#!/bin/bash
# Windows "Source/Sink" speaker volume -> USB gadget Feature Unit (numid=7, PCM
# Capture Volume 0-100) + mute (numid=6). Mirror it onto the USB headset sink so
# the Windows volume slider actually controls what the user hears in the headset.
# Poll-based (200ms), only acts on change to avoid hammering the mixer on the
# gadget's ~10Hz async rate-feedback events.
set -u
export XDG_RUNTIME_DIR=/run/user/1000
CG=UAC2Gadget
HSSINK=alsa_output.usb-Logi_USB_Headset_Logi_USB_Headset-00.analog-stereo
last=-1; lastm=-1
while true; do
  v=$(amixer -c "$CG" cget numid=7 2>/dev/null | awk -F= '/: values=/{print $2; exit}')
  m=$(amixer -c "$CG" cget numid=6 2>/dev/null | awk -F= '/: values=/{print $2; exit}')
  if [ -n "$v" ] && { [ "$v" != "$last" ] || [ "$m" != "$lastm" ]; }; then
    pactl set-sink-volume "$HSSINK" "${v}%" >/dev/null 2>&1
    case "$m" in
      off|0) pactl set-sink-mute "$HSSINK" 1 >/dev/null 2>&1 ;;
      *)     pactl set-sink-mute "$HSSINK" 0 >/dev/null 2>&1 ;;
    esac
    last="$v"; lastm="$m"
  fi
  sleep 0.2
done