the-algorithm/product-mixer/core/src/main/scala/com/twitter/product_mixer/core/module/stringcenter/ProductScopeStringCenterModule.scala

package com.twitter.product_mixer.core.module.stringcenter

import com.google.inject.Provides
import com.twitter.abdecider.LoggingABDecider
import com.twitter.conversions.DurationOps._
import com.twitter.finagle.stats.StatsReceiver
import com.twitter.util.jackson.ScalaObjectMapper
import com.twitter.inject.TwitterModule
import com.twitter.inject.annotations.Flag
import com.twitter.product_mixer.core.product.guice.scope.ProductScoped
import com.twitter.product_mixer.core.model.marshalling.request.Product
import com.twitter.stringcenter.client.ExternalStringRegistry
import com.twitter.stringcenter.client.StringCenter
import com.twitter.stringcenter.client.StringCenterClientConfig
import com.twitter.stringcenter.client.sources.RefreshingStringSource
import com.twitter.stringcenter.client.sources.RefreshingStringSourceConfig
import com.twitter.stringcenter.client.sources.StringSource
import com.twitter.translation.Languages
import javax.inject.Singleton
import scala.collection.concurrent

/*
 * Fun trivia - this has to be a Class not an Object, otherwise when you ./bazel test blah/...
 * and glob multiple feature tests together it'll reuse the concurrentMaps below across
 * executions / different server objects.
 */
class ProductScopeStringCenterModule extends TwitterModule {

  private val loadNothing =
    flag[Boolean](name = "stringcenter.dontload", default = false, help = "Avoid loading any files")

  flag[Boolean](
    name = "stringcenter.handle.language.fallback",
    default = true,
    help = "Handle language fallback for services that don't already handle it")

  flag[String](
    name = "stringcenter.default_bundle_path",
    default = "stringcenter",
    help = "The path on disk to the default bundle available at startup time")

  private val refreshingInterval = flag[Int](
    name = "stringcenter.refresh_interval_minutes",
    default = 3,
    help = "How often to poll the refreshing bundle path to check for new bundles")

  /* The Guice injector is single threaded, but out of a preponderance of caution we use a concurrent Map.
   *
   * We need to ensure that we only build one StringSource, StringCenter client, and External String
   * Registry for each String Center Project. @ProductScoped doesn't ensure this on its own as
   * two products can have the same String Center Project set.
   */
  val stringSources: concurrent.Map[String, StringSource] = concurrent.TrieMap.empty
  val stringCenterClients: concurrent.Map[String, StringCenter] = concurrent.TrieMap.empty
  val externalStringRegistries: concurrent.Map[String, ExternalStringRegistry] =
    concurrent.TrieMap.empty

  @ProductScoped
  @Provides
  def providesStringCenterClients(
    abDecider: LoggingABDecider,
    stringSource: StringSource,
    languages: Languages,
    statsReceiver: StatsReceiver,
    clientConfig: StringCenterClientConfig,
    product: Product
  ): StringCenter = {
    stringCenterClients.getOrElseUpdate(
      stringCenterForProduct(product), {
        new StringCenter(
          abDecider,
          stringSource,
          languages,
          statsReceiver,
          clientConfig
        )
      })
  }

  @ProductScoped
  @Provides
  def providesExternalStringRegistries(
    product: Product
  ): ExternalStringRegistry = {
    externalStringRegistries.getOrElseUpdate(
      stringCenterForProduct(product), {
        new ExternalStringRegistry()
      })
  }

  @ProductScoped
  @Provides
  def providesStringCenterSources(
    mapper: ScalaObjectMapper,
    statsReceiver: StatsReceiver,
    product: Product,
    @Flag("stringcenter.default_bundle_path") defaultBundlePath: String
  ): StringSource = {
    if (loadNothing()) {
      StringSource.Empty
    } else {
      val stringCenterProduct = stringCenterForProduct(product)

      stringSources.getOrElseUpdate(
        stringCenterProduct, {
          val config = RefreshingStringSourceConfig(
            stringCenterProduct,
            defaultBundlePath,
            "stringcenter/downloaded/current/stringcenter",
            refreshingInterval().minutes
          )
          new RefreshingStringSource(
            config,
            mapper,
            statsReceiver
              .scope("StringCenter", "refreshing", "project", stringCenterProduct))
        }
      )
    }
  }

  private def stringCenterForProduct(product: Product): String =
    product.stringCenterProject.getOrElse {
      throw new UnsupportedOperationException(
        s"No StringCenter project defined for Product ${product.identifier}")
    }

  @Singleton
  @Provides
  def providesStringCenterClientConfig(
    @Flag("stringcenter.handle.language.fallback") handleLanguageFallback: Boolean
  ): StringCenterClientConfig = {
    StringCenterClientConfig(handleLanguageFallback = handleLanguageFallback)
  }
}