'use strict';

/**
 * Legacy SRS keys included lesson_id while the course pool used NULL. The same
 * word pair could therefore receive parallel schedules. Keep the most advanced
 * record, preserve its earliest due time, and remove only exact course-wide
 * duplicates.
 */
module.exports = {
  async up(queryInterface) {
    await queryInterface.sequelize.query(`
      WITH grouped AS (
        SELECT
          id,
          FIRST_VALUE(id) OVER bucket AS keeper_id,
          MIN(next_due_at) OVER bucket AS earliest_due_at,
          MAX(correct_count) OVER bucket AS max_correct_count,
          MAX(wrong_count) OVER bucket AS max_wrong_count,
          MAX(lapse_count) OVER bucket AS max_lapse_count,
          BOOL_OR(is_hard) OVER bucket AS any_hard,
          ROW_NUMBER() OVER bucket AS row_number
        FROM community.vocab_srs_item
        WINDOW bucket AS (
          PARTITION BY user_id, course_id, UPPER(direction),
            LOWER(REGEXP_REPLACE(learning, '[[:punct:][:space:]]+', ' ', 'g')),
            LOWER(REGEXP_REPLACE(reference, '[[:punct:][:space:]]+', ' ', 'g'))
          ORDER BY correct_count DESC, last_reviewed_at DESC NULLS LAST, id ASC
          ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
        )
      ), updated AS (
        UPDATE community.vocab_srs_item AS item
        SET next_due_at = grouped.earliest_due_at,
            correct_count = grouped.max_correct_count,
            wrong_count = grouped.max_wrong_count,
            lapse_count = grouped.max_lapse_count,
            is_hard = grouped.any_hard
        FROM grouped
        WHERE item.id = grouped.keeper_id
        RETURNING item.id
      )
      DELETE FROM community.vocab_srs_item AS item
      USING grouped
      WHERE item.id = grouped.id
        AND grouped.row_number > 1;
    `);
  },
  async down() {
    // Duplicate rows are intentionally not recreated.
  }
};