# frozen_string_literal: true

# Service for managing DuckDB analytics database
# Provides fast analytical queries on events data using columnar storage
class AnalyticsDuckdbService
  include Singleton

  DUCKDB_PATH = Rails.root.join("storage", "analytics.duckdb").to_s
  BATCH_SIZE = 10_000

  # Execute block with connection, ensuring database and connection are closed afterward
  def with_connection
    db = DuckDB::Database.open(DUCKDB_PATH)
    conn = db.connect
    yield conn
  ensure
    conn&.close
    db&.close
  end

  # Create events table if it doesn't exist (must be called within with_connection block)
  def setup_schema(conn)
    conn.execute(<<~SQL)
      CREATE TABLE IF NOT EXISTS events (
        id BIGINT PRIMARY KEY,
        timestamp TIMESTAMP NOT NULL,
        ip_address VARCHAR,
        network_range_id BIGINT,
        country VARCHAR,
        company VARCHAR,
        asn INTEGER,
        asn_org VARCHAR,
        is_datacenter BOOLEAN,
        is_vpn BOOLEAN,
        is_proxy BOOLEAN,
        waf_action INTEGER,
        request_path VARCHAR,
        user_agent VARCHAR
      )
    SQL

    Rails.logger.info "[DuckDB] Schema setup complete"
  end

  # Get timestamp of oldest event in DuckDB
  # Returns nil if table is empty
  def oldest_event_timestamp
    with_connection do |conn|
      result = conn.query("SELECT MIN(timestamp) as oldest FROM events")
      first_row = result.first
      first_row&.first # Returns the value or nil
    end
  rescue StandardError => e
    Rails.logger.error "[DuckDB] Error getting oldest timestamp: #{e.message}"
    nil
  end

  # Get timestamp of newest event in DuckDB
  # Returns nil if table is empty
  def newest_event_timestamp
    with_connection do |conn|
      result = conn.query("SELECT MAX(timestamp) as newest FROM events")
      first_row = result.first
      first_row&.first # Returns the value or nil
    end
  rescue StandardError => e
    Rails.logger.error "[DuckDB] Error getting newest timestamp: #{e.message}"
    nil
  end

  # Get maximum event ID already synced to DuckDB
  def max_synced_id
    with_connection do |conn|
      result = conn.query("SELECT COALESCE(MAX(id), 0) as max_id FROM events")
      first_row = result.first
      first_row&.first || 0
    end
  rescue StandardError => e
    Rails.logger.error "[DuckDB] Error getting max ID: #{e.message}"
    0
  end

  # Sync new events from PostgreSQL to DuckDB
  # Uses PostgreSQL cursor for memory-efficient streaming
  # Uses Appender API for fast bulk inserts
  # Filters by ID to avoid duplicates
  def sync_new_events(from_timestamp)
    total_synced = 0

    with_connection do |conn|
      # Ensure table exists
      setup_schema(conn)

      # Get max ID already in DuckDB to avoid duplicates
      max_id_result = conn.query("SELECT COALESCE(MAX(id), 0) as max_id FROM events")
      max_id = max_id_result.first&.first || 0
      Rails.logger.info "[DuckDB] Syncing events from #{from_timestamp}, max_id=#{max_id}"

      start_time = Time.current
      appender = nil
      batch_count = 0

      begin
        # Use PostgreSQL cursor for memory-efficient streaming
        Event.where("timestamp >= ? AND id > ?", from_timestamp, max_id)
             .select(
               :id,
               :timestamp,
               :ip_address,
               :network_range_id,
               :country,
               :company,
               :asn,
               :asn_org,
               :is_datacenter,
               :is_vpn,
               :is_proxy,
               :waf_action,
               :request_path,
               :user_agent
             )
             .order(:id)
             .each_row(block_size: BATCH_SIZE) do |event_data|
          # Create new appender for each batch
          if batch_count % BATCH_SIZE == 0
            appender&.close # Close previous appender
            appender = conn.appender("events")
          end

          # Unpack event data from cursor row (Hash from each_row)
          begin
            appender.append_row(
              event_data["id"],
              event_data["timestamp"],
              event_data["ip_address"]&.to_s,
              event_data["network_range_id"],
              event_data["country"],
              event_data["company"],
              event_data["asn"],
              event_data["asn_org"],
              event_data["is_datacenter"],
              event_data["is_vpn"],
              event_data["is_proxy"],
              event_data["waf_action"],
              event_data["request_path"],
              event_data["user_agent"]
            )
          rescue StandardError => e
            Rails.logger.error "[DuckDB] Error appending event #{event_data['id']}: #{e.message}"
            Rails.logger.error "[DuckDB] event_data = #{event_data.inspect}"
            raise
          end

          batch_count += 1
          total_synced += 1

          # Log progress every BATCH_SIZE events
          if batch_count % BATCH_SIZE == 0
            Rails.logger.info "[DuckDB] Synced batch (total: #{total_synced} events)"
          end
        end

        # Close final appender
        appender&.close

        duration = Time.current - start_time
        rate = total_synced / duration if duration > 0
        Rails.logger.info "[DuckDB] Sync complete: #{total_synced} events in #{duration.round(2)}s (~#{rate&.round(0)} events/sec)"
      rescue StandardError => e
        appender&.close rescue nil # Ensure appender is closed on error
        Rails.logger.error "[DuckDB] Error syncing events: #{e.message}"
        Rails.logger.error e.backtrace.join("\n")
        raise # Re-raise to be caught by outer rescue
      end
    end

    total_synced
  rescue StandardError => e
    Rails.logger.error "[DuckDB] Sync failed: #{e.message}"
    0
  end

  # Execute analytical query on DuckDB
  def query(sql, *params)
    with_connection do |conn|
      conn.query(sql, *params)
    end
  rescue StandardError => e
    Rails.logger.error "[DuckDB] Query error: #{e.message}"
    Rails.logger.error "SQL: #{sql}"
    raise
  end

  # Get event count in DuckDB
  def event_count
    with_connection do |conn|
      result = conn.query("SELECT COUNT(*) as count FROM events")
      first_row = result.first
      first_row&.first || 0
    end
  rescue StandardError => e
    Rails.logger.error "[DuckDB] Error getting event count: #{e.message}"
    0
  end

  # Analytics query: Total events since timestamp
  def total_events_since(start_time)
    with_connection do |conn|
      result = conn.query("SELECT COUNT(*) as count FROM events WHERE timestamp >= ?", start_time)
      result.first&.first || 0
    end
  end

  # Analytics query: Event breakdown by WAF action
  def event_breakdown_by_action(start_time)
    with_connection do |conn|
      result = conn.query(<<~SQL, start_time)
        SELECT waf_action, COUNT(*) as count
        FROM events
        WHERE timestamp >= ?
        GROUP BY waf_action
      SQL

      # Convert to hash like PostgreSQL returns
      result.to_a.to_h { |row| [row["waf_action"], row["count"]] }
    end
  end

  # Analytics query: Top countries
  def top_countries(start_time, limit = 10)
    with_connection do |conn|
      result = conn.query(<<~SQL, start_time, limit)
        SELECT country, COUNT(*) as count
        FROM events
        WHERE timestamp >= ? AND country IS NOT NULL
        GROUP BY country
        ORDER BY count DESC
        LIMIT ?
      SQL

      result.to_a.map { |row| [row["country"], row["count"]] }
    end
  end

  # Analytics query: Top blocked IPs
  def top_blocked_ips(start_time, limit = 10)
    with_connection do |conn|
      result = conn.query(<<~SQL, start_time, limit)
        SELECT ip_address, COUNT(*) as count
        FROM events
        WHERE timestamp >= ? AND waf_action = 0
        GROUP BY ip_address
        ORDER BY count DESC
        LIMIT ?
      SQL

      result.to_a.map { |row| [row["ip_address"], row["count"]] }
    end
  end

  # Analytics query: Hourly timeline (events grouped by hour)
  def hourly_timeline(start_time, end_time)
    with_connection do |conn|
      result = conn.query(<<~SQL, start_time, end_time)
        SELECT
          DATE_TRUNC('hour', timestamp) as hour,
          COUNT(*) as count
        FROM events
        WHERE timestamp >= ? AND timestamp < ?
        GROUP BY hour
        ORDER BY hour
      SQL

      # Convert to hash with Time keys like PostgreSQL
      result.to_a.to_h { |row| [row["hour"], row["count"]] }
    end
  end

  # Close DuckDB connection (for cleanup/testing)
  def close
    @connection&.close
    @connection = nil
  end
end