the-algorithm/tweetypie/server/src/main/scala/com/twitter/tweetypie/handler/UserTakedownHandler.scala

package com.twitter.tweetypie
package handler

import com.twitter.servo.util.FutureArrow
import com.twitter.tweetypie.store.Takedown
import com.twitter.tweetypie.thriftscala.DataError
import com.twitter.tweetypie.thriftscala.DataErrorCause
import com.twitter.tweetypie.thriftscala.SetTweetUserTakedownRequest

trait UserTakedownHandler {
  val setTweetUserTakedownRequest: FutureArrow[SetTweetUserTakedownRequest, Unit]
}

/**
 * This handler processes SetTweetUserTakedownRequest objects sent to Tweetypie's
 * setTweetUserTakedown endpoint.  These requests originate from tweetypie daemon and the
 * request object specifies the user ID of the user who is being modified, and a boolean value
 * to indicate whether takedown is being added or removed.
 *
 * If takedown is being added, the hasTakedown bit is set on all of the user's tweets.
 * If takedown is being removed, we can't automatically unset the hasTakedown bit on all tweets
 * since some of the tweets might have tweet-specific takedowns, in which case the hasTakedown bit
 * needs to remain set.  Instead, we flush the user's tweets from cache, and let the repairer
 * unset the bit when hydrating tweets where the bit is set but no user or tweet
 * takedown country codes are present.
 */
object UserTakedownHandler {
  type Type = FutureArrow[SetTweetUserTakedownRequest, Unit]

  def takedownEvent(userHasTakedown: Boolean): Tweet => Option[Takedown.Event] =
    tweet => {
      val tweetHasTakedown =
        TweetLenses.tweetypieOnlyTakedownCountryCodes(tweet).exists(_.nonEmpty) ||
          TweetLenses.tweetypieOnlyTakedownReasons(tweet).exists(_.nonEmpty)
      val updatedHasTakedown = userHasTakedown || tweetHasTakedown
      if (updatedHasTakedown == TweetLenses.hasTakedown(tweet))
        None
      else
        Some(
          Takedown.Event(
            tweet = TweetLenses.hasTakedown.set(tweet, updatedHasTakedown),
            timestamp = Time.now,
            eventbusEnqueue = false,
            scribeForAudit = false,
            updateCodesAndReasons = false
          )
        )
    }

  def setHasTakedown(
    tweetTakedown: FutureEffect[Takedown.Event],
    userHasTakedown: Boolean
  ): FutureEffect[Seq[Tweet]] =
    tweetTakedown.contramapOption(takedownEvent(userHasTakedown)).liftSeq

  def verifyTweetUserId(expectedUserId: Option[UserId], tweet: Tweet): Unit = {
    val tweetUserId: UserId = getUserId(tweet)
    val tweetId: Long = tweet.id
    expectedUserId.filter(_ != tweetUserId).foreach { u =>
      throw DataError(
        message =
          s"SetTweetUserTakedownRequest userId $u does not match userId $tweetUserId for Tweet: $tweetId",
        errorCause = Some(DataErrorCause.UserTweetRelationship),
      )
    }
  }

  def apply(
    getTweet: FutureArrow[TweetId, Option[Tweet]],
    tweetTakedown: FutureEffect[Takedown.Event],
  ): Type =
    FutureArrow { request =>
      for {
        tweet <- getTweet(request.tweetId)
        _ = tweet.foreach(t => verifyTweetUserId(request.userId, t))
        _ <- setHasTakedown(tweetTakedown, request.hasTakedown)(tweet.toSeq)
      } yield ()
    }
}