/**
 * Rollback script for LNM-21-102-DEV legacy advisory backfill migration.
 * Removes backfilled observations and linksets by querying the backfill_marker field,
 * then clears the tombstone markers from advisory_raw.
 *
 * Usage:
 *   mongo concelier ops/devops/scripts/rollback-lnm-backfill.js
 *
 * Environment variables:
 *   DRY_RUN - if set to "1", only reports what would be deleted without making changes.
 *   BATCH_SIZE - optional batch size for deletions (default 500).
 *
 * After running this script, delete the migration record:
 *   db.schema_migrations.deleteOne({ _id: "20251127_lnm_legacy_backfill" })
 *
 * Then restart the Concelier service.
 */
(function () {
  var BACKFILL_MARKER = "lnm_21_102_dev";

  function toInt(value, fallback) {
    var parsed = parseInt(value, 10);
    return Number.isFinite(parsed) && parsed > 0 ? parsed : fallback;
  }

  function toBool(value) {
    return value === "1" || value === "true" || value === true;
  }

  var dryRun = typeof DRY_RUN !== "undefined" ? toBool(DRY_RUN) : false;
  var batchSize = typeof BATCH_SIZE !== "undefined" ? toInt(BATCH_SIZE, 500) : 500;
  var database = db.getName ? db.getSiblingDB(db.getName()) : db;
  if (!database) {
    throw new Error("Unable to resolve database handle");
  }

  print("");
  print("== LNM-21-102-DEV Backfill Rollback ==");
  print("Database  : " + database.getName());
  print("Dry Run   : " + dryRun);
  print("Batch Size: " + batchSize);
  print("");

  // Step 1: Count and delete backfilled observations
  var observationsCollection = database.getCollection("advisory_observations");
  var observationsFilter = { backfill_marker: BACKFILL_MARKER };
  var observationsCount = observationsCollection.countDocuments(observationsFilter);

  print("Found " + observationsCount + " backfilled observations to remove.");

  if (!dryRun && observationsCount > 0) {
    var obsResult = observationsCollection.deleteMany(observationsFilter);
    print("Deleted " + obsResult.deletedCount + " observations.");
  }

  // Step 2: Count and delete backfilled linksets
  var linksetsCollection = database.getCollection("advisory_linksets");
  var linksetsFilter = { backfill_marker: BACKFILL_MARKER };
  var linksetsCount = linksetsCollection.countDocuments(linksetsFilter);

  print("Found " + linksetsCount + " backfilled linksets to remove.");

  if (!dryRun && linksetsCount > 0) {
    var linkResult = linksetsCollection.deleteMany(linksetsFilter);
    print("Deleted " + linkResult.deletedCount + " linksets.");
  }

  // Step 3: Clear tombstone markers from advisory_raw
  var rawCollection = database.getCollection("advisory_raw");
  var rawFilter = { backfill_marker: BACKFILL_MARKER };
  var rawCount = rawCollection.countDocuments(rawFilter);

  print("Found " + rawCount + " advisory_raw documents with tombstone markers to clear.");

  if (!dryRun && rawCount > 0) {
    var rawResult = rawCollection.updateMany(rawFilter, { $unset: { backfill_marker: "" } });
    print("Cleared tombstone markers from " + rawResult.modifiedCount + " advisory_raw documents.");
  }

  // Step 4: Summary
  print("");
  print("== Rollback Summary ==");
  if (dryRun) {
    print("DRY RUN - No changes were made.");
    print("Would delete " + observationsCount + " observations.");
    print("Would delete " + linksetsCount + " linksets.");
    print("Would clear " + rawCount + " tombstone markers.");
  } else {
    print("Observations deleted: " + observationsCount);
    print("Linksets deleted    : " + linksetsCount);
    print("Tombstones cleared  : " + rawCount);
  }

  print("");
  print("Next steps:");
  print("1. Delete the migration record:");
  print('   db.schema_migrations.deleteOne({ _id: "20251127_lnm_legacy_backfill" })');
  print("2. Restart the Concelier service.");
  print("");
})();