#!/usr/bin/env bash

# Enumerates GPUs that can report utilisation, with a readable name for each.
#
# Panama's vitals readout needs one specific sysfs file, and the card numbering
# is neither stable across machines nor meaningful to a person: this box has
# card1 and card2, both amdgpu, one discrete and one integrated. Picking a
# number blindly shows whichever the kernel happened to enumerate first.
#
# Names come from lspci where available, because the sysfs device directory
# exposes only numeric vendor/device ids.

set -euo pipefail

first=true
printf '['

for busy in /sys/class/drm/card*/device/gpu_busy_percent; do
    [[ -r "$busy" ]] || continue

    device_dir="$(dirname "$busy")"
    card="$(basename "$(dirname "$device_dir")")"

    # The device directory is a symlink into the PCI tree; its target's basename
    # is the PCI address lspci wants.
    pci="$(basename "$(readlink -f "$device_dir")" 2>/dev/null || true)"
    name=""
    if [[ -n "$pci" ]] && command -v lspci >/dev/null 2>&1; then
        # Strip the leading domain: lspci -s wants 00:02.0, sysfs gives 0000:00:02.0
        short="${pci#*:}"
        name="$(lspci -s "$short" 2>/dev/null | sed -E 's/^[^ ]+ [^:]+: //' | head -1)"
    fi
    if [[ -z "$name" ]]; then
        driver="$(sed -n 's/^DRIVER=//p' "$device_dir/uevent" 2>/dev/null | head -1)"
        name="${driver:-Graphics} ($card)"
    fi

    reading="$(cat "$busy" 2>/dev/null || printf '')"
    [[ "$reading" =~ ^[0-9]+$ ]] || reading=-1

    [[ "$first" == true ]] || printf ','
    first=false
    printf '{"card":"%s","path":"%s","name":%s,"busy":%s}' \
        "$card" "$busy" "$(printf '%s' "$name" | jq -Rs .)" "$reading"
done

printf ']\n'