#!/usr/bin/env bash
# Boot a THROWAWAY copy-on-write overlay of the golden image, run commands over
# the serial console, then discard the overlay. The golden image is never
# mutated, so every boot starts from the exact same snapshot.
#
# Usage: boot-overlay.sh <golden.qcow2> [command ...]
#   With no command, runs a nina smoke test (help / hello / status).
# Tunables via env: MEM_MB (2048), SMP (2), BOOT_TIMEOUT (600)
set -euo pipefail

GOLDEN="${1:?usage: boot-overlay.sh <golden.qcow2> [command...]}"
shift || true
MEM_MB="${MEM_MB:-2048}"
SMP="${SMP:-2}"
BOOT_TIMEOUT="${BOOT_TIMEOUT:-600}"
[ -f "$GOLDEN" ] || { echo "missing golden: $GOLDEN" >&2; exit 1; }

if [ "$#" -gt 0 ]; then CMD="$*"; else
  CMD='/root/nina help; echo ---; /root/nina hello; echo ---; /root/nina --version 2>/dev/null || true'
fi

work="$(mktemp -d)"
trap 'rm -rf "$work"' EXIT
overlay="$work/overlay.qcow2"
qemu-img create -f qcow2 -b "$(cd "$(dirname "$GOLDEN")" && pwd)/$(basename "$GOLDEN")" -F qcow2 "$overlay" >/dev/null
echo "throwaway overlay: $overlay  (backing: $GOLDEN)"

export BO_OVERLAY="$overlay" BO_MEM="$MEM_MB" BO_SMP="$SMP" \
       BO_TIMEOUT="$BOOT_TIMEOUT" BO_CMD="$CMD"

expect -c '
  set timeout $env(BO_TIMEOUT)
  set overlay $env(BO_OVERLAY)
  set mem     $env(BO_MEM)
  set smp     $env(BO_SMP)
  set cmd     $env(BO_CMD)

  spawn qemu-system-x86_64 \
    -machine q35 -accel tcg -cpu max -smp $smp -m $mem \
    -drive file=$overlay,if=virtio,format=qcow2 \
    -netdev user,id=n0 -device virtio-net-pci,netdev=n0 \
    -nographic

  expect {
    timeout { puts "\n!! no autologin on serial"; exit 2 }
    "automatic login" {}
  }
  sleep 6
  send "echo NINA_SMOKE_BEGIN\r"
  expect { timeout { puts "\n!! shell not ready"; exit 3 } "NINA_SMOKE_BEGIN" {} }
  send "$cmd\r"
  send "echo NINA_SMOKE_END_RC=\$?\r"
  expect {
    timeout { puts "\n!! command timed out"; exit 3 }
    -re {NINA_SMOKE_END_RC=[0-9]+} {}
  }
  send "poweroff\r"
  set timeout 120
  expect eof
'

echo "=== overlay discarded; golden image unchanged ==="