#!/usr/bin/env bash
#
# setup-auto-updates.sh
#
# Universal unattended-upgrades setup for Debian & Ubuntu.
# - Uses Origins-Pattern (not legacy Allowed-Origins) for forward-compatibility
# - Works with sources.list and deb822 .sources
# - Enables security + updates pockets; optional Ubuntu ESM if present
# - Validates with a dry-run; resilient to apt/dpkg locks
#
# Notes:
#   * Backports/proposed are intentionally not enabled.
#   * On non-systemd hosts, APT::Periodic drives execution via cron.

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

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

OS=""
CODENAME=""
declare -a POLICY_PAIRS=()     # "Origin:Archive" from apt-cache
declare -a ORIGIN_PATTERNS=()  # "origin=...,archive=..."

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
  case "${ID,,}" in
    debian) OS="debian" ;;
    ubuntu) OS="ubuntu" ;;
    *) [[ "${ID_LIKE:-}" =~ debian ]] && OS="debian" || { echo "[ERROR] Unsupported OS: ${ID}."; exit 1; } ;;
  esac

  CODENAME="${VERSION_CODENAME:-${UBUNTU_CODENAME:-}}"
  if [[ -z "$CODENAME" ]] && command -v lsb_release >/dev/null 2>&1; then
    CODENAME="$(lsb_release -cs 2>/dev/null || true)"
  fi
  if [[ -z "$CODENAME" ]]; then
    CODENAME="$(apt-cache policy 2>/dev/null | sed -n 's/.*n=\([^,]*\).*/\1/p' | grep -E '^[a-z]+$' | head -n1 || true)"
  fi
  echo "[INFO] Detected OS: $OS  codename: ${CODENAME:-unknown}"
}

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
  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
}

extract_policy_pairs() {
  # Extract unique Origin:Archive pairs from apt-cache policy lines
  mapfile -t POLICY_PAIRS < <(
    apt-cache policy 2>/dev/null \
      | sed -n 's/.*o=\([^,]*\),a=\([^,]*\).*/\1:\2/p' \
      | awk 'NF' | sort -u
  )
}

build_origin_patterns() {
  ORIGIN_PATTERNS=()

  have_pair() { printf '%s\n' "${POLICY_PAIRS[@]}" | grep -Fxq -- "$1"; }
  add_pat()   { ORIGIN_PATTERNS+=("origin=$1,archive=$2"); }

  if [[ "$OS" == "debian" ]]; then
    # Consider common Debian suites (codename/stable/testing variants)
    local want=( "$CODENAME" "$CODENAME-updates" "$CODENAME-security"
                 stable stable-updates stable-security
                 testing testing-security )
    for a in "${want[@]}"; do
      have_pair "Debian:$a" && add_pat "Debian" "$a"
    done
    # Fallback if apt-cache didn’t show anything yet
    if [[ ${#ORIGIN_PATTERNS[@]} -eq 0 ]]; then
      ORIGIN_PATTERNS+=("origin=Debian,archive=$CODENAME"
                        "origin=Debian,archive=${CODENAME}-updates"
                        "origin=Debian,archive=${CODENAME}-security")
    fi
  else # ubuntu
    # Standard pockets
    for a in "$CODENAME" "${CODENAME}-updates" "${CODENAME}-security"; do
      have_pair "Ubuntu:$a" && add_pat "Ubuntu" "$a"
    done
    # Optional ESM, only if attached and present
    have_pair "UbuntuESM:${CODENAME}-infra-security"  && add_pat "UbuntuESM"    "${CODENAME}-infra-security"
    have_pair "UbuntuESMApps:${CODENAME}-apps-security" && add_pat "UbuntuESMApps" "${CODENAME}-apps-security"

    if [[ ${#ORIGIN_PATTERNS[@]} -eq 0 ]]; then
      ORIGIN_PATTERNS+=("origin=Ubuntu,archive=$CODENAME"
                        "origin=Ubuntu,archive=${CODENAME}-updates"
                        "origin=Ubuntu,archive=${CODENAME}-security")
    fi
  fi

  echo "[INFO] Origins-Pattern to be written:"
  printf '  %s\n' "${ORIGIN_PATTERNS[@]}"
}

write_50unattended() {
  local patterns=""
  for p in "${ORIGIN_PATTERNS[@]}"; do
    patterns+="    \"$p\";\n"
  done

  cat > /etc/apt/apt.conf.d/50unattended-upgrades <<EOF
// Auto-installed by setup-auto-updates.sh
// Use Origins-Pattern (modern) and explicitly clear legacy Allowed-Origins.

// Clear legacy stanzas to avoid legacy parser bugs.
#clear Unattended-Upgrade::Allowed-Origins;
#clear Unattended-Upgrade::Origins-Pattern;

Unattended-Upgrade::Origins-Pattern {
${patterns}
};

// Reboot policy
Unattended-Upgrade::Automatic-Reboot "true";
Unattended-Upgrade::Automatic-Reboot-Time "${REBOOT_TIME}";
Unattended-Upgrade::Automatic-Reboot-WithUsers "false";

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

// Logging
Unattended-Upgrade::SyslogEnable "true";
Unattended-Upgrade::Verbose "0";
EOF
}

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 $log"
    return 1
  fi
  grep -E "Allowed origins are" "$log" | head -n1 || true
  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
  extract_policy_pairs
  build_origin_patterns
  write_50unattended
  write_20auto
  enable_timers_if_systemd

  set +e
  validate_with_dryrun
  vr=$?
  set -e
  if (( vr != 0 )); then
    echo "[WARN] Validation failed or timed out. Config is written; normal timers/periodic will still run. Inspect the log above if needed."
  fi

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

main "$@"