commonMain.dk.cachet.carp.common.infrastructure.serialization.MapAsArraySerializer.kt Maven / Gradle / Ivy

Go to download
package dk.cachet.carp.common.infrastructure.serialization

import kotlinx.serialization.ExperimentalSerializationApi
import kotlinx.serialization.KSerializer
import kotlinx.serialization.Serializable
import kotlinx.serialization.builtins.ArraySerializer
import kotlinx.serialization.descriptors.SerialDescriptor
import kotlinx.serialization.encoding.Decoder
import kotlinx.serialization.encoding.Encoder


/**
 * Serializes a [Map] as an array of JSON objects which each have a "key" and "value"
 * instead of a single JSON object containing values for all keys in the map, which is the default.
 *
 * This is useful when using JSON serialization and the serialized keys in a map violate JSON recommendations.
 * E.g., the key may include discouraged symbols such as '.', or '$' for BSON.
 */
@OptIn( ExperimentalSerializationApi::class )
class MapAsArraySerializer(
    private val keySerializer: KSerializer,
    private val valueSerializer: KSerializer
) : KSerializer>
{
    @Serializable
    data class KeyValue( val key: K, val value: V )

    private val arraySerializer = ArraySerializer( KeyValue.serializer( keySerializer, valueSerializer ) )
    override val descriptor: SerialDescriptor = arraySerializer.descriptor

    override fun deserialize( decoder: Decoder ): Map = decoder
        .decodeSerializableValue( arraySerializer )
        .map { it.key to it.value }
        .toMap()

    override fun serialize( encoder: Encoder, value: Map ) = encoder
        .encodeSerializableValue(
            arraySerializer,
            value.map { KeyValue( it.key, it.value ) }.toTypedArray()
        )
}