is_reachable(host):
        print(f"[DOWN] {name:<16} {host}")
        unreachable += 1
        continue

    print(f"[UP]   {name:<16} {host}")

print(f"\n{len(HOSTS) - unreachable} of {len(HOSTS)} hosts reachable.")

if unreachable > 0:
    sys.exit(1)