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

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Helper classes and base types relied upon by all subsystems. This library does not contain any domain logic.

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package dk.cachet.carp.common.infrastructure.serialization

import kotlinx.serialization.*
import kotlinx.serialization.builtins.*
import kotlinx.serialization.descriptors.*
import kotlinx.serialization.encoding.*


/**
 * 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.
 */
class MapAsArraySerializer(
    private val keySerializer: KSerializer,
    private val valueSerializer: KSerializer
) : KSerializer>
{
    @Serializable
    data class KeyValue( val key: K, val value: V )

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

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

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