pipelinedp4j/main/com/google/privacy/differentialprivacy/pipelinedp4j/core/Encoders.kt

/*
 * Copyright 2024 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.privacy.differentialprivacy.pipelinedp4j.core

import com.google.protobuf.Message
import kotlin.reflect.KClass

/**
 * A serializer and a deserializer for the data types processed by PipelineDP4j.
 *
 * An [Encoder] converts between regular Kotlin values and encoded byte-string representations
 * stored in a [FrameworkCollection], which are automatically invoked by the rest of the
 * PipelineDP4j system whenever it needs to convert between an in-memory Kotlin object and an
 * externalizable byte-string representation.
 */
interface Encoder<T> {}

/** A factory for [Encoder]s */
interface EncoderFactory {
  /** Returns an [Encoder] for a [String] value, which can be stored in a [FrameworkCollection]. */
  fun strings(): Encoder<String>

  /** Returns an [Encoder] for a double value, which can be stored in a [FrameworkCollection]. */
  fun doubles(): Encoder<Double>

  /** Returns an [Encoder] for an integer value, which can be stored in a [FrameworkCollection]. */
  fun ints(): Encoder<Int>

  /** Encoder for data classes. */
  fun <T : Any> records(recordClass: KClass<T>): Encoder<T>

  /** Returns an [Encoder] for a protobuf value, which can be stored in a [FrameworkCollection]. */
  fun <T : Message> protos(protoClass: KClass<T>): Encoder<T>

  /** Returns an [Encoder] for a pair of tuples, which can be stored in a [FrameworkCollection]. */
  fun <T1 : Any, T2 : Any> tuple2sOf(first: Encoder<T1>, second: Encoder<T2>): Encoder<Pair<T1, T2>>
}

inline fun <reified T : Any> EncoderFactory.records() = this.records(T::class)

inline fun <reified T : Message> EncoderFactory.protos() = this.protos(T::class)