package com.twitter.tweetypie.jiminy.tweetypie

import com.twitter.finagle.stats.CategorizingExceptionStatsHandler
import com.twitter.finagle.stats.Stat
import com.twitter.finagle.stats.StatsReceiver
import com.twitter.incentives.jiminy.thriftscala._
import com.twitter.servo.util.FutureArrow
import com.twitter.servo.util.Gate
import com.twitter.stitch.Stitch
import com.twitter.strato.thrift.ScroogeConvImplicits._
import com.twitter.strato.client.{Client => StratoClient}
import com.twitter.tweetypie.core.TweetCreateFailure
import com.twitter.util.Future
import com.twitter.util.Return
import com.twitter.util.Throw

case class NudgeBuilderRequest(
  text: String,
  inReplyToTweetId: Option[NudgeBuilder.TweetId],
  conversationId: Option[NudgeBuilder.TweetId],
  hasQuotedTweet: Boolean,
  nudgeOptions: Option[CreateTweetNudgeOptions],
  tweetId: Option[NudgeBuilder.TweetId])

trait NudgeBuilder extends FutureArrow[NudgeBuilderRequest, Unit] {

  /**
   * Check whether the user should receive a nudge instead of creating
   * the Tweet. If nudgeOptions is None, then no nudge check will be
   * performed.
   *
   * @return a Future.exception containing a [[TweetCreateFailure]] if the
   *   user should be nudged, or Future.Unit if the user should not be
   *   nudged.
   */
  def apply(
    request: NudgeBuilderRequest
  ): Future[Unit]
}

object NudgeBuilder {
  type Type = FutureArrow[NudgeBuilderRequest, Unit]
  type TweetId = Long

  // darkTrafficCreateNudgeOptions ensure that our dark traffic sends a request that will
  // accurately test the Jiminy backend. in this case, we specify that we want checks for all
  // possible nudge types
  private[this] val darkTrafficCreateNudgeOptions = Some(
    CreateTweetNudgeOptions(
      requestedNudgeTypes = Some(
        Set(
          TweetNudgeType.PotentiallyToxicTweet,
          TweetNudgeType.ReviseOrMute,
          TweetNudgeType.ReviseOrHideThenBlock,
          TweetNudgeType.ReviseOrBlock
        )
      )
    )
  )

  private[this] def mkJiminyRequest(
    request: NudgeBuilderRequest,
    isDarkRequest: Boolean = false
  ): CreateTweetNudgeRequest = {
    val tweetType =
      if (request.inReplyToTweetId.nonEmpty) TweetType.Reply
      else if (request.hasQuotedTweet) TweetType.QuoteTweet
      else TweetType.OriginalTweet

    CreateTweetNudgeRequest(
      tweetText = request.text,
      tweetType = tweetType,
      inReplyToTweetId = request.inReplyToTweetId,
      conversationId = request.conversationId,
      createTweetNudgeOptions =
        if (isDarkRequest) darkTrafficCreateNudgeOptions else request.nudgeOptions,
      tweetId = request.tweetId
    )
  }

  /**
   * NudgeBuilder implemented by calling the strato column `incentives/createNudge`.
   *
   * Stats recorded:
   *   - latency_ms: Latency histogram (also implicitly number of
   *     invocations). This is counted only in the case that a nudge
   *     check was requested (`nudgeOptions` is non-empty)
   *
   *   - nudge: The nudge check succeeded and a nudge was created.
   *
   *   - no_nudge: The nudge check succeeded, but no nudge was created.
   *
   *   - failures: Calling strato to create a nudge failed. Broken out
   *     by exception.
   */

  def apply(
    nudgeArrow: FutureArrow[CreateTweetNudgeRequest, CreateTweetNudgeResponse],
    enableDarkTraffic: Gate[Unit],
    stats: StatsReceiver
  ): NudgeBuilder = {
    new NudgeBuilder {
      private[this] val nudgeLatencyStat = stats.stat("latency_ms")
      private[this] val nudgeCounter = stats.counter("nudge")
      private[this] val noNudgeCounter = stats.counter("no_nudge")
      private[this] val darkRequestCounter = stats.counter("dark_request")
      private[this] val nudgeExceptionHandler = new CategorizingExceptionStatsHandler

      override def apply(
        request: NudgeBuilderRequest
      ): Future[Unit] =
        request.nudgeOptions match {
          case None =>
            if (enableDarkTraffic()) {
              darkRequestCounter.incr()
              Stat
                .timeFuture(nudgeLatencyStat) {
                  nudgeArrow(mkJiminyRequest(request, isDarkRequest = true))
                }
                .transform { _ =>
                  // ignore the response since it is a dark request
                  Future.Done
                }
            } else {
              Future.Done
            }

          case Some(_) =>
            Stat
              .timeFuture(nudgeLatencyStat) {
                nudgeArrow(mkJiminyRequest(request))
              }
              .transform {
                case Throw(e) =>
                  nudgeExceptionHandler.record(stats, e)
                  // If we failed to invoke the nudge column, then
                  // just continue on with the Tweet creation.
                  Future.Done

                case Return(CreateTweetNudgeResponse(Some(nudge))) =>
                  nudgeCounter.incr()
                  Future.exception(TweetCreateFailure.Nudged(nudge = nudge))

                case Return(CreateTweetNudgeResponse(None)) =>
                  noNudgeCounter.incr()
                  Future.Done
              }
        }
    }
  }

  def apply(
    strato: StratoClient,
    enableDarkTraffic: Gate[Unit],
    stats: StatsReceiver
  ): NudgeBuilder = {
    val executer =
      strato.executer[CreateTweetNudgeRequest, CreateTweetNudgeResponse](
        "incentives/createTweetNudge")
    val nudgeArrow: FutureArrow[CreateTweetNudgeRequest, CreateTweetNudgeResponse] = { req =>
      Stitch.run(executer.execute(req))
    }
    apply(nudgeArrow, enableDarkTraffic, stats)
  }
}