#!/usr/bin/env bash
#
# omatether — iPhone USB tethering for Omarchy / Arch (systemd-networkd + iwd)
#
# Plug an iPhone in over USB and use its internet connection (the phone's
# Wi-Fi, or cellular if it isn't on Wi-Fi). Works headless — no GUI needed.
#
# Usage: omatether.sh <install|pair|unpair|status|priority|uninstall|help>
#
set -euo pipefail

NETFILE="/etc/systemd/network/10-iphone-tether.network"

# Route metrics: Omarchy ships ethernet=100, wifi=600, wwan=700.
METRIC_FALLBACK=750   # tether used only when nothing better is up (default)
METRIC_PREFERRED=50   # tether beats ethernet/wifi while plugged in

RED=$'\e[31m'; GRN=$'\e[32m'; YLW=$'\e[33m'; RST=$'\e[0m'
say()  { printf '%s\n' "$*"; }
ok()   { printf '%s\n' "${GRN}✓${RST} $*"; }
warn() { printf '%s\n' "${YLW}!${RST} $*"; }
die()  { printf '%s\n' "${RED}✗${RST} $*" >&2; exit 1; }

as_root() {
  if [[ $EUID -eq 0 ]]; then "$@"; else sudo "$@"; fi
}

# Find the network interface backed by the ipheth driver, if any.
tether_iface() {
  local dev drv
  for dev in /sys/class/net/*; do
    drv=$(readlink -f "$dev/device/driver" 2>/dev/null) || continue
    [[ ${drv##*/} == ipheth ]] && { basename "$dev"; return 0; }
  done
  return 1
}

write_netfile() {
  local metric=$1
  as_root tee "$NETFILE" >/dev/null <<EOF
# Installed by omatether — iPhone USB tethering.
# Matches by driver so it wins over 20-ethernet.network's Name=eth* glob
# (networkd applies the lexically-first matching file).
[Match]
Driver=ipheth

[Link]
# Never block boot / network-online.target waiting for a phone.
RequiredForOnline=no

[Network]
DHCP=yes

# DNS is global-static via systemd-resolved on Omarchy; match the
# UseDNS=no convention of the stock 20-*.network files.
[DHCPv4]
UseDNS=no
RouteMetric=${metric}

[IPv6AcceptRA]
UseDNS=no
RouteMetric=${metric}
EOF
}

reload_networkd() {
  as_root networkctl reload
  local iface
  if iface=$(tether_iface); then
    as_root networkctl reconfigure "$iface" || true
  fi
}

cmd_install() {
  say "Installing iPhone USB tethering support…"
  as_root pacman -S --needed --noconfirm usbmuxd libimobiledevice
  ok "usbmuxd + libimobiledevice installed (usbmuxd starts on demand via udev)"

  write_netfile "$METRIC_FALLBACK"
  reload_networkd
  ok "networkd profile written: $NETFILE (fallback priority, metric $METRIC_FALLBACK)"

  # Nudge udev in case the phone was already plugged in before install.
  as_root udevadm trigger -s usb --action=add 2>/dev/null || true

  say ""
  say "Next: unlock the iPhone, then run:  $0 pair"
}

cmd_pair() {
  command -v idevicepair >/dev/null || die "libimobiledevice not installed — run: $0 install"
  idevice_id -l 2>/dev/null | grep -q . || die "No iPhone detected over USB. Plug it in and try again."

  say "Pairing — unlock the iPhone and tap ${GRN}Trust${RST} when prompted…"
  local out
  if out=$(idevicepair pair 2>&1); then
    ok "$out"
  else
    case $out in
      *passcode*) die "Phone is locked. Unlock it, then re-run: $0 pair" ;;
      *user\ denied*|*denied\ the\ trust*) die "Trust was declined on the phone. Re-run and tap Trust." ;;
      *Please\ accept*) warn "Trust dialog is showing on the phone — tap Trust, then re-run: $0 pair"; exit 1 ;;
      *) die "$out" ;;
    esac
  fi

  say ""
  say "Now enable the hotspot on the phone:"
  say "  Settings → Personal Hotspot → Allow Others to Join: ON"
  say "The connection comes up automatically. Check with:  $0 status"
}

cmd_unpair() {
  idevicepair unpair && ok "Unpaired."
}

cmd_status() {
  local iface udid name

  if udid=$(idevice_id -l 2>/dev/null | head -1) && [[ -n $udid ]]; then
    name=$(ideviceinfo -k DeviceName 2>/dev/null || echo "unknown")
    ok "iPhone connected over USB: $name"
    if idevicepair validate >/dev/null 2>&1; then
      ok "Paired (trusted)"
    else
      warn "Not paired — run: $0 pair"
    fi
  else
    warn "No iPhone detected over USB"
  fi

  if iface=$(tether_iface); then
    local state addr
    state=$(networkctl status "$iface" 2>/dev/null | awk '/State:/{print $2; exit}')
    ok "Tether interface: $iface ($state)"
    addr=$(ip -4 -br addr show "$iface" | awk '{print $3}')
    if [[ -n $addr ]]; then
      ok "IPv4: $addr"
      ip route show default dev "$iface" | sed 's/^/  /'
      if curl -sf --interface "$iface" --max-time 5 -o /dev/null https://www.google.com; then
        ok "Internet via $iface works"
      else
        warn "No internet through $iface yet (is Personal Hotspot on?)"
      fi
    else
      warn "No IP yet — enable Personal Hotspot on the phone (Allow Others to Join)"
    fi
  else
    warn "No tether interface — phone unplugged, untrusted, or hotspot off"
  fi
}

cmd_priority() {
  [[ -f $NETFILE ]] || die "Not installed — run: $0 install"
  case ${1:-} in
    high)
      write_netfile "$METRIC_PREFERRED"
      reload_networkd
      ok "Tether now PREFERRED (metric $METRIC_PREFERRED) — traffic routes via the phone when plugged in"
      ;;
    low)
      write_netfile "$METRIC_FALLBACK"
      reload_networkd
      ok "Tether now FALLBACK (metric $METRIC_FALLBACK) — ethernet/wifi win when available"
      ;;
    *)
      local cur
      cur=$(awk -F= '/^RouteMetric/{print $2; exit}' "$NETFILE")
      say "Current metric: $cur  (ethernet=100, wifi=600)"
      say "Usage: $0 priority <high|low>"
      ;;
  esac
}

cmd_uninstall() {
  as_root rm -f "$NETFILE"
  as_root networkctl reload
  ok "Removed $NETFILE (usbmuxd/libimobiledevice left installed)"
}

case ${1:-help} in
  install)   cmd_install ;;
  pair)      cmd_pair ;;
  unpair)    cmd_unpair ;;
  status)    cmd_status ;;
  priority)  shift; cmd_priority "${1:-}" ;;
  uninstall) cmd_uninstall ;;
  help|-h|--help)
    sed -n '2,10p' "$0" | sed 's/^# \{0,1\}//'
    ;;
  *) die "Unknown command: $1 (try: $0 help)" ;;
esac