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

URI="qemu:///system"

IMGROOT="/var/lib/libvirt/images"
BASEDIR="$IMGROOT/base"
LABDIR="$IMGROOT/lab"

TEMPLATE_DOMAIN="debian13-template"
TEMPLATE_BASE="$BASEDIR/debian13-template.qcow2"

usage() {
  echo "Usage: kvm-lab-create <lab-name> [--base template|work01|/abs/path.qcow2] [--start]"
  echo "Examples:"
  echo "  kvm-lab-create lab10 --base template --start"
  echo "  kvm-lab-create lab11 --base work01 --start"
  echo "  kvm-lab-create lab12 --base /var/lib/libvirt/images/base/custom.qcow2 --start"
}

# --- Parse args ---
NAME="${1:-}"
shift || true

BASESEL="template"
START="no"

while [[ $# -gt 0 ]]; do
  case "$1" in
    --base)
      BASESEL="${2:-}"
      shift 2
      ;;
    --start)
      START="yes"
      shift
      ;;
    -h|--help)
      usage
      exit 0
      ;;
    *)
      echo "ERROR: Unknown argument: $1"
      usage
      exit 1
      ;;
  esac
done

if [[ -z "$NAME" ]]; then
  usage
  exit 1
fi

DISK="${LABDIR}/${NAME}.qcow2"
XML_TMP="$(mktemp "/tmp/${NAME}.xml.XXXXXX")"
cleanup() { rm -f "$XML_TMP"; }
trap cleanup EXIT

# --- Resolve base selection ---
resolve_base() {
  local sel="$1"
  if [[ "$sel" == "template" ]]; then
    echo "$TEMPLATE_BASE"
    return 0
  fi

  if [[ "$sel" == "work01" ]]; then
    # Pick newest promoted work01 base (must exist first)
    local latest
    latest="$(ls -1t "$BASEDIR"/work01-base-*.qcow2 2>/dev/null | head -n 1 || true)"
    if [[ -z "$latest" ]]; then
      echo "ERROR: No work01 base found in $BASEDIR (expected work01-base-*.qcow2)."
      echo "Action: run your promote script to create one."
      return 1
    fi
    echo "$latest"
    return 0
  fi

  # Absolute path base
  if [[ "$sel" == /* ]]; then
    echo "$sel"
    return 0
  fi

  echo "ERROR: Invalid --base '$sel' (use template|work01|/abs/path.qcow2)"
  return 1
}

BASE="$(resolve_base "$BASESEL")"

# --- Preconditions (read-only checks) ---
if [[ ! -d "$LABDIR" ]]; then
  echo "ERROR: Lab directory missing: $LABDIR"
  exit 1
fi

if ! sudo test -r "$BASE"; then
  echo "ERROR: Base image not readable (via sudo): $BASE"
  exit 1
fi

if [[ -e "$DISK" ]]; then
  echo "ERROR: Disk already exists: $DISK"
  exit 1
fi

if virsh -c "$URI" dominfo "$NAME" &>/dev/null; then
  echo "ERROR: Domain already exists: $NAME"
  exit 1
fi

if ! virsh -c "$URI" dominfo "$TEMPLATE_DOMAIN" &>/dev/null; then
  echo "ERROR: Template domain not found in $URI: $TEMPLATE_DOMAIN"
  exit 1
fi

# --- Create overlay disk ---
echo "Using base: $BASE"
echo "Creating overlay disk: $DISK"
sudo qemu-img create -f qcow2 -F qcow2 -b "$BASE" "$DISK" >/dev/null
sudo chown libvirt-qemu:libvirt "$DISK"
sudo chmod 0660 "$DISK"

echo "Validating backing file..."
sudo qemu-img info "$DISK" | grep -E "file format:|virtual size:|backing file:" || true

# --- Clone domain XML ---
echo "Cloning domain XML from: $TEMPLATE_DOMAIN"
virsh -c "$URI" dumpxml "$TEMPLATE_DOMAIN" > "$XML_TMP"

# Set name, disk path, and force NAT-only network "default"
sed -i \
  -e "s|<name>${TEMPLATE_DOMAIN}</name>|<name>${NAME}</name>|" \
  -e "s|${TEMPLATE_BASE}|${DISK}|g" \
  -e "s|<source network='[^']*'|<source network='default'|g" \
  "$XML_TMP"

# Remove UUID to avoid collision with template
sed -i -E '/<uuid>[^<]*<\/uuid>/d' "$XML_TMP"

# Remove any host filesystem passthrough (if present)
perl -0777 -i -pe 's/<filesystem[\s\S]*?<\/filesystem>\n?//g' "$XML_TMP"

# --- Define domain ---
echo "Defining domain: $NAME"
virsh -c "$URI" define "$XML_TMP" >/dev/null

# --- Optional start ---
if [[ "$START" == "yes" ]]; then
  echo "Starting domain: $NAME"
  virsh -c "$URI" start "$NAME" >/dev/null
fi

echo "OK: Lab '$NAME' created (disk: $DISK)."
if [[ "$START" != "yes" ]]; then
  echo "To start: virsh -c $URI start $NAME"
fi