the-algorithm/visibilitylib/src/main/scala/com/twitter/visibility/rules/generators/TweetRuleGenerator.scala

package com.twitter.visibility.rules.generators

import com.twitter.visibility.models.SafetyLevel
import com.twitter.visibility.models.SafetyLevelGroup
import com.twitter.visibility.models.ViolationLevel
import com.twitter.visibility.rules.FreedomOfSpeechNotReachActions
import com.twitter.visibility.rules.FreedomOfSpeechNotReachRules
import com.twitter.visibility.rules.Rule
import com.twitter.visibility.rules.generators.TweetRuleGenerator.violationLevelPolicies

object TweetRuleGenerator {
  private val level3LimitedActions: Seq[String] = Seq(
    "like",
    "reply",
    "retweet",
    "quote_tweet",
    "share_tweet_via",
    "add_to_bookmarks",
    "pin_to_profile",
    "copy_link",
    "send_via_dm")
  private val violationLevelPolicies: Map[
    ViolationLevel,
    Map[UserType, TweetVisibilityPolicy]
  ] = Map(
    ViolationLevel.Level1 -> Map(
      UserType.Follower -> TweetVisibilityPolicy
        .builder()
        .addGlobalRule(FreedomOfSpeechNotReachActions.SoftInterventionAvoidAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.Notifications,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.Recommendations,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.Search,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TopicRecommendations,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelRule(
          SafetyLevel.TimelineHomeRecommendations,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelRule(
          SafetyLevel.TrendsRepresentativeTweet,
          FreedomOfSpeechNotReachActions.DropAction())
        .build,
      UserType.Author -> TweetVisibilityPolicy
        .builder()
        .addGlobalRule(FreedomOfSpeechNotReachActions.AppealableAction())
        .build,
      UserType.Other -> TweetVisibilityPolicy
        .builder()
        .addGlobalRule(FreedomOfSpeechNotReachActions.SoftInterventionAvoidAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.Notifications,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.Recommendations,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TimelineHome,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.Search,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TopicRecommendations,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelRule(
          SafetyLevel.TrendsRepresentativeTweet,
          FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelRule(
          SafetyLevel.ConversationReply,
          FreedomOfSpeechNotReachActions.SoftInterventionAvoidAbusiveQualityReplyAction())
        .build,
    ),
    ViolationLevel.Level3 -> Map(
      UserType.Follower -> TweetVisibilityPolicy
        .builder()
        .addGlobalRule(FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TimelineProfile,
          FreedomOfSpeechNotReachActions.SoftInterventionAvoidLimitedEngagementsAction(
            limitedActionStrings = Some(level3LimitedActions))
        )
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TweetDetails,
          FreedomOfSpeechNotReachActions.SoftInterventionAvoidLimitedEngagementsAction(
            limitedActionStrings = Some(level3LimitedActions))
        )
        .addSafetyLevelRule(
          SafetyLevel.ConversationReply,
          FreedomOfSpeechNotReachActions.SoftInterventionAvoidLimitedEngagementsAction(
            limitedActionStrings = Some(level3LimitedActions))
        )
        .addSafetyLevelRule(
          SafetyLevel.ConversationFocalTweet,
          FreedomOfSpeechNotReachActions.SoftInterventionAvoidLimitedEngagementsAction(
            limitedActionStrings = Some(level3LimitedActions))
        )
        .build,
      UserType.Author -> TweetVisibilityPolicy
        .builder()
        .addGlobalRule(
          FreedomOfSpeechNotReachActions.AppealableAvoidLimitedEngagementsAction(
            limitedActionStrings = Some(level3LimitedActions))
        )
        .build,
      UserType.Other -> TweetVisibilityPolicy
        .builder()
        .addGlobalRule(FreedomOfSpeechNotReachActions.DropAction())
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TimelineProfile,
          FreedomOfSpeechNotReachActions
            .InterstitialLimitedEngagementsAvoidAction(limitedActionStrings =
              Some(level3LimitedActions))
        )
        .addSafetyLevelGroupRule(
          SafetyLevelGroup.TweetDetails,
          FreedomOfSpeechNotReachActions
            .InterstitialLimitedEngagementsAvoidAction(limitedActionStrings =
              Some(level3LimitedActions))
        )
        .addSafetyLevelRule(
          SafetyLevel.ConversationReply,
          FreedomOfSpeechNotReachActions
            .InterstitialLimitedEngagementsAvoidAction(limitedActionStrings =
              Some(level3LimitedActions))
        )
        .addSafetyLevelRule(
          SafetyLevel.ConversationFocalTweet,
          FreedomOfSpeechNotReachActions
            .InterstitialLimitedEngagementsAvoidAction(limitedActionStrings =
              Some(level3LimitedActions))
        )
        .build,
    ),
  )
}
sealed trait UserType
object UserType {
  case object Author extends UserType

  case object Follower extends UserType

  case object Other extends UserType
}
class TweetRuleGenerator extends RuleGenerator {

  private[rules] val tweetRulesForSurface: Map[SafetyLevel, Seq[Rule]] = generateTweetPolicies()

  private[rules] def getViolationLevelPolicies = violationLevelPolicies

  override def rulesForSurface(safetyLevel: SafetyLevel): Seq[Rule] =
    tweetRulesForSurface.getOrElse(safetyLevel, Seq())

  private def generateRulesForPolicy(
    violationLevel: ViolationLevel,
    userType: UserType,
    tweetVisibilityPolicy: TweetVisibilityPolicy
  ): Seq[(SafetyLevel, Rule)] = {
    tweetVisibilityPolicy
      .getRules()
      .map {
        case (safetyLevel, actionBuilder) =>
          safetyLevel -> (userType match {
            case UserType.Author =>
              FreedomOfSpeechNotReachRules.ViewerIsAuthorAndTweetHasViolationOfLevel(
                violationLevel = violationLevel,
                actionBuilder = actionBuilder.withViolationLevel(violationLevel = violationLevel))
            case UserType.Follower =>
              FreedomOfSpeechNotReachRules.ViewerIsFollowerAndTweetHasViolationOfLevel(
                violationLevel = violationLevel,
                actionBuilder = actionBuilder.withViolationLevel(violationLevel = violationLevel))
            case UserType.Other =>
              FreedomOfSpeechNotReachRules.ViewerIsNonFollowerNonAuthorAndTweetHasViolationOfLevel(
                violationLevel = violationLevel,
                actionBuilder = actionBuilder.withViolationLevel(violationLevel = violationLevel))
          })
      }.toSeq
  }

  private def generatePoliciesForViolationLevel(
    violationLevel: ViolationLevel
  ): Seq[(SafetyLevel, Rule)] = {
    getViolationLevelPolicies
      .get(violationLevel).map { policiesPerUserType =>
        Seq(UserType.Author, UserType.Follower, UserType.Other).foldLeft(
          List.empty[(UserType, SafetyLevel, Rule)]) {
          case (rulesForAllUserTypes, userType) =>
            rulesForAllUserTypes ++ generateRulesForPolicy(
              violationLevel = violationLevel,
              userType = userType,
              tweetVisibilityPolicy = policiesPerUserType(userType)).map {
              case (safetyLevel, rule) => (userType, safetyLevel, rule)
            }
        }
      }
      .map(policy => optimizePolicy(policy = policy, violationLevel = violationLevel))
      .getOrElse(List())
  }

  private def injectFallbackRule(rules: Seq[Rule]): Seq[Rule] = {
    rules :+ FreedomOfSpeechNotReachRules.TweetHasViolationOfAnyLevelFallbackDropRule
  }

  private def optimizePolicy(
    policy: Seq[(UserType, SafetyLevel, Rule)],
    violationLevel: ViolationLevel
  ): Seq[(SafetyLevel, Rule)] = {
    val policiesByUserType = policy.groupBy { case (userType, _, _) => userType }.map {
      case (userType, aggregated) =>
        (userType, aggregated.map { case (_, safetyLevel, rules) => (safetyLevel, rules) })
    }
    val followerPolicies = aggregateRulesBySafetyLevel(
      policiesByUserType.getOrElse(UserType.Follower, Seq()))
    val otherPolicies = aggregateRulesBySafetyLevel(
      policiesByUserType.getOrElse(UserType.Other, Seq()))
    policiesByUserType(UserType.Author) ++
      followerPolicies.collect {
        case (safetyLevel, rule) if !otherPolicies.contains(safetyLevel) =>
          (safetyLevel, rule)
      } ++
      otherPolicies.collect {
        case (safetyLevel, rule) if !followerPolicies.contains(safetyLevel) =>
          (safetyLevel, rule)
      } ++
      followerPolicies.keySet
        .intersect(otherPolicies.keySet).foldLeft(List.empty[(SafetyLevel, Rule)]) {
          case (aggr, safetyLevel)
              if followerPolicies(safetyLevel).actionBuilder == otherPolicies(
                safetyLevel).actionBuilder =>
            (
              safetyLevel,
              FreedomOfSpeechNotReachRules.ViewerIsNonAuthorAndTweetHasViolationOfLevel(
                violationLevel = violationLevel,
                actionBuilder = followerPolicies(safetyLevel).actionBuilder
              )) :: aggr
          case (aggr, safetyLevel) =>
            (safetyLevel, followerPolicies(safetyLevel)) ::
              (safetyLevel, otherPolicies(safetyLevel)) :: aggr
        }
  }

  private def aggregateRulesBySafetyLevel(
    policy: Seq[(SafetyLevel, Rule)]
  ): Map[SafetyLevel, Rule] = {
    policy
      .groupBy {
        case (safetyLevel, _) => safetyLevel
      }.map {
        case (safetyLevel, Seq((_, rule))) =>
          (safetyLevel, rule)
        case _ => throw new Exception("Policy optimization failure")
      }
  }

  private def generateTweetPolicies(): Map[SafetyLevel, Seq[Rule]] = {
    Seq(ViolationLevel.Level4, ViolationLevel.Level3, ViolationLevel.Level2, ViolationLevel.Level1)
      .foldLeft(List.empty[(SafetyLevel, Rule)]) {
        case (rulesForAllViolationLevels, violationLevel) =>
          rulesForAllViolationLevels ++
            generatePoliciesForViolationLevel(violationLevel)
      }
      .groupBy { case (safetyLevel, _) => safetyLevel }
      .map {
        case (safetyLevel, list) =>
          (safetyLevel, injectFallbackRule(list.map { case (_, rule) => rule }))
      }
  }
}