main.app.cash.backfila.client.stat.internal.StaticDatasourceBackend.kt Maven / Gradle / Ivy

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Backfila is a service that manages backfill state, calling into other services to do batched work.

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package app.cash.backfila.client.stat.internal

import app.cash.backfila.client.DeleteBy
import app.cash.backfila.client.Description
import app.cash.backfila.client.parseDeleteByDate
import app.cash.backfila.client.spi.BackfilaParametersOperator
import app.cash.backfila.client.spi.BackfillBackend
import app.cash.backfila.client.spi.BackfillOperator
import app.cash.backfila.client.spi.BackfillRegistration
import app.cash.backfila.client.stat.ForStaticBackend
import app.cash.backfila.client.stat.StaticDatasourceBackfillBase
import com.google.inject.Injector
import com.google.inject.TypeLiteral
import com.squareup.moshi.Types
import java.lang.reflect.ParameterizedType
import javax.inject.Inject
import javax.inject.Singleton
import kotlin.reflect.KClass
import kotlin.reflect.full.findAnnotation

@Singleton
class StaticDatasourceBackend @Inject constructor(
  private val injector: Injector,
  @ForStaticBackend private val backfills: MutableMap>>,
) : BackfillBackend {

  /** Creates Backfill instances. Each backfill ID gets a new Backfill instance. */
  private fun getBackfill(name: String): StaticDatasourceBackfillBase<*, *>? {
    val backfillClass = backfills[name]
    return if (backfillClass != null) {
      injector.getInstance(backfillClass.java) as StaticDatasourceBackfillBase<*, *>
    } else {
      null
    }
  }

  private fun  createStaticDatasourceOperator(
    backfill: StaticDatasourceBackfillBase,
  ) = StaticDatasourceBackfillOperator(
    backfill,
    BackfilaParametersOperator(parametersClass(backfill::class)),
  )

  override fun create(backfillName: String): BackfillOperator? {
    val backfill = getBackfill(backfillName)

    if (backfill != null) {
      @Suppress("UNCHECKED_CAST") // We don't know the types statically, so fake them.
      return createStaticDatasourceOperator(backfill as StaticDatasourceBackfillBase)
    }

    return null
  }

  override fun backfills(): Set {
    return backfills.map {
      BackfillRegistration(
        name = it.key,
        description = it.value.findAnnotation()?.text,
        parametersClass = parametersClass(it.value as KClass>),
        deleteBy = it.value.findAnnotation()?.parseDeleteByDate(),
      )
    }.toSet()
  }

  private fun  parametersClass(backfillClass: KClass>): KClass
 {
    // Like MyBackfill.
    val thisType = TypeLiteral.get(backfillClass.java)

    // Like StaticDatasourceBackfillBase.
    val supertype = thisType.getSupertype(StaticDatasourceBackfillBase::class.java).type as ParameterizedType

    // Like MyParameterClass
    return (Types.getRawType(supertype.actualTypeArguments[1]) as Class).kotlin
  }
}