the-algorithm/cr-mixer/server/src/main/scala/com/twitter/cr_mixer/filter/ImpressedTweetlistFilter.scala

package com.twitter.cr_mixer.filter

import com.twitter.cr_mixer.model.CandidateGeneratorQuery
import com.twitter.cr_mixer.model.InitialCandidate
import com.twitter.simclusters_v2.common.TweetId
import com.twitter.simclusters_v2.thriftscala.InternalId
import com.twitter.util.Future
import javax.inject.Singleton

@Singleton
case class ImpressedTweetlistFilter() extends FilterBase {
  import ImpressedTweetlistFilter._

  override val name: String = this.getClass.getCanonicalName

  override type ConfigType = FilterConfig

  /*
   Filtering removes some candidates based on configurable criteria.
   */
  override def filter(
    candidates: Seq[Seq[InitialCandidate]],
    config: FilterConfig
  ): Future[Seq[Seq[InitialCandidate]]] = {
    // Remove candidates which match a source tweet, or which are passed in impressedTweetList
    val sourceTweetsMatch = candidates
      .flatMap {

        /***
         * Within a Seq[Seq[InitialCandidate]], all candidates within a inner Seq
         * are guaranteed to have the same sourceInfo. Hence, we can pick .headOption
         * to represent the whole list when filtering by the internalId of the sourceInfoOpt.
         * But of course the similarityEngineInfo could be different.
         */
        _.headOption.flatMap { candidate =>
          candidate.candidateGenerationInfo.sourceInfoOpt.map(_.internalId)
        }
      }.collect {
        case InternalId.TweetId(id) => id
      }

    val impressedTweetList: Set[TweetId] =
      config.impressedTweetList ++ sourceTweetsMatch

    val filteredCandidateMap: Seq[Seq[InitialCandidate]] =
      candidates.map {
        _.filterNot { candidate =>
          impressedTweetList.contains(candidate.tweetId)
        }
      }
    Future.value(filteredCandidateMap)
  }

  override def requestToConfig[CGQueryType <: CandidateGeneratorQuery](
    request: CGQueryType
  ): FilterConfig = {
    FilterConfig(request.impressedTweetList)
  }
}

object ImpressedTweetlistFilter {
  case class FilterConfig(impressedTweetList: Set[TweetId])
}