#!/usr/bin/env bash

set -euo pipefail

[ -z "${1:-}" ] && { echo "Usage: $0 <tarball>"; exit 1; }

tarball=$(realpath "$1")
top_dir=$(tar -tf "$tarball" | sed -e 's/^\.\///' | cut -d/ -f1 | sort -u)

if [ "$(echo "$top_dir" | wc -l)" -ne 1 ]; then
    echo "Error: Tarball must contain a single top-level directory."
    exit 1
fi

mountpoint=$(mktemp -d)
cleanup() {
    cd /
    umount "$mountpoint" 2>/dev/null || true
    rmdir "$mountpoint"
}
trap cleanup EXIT

sudo mount -t tmpfs -o size=8G tmpfs "$mountpoint"
tar -xf "$tarball" -C "$mountpoint"

cd "$mountpoint/$top_dir"
echo "Spawning shell in tmpfs. Type 'exit' to finish and cleanup."
bash
