# frozen_string_literal: true

class AddCompositeIndexToStats < ActiveRecord::Migration[8.0]
  disable_ddl_transaction!

  BATCH_SIZE = 1000

  def change
    total_duplicates = execute(<<-SQL.squish).first['count'].to_i
      SELECT COUNT(*) as count
      FROM stats s1
      WHERE EXISTS (
        SELECT 1 FROM stats s2
        WHERE s2.user_id = s1.user_id
          AND s2.year = s1.year
          AND s2.month = s1.month
          AND s2.id > s1.id
      )
    SQL

    if total_duplicates.positive?
      Rails.logger.info(
        "Found #{total_duplicates} duplicate stats records. Starting cleanup in batches of #{BATCH_SIZE}..."
      )
    end

    deleted_count = 0
    loop do
      batch_deleted = execute(<<-SQL.squish).cmd_tuples
        DELETE FROM stats
        WHERE id IN (
          SELECT s1.id
          FROM stats s1
          WHERE EXISTS (
            SELECT 1 FROM stats s2
            WHERE s2.user_id = s1.user_id
              AND s2.year = s1.year
              AND s2.month = s1.month
              AND s2.id > s1.id
          )
          LIMIT #{BATCH_SIZE}
        )
      SQL

      break if batch_deleted.zero?

      deleted_count += batch_deleted
      Rails.logger.info("Cleaned up #{deleted_count}/#{total_duplicates} duplicate stats records")
    end

    Rails.logger.info("Completed cleanup: removed #{deleted_count} duplicate stats records") if deleted_count.positive?

    add_index :stats, %i[user_id year month],
              name: 'index_stats_on_user_id_year_month',
              unique: true,
              algorithm: :concurrently,
              if_not_exists: true

    BulkStatsCalculatingJob.perform_later
  end
end