#!/bin/bash
set -euo pipefail

WIFI_IFACE="wlan0"
KNOWN_CONNECTIONS=(
  "4pi:4pi"
  "eskimue.de:netplan-wlan0-eskimue.de"
)
FALLBACK_AP_CONN="CUNO-AP"
SCAN_WAIT_SECONDS=10

get_active_connection() {
  nmcli -t -f GENERAL.CONNECTION device show "$WIFI_IFACE" 2>/dev/null | head -n 1 | cut -d: -f2-
}

activate_connection() {
  local connection_name="$1"
  nmcli --wait 15 connection up "$connection_name" ifname "$WIFI_IFACE" >/dev/null 2>&1
}

is_known_connection() {
  local active_connection="$1"
  local entry

  for entry in "${KNOWN_CONNECTIONS[@]}"; do
    local connection_name="${entry#*:}"
    if [[ "$active_connection" == "$connection_name" ]]; then
      return 0
    fi
  done

  return 1
}

scan_for_known_connection() {
  local visible_ssids
  local entry

  nmcli device wifi rescan ifname "$WIFI_IFACE" >/dev/null 2>&1 || true
  sleep "$SCAN_WAIT_SECONDS"
  visible_ssids="$(nmcli -t -f SSID device wifi list ifname "$WIFI_IFACE" 2>/dev/null || true)"

  for entry in "${KNOWN_CONNECTIONS[@]}"; do
    local ssid="${entry%%:*}"
    local connection_name="${entry#*:}"
    if printf '%s\n' "$visible_ssids" | grep -Fxq "$ssid"; then
      echo "$connection_name"
      return 0
    fi
  done

  return 1
}

activate_initial_connection() {
  local active_connection
  local selected_connection

  active_connection="$(get_active_connection)"
  if is_known_connection "$active_connection"; then
    return 0
  fi

  if selected_connection="$(scan_for_known_connection)"; then
    activate_connection "$selected_connection"
    return 0
  fi

  activate_connection "$FALLBACK_AP_CONN" || true
}

activate_initial_connection