com.github.mjakubowski84.parquet4s.ValueDecoder.scala Maven / Gradle / Ivy

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package com.github.mjakubowski84.parquet4s

import scala.annotation.implicitNotFound

trait AllValueDecoders extends PrimitiveValueDecoders with TimeValueDecoders with ComplexValueDecoders

/** Contains implicit instances of all [[ValueDecoder]]
  */
object ValueDecoder extends AllValueDecoders

@implicitNotFound(
  "Missing ValueDecoder for value type ${T}. Implement your own decoder in order to deserialise your data."
)
trait ValueDecoder[T] {

  /** @param value
    *   source Parquet [[Value]]
    * @param configuration
    *   [ValueCodecConfiguration] used by some codecs
    * @return
    *   data decoded from [[Value]]
    */
  def decode(value: Value, configuration: ValueCodecConfiguration): T
}

/** Decoder for non-null type of [[Value]]
  * @tparam T
  *   data type to decode from
  */
trait RequiredValueDecoder[T] extends ValueDecoder[T] {

  final override def decode(value: Value, configuration: ValueCodecConfiguration): T =
    value match {
      case NullValue =>
        throw new IllegalArgumentException("NullValue cannot be decoded to required type")
      case other =>
        decodeNonNull(other, configuration)
    }

  protected def decodeNonNull(value: Value, configuration: ValueCodecConfiguration): T

}

/** Decoder for [[Value]] that can be null.
  * @tparam T
  *   data type to decode from
  */
trait OptionalValueDecoder[T] extends ValueDecoder[T] {

  final override def decode(value: Value, configuration: ValueCodecConfiguration): T =
    value match {
      case NullValue => null.asInstanceOf[T]
      case other     => decodeNonNull(other, configuration)
    }

  protected def decodeNonNull(value: Value, configuration: ValueCodecConfiguration): T

}