maps-kt/maps-kt-features/src/commonMain/kotlin/center.sciprog.attributes/AttributesSerializer.kt

@file:Suppress("UNCHECKED_CAST")

package center.sciprog.attributes

import kotlinx.serialization.KSerializer
import kotlinx.serialization.descriptors.SerialDescriptor
import kotlinx.serialization.encoding.Decoder
import kotlinx.serialization.encoding.Encoder
import kotlinx.serialization.json.*

public class AttributesSerializer(
    private val serializableAttributes: Set<SerializableAttribute<*>>,
) : KSerializer<Attributes> {
    private val jsonSerializer = JsonObject.serializer()
    override val descriptor: SerialDescriptor get() = jsonSerializer.descriptor

    override fun deserialize(decoder: Decoder): Attributes {
        val jsonElement = jsonSerializer.deserialize(decoder)
        val attributeMap: Map<SerializableAttribute<*>, Any> = jsonElement.entries.associate { (key, element) ->
            val attr = serializableAttributes.find { it.serialId == key }
                ?: error("Attribute serializer for key $key not found")

            val json = if (decoder is JsonDecoder) {
                decoder.json
            } else {
                Json { serializersModule = decoder.serializersModule }
            }
            val value = json.decodeFromJsonElement(attr.serializer, element) ?: error("Null values are not allowed")

            attr to value
        }
        return Attributes(attributeMap)
    }

    override fun serialize(encoder: Encoder, value: Attributes) {
        val json = buildJsonObject {
            value.content.forEach { (key, value) ->
                if (key !in serializableAttributes) error("An attribute key $key is not in the list of allowed attributes for this serializer")
                val serializableKey = key as SerializableAttribute

                val json = if (encoder is JsonEncoder) {
                    encoder.json
                } else {
                    Json { serializersModule = encoder.serializersModule }
                }

                put(
                    serializableKey.serialId,
                    json.encodeToJsonElement(serializableKey.serializer as KSerializer<Any>, value)
                )
            }
        }
        jsonSerializer.serialize(encoder, json)
    }
}