#!/usr/bin/env python3
import argparse
import json
import re
import sys
import time
import traceback

import paramiko

from checker import nagios
from checker.result import quit_check
from checker.types import try_int, try_float

WIFI_2 = list(range(1, 12))
WIFI_5 = list(range(32, 178))


def main(args):
    command = f'iwinfo {args.interface} scan'
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

    for retry_i in range(args.retries):
        try:
            ssh.connect(args.host, username='root')
        except paramiko.ssh_exception.AuthenticationException:
            quit_check(f'SSH authentication to root@{args.host} failed! Make sure your key exists on the remote system or copy it over with ssh-copy-id', nagios.STATE_UNKNOWN)
            sys.exit(nagios.STATE_UNKNOWN)
        except paramiko.ssh_exception.NoValidConnectionsError:
            quit_check(f'SSH connection failed to {args.host}', nagios.STATE_UNKNOWN)

        stdin, stdout, stderr = ssh.exec_command(command)
        if stdout.channel.recv_exit_status() != 0:
            quit_check(f'command failed:\nSTDOUT: {"".join(stdout.readlines())}\nSTDERR: {"".join(stderr.readlines())}', nagios.STATE_UNKNOWN)
        output = [str(x).strip('\n').strip(' ') for x in stdout.readlines()]

        cells = {}

        for line in output:
            if line.startswith('Cell '):
                address = re.search(r'Address:\s(.*?)$', line).group(1)
                cells[address] = {}
            elif line.startswith('ESSID: '):
                if line == 'ESSID: unknown':
                    ssid = None
                else:
                    ssid = re.search(r'ESSID:\s"(.*?)"$', line).group(1)
                cells[list(cells.keys())[-1]]['ssid'] = ssid
            elif line.startswith('Mode: '):
                m = re.search(r'Mode: .*?\s\sFrequency: ([0-9.]*) GHz\s\sBand: ([0-9.]*) GHz\s\sChannel: ([0-9]*)$', line)
                if not m:
                    # Older OpenWRT versions display this info differently.
                    m = re.search(r'Mode: .*?\s\sChannel: ([0-9]*)$', line)
                    chan = try_int(m.group(1))
                    if chan in WIFI_2:
                        band = 2.4
                    elif chan in WIFI_5:
                        band = 5
                    else:
                        raise Exception
                    freq = -1
                else:
                    freq = try_float(m.group(1))
                    band = try_float(m.group(2))
                    chan = try_int(m.group(3))
                cells[list(cells.keys())[-1]]['freq'] = freq
                cells[list(cells.keys())[-1]]['band'] = band
                cells[list(cells.keys())[-1]]['chan'] = chan
            elif line.startswith('Encryption: '):
                enc = re.search(r'Encryption: (.*?)$', line).group(1)
                cells[list(cells.keys())[-1]]['enc'] = enc
            elif line.startswith('Channel Width: '):
                width = re.search(r'Channel Width: (.*?)$', line).group(1)
                cells[list(cells.keys())[-1]]['chan_width'] = width
            elif line.startswith('Signal: '):
                m = re.search(r'Signal: (-[0-9]*) dBm\s\sQuality: ([0-9]*)/([0-9]*)$', line)
                cells[list(cells.keys())[-1]]['signal'] = try_int(m.group(1))
                cells[list(cells.keys())[-1]]['quality'] = (try_int(m.group(2)), try_int(m.group(3)))

        if args.print:
            print(json.dumps(cells))
            sys.exit(nagios.STATE_UNKNOWN)

        # ============================================
        # Check if we need to retry

        if retry_i + 1 < args.retries:
            if args.target_mac not in list(cells.keys()):
                time.sleep(10)
                continue

            if not cells[args.target_mac]['ssid']:
                time.sleep(10)
                continue

            if cells[args.target_mac]['ssid'] != args.expected_ssid:
                time.sleep(10)
                continue

        # ============================================

        ap_data = cells.get(args.target_mac)
        if not ap_data:
            quit_check(f'AP address not found: {args.target_mac}', nagios.STATE_CRIT)

        computed_quality = int(try_float(ap_data['quality'][0]) / try_float(ap_data['quality'][1]) * 100)

        chan_width = ap_data['chan_width'].strip(' MHz')
        if re.search(r'[a-zA-Z]', chan_width):
            # OpenWRT may be unsure about the channel width.
            chan_width = -1

        perfdata = {
            'signal': {'value': try_int(ap_data['signal']), 'warn': args.signal_warn, 'crit': args.signal_crit},
            'quality': {'value': int(computed_quality), 'warn': args.quality_warn, 'crit': args.quality_crit, 'unit': '%'},
            'freq': {'value': ap_data['freq']},
            'band': {'value': ap_data['band']},
            'chan': {'value': ap_data['chan']},
            'chan_width': {'value': chan_width},
        }

        if ap_data['ssid'] != args.expected_ssid:
            quit_check(f'AP does not have the right SSID.\n{json.dumps(ap_data)}', nagios.STATE_CRIT, perfdata=perfdata)

        if ap_data['signal'] <= args.signal_crit:
            quit_check(f'Signal strength is weak: {ap_data["signal"]} dBm', nagios.STATE_CRIT, perfdata=perfdata)

        if ap_data['signal'] <= args.signal_warn:
            quit_check(f'Signal strength is weak: {ap_data["signal"]} dBm', nagios.STATE_WARN, perfdata=perfdata)

        if computed_quality <= args.quality_crit:
            quit_check(f'Signal quality is low: {ap_data["quality"][0]}/{ap_data["quality"][1]} ({computed_quality}%)', nagios.STATE_CRIT, perfdata=perfdata)

        if computed_quality <= args.quality_warn:
            quit_check(f'Signal quality is low: {ap_data["quality"][0]}/{ap_data["quality"][1]} ({computed_quality}%)', nagios.STATE_WARN, perfdata=perfdata)

        quit_check(f"{ap_data['ssid']} ({args.target_mac}) is healthy. Signal: {ap_data['signal']} dBm. Quality: {computed_quality}%. Channel: {ap_data['chan']} @ {ap_data['chan_width']} width. Band: {ap_data['band']} GHz. Frequency: {ap_data['freq']} GHz. Encryption: {ap_data['enc']}.",
                   nagios.STATE_OK,
                   perfdata=perfdata)

    quit_check(f'AP address not found: {args.target_mac}', nagios.STATE_CRIT)


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('--host', required=True, help='The host to SSH into.')
    parser.add_argument('--interface', required=True, help='The wireless interface to use (example: `wlan0`).')
    parser.add_argument('--retries', default=4, help='If the target AP is not found, do this many retries.')
    parser.add_argument('--print', action='store_true', help='Print the found APs.')
    parser.add_argument('--target-mac', required=True, help='The MAC address of the target AP.')
    parser.add_argument('--expected-ssid', required=True, help="The AP's expected SSID.")
    parser.add_argument('--signal-warn', type=int, required=True, help='If the signal strength is less than this, trigger warn.')
    parser.add_argument('--signal-crit', type=int, required=True, help='If the signal strength is less than this, trigger crit.')
    parser.add_argument('--quality-warn', type=int, required=True, help='If the signal quality is less than this percentage, trigger warn.')
    parser.add_argument('--quality-crit', type=int, required=True, help='If the signal quality is less than this percentage, trigger crit.')
    args = parser.parse_args()

    try:
        main(args)
    except Exception as e:
        print(f'UNKNOWN - exception "{e}"')
        traceback.print_exc()
        sys.exit(nagios.STATE_UNKNOWN)