#!/usr/bin/env ruby
# frozen_string_literal: true

# One-time backfill script to populate new columns in existing DuckDB events
# This uses DuckDB's JOIN-based UPDATE for maximum performance

require 'csv'
require 'tempfile'

puts "DuckDB Column Backfill Script (JOIN-based UPDATE)"
puts "=" * 60
puts "This will update existing DuckDB events with data from PostgreSQL"
puts "using a fast JOIN-based approach"
puts

BATCH_SIZE = 50_000

AnalyticsDuckdbService.instance.with_connection do |conn|
  # Get total events in DuckDB
  puts "Step 1: Counting events to backfill..."
  result = conn.query("SELECT COUNT(*) FROM events WHERE request_method IS NULL")
  total_to_backfill = result.first&.first || 0

  result = conn.query("SELECT COUNT(*) FROM events")
  total_events = result.first&.first || 0

  puts "  Total events in DuckDB: #{total_events}"
  puts "  Events needing backfill: #{total_to_backfill}"

  if total_to_backfill == 0
    puts "\n✓ All events already have new columns populated!"
    exit 0
  end

  # Get min and max event IDs in DuckDB
  result = conn.query("SELECT MIN(id), MAX(id) FROM events WHERE request_method IS NULL")
  min_id, max_id = result.first
  puts "  ID range to backfill: #{min_id} to #{max_id}"

  puts "\nStep 2: Exporting PostgreSQL data in batches..."
  current_id = min_id
  batch_num = 0
  total_updated = 0

  # Create temporary CSV file for data transfer
  temp_csv = Tempfile.new(['events_backfill', '.csv'])

  begin
    CSV.open(temp_csv.path, 'w') do |csv|
      # Header
      csv << ['id', 'request_method', 'response_status', 'rule_id']

      while current_id <= max_id
        batch_num += 1
        batch_end_id = [current_id + BATCH_SIZE - 1, max_id].min

        print "  Batch #{batch_num}: Exporting IDs #{current_id}-#{batch_end_id}..."

        # Fetch from PostgreSQL
        pg_events = Event.where("id >= ? AND id <= ?", current_id, batch_end_id)
                         .select(:id, :request_method, :response_status, :rule_id)

        count = 0
        pg_events.find_each do |event|
          csv << [
            event.id,
            event.request_method,
            event.response_status,
            event.rule_id
          ]
          count += 1
        end

        puts " #{count} events"
        current_id = batch_end_id + 1
      end
    end

    temp_csv.close

    puts "\n✓ Exported to temporary CSV: #{temp_csv.path}"
    puts "  File size: #{(File.size(temp_csv.path) / 1024.0 / 1024.0).round(2)} MB"

    puts "\nStep 3: Loading CSV into temporary DuckDB table..."
    conn.execute("DROP TABLE IF EXISTS events_updates")
    conn.execute(<<~SQL)
      CREATE TABLE events_updates (
        id BIGINT,
        request_method INTEGER,
        response_status INTEGER,
        rule_id BIGINT
      )
    SQL

    conn.execute(<<~SQL)
      COPY events_updates FROM '#{temp_csv.path}' (FORMAT CSV, HEADER TRUE, NULL '')
    SQL

    result = conn.query("SELECT COUNT(*) FROM events_updates")
    loaded_count = result.first&.first || 0
    puts "✓ Loaded #{loaded_count} rows into temporary table"

    puts "\nStep 4: Performing bulk UPDATE via JOIN..."
    start_time = Time.current

    # DuckDB's efficient UPDATE...FROM syntax
    conn.execute(<<~SQL)
      UPDATE events
      SET
        request_method = events_updates.request_method,
        response_status = events_updates.response_status,
        rule_id = events_updates.rule_id
      FROM events_updates
      WHERE events.id = events_updates.id
    SQL

    duration = Time.current - start_time
    puts "✓ Bulk update complete in #{duration.round(2)}s!"

    puts "\nStep 5: Cleaning up temporary table..."
    conn.execute("DROP TABLE events_updates")
    puts "✓ Temporary table dropped"

  ensure
    # Clean up temp file
    temp_csv.unlink if temp_csv
  end

  puts "\nStep 6: Verifying backfill..."
  result = conn.query("SELECT COUNT(*) FROM events WHERE request_method IS NOT NULL OR response_status IS NOT NULL OR rule_id IS NOT NULL")
  filled_count = result.first&.first || 0

  result = conn.query("SELECT COUNT(*) FROM events WHERE request_method IS NULL AND response_status IS NULL AND rule_id IS NULL")
  still_null_count = result.first&.first || 0

  puts "  Events with new columns populated: #{filled_count}"
  puts "  Events still with NULL columns: #{still_null_count}"

  if still_null_count > 0
    puts "\n⚠ Note: #{still_null_count} events still have NULL values."
    puts "  This is normal if those events don't exist in PostgreSQL anymore"
    puts "  (they may have been cleaned up due to retention policy)"
  else
    puts "\n✓ Backfill complete! All events have new columns populated."
  end
end

puts "\n" + "=" * 60
puts "Backfill complete!"
puts "\nNext steps:"
puts "1. Test the events index page to verify everything works"
puts "2. Monitor performance improvements from DuckDB queries"