#!/bin/bash
# detect-usb-role.sh — Detect whether USB-C should be gadget or host.
# Writes result to /run/usb-role for consumption by pd-synth-auto.service.
#
# Detection methods (tried in order):
#   1. extcon  — USB cable detection (most reliable on Qualcomm)
#   2. dwc3 debug — USB controller mode
#   3. UDC state — if a UDC is bound as configured, we're in gadget mode
#   4. lsusb    — if USB devices appear (after host controller init), we're host
#
# Exit code: 0 if role detected, 1 if unknown

set -euo pipefail

ROLE_FILE="/run/usb-role"
unset ROLE

die() { echo "[USB-ROLE] $*" >&2; exit 1; }

# --- Method 1: extcon ---
check_extcon() {
    for path in /sys/class/extcon/*/state; do
        [ -f "$path" ] || continue
        local state
        state=$(cat "$path" 2>/dev/null || true)
        if echo "$state" | grep -q "USB=1"; then
            echo "gadget"
            return 0
        fi
    done
    return 1
}

# --- Method 2: dwc3 debugfs ---
check_dwc3() {
    local mode_file
    for mode_file in /sys/kernel/debug/usb/dwc3*/mode; do
        [ -f "$mode_file" ] || continue
        local mode
        mode=$(cat "$mode_file" 2>/dev/null || true)
        case "$mode" in
            *peripheral*) echo "gadget"; return 0 ;;
            *host*)       echo "host";   return 0 ;;
        esac
    done
    return 1
}

# --- Method 3: UDC state ---
check_udc() {
    for path in /sys/class/udc/*/state; do
        [ -f "$path" ] || continue
        local state
        state=$(cat "$path" 2>/dev/null || true)
        case "$state" in
            configured) echo "gadget"; return 0 ;;
        esac
    done
    return 1
}

# --- Method 4: USB host devices ---
check_lsusb() {
    if command -v lsusb &>/dev/null; then
        local count
        count=$(lsusb 2>/dev/null | grep -v "Linux Foundation" | wc -l)
        # If we see non-root-hub devices, likely we're the host
        if [ "$count" -gt 1 ]; then
            echo "host"
            return 0
        fi
    fi
    return 1
}

# Try methods in order
ROLE=$(check_extcon || check_dwc3 || check_udc || echo "")

# If still unknown, check lsusb after brief delay (host controller needs time)
if [ -z "$ROLE" ]; then
    sleep 2
    ROLE=$(check_lsusb || echo "")
fi

# Write result
if [ -n "$ROLE" ]; then
    echo "$ROLE" > "$ROLE_FILE"
    echo "[USB-ROLE] Detected: $ROLE"
    exit 0
else
    echo "[USB-ROLE] Unknown — defaulting to gadget"
    echo "gadget" > "$ROLE_FILE"
    exit 0
fi