#!/usr/bin/env bash
#
# setup-auto-updates.sh
#
# Universal unattended-upgrades setup for Debian & Ubuntu.
# - Uses Origins-Pattern (modern) with ${distro_id}/${distro_codename} macros
# - Safe for Debian Bookworm/Trixie and Ubuntu Noble+ (classic & deb822 sources)
# - Clears legacy Allowed-Origins to avoid fragile legacy parser
# - Enables APT Periodic + systemd timers (when present)
# - Dry-run validation that won’t abort the run if APT is busy
#
# Re-run safe: overwrites 50unattended-upgrades and 20auto-upgrades.

set -Eeuo pipefail
trap 'echo "[ERROR] Line $LINENO failed" >&2' ERR

REBOOT_TIME="${REBOOT_TIME:-04:00}"

require_root() {
  if [[ $EUID -ne 0 ]]; then
    echo "[ERROR] Run as root (sudo)." >&2
    exit 1
  fi
}

detect_os() {
  [[ -f /etc/os-release ]] || { echo "[ERROR] /etc/os-release not found." >&2; exit 1; }
  # shellcheck disable=SC1091
  . /etc/os-release
  local id="${ID,,}"
  case "$id" in
    debian|ubuntu) : ;;
    *) [[ "${ID_LIKE:-}" =~ debian ]] || { echo "[ERROR] Unsupported OS: $ID."; exit 1; } ;;
  esac
  echo "[INFO] Detected OS: ${PRETTY_NAME:-$ID}"
}

wait_for_apt() {
  echo "[INFO] Checking for apt/dpkg locks…"
  local locks=(/var/lib/dpkg/lock-frontend /var/lib/dpkg/lock /var/lib/apt/lists/lock)
  for i in {1..90}; do
    if ! fuser "${locks[@]}" >/dev/null 2>&1; then
      echo "[INFO] No locks detected."
      return 0
    fi
    (( i % 10 == 0 )) && echo "[INFO] apt/dpkg busy…waiting $(($i*2))s"
    sleep 2
  done
  echo "[WARN] apt/dpkg still busy after ~180s; continuing anyway."
  return 1
}

apt_refresh_and_install() {
  wait_for_apt || true
  echo "[INFO] Updating APT cache…"
  apt-get update -qq || true

  wait_for_apt || true
  echo "[INFO] Installing unattended-upgrades…"
  DEBIAN_FRONTEND=noninteractive apt-get install -y unattended-upgrades >/dev/null || true

  # Ensure periodic is enabled via debconf
  echo 'unattended-upgrades unattended-upgrades/enable_auto_updates boolean true' | debconf-set-selections || true
  DEBIAN_FRONTEND=noninteractive dpkg-reconfigure -f noninteractive unattended-upgrades >/dev/null || true
}

write_50unattended() {
  # Use a single-quoted heredoc to avoid expanding ${distro_*} macros here.
  # Then substitute REBOOT_TIME safely afterward.
  cat > /etc/apt/apt.conf.d/50unattended-upgrades <<'EOF'
// Auto-installed by setup-auto-updates.sh
// Use Origins-Pattern only; clear legacy to avoid fragile parsing.

#clear Unattended-Upgrade::Allowed-Origins;
#clear Unattended-Upgrade::Origins-Pattern;

Unattended-Upgrade::Origins-Pattern {
    // Cross-distro (Debian or Ubuntu) standard pockets (archive form)
    "origin=${distro_id},archive=${distro_codename}";
    "origin=${distro_id},archive=${distro_codename}-updates";
    "origin=${distro_id},archive=${distro_codename}-security";

    // Also allow codename form to match mirrors that expose only n=
    "origin=${distro_id},codename=${distro_codename}";
    "origin=${distro_id},codename=${distro_codename}-updates";
    "origin=${distro_id},codename=${distro_codename}-security";

    // Ubuntu ESM (harmless on Debian; matches only if present/attached)
    "origin=UbuntuESM,archive=${distro_codename}-infra-security";
    "origin=UbuntuESMApps,archive=${distro_codename}-apps-security";
};

Unattended-Upgrade::Automatic-Reboot "true";
Unattended-Upgrade::Automatic-Reboot-Time "REBOOT_TIME_PLACEHOLDER";
Unattended-Upgrade::Automatic-Reboot-WithUsers "false";

Unattended-Upgrade::Remove-Unused-Dependencies "true";
Unattended-Upgrade::Remove-New-Unused-Dependencies "true";

Unattended-Upgrade::SyslogEnable "true";
Unattended-Upgrade::Verbose "0";
EOF

  # Inject the desired reboot time without touching macro lines
  sed -i "s/REBOOT_TIME_PLACEHOLDER/${REBOOT_TIME}/" /etc/apt/apt.conf.d/50unattended-upgrades
}

write_20auto() {
  cat > /etc/apt/apt.conf.d/20auto-upgrades <<'EOF'
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "1";
APT::Periodic::Unattended-Upgrade "1";
APT::Periodic::AutocleanInterval "7";
EOF
}

enable_timers_if_systemd() {
  if command -v systemctl >/dev/null 2>&1; then
    systemctl enable --now apt-daily.timer apt-daily-upgrade.timer 2>/dev/null || true
  fi
}

validate_with_dryrun() {
  wait_for_apt || true
  echo "[INFO] Validating unattended-upgrades with a dry run…"
  local log="/tmp/unattended-upgrades-dryrun.$$"
  if ! timeout 180 unattended-upgrades --dry-run --debug >"$log" 2>&1; then
    echo "[WARN] Dry run timed out or failed; see $log"
    return 1
  fi
  # Show the header line so you can see what matched
  grep -E "Allowed origins are" "$log" | head -n1 || true
  # Catch real parser errors
  if grep -qiE "Unable to parse|ValueError|AttributeError|ImportError" "$log"; then
    echo "[ERROR] Parsing error detected; see $log"
    return 1
  fi
}

show_status() {
  echo
  echo "[INFO] Config files:"
  ls -la /etc/apt/apt.conf.d/20auto-upgrades /etc/apt/apt.conf.d/50unattended-upgrades 2>/dev/null || true
  echo
  if command -v systemctl >/dev/null 2>&1; then
    echo "[INFO] Timers:"
    systemctl list-timers --all | grep -E 'apt-(daily|daily-upgrade)\.timer' || true
  else
    echo "[INFO] systemd not present; relying on APT::Periodic via cron."
  fi
}

main() {
  echo "[INFO] Unattended-upgrades configurator (Debian/Ubuntu)"
  require_root
  detect_os
  apt_refresh_and_install
  write_50unattended
  write_20auto

  # If detect_os didn't export OS, derive it so we can gate ESM cleanup.
  if [[ -z "${OS:-}" ]] && [[ -r /etc/os-release ]]; then
    # shellcheck disable=SC1091
    . /etc/os-release
    OS="${ID,,}"
  fi

  # Drop Ubuntu ESM patterns on non-Ubuntu systems (cosmetic; harmless if kept).
  if [[ "${OS:-}" != "ubuntu" ]]; then
    sed -i '/UbuntuESM/d' /etc/apt/apt.conf.d/50unattended-upgrades
  fi

  enable_timers_if_systemd

  # Non-fatal validation (avoid aborting the run if APT is busy).
  set +e
  validate_with_dryrun
  vr=$?
  set -e
  if (( vr != 0 )); then
    echo "[WARN] Validation failed or timed out. Config is written; timers/periodic will still run."
  fi

  show_status
  echo
  echo "[OK] Unattended updates configured. Regular + security updates will apply automatically; reboot at ${REBOOT_TIME} if needed."
}

main "$@"