#!/bin/bash
# Emits {"gpu":<pct>} (or {"gpu":null} if unavailable/disabled).
set -uo pipefail

VENDOR="auto"
while (($# > 0)); do
    case "$1" in
    --vendor)
        VENDOR="${2:-auto}"
        shift 2
        ;;
    *) shift ;;
    esac
done

detect_vendor() {
    if command -v nvidia-smi >/dev/null 2>&1; then
        echo "nvidia"
    elif compgen -G "/sys/class/drm/card*/device/gpu_busy_percent" >/dev/null; then
        echo "amd"
    elif command -v intel_gpu_top >/dev/null 2>&1; then
        echo "intel"
    else
        echo "none"
    fi
}

vendor="$VENDOR"
[[ "$vendor" == "auto" ]] && vendor=$(detect_vendor)

gpu_pct="null"
case "$vendor" in
nvidia)
    if command -v nvidia-smi >/dev/null 2>&1; then
        v=$(nvidia-smi --query-gpu=utilization.gpu --format=csv,noheader,nounits 2>/dev/null | head -1 | tr -dc '0-9')
        [[ -n "$v" ]] && gpu_pct="$v"
    fi
    ;;
amd)
    f=$(compgen -G "/sys/class/drm/card*/device/gpu_busy_percent" | head -1)
    if [[ -n "$f" && -r "$f" ]]; then
        v=$(<"$f")
        [[ "$v" =~ ^[0-9]+$ ]] && gpu_pct="$v"
    fi
    ;;
intel)
    if command -v intel_gpu_top >/dev/null 2>&1 && command -v jq >/dev/null 2>&1; then
        v=$(timeout 1 intel_gpu_top -J -o - -s 200 -n 1 2>/dev/null | jq -r '.[0].engines["Render/3D"].busy // empty' 2>/dev/null)
        [[ -n "$v" ]] && gpu_pct=$(awk -v r="$v" 'BEGIN { p=r+0; if(p<0)p=0; if(p>100)p=100; printf "%.0f", p }')
    fi
    ;;
esac

printf '{"gpu":%s}\n' "$gpu_pct"