#!/usr/bin/env bash
#
# snapshot-cgroup - Copy cgroup v2 files from the live system into a
# directory tree suitable for use with TestIntegrationCgroupLimits.
#
# Usage: snapshot-cgroup <output-dir>
#
# The script reads /proc/self/cgroup to find the v2 group path and copies
# exactly the files that the cgroup package needs:
#
#   proc/self/cgroup
#   sys/fs/cgroup/<group>/cpu.max
#   sys/fs/cgroup/<group>/memory.max

set -euo pipefail

if [[ $# -ne 1 ]]; then
    echo "Usage: $0 <output-dir>" >&2
    exit 1
fi

out="$1"
mkdir -p "$out"

copy_file() {
    local src="$1" dst="$out/$2"
    mkdir -p "$(dirname "$dst")"
    cp "$src" "$dst"
}

copy_file /proc/self/cgroup proc/self/cgroup

group=$(awk -F: '/^0::/ { print $3 }' /proc/self/cgroup)
cgdir="/sys/fs/cgroup${group}"

for f in cpu.max memory.max; do
    if [[ -f "$cgdir/$f" ]]; then
        copy_file "$cgdir/$f" "sys/fs/cgroup${group}/$f"
    fi
done

echo "Snapshot written to $out"