sealed class serialisation

core/src/main/java/info/nightscout/androidaps/utils/SealedClassHelper.kt

@@ -0,0 +1,71 @@
+package info.nightscout.androidaps.utils
+
+import com.google.gson.Gson
+import com.google.gson.GsonBuilder
+import com.google.gson.TypeAdapter
+import com.google.gson.TypeAdapterFactory
+import com.google.gson.reflect.TypeToken
+import com.google.gson.stream.JsonReader
+import com.google.gson.stream.JsonWriter
+import info.nightscout.androidaps.database.entities.XXXValueWithUnit
+import kotlin.jvm.internal.Reflection
+import kotlin.reflect.KClass
+
+fun generateGson() = GsonBuilder().registerTypeAdapterFactory(
+    object : TypeAdapterFactory {
+        override fun <T : Any> create(gson: Gson, type: TypeToken<T>): TypeAdapter<T> {
+            val kclass = Reflection.getOrCreateKotlinClass(type.rawType)
+            return if (kclass.sealedSubclasses.any()) {
+                SealedClassTypeAdapter<T>(kclass, gson)
+            } else
+                gson.getDelegateAdapter(this, type)
+        }
+    }).create()
+
+/*fun testSealedClass(): XXXValueWithUnit.SimpleString? {
+
+    val gson = generateGson()
+    val someValueWithUnit: Container = Container(XXXValueWithUnit.SimpleString("hello"))
+    val serialised = gson.toJson(someValueWithUnit)
+
+    val deserialised : Container = gson.fromJson(serialised, Container::class.java)
+
+    return deserialised.c as? XXXValueWithUnit.SimpleString
+
+}*/
+
+fun toSealedClassJson(list: List<XXXValueWithUnit>): String =
+    list.map { Container(it) }.let { generateGson().toJson(it) }
+
+fun fromJson(string: String) : List<XXXValueWithUnit> {
+    val itemType = object : TypeToken<List<Container>>() {}.type
+
+    return generateGson().fromJson<List<Container>>(string, itemType).map { it.wrapped }
+}
+
+data class Container(val wrapped: XXXValueWithUnit)
+
+class SealedClassTypeAdapter<T : Any>(private val kclass: KClass<Any>, val gson: Gson) : TypeAdapter<T>() {
+
+    override fun read(jsonReader: JsonReader): T? {
+        jsonReader.beginObject() //start reading the object
+        val nextName = jsonReader.nextName() //get the name on the object
+        val innerClass = kclass.sealedSubclasses.firstOrNull {
+            it.simpleName!!.contains(nextName)
+        }
+            ?: throw Exception("$nextName is not found to be a data class of the sealed class ${kclass.qualifiedName}")
+        val x = gson.fromJson<T>(jsonReader, innerClass.javaObjectType)
+        jsonReader.endObject()
+        //if there a static object, actually return that back to ensure equality and such!
+        return innerClass.objectInstance as T? ?: x
+    }
+
+    override fun write(out: JsonWriter, value: T) {
+        val jsonString = gson.toJson(value)
+        out.beginObject()
+        val name = value.javaClass.canonicalName
+        out.name(name.splitToSequence(".").last()).jsonValue(jsonString)
+        out.endObject()
+    }
+
+}

core/src/test/java/info/nightscout/androidaps/utils/SealedClassHelperKtTest.kt

@@ -0,0 +1,39 @@
+package info.nightscout.androidaps.utils
+
+import info.nightscout.androidaps.database.entities.XXXValueWithUnit
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Test
+
+class SealedClassHelperKtTest {
+
+
+
+    @Test
+    fun testSerialisationDeserization() {
+
+        val list = listOf<XXXValueWithUnit>(
+            XXXValueWithUnit.SimpleString("hello"),
+            XXXValueWithUnit.SimpleInt(5),
+            XXXValueWithUnit.UNKNOWN
+        )
+
+        val serialized = toSealedClassJson(list)
+        val deserialized = fromJson(serialized)
+
+        assertEquals(3, list.size)
+        assertEquals(list, deserialized)
+    }
+
+    @Test
+    fun testEmptyList() {
+
+        val list = listOf<XXXValueWithUnit>()
+
+        val serialized = toSealedClassJson(list)
+        val deserialized = fromJson(serialized)
+
+        assertEquals(0, list.size)
+        assertEquals(list, deserialized)
+    }
+}

database/build.gradle

@@ -39,4 +39,5 @@ dependencies {
 
     implementation "com.google.dagger:dagger-android:$dagger_version"
     implementation "com.google.dagger:dagger-android-support:$dagger_version"
+    api "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"
 }

database/src/main/java/info/nightscout/androidaps/database/Converters.kt

@@ -1,6 +1,7 @@
 package info.nightscout.androidaps.database
 
 import androidx.room.TypeConverter
+import com.google.gson.JsonArray
 import info.nightscout.androidaps.database.data.Block
 import info.nightscout.androidaps.database.data.TargetBlock
 import info.nightscout.androidaps.database.embedments.InterfaceIDs
@@ -18,8 +19,7 @@ class Converters {
     fun toAction(action: String?) = action?.let { Action.fromString(it) }
 
     @TypeConverter
-    fun fromMutableListOfValueWithUnit(values: MutableList<ValueWithUnit>?): String? {
+    fun fromMutableListOfValueWithUnit(values: MutableList<ValueWithUnit>): String {
-        if (values == null) return null
         val jsonArray = JSONArray()
         values.forEach {
             if (it.condition) {
@@ -32,8 +32,7 @@ class Converters {
     }
 
     @TypeConverter
-    fun toMutableListOfValueWithUnit(jsonString: String?): MutableList<ValueWithUnit>? {
+    fun toMutableListOfValueWithUnit(jsonString: String): MutableList<ValueWithUnit> {
-        if (jsonString == null) return null
         val jsonArray = JSONArray(jsonString)
         val list = mutableListOf<ValueWithUnit>()
         for (i in 0 until jsonArray.length()) {