#!/usr/bin/env bash
set -euo pipefail

URI="qemu:///system"
IMGROOT="/var/lib/libvirt/images"
BASEDIR="$IMGROOT/base"
SNAPROOT="$HOME/.backup/kvm-labs"

usage() {
  echo "Usage: kvm-promote-to-base <vm-name> [--disk vda]"
  echo "Creates: $BASEDIR/<vm-name>-base-YYYY-MM-DD_HHMMSS.qcow2"
  exit 1
}

VM="${1:-}"
DISKTGT="vda"

shift || true
while [[ $# -gt 0 ]]; do
  case "$1" in
    --disk)
      DISKTGT="${2:-}"
      shift 2
      ;;
    -h|--help)
      usage
      ;;
    *)
      echo "ERROR: Unknown arg: $1"
      usage
      ;;
  esac
done

if [[ -z "$VM" ]]; then
  usage
fi

if [[ ! -d "$BASEDIR" ]]; then
  echo "ERROR: Base directory missing: $BASEDIR"
  exit 1
fi

state="$(virsh -c "$URI" domstate "$VM" 2>/dev/null | tr -d '\r' || true)"
if [[ "$state" != "shut off" ]]; then
  echo "ERROR: VM must be shut off for consistent promotion."
  echo "VM: $VM"
  echo "State: ${state:-unknown}"
  exit 1
fi

DISK="$(virsh -c "$URI" domblklist "$VM" --details | awk -v t="$DISKTGT" '$3==t{print $4}')"
if [[ -z "$DISK" || ! -f "$DISK" ]]; then
  echo "ERROR: Cannot locate disk for $VM target=$DISKTGT"
  echo "Detected: '$DISK'"
  exit 1
fi

TS="$(date +%F_%H%M%S)"
SNAPDIR="$SNAPROOT/${TS}-promote-${VM}"
NEWBASE="$BASEDIR/${VM}-base-${TS}.qcow2"

mkdir -p "$SNAPDIR"

# Snapshot metadata (read-only)
virsh -c "$URI" dumpxml "$VM" > "$SNAPDIR/${VM}.xml"
sudo qemu-img info --backing-chain "$DISK" > "$SNAPDIR/${VM}.${DISKTGT}.backing-chain.txt" || true
sudo ls -l "$DISK" > "$SNAPDIR/${VM}.${DISKTGT}.ls.txt" || true

echo "Creating base image:"
echo "  VM:     $VM"
echo "  Disk:   $DISK (target: $DISKTGT)"
echo "  Target: $NEWBASE"

sudo qemu-img convert -O qcow2 "$DISK" "$NEWBASE"
sudo chown libvirt-qemu:libvirt "$NEWBASE"
sudo chmod 0660 "$NEWBASE"

echo "Verifying new base has no backing file..."
if sudo qemu-img info "$NEWBASE" | grep -q '^backing file:'; then
  echo "ERROR: New base unexpectedly has a backing file. Aborting."
  exit 1
fi

echo "SUCCESS: $NEWBASE"
echo "Snapshot: $SNAPDIR"