#!/bin/bash
# configure-usb-audio.sh
# Configure the Arduino Uno Q as a composite USB gadget:
#   UAC1 (USB Audio Class) + gmidi (USB MIDI)
#
# The host sees one device with both an audio sink and a MIDI port,
# allowing MIDI input over the same USB connection as audio output.
#
# Based on Linux USB gadget configfs setup.
# The Uno Q's USB peripheral controller is exposed via configfs.

set -euo pipefail

GADGET_DIR="/sys/kernel/config/usb_gadget"
GADGET_NAME="g1"
UDC_DIR="/sys/class/udc"

# Gadget config
VID="0x2341"        # Arduino VID
PID="0x006A"        # Custom PID (Uno Q audio + MIDI)
SERIAL="$(cat /sys/firmware/devicetree/base/serial-number 2>/dev/null | tr -d '\0' || cat /proc/cpuinfo 2>/dev/null | grep Serial | head -1 | awk '{print $3}' || echo 'UnoQ')"
MANUFACTURER="Arduino"
PRODUCT="Uno Q Audio Synth"

# USB audio params
CHANNELS=2       # stereo out
SAMPLE_RATE=48000
SAMPLE_SIZE=2    # bytes (2 = 16-bit; kernel UAC1 gadget expects bytes, not bits)

# Find UDC (USB Device Controller)
find_udc() {
    for controller in "$UDC_DIR"/*; do
        if [ -d "$controller" ]; then
            basename "$controller"
            return 0
        fi
    done
    echo "ERROR: No UDC found" >&2
    exit 1
}

create_gadget() {
    local udc="$1"

    # Remove existing gadget if present
    if [ -d "$GADGET_DIR/$GADGET_NAME" ]; then
        echo "" > "$GADGET_DIR/$GADGET_NAME/UDC" 2>/dev/null || true
        for _ in $(seq 1 50); do
            if [ ! -f "$GADGET_DIR/$GADGET_NAME/UDC" ] || [ -z "$(cat "$GADGET_DIR/$GADGET_NAME/UDC" 2>/dev/null)" ]; then
                break
            fi
            sleep 0.1
        done
        for config in "$GADGET_DIR/$GADGET_NAME/configs"/*/; do
            config=$(basename "$config")
            for func in "$GADGET_DIR/$GADGET_NAME/configs/$config/"*.*/; do
                func=$(basename "$func")
                [ -L "$GADGET_DIR/$GADGET_NAME/configs/$config/$func" ] && rm -f "$GADGET_DIR/$GADGET_NAME/configs/$config/$func"
            done
            rmdir "$GADGET_DIR/$GADGET_NAME/configs/$config" 2>/dev/null || true
        done
        for func in "$GADGET_DIR/$GADGET_NAME/functions"/*/; do
            func=$(basename "$func")
            rmdir "$GADGET_DIR/$GADGET_NAME/functions/$func" 2>/dev/null || true
        done
        rmdir "$GADGET_DIR/$GADGET_NAME" 2>/dev/null || true
    fi

    mkdir -p "$GADGET_DIR/$GADGET_NAME"
    echo "$VID" > "$GADGET_DIR/$GADGET_NAME/idVendor"
    echo "$PID" > "$GADGET_DIR/$GADGET_NAME/idProduct"
    echo "0x0100" > "$GADGET_DIR/$GADGET_NAME/bcdDevice"
    echo "0x0200" > "$GADGET_DIR/$GADGET_NAME/bcdUSB"

    mkdir -p "$GADGET_DIR/$GADGET_NAME/strings/0x409"
    echo "$SERIAL" > "$GADGET_DIR/$GADGET_NAME/strings/0x409/serialnumber"
    echo "$MANUFACTURER" > "$GADGET_DIR/$GADGET_NAME/strings/0x409/manufacturer"
    echo "$PRODUCT" > "$GADGET_DIR/$GADGET_NAME/strings/0x409/product"

    # Create UAC1 function (audio output, wide host compatibility)
    mkdir -p "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0"
    echo "$CHANNELS" > "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0/p_chmask"
    echo "$SAMPLE_RATE" > "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0/p_srate"
    echo "$SAMPLE_SIZE" > "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0/p_ssize"
    echo "$CHANNELS" > "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0/c_chmask"
    echo "$SAMPLE_RATE" > "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0/c_srate"
    echo "$SAMPLE_SIZE" > "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0/c_ssize"

    # Create MIDI function (MIDI input from host)
    mkdir -p "$GADGET_DIR/$GADGET_NAME/functions/midi.gs0"
    echo 1 > "$GADGET_DIR/$GADGET_NAME/functions/midi.gs0/in_ports"
    echo 1 > "$GADGET_DIR/$GADGET_NAME/functions/midi.gs0/out_ports"

    # Create configuration
    mkdir -p "$GADGET_DIR/$GADGET_NAME/configs/c.1"
    mkdir -p "$GADGET_DIR/$GADGET_NAME/configs/c.1/strings/0x409"
    echo "Audio + MIDI" > "$GADGET_DIR/$GADGET_NAME/configs/c.1/strings/0x409/configuration"
    echo 250 > "$GADGET_DIR/$GADGET_NAME/configs/c.1/MaxPower"

    # Link both functions to the same config (composite device)
    ln -s "$GADGET_DIR/$GADGET_NAME/functions/uac1.gs0" "$GADGET_DIR/$GADGET_NAME/configs/c.1/"
    ln -s "$GADGET_DIR/$GADGET_NAME/functions/midi.gs0" "$GADGET_DIR/$GADGET_NAME/configs/c.1/"

    # Bind to UDC
    echo "$udc" > "$GADGET_DIR/$GADGET_NAME/UDC"
    echo "USB gadget '$GADGET_NAME' bound to $udc (UAC1 audio + gmidi)"
}

case "${1:-start}" in
    start)
        udc=$(find_udc)
        create_gadget "$udc"
        ;;
    stop)
        if [ -d "$GADGET_DIR/$GADGET_NAME" ]; then
            udc=$(cat "$GADGET_DIR/$GADGET_NAME/UDC" 2>/dev/null || true)
            [ -n "$udc" ] && echo "" > "$GADGET_DIR/$GADGET_NAME/UDC" 2>/dev/null || true
        fi
        echo "USB gadget '$GADGET_NAME' stopped"
        ;;
    status)
        if [ -d "$GADGET_DIR/$GADGET_NAME/UDC" ]; then
            echo "Gadget: $(cat "$GADGET_DIR/$GADGET_NAME/UDC" 2>/dev/null || echo 'not bound')"
        else
            echo "Gadget: not configured"
        fi
        ;;
    *)
        echo "Usage: $0 {start|stop|status}"
        exit 1
        ;;
esac