import db from '@adonisjs/lucid/services/db'

/**
 * range_blocks (migration 3900): per group, each run of consecutive done ranges with its posting time span, read by
 * release_final(). A few thousand rows from ~650k ranges, rebuilt whole in one statement each time; a run breaks at a
 * range that isn't done or doesn't start where the one before ended.
 */
class RangeBlocks {
  async rebuild(): Promise<number> {
    return db.transaction(async (trx) => {
      await trx.rawQuery(`DELETE FROM range_blocks`)
      const result = await trx.rawQuery(
        `WITH r AS (
           SELECT group_id, start_id, end_id, status = 'done' AS done, posted_low, posted_high,
                  min(start_id) OVER (PARTITION BY group_id) AS group_first,
                  lag(status = 'done') OVER w AS done_before, lag(end_id) OVER w AS end_before
           FROM ranges WINDOW w AS (PARTITION BY group_id ORDER BY start_id)),
         runs AS (
           SELECT *, sum(CASE WHEN done IS DISTINCT FROM done_before OR end_before IS DISTINCT FROM start_id - 1 THEN 1 ELSE 0 END)
                       OVER (PARTITION BY group_id ORDER BY start_id) AS run
           FROM r)
         INSERT INTO range_blocks (group_id, start_id, end_id, posted_low, posted_high, at_group_start)
         SELECT group_id, min(start_id), max(end_id), min(posted_low), max(posted_high), min(start_id) = min(group_first)
         FROM runs WHERE done GROUP BY group_id, run`
      )
      return result.rowCount ?? 0
    })
  }
}

export default new RangeBlocks()