the-algorithm/tweetypie/common/src/scala/com/twitter/tweetypie/storage/GetDeletedTweetsHandler.scala

package com.twitter.tweetypie.storage

import com.twitter.finagle.stats.StatsReceiver
import com.twitter.stitch.Stitch
import com.twitter.storage.client.manhattan.kv.DeniedManhattanException
import com.twitter.tweetypie.storage.Response.TweetResponseCode
import com.twitter.tweetypie.storage.TweetUtils._
import com.twitter.tweetypie.storage_internal.thriftscala.StoredTweet
import com.twitter.tweetypie.thriftscala.DeletedTweet
import scala.util.control.NonFatal

sealed trait DeleteState
object DeleteState {

  /**
   * This tweet is deleted but has not been permanently deleted from Manhattan. Tweets in this state
   * may be undeleted.
   */
  case object SoftDeleted extends DeleteState

  /**
   * This tweet is deleted after being bounced for violating the Twitter Rules but has not been
   * permanently deleted from Manhattan. Tweets in this state may NOT be undeleted.
   */
  case object BounceDeleted extends DeleteState

  /**
   * This tweet has been permanently deleted from Manhattan.
   */
  case object HardDeleted extends DeleteState

  /**
   * There is no data in Manhattan to distinguish this tweet id from one that never existed.
   */
  case object NotFound extends DeleteState

  /**
   * This tweet exists and is not in a deleted state.
   */
  case object NotDeleted extends DeleteState
}

case class DeletedTweetResponse(
  tweetId: TweetId,
  overallResponse: TweetResponseCode,
  deleteState: DeleteState,
  tweet: Option[DeletedTweet])

object GetDeletedTweetsHandler {
  def apply(
    read: ManhattanOperations.Read,
    stats: StatsReceiver
  ): TweetStorageClient.GetDeletedTweets =
    (unfilteredTweetIds: Seq[TweetId]) => {
      val tweetIds = unfilteredTweetIds.filter(_ > 0)

      Stats.addWidthStat("getDeletedTweets", "tweetIds", tweetIds.size, stats)

      val stitches = tweetIds.map { tweetId =>
        read(tweetId)
          .map { mhRecords =>
            val storedTweet = buildStoredTweet(tweetId, mhRecords)

            TweetStateRecord.mostRecent(mhRecords) match {
              case Some(m: TweetStateRecord.SoftDeleted) => softDeleted(m, storedTweet)
              case Some(m: TweetStateRecord.BounceDeleted) => bounceDeleted(m, storedTweet)
              case Some(m: TweetStateRecord.HardDeleted) => hardDeleted(m, storedTweet)
              case _ if storedTweet.getFieldBlobs(expectedFields).isEmpty => notFound(tweetId)
              case _ => notDeleted(tweetId, storedTweet)
            }
          }
          .handle {
            case _: DeniedManhattanException =>
              DeletedTweetResponse(
                tweetId,
                TweetResponseCode.OverCapacity,
                DeleteState.NotFound,
                None
              )

            case NonFatal(ex) =>
              TweetUtils.log.warning(
                ex,
                s"Unhandled exception in GetDeletedTweetsHandler for tweetId: $tweetId"
              )
              DeletedTweetResponse(tweetId, TweetResponseCode.Failure, DeleteState.NotFound, None)
          }
      }

      Stitch.collect(stitches)
    }

  private def notFound(tweetId: TweetId) =
    DeletedTweetResponse(
      tweetId = tweetId,
      overallResponse = TweetResponseCode.Success,
      deleteState = DeleteState.NotFound,
      tweet = None
    )

  private def softDeleted(record: TweetStateRecord.SoftDeleted, storedTweet: StoredTweet) =
    DeletedTweetResponse(
      record.tweetId,
      TweetResponseCode.Success,
      DeleteState.SoftDeleted,
      Some(
        StorageConversions
          .toDeletedTweet(storedTweet)
          .copy(deletedAtMsec = Some(record.createdAt))
      )
    )

  private def bounceDeleted(record: TweetStateRecord.BounceDeleted, storedTweet: StoredTweet) =
    DeletedTweetResponse(
      record.tweetId,
      TweetResponseCode.Success,
      DeleteState.BounceDeleted,
      Some(
        StorageConversions
          .toDeletedTweet(storedTweet)
          .copy(deletedAtMsec = Some(record.createdAt))
      )
    )

  private def hardDeleted(record: TweetStateRecord.HardDeleted, storedTweet: StoredTweet) =
    DeletedTweetResponse(
      record.tweetId,
      TweetResponseCode.Success,
      DeleteState.HardDeleted,
      Some(
        StorageConversions
          .toDeletedTweet(storedTweet)
          .copy(
            hardDeletedAtMsec = Some(record.createdAt),
            deletedAtMsec = Some(record.deletedAt)
          )
      )
    )

  /**
   * notDeleted returns a tweet to simplify tweetypie.handler.UndeleteTweetHandler
   */
  private def notDeleted(tweetId: TweetId, storedTweet: StoredTweet) =
    DeletedTweetResponse(
      tweetId = tweetId,
      overallResponse = TweetResponseCode.Success,
      deleteState = DeleteState.NotDeleted,
      tweet = Some(StorageConversions.toDeletedTweet(storedTweet))
    )
}