#!/bin/bash
# yaris-netwatch.sh
#
# Runs periodically via yaris-netwatch.timer. If wlan0 is currently in
# AP/hotspot mode, briefly attempts to reconnect to the known home WiFi.
# If that succeeds, we're back on home WiFi (used for syncing itinerary/
# dashcam data to the remote server). If it fails (still out of range),
# reactivates the hotspot so the web UI stays reachable locally in the car.
#
# The Pi's onboard WiFi radio (BCM43438) cannot act as an AP and scan for
# client networks at the same time, so this brief switch-and-check is the
# only way to detect "home WiFi is back in range" while sitting in AP mode.
# The reverse direction (home WiFi -> hotspot, i.e. leaving range) is handled
# automatically by NetworkManager's own autoconnect-priority mechanism and
# needs no watcher: the "home-wifi" profile has a higher
# connection.autoconnect-priority than Hotspot, so NM tries it first whenever
# the device needs to reconnect, and falls through to Hotspot on its own once
# home WiFi drops out of range.

set -u

LOG_TAG="yaris-netwatch"
HOME_CON="home-wifi"
AP_CON="Hotspot"
IFACE="wlan0"
LAST_LOG="/tmp/yaris-netwatch-last.log"

active_con() {
    nmcli -t -f DEVICE,CONNECTION device status | awk -F: -v d="$IFACE" '$1==d {print $2}'
}

current="$(active_con)"

if [ "$current" != "$AP_CON" ]; then
    # Already on home WiFi (or something else) - nothing to do.
    logger -t "$LOG_TAG" "wlan0 is on '$current', no action needed"
    exit 0
fi

logger -t "$LOG_TAG" "wlan0 is on hotspot, checking for home WiFi ($HOME_CON)..."

# Real-hardware finding: a plain "nmcli con up home-wifi" straight out of AP
# mode reliably reports "not found" even when actually in range, repeatedly
# (confirmed: 4 failures in a row over 13min while sitting right next to the
# router). NM's scan cache for wlan0 is stale/empty coming out of AP mode
# (the radio literally can't scan while acting as an AP - see comment above),
# and a single con-up attempt doesn't wait for a fresh scan to land before
# giving up. Fix: explicitly drop the AP connection first to free the radio,
# force a fresh scan and give it a few seconds to populate, then retry the
# connect attempt with a longer timeout up to 2 times before conceding and
# restoring the hotspot.
nmcli con down "$AP_CON" >"$LAST_LOG" 2>&1

connected=false
for attempt in 1 2; do
    nmcli device wifi rescan ifname "$IFACE" >>"$LAST_LOG" 2>&1
    sleep 5
    if nmcli --wait 30 con up "$HOME_CON" >>"$LAST_LOG" 2>&1; then
        connected=true
        break
    fi
    logger -t "$LOG_TAG" "home WiFi attempt $attempt failed, retrying..."
done

if [ "$connected" = true ]; then
    logger -t "$LOG_TAG" "home WiFi found, switched to '$HOME_CON'"
else
    logger -t "$LOG_TAG" "home WiFi not found after retries, restoring hotspot"
    nmcli con up "$AP_CON" >>"$LAST_LOG" 2>&1
fi