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

OUTPUT_PATH="${OUTPUT_PATH:-/mnt/user/services/posture-check/last.json}"
NTFY_BASE_URL="${NTFY_BASE_URL:-https://ntfy.kaleschke.info}"
WARNING_TOPIC="${WARNING_TOPIC:-homelab-alerts}"
CRITICAL_TOPIC="${CRITICAL_TOPIC:-homelab-alerts}"
SEND_NTFY="${SEND_NTFY:-1}"
TMP_DIR="${TMP_DIR:-/tmp/kallilab-posture-check}"
ALLOW_DISK1_NTFS="${ALLOW_DISK1_NTFS:-0}"
ALERT_STATE_PATH="${ALERT_STATE_PATH:-/mnt/user/services/posture-check/last-alert.state}"
ALERT_REPEAT_SECONDS="${ALERT_REPEAT_SECONDS:-86400}"
SKIP_AUTHELIA_DRIFT="${SKIP_AUTHELIA_DRIFT:-0}"
AUTHELIA_DIFF_SCRIPT="${AUTHELIA_DIFF_SCRIPT:-/mnt/user/services/homelab-infra/services/authelia-diff.sh}"

mkdir -p "$TMP_DIR"
RESULTS_FILE="$TMP_DIR/results.$$"
: > "$RESULTS_FILE"

cleanup() {
  rm -f "$RESULTS_FILE"
}
trap cleanup EXIT

json_escape() {
  sed \
    -e 's/\\/\\\\/g' \
    -e 's/"/\\"/g' \
    -e 's/\t/\\t/g'
}

add_result() {
  local severity="$1"
  local name="$2"
  local message="$3"
  printf '%s\t%s\t%s\n' "$severity" "$name" "$message" >> "$RESULTS_FILE"
}

need_cmd() {
  if ! command -v "$1" >/dev/null 2>&1; then
    add_result "warning" "command_$1" "Command missing: $1"
    return 1
  fi
}

check_fstype() {
  local path="$1"
  local expected="$2"
  local severity="$3"
  local name="$4"
  local actual

  if ! command -v findmnt >/dev/null 2>&1; then
    add_result "warning" "$name" "Cannot check $path filesystem because findmnt is missing"
    return
  fi

  if ! actual="$(findmnt -no FSTYPE "$path" 2>/dev/null)"; then
    add_result "$severity" "$name" "Mount not found: $path"
    return
  fi

  if [ "$actual" = "$expected" ]; then
    add_result "ok" "$name" "$path filesystem is $actual"
  else
    add_result "$severity" "$name" "$path filesystem is $actual, expected $expected"
  fi
}

check_disk1_fstype() {
  local actual

  if ! command -v findmnt >/dev/null 2>&1; then
    add_result "warning" "disk1_fstype" "Cannot check /mnt/disk1 filesystem because findmnt is missing"
    return
  fi

  if ! actual="$(findmnt -no FSTYPE "/mnt/disk1" 2>/dev/null)"; then
    add_result "warning" "disk1_fstype" "Mount not found: /mnt/disk1"
    return
  fi

  if [ "$ALLOW_DISK1_NTFS" = "1" ]; then
    if [ "$actual" = "ntfs3" ] || [ "$actual" = "fuseblk" ]; then
      add_result "ok" "disk1_fstype" "/mnt/disk1 filesystem is $actual; temporarily allowed until Disk1 phase 2 migration"
    else
      add_result "warning" "disk1_fstype" "/mnt/disk1 filesystem is $actual, expected ntfs3/fuseblk during temporary Disk1 migration exception"
    fi
  else
    if [ "$actual" = "xfs" ]; then
      add_result "ok" "disk1_fstype" "/mnt/disk1 filesystem is $actual"
    else
      add_result "critical" "disk1_fstype" "/mnt/disk1 filesystem is $actual, expected xfs"
    fi
  fi
}

check_no_ntfs_on_core_mounts() {
  local hits
  local pattern="^/mnt/(cache|disk1)(/|$)"

  if ! command -v findmnt >/dev/null 2>&1; then
    add_result "warning" "no_ntfs_core_mounts" "Cannot check NTFS mounts because findmnt is missing"
    return
  fi

  if [ "$ALLOW_DISK1_NTFS" = "1" ]; then
    pattern="^/mnt/cache(/|$)"
  fi

  hits="$(findmnt -rn -o TARGET,FSTYPE 2>/dev/null | awk -v pattern="$pattern" '$1 ~ pattern && ($2 == "ntfs3" || $2 == "fuseblk") { print $1 ":" $2 }' | paste -sd ',' -)"
  if [ -n "$hits" ]; then
    add_result "critical" "no_ntfs_core_mounts" "NTFS-like filesystem on core mount: $hits"
  elif [ "$ALLOW_DISK1_NTFS" = "1" ]; then
    add_result "ok" "no_ntfs_core_mounts" "No NTFS on /mnt/cache; /mnt/disk1 NTFS is temporarily allowed until Disk1 phase 2 migration"
  else
    add_result "ok" "no_ntfs_core_mounts" "No ntfs3/fuseblk mounts below /mnt/cache or /mnt/disk1"
  fi
}

check_mover_drift() {
  local path="/mnt/disk1/appdata"
  if [ ! -d "$path" ]; then
    add_result "ok" "mover_drift_appdata" "$path does not exist"
    return
  fi

  if find "$path" -mindepth 1 -print -quit | grep -q .; then
    add_result "critical" "mover_drift_appdata" "$path contains entries; appdata should stay cache-only"
  else
    add_result "ok" "mover_drift_appdata" "$path is empty"
  fi
}

check_inode_usage() {
  local path="$1"
  local max_percent="$2"
  local name="$3"
  local use_percent

  if ! use_percent="$(df -Pi "$path" 2>/dev/null | awk 'NR==2 { gsub("%", "", $5); print $5 }')"; then
    add_result "warning" "$name" "Cannot read inode usage for $path"
    return
  fi
  if ! printf '%s' "$use_percent" | grep -Eq '^[0-9]+$'; then
    add_result "warning" "$name" "$path inode usage unavailable (${use_percent:-unknown})"
    return
  fi

  if [ "$use_percent" -lt "$max_percent" ]; then
    add_result "ok" "$name" "$path inode usage ${use_percent}%"
  else
    add_result "warning" "$name" "$path inode usage ${use_percent}% >= ${max_percent}%"
  fi
}

check_disk1_inode_usage() {
  if [ "$ALLOW_DISK1_NTFS" = "1" ]; then
    add_result "ok" "disk1_inode_usage" "/mnt/disk1 inode usage skipped; NTFS transition filesystem does not expose POSIX inode usage"
    return
  fi

  check_inode_usage "/mnt/disk1" 80 "disk1_inode_usage"
}

check_filesystem_usage() {
  local path="$1"
  local max_percent="$2"
  local name="$3"
  local severity="$4"
  local use_percent

  if ! use_percent="$(df -P "$path" 2>/dev/null | awk 'NR==2 { gsub("%", "", $5); print $5 }')"; then
    add_result "warning" "$name" "Cannot read filesystem usage for $path"
    return
  fi

  if [ "$use_percent" -lt "$max_percent" ]; then
    add_result "ok" "$name" "$path usage ${use_percent}%"
  else
    add_result "$severity" "$name" "$path usage ${use_percent}% >= ${max_percent}%"
  fi
}

check_nvme_smart() {
  local device="${NVME_DEVICE:-/dev/nvme0n1}"
  local smart
  local warning
  local percentage_used
  local media_errors

  if ! need_cmd nvme; then
    return
  fi

  if ! smart="$(nvme smart-log "$device" 2>/dev/null)"; then
    add_result "critical" "nvme_smart" "Cannot read nvme smart-log for $device"
    return
  fi

  warning="$(printf '%s\n' "$smart" | awk -F: '/critical_warning/ { gsub(/[[:space:]]/, "", $2); print $2; exit }')"
  percentage_used="$(printf '%s\n' "$smart" | awk -F: '/percentage_used/ { gsub(/[^0-9]/, "", $2); print $2; exit }')"
  media_errors="$(printf '%s\n' "$smart" | awk -F: '/media_errors/ { gsub(/[^0-9]/, "", $2); print $2; exit }')"

  if [ "${warning:-0}" = "0" ] || [ "${warning:-0}" = "0x00" ]; then
    add_result "ok" "nvme_critical_warning" "$device critical_warning ${warning:-0}"
  else
    add_result "critical" "nvme_critical_warning" "$device critical_warning ${warning}"
  fi

  if [ -n "${percentage_used:-}" ] && [ "$percentage_used" -lt 80 ]; then
    add_result "ok" "nvme_percentage_used" "$device percentage_used ${percentage_used}%"
  else
    add_result "critical" "nvme_percentage_used" "$device percentage_used ${percentage_used:-unknown}, expected <80"
  fi

  if [ "${media_errors:-0}" = "0" ]; then
    add_result "ok" "nvme_media_errors" "$device media_errors 0"
  else
    add_result "warning" "nvme_media_errors" "$device media_errors ${media_errors}"
  fi
}

check_authelia_config_drift() {
  if [ "$SKIP_AUTHELIA_DRIFT" = "1" ]; then
    add_result "ok" "authelia_config_drift" "Authelia drift check skipped via SKIP_AUTHELIA_DRIFT=1"
    return
  fi

  if [ ! -x "$AUTHELIA_DIFF_SCRIPT" ] && [ ! -f "$AUTHELIA_DIFF_SCRIPT" ]; then
    add_result "warning" "authelia_config_drift" "Authelia diff script missing: $AUTHELIA_DIFF_SCRIPT"
    return
  fi

  local output
  local rc
  output="$(bash "$AUTHELIA_DIFF_SCRIPT" 2>&1)"
  rc=$?

  case "$rc" in
    0)
      add_result "ok" "authelia_config_drift" "Authelia repo baseline matches host config (access_control)"
      ;;
    1)
      add_result "warning" "authelia_config_drift" "Authelia repo<->host drift in access_control; run authelia-diff.sh for details"
      ;;
    2)
      add_result "warning" "authelia_config_drift" "Authelia diff aborted: $output"
      ;;
    3)
      add_result "warning" "authelia_config_drift" "Authelia diff: section missing in repo or host: $output"
      ;;
    *)
      add_result "warning" "authelia_config_drift" "Authelia diff returned unexpected rc=$rc: $output"
      ;;
  esac
}

send_ntfy() {
  local severity="$1"
  local topic="$2"
  local body="$3"

  if [ "$SEND_NTFY" != "1" ]; then
    return
  fi

  if command -v curl >/dev/null 2>&1; then
    printf '%s\n' "$body" | curl -fsS \
      -H "Title: KalliLab posture-check $severity" \
      -H "Priority: high" \
      --data-binary @- \
      "$NTFY_BASE_URL/$topic" >/dev/null || true
  fi
}

alert_fingerprint() {
  awk -F '\t' '$1 != "ok" { printf "%s|%s|%s\n", $1, $2, $3 }' "$RESULTS_FILE" | cksum | awk '{ print $1 ":" $2 }'
}

alert_summary() {
  awk -F '\t' '$1 != "ok" { printf "%s:%s; ", $1, $2 }' "$RESULTS_FILE" | sed 's/; $//'
}

should_send_alert() {
  local fingerprint="$1"
  local now
  local last_fingerprint=""
  local last_sent="0"

  now="$(date +%s)"

  if ! printf '%s' "$ALERT_REPEAT_SECONDS" | grep -Eq '^[0-9]+$'; then
    ALERT_REPEAT_SECONDS=86400
  fi

  if [ -f "$ALERT_STATE_PATH" ]; then
    IFS="$(printf '\t')" read -r last_fingerprint last_sent < "$ALERT_STATE_PATH" || true
  fi

  if [ "$fingerprint" != "$last_fingerprint" ]; then
    return 0
  fi

  if ! printf '%s' "$last_sent" | grep -Eq '^[0-9]+$'; then
    return 0
  fi

  if [ $((now - last_sent)) -ge "$ALERT_REPEAT_SECONDS" ]; then
    return 0
  fi

  return 1
}

remember_alert() {
  local fingerprint="$1"
  local now

  now="$(date +%s)"
  mkdir -p "$(dirname "$ALERT_STATE_PATH")"
  printf '%s\t%s\n' "$fingerprint" "$now" > "$ALERT_STATE_PATH.tmp"
  mv "$ALERT_STATE_PATH.tmp" "$ALERT_STATE_PATH"
}

clear_alert_state() {
  rm -f "$ALERT_STATE_PATH" "$ALERT_STATE_PATH.tmp"
}

send_alert_once() {
  local severity="$1"
  local topic="$2"
  local body="$3"
  local fingerprint
  local summary

  fingerprint="$(alert_fingerprint)"
  summary="$(alert_summary)"

  if [ -n "$summary" ]; then
    body="$body Checks: $summary"
  fi

  if should_send_alert "$fingerprint"; then
    send_ntfy "$severity" "$topic" "$body"
    remember_alert "$fingerprint"
  fi
}

write_json() {
  local timestamp
  local critical_count
  local warning_count
  local status
  local first=1

  timestamp="$(date -Iseconds)"
  critical_count="$(awk -F '\t' '$1 == "critical" { count++ } END { print count + 0 }' "$RESULTS_FILE")"
  warning_count="$(awk -F '\t' '$1 == "warning" { count++ } END { print count + 0 }' "$RESULTS_FILE")"

  if [ "$critical_count" -gt 0 ]; then
    status="critical"
  elif [ "$warning_count" -gt 0 ]; then
    status="warning"
  else
    status="ok"
  fi

  mkdir -p "$(dirname "$OUTPUT_PATH")"
  {
    printf '{\n'
    printf '  "timestamp": "%s",\n' "$(printf '%s' "$timestamp" | json_escape)"
    printf '  "status": "%s",\n' "$status"
    printf '  "critical_count": %s,\n' "$critical_count"
    printf '  "warning_count": %s,\n' "$warning_count"
    printf '  "checks": [\n'
    while IFS="$(printf '\t')" read -r severity name message; do
      if [ "$first" -eq 0 ]; then
        printf ',\n'
      fi
      first=0
      printf '    {"severity":"%s","name":"%s","message":"%s"}' \
        "$(printf '%s' "$severity" | json_escape)" \
        "$(printf '%s' "$name" | json_escape)" \
        "$(printf '%s' "$message" | json_escape)"
    done < "$RESULTS_FILE"
    printf '\n  ]\n'
    printf '}\n'
  } > "$OUTPUT_PATH.tmp"
  mv "$OUTPUT_PATH.tmp" "$OUTPUT_PATH"

  cat "$OUTPUT_PATH"

  if [ "$status" = "critical" ]; then
    send_alert_once "critical" "$CRITICAL_TOPIC" "Posture-check critical: $critical_count critical, $warning_count warning. See $OUTPUT_PATH"
    return 2
  fi
  if [ "$status" = "warning" ]; then
    send_alert_once "warning" "$WARNING_TOPIC" "Posture-check warning: $warning_count warning. See $OUTPUT_PATH"
    return 1
  fi

  clear_alert_state
}

main() {
  need_cmd findmnt || true
  need_cmd df || true
  need_cmd awk || true

  check_fstype "/mnt/cache" "xfs" "critical" "cache_fstype"
  check_disk1_fstype
  check_no_ntfs_on_core_mounts
  check_mover_drift
  check_inode_usage "/mnt/cache" 80 "cache_inode_usage"
  check_disk1_inode_usage
  check_filesystem_usage "/mnt/cache" 70 "cache_fill_level" "warning"

  for share in appdata system domains; do
    if [ -e "/mnt/user/$share" ]; then
      check_filesystem_usage "/mnt/user/$share" 70 "share_${share}_fill_level" "warning"
    else
      add_result "warning" "share_${share}_fill_level" "/mnt/user/$share missing"
    fi
  done

  check_nvme_smart
  check_authelia_config_drift
  write_json
}

main "$@"