Add interfaces and polymorphic serialization to OpenAPI generator

openapi-generator/src/main/kotlin/org/jellyfin/openapi/MainModule.kt

@@ -14,6 +14,7 @@ import org.jellyfin.openapi.builder.extra.FileSpecBuilder
 import org.jellyfin.openapi.builder.extra.TypeSerializerBuilder
 import org.jellyfin.openapi.builder.model.EmptyModelBuilder
 import org.jellyfin.openapi.builder.model.EnumModelBuilder
+import org.jellyfin.openapi.builder.model.InterfaceModelBuilder
 import org.jellyfin.openapi.builder.model.ModelBuilder
 import org.jellyfin.openapi.builder.model.ModelsBuilder
 import org.jellyfin.openapi.builder.model.ObjectModelBuilder
@@ -65,11 +66,12 @@ val mainModule = module {
 	single { ApiClientExtensionsBuilder(get()) }
 
 	// Models
-	single { ModelBuilder(get(), get(), get()) }
+	single { ModelBuilder(get(), get(), get(), get()) }
 	single { ModelsBuilder(get(), get()) }
 	single { EmptyModelBuilder(get(), get()) }
 	single { EnumModelBuilder(get(), get()) }
 	single { ObjectModelBuilder(get(), get(), get()) }
+	single { InterfaceModelBuilder(get(), get()) }
 	single { RequestModelBuilder(get()) }
 
 	// Files

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/api/ApiBuilder.kt

@@ -82,7 +82,7 @@ class ApiBuilder(
 
 				// Request model variant
 				if (createRequestModelVariant) {
-					context += fileSpecBuilder.build(requestModelBuilder.build(namedOperation))
+					context += fileSpecBuilder.build(requestModelBuilder.build(context, namedOperation))
 					addFunction(operationParameterModelBuilder.build(namedOperation))
 				}
 

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/EmptyModelBuilder.kt

@@ -1,5 +1,6 @@
 package org.jellyfin.openapi.builder.model
 
+import com.squareup.kotlinpoet.ClassName
 import com.squareup.kotlinpoet.TypeSpec
 import net.pearx.kasechange.CaseFormat
 import net.pearx.kasechange.toPascalCase
@@ -20,6 +21,15 @@ class EmptyModelBuilder(
 	override fun build(data: EmptyApiModel): JellyFile {
 		return TypeSpec.classBuilder(data.name.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL))
 			.apply {
+				data.interfaces.forEach { interfaceName ->
+					addSuperinterface(
+						ClassName(
+							Packages.MODEL,
+							interfaceName.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL)
+						)
+					)
+				}
+
 				descriptionBuilder.build(DescriptionType.MODEL, data.description)?.let {
 					addKdoc("%L", it)
 				}

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/EnumModelBuilder.kt

@@ -28,6 +28,16 @@ class EnumModelBuilder(
 	override fun build(data: EnumApiModel): JellyFile {
 		return TypeSpec.enumBuilder(data.name.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL))
 			.apply {
+				// Super
+				data.interfaces.forEach { interfaceName ->
+					addSuperinterface(
+						ClassName(
+							Packages.MODEL,
+							interfaceName.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL)
+						)
+					)
+				}
+
 				// Constructor
 				primaryConstructor(FunSpec.constructorBuilder().apply {
 					addParameter("serialName", Types.STRING)

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/InterfaceModelBuilder.kt

@@ -0,0 +1,76 @@
+package org.jellyfin.openapi.builder.model
+
+import com.squareup.kotlinpoet.AnnotationSpec
+import com.squareup.kotlinpoet.ClassName
+import com.squareup.kotlinpoet.KModifier
+import com.squareup.kotlinpoet.PropertySpec
+import com.squareup.kotlinpoet.TypeSpec
+import net.pearx.kasechange.CaseFormat
+import net.pearx.kasechange.toPascalCase
+import org.jellyfin.openapi.builder.ContextBuilder
+import org.jellyfin.openapi.builder.extra.DeprecatedAnnotationSpecBuilder
+import org.jellyfin.openapi.builder.extra.DescriptionBuilder
+import org.jellyfin.openapi.constants.Packages
+import org.jellyfin.openapi.constants.Strings
+import org.jellyfin.openapi.constants.Types
+import org.jellyfin.openapi.model.DescriptionType
+import org.jellyfin.openapi.model.GeneratorContext
+import org.jellyfin.openapi.model.InterfaceApiModel
+import org.jellyfin.openapi.model.JellyFile
+
+class InterfaceModelBuilder(
+	private val descriptionBuilder: DescriptionBuilder,
+	private val deprecatedAnnotationSpecBuilder: DeprecatedAnnotationSpecBuilder,
+) : ContextBuilder<InterfaceApiModel, JellyFile> {
+	@Suppress("ComplexMethod")
+	override fun build(context: GeneratorContext, data: InterfaceApiModel): JellyFile {
+		val interfacePropertyNames = data.interfaces
+			.flatMap { (context.getOrGenerateModel(it) as? InterfaceApiModel)?.properties.orEmpty() }
+			.map { it.name }
+
+		// Create class properties
+		val properties = data.properties.map { property ->
+			PropertySpec
+				.builder(property.name, property.type)
+				.apply {
+					descriptionBuilder.build(DescriptionType.MODEL_PROPERTY, property.description)?.let {
+						addKdoc("%L", it)
+					}
+
+					// Add override modifier if in interface
+					if (property.name in interfacePropertyNames) modifiers += KModifier.OVERRIDE
+
+					if (property.deprecated) addAnnotation(deprecatedAnnotationSpecBuilder.build(Strings.DEPRECATED_MEMBER))
+				}
+				.build()
+		}
+
+		// Create class
+		return TypeSpec.interfaceBuilder(data.name.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL))
+			.apply {
+				data.interfaces.forEach { interfaceName ->
+					addSuperinterface(
+						ClassName(
+							Packages.MODEL,
+							interfaceName.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL)
+						)
+					)
+				}
+
+				modifiers += KModifier.SEALED
+				descriptionBuilder.build(DescriptionType.MODEL, data.description)?.let {
+					addKdoc("%L", it)
+				}
+				if (data.deprecated) addAnnotation(deprecatedAnnotationSpecBuilder.build(Strings.DEPRECATED_CLASS))
+
+				// Only allow serialization when a discriminator is defined
+				data.polymorphicDiscriminator?.let {
+					addAnnotation(AnnotationSpec.builder(Types.SERIALIZABLE).build())
+					addAnnotation(AnnotationSpec.builder(Types.JSON_DISCRIMINATOR).addMember("%S", it).build())
+				}
+			}
+			.addProperties(properties)
+			.build()
+			.let { JellyFile(Packages.MODEL, emptySet(), it) }
+	}
+}

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/ModelBuilder.kt

@@ -1,22 +1,26 @@
 package org.jellyfin.openapi.builder.model
 
 import org.jellyfin.openapi.OpenApiGeneratorError
-import org.jellyfin.openapi.builder.Builder
+import org.jellyfin.openapi.builder.ContextBuilder
 import org.jellyfin.openapi.model.ApiModel
 import org.jellyfin.openapi.model.EmptyApiModel
 import org.jellyfin.openapi.model.EnumApiModel
+import org.jellyfin.openapi.model.GeneratorContext
+import org.jellyfin.openapi.model.InterfaceApiModel
 import org.jellyfin.openapi.model.JellyFile
 import org.jellyfin.openapi.model.ObjectApiModel
 
 class ModelBuilder(
 	private val emptyModelBuilder: EmptyModelBuilder,
 	private val enumModelBuilder: EnumModelBuilder,
-	private val objectModelBuilder: ObjectModelBuilder
-) : Builder<ApiModel, JellyFile> {
-	override fun build(data: ApiModel) = when (data) {
+	private val objectModelBuilder: ObjectModelBuilder,
+	private val interfaceModelBuilder: InterfaceModelBuilder,
+) : ContextBuilder<ApiModel, JellyFile> {
+	override fun build(context: GeneratorContext, data: ApiModel) = when (data) {
 		is EmptyApiModel -> emptyModelBuilder.build(data)
 		is EnumApiModel -> enumModelBuilder.build(data)
-		is ObjectApiModel -> objectModelBuilder.build(data)
+		is ObjectApiModel -> objectModelBuilder.build(context, data)
+		is InterfaceApiModel -> interfaceModelBuilder.build(context, data)
 		else -> throw OpenApiGeneratorError("Unknown model class ${data::class.qualifiedName}")
 	}
 }

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/ModelsBuilder.kt

@@ -11,7 +11,7 @@ class ModelsBuilder(
 ) : ContextBuilder<Collection<ApiModel>, Unit> {
 	override fun build(context: GeneratorContext, data: Collection<ApiModel>) {
 		for (model in data) {
-			val file = modelBuilder.build(model)
+			val file = modelBuilder.build(context, model)
 			context += fileSpecBuilder.build(file)
 		}
 	}

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/ObjectModelBuilder.kt

@@ -1,6 +1,7 @@
 package org.jellyfin.openapi.builder.model
 
 import com.squareup.kotlinpoet.AnnotationSpec
+import com.squareup.kotlinpoet.ClassName
 import com.squareup.kotlinpoet.FunSpec
 import com.squareup.kotlinpoet.KModifier
 import com.squareup.kotlinpoet.ParameterSpec
@@ -9,7 +10,7 @@ import com.squareup.kotlinpoet.TypeName
 import com.squareup.kotlinpoet.TypeSpec
 import net.pearx.kasechange.CaseFormat
 import net.pearx.kasechange.toPascalCase
-import org.jellyfin.openapi.builder.Builder
+import org.jellyfin.openapi.builder.ContextBuilder
 import org.jellyfin.openapi.builder.extra.DeprecatedAnnotationSpecBuilder
 import org.jellyfin.openapi.builder.extra.DescriptionBuilder
 import org.jellyfin.openapi.builder.extra.TypeSerializerBuilder
@@ -17,7 +18,10 @@ import org.jellyfin.openapi.builder.extra.defaultValue
 import org.jellyfin.openapi.constants.Packages
 import org.jellyfin.openapi.constants.Strings
 import org.jellyfin.openapi.constants.Types
+import org.jellyfin.openapi.model.DefaultValue
 import org.jellyfin.openapi.model.DescriptionType
+import org.jellyfin.openapi.model.GeneratorContext
+import org.jellyfin.openapi.model.InterfaceApiModel
 import org.jellyfin.openapi.model.JellyFile
 import org.jellyfin.openapi.model.ObjectApiModel
 
@@ -25,11 +29,32 @@ class ObjectModelBuilder(
 	private val descriptionBuilder: DescriptionBuilder,
 	private val deprecatedAnnotationSpecBuilder: DeprecatedAnnotationSpecBuilder,
 	private val typeSerializerBuilder: TypeSerializerBuilder
-) : Builder<ObjectApiModel, JellyFile> {
-	@Suppress("ComplexMethod")
-	override fun build(data: ObjectApiModel): JellyFile {
+) : ContextBuilder<ObjectApiModel, JellyFile> {
+	@Suppress("ComplexMethod", "LoopWithTooManyJumpStatements", "LongMethod", "NestedBlockDepth")
+	override fun build(context: GeneratorContext, data: ObjectApiModel): JellyFile {
 		val properties = mutableListOf<PropertySpec>()
 		val serializers = mutableSetOf<TypeName>()
+
+		var polymorphicProperty: String? = null
+		var polymorphicPropertyValue: String? = null
+		val superPropertyNames = mutableSetOf<String>()
+
+		for (interfaceName in data.interfaces) {
+			// Add shared properties
+			val interfaceModel = context.getOrGenerateModel(interfaceName) as? InterfaceApiModel ?: continue
+			interfaceModel.properties.forEach { superPropertyNames.add(it.name) }
+
+			if (interfaceModel.polymorphicDiscriminator == null) continue
+
+			// Determine discriminator property name
+			val discriminator = interfaceModel.polymorphicDiscriminator
+			require(polymorphicProperty == null || polymorphicProperty == discriminator) {
+				"Multiple polymorphic interfaces with different discriminator are not supported." +
+						" (a=$polymorphicProperty, b=$discriminator)."
+			}
+			polymorphicProperty = discriminator
+		}
+
 		val constructor = FunSpec.constructorBuilder().apply {
 			data.properties.forEach { property ->
 				// Create constructor parameter
@@ -46,8 +71,13 @@ class ObjectModelBuilder(
 							addKdoc("%L", it)
 						}
 
+						// Add override modifier if in interface
+						if (property.name in superPropertyNames) modifiers += KModifier.OVERRIDE
+
 						if (property.deprecated) addAnnotation(deprecatedAnnotationSpecBuilder.build(Strings.DEPRECATED_MEMBER))
-						addAnnotation(AnnotationSpec.builder(Types.SERIAL_NAME).addMember("%S", property.originalName).build())
+						addAnnotation(
+							AnnotationSpec.builder(Types.SERIAL_NAME).addMember("%S", property.originalName).build()
+						)
 					}
 					.build()
 				)
@@ -55,6 +85,19 @@ class ObjectModelBuilder(
 				// Check if serializer is required
 				val serializer = typeSerializerBuilder.build(property.type)
 				if (serializer != null && serializer !in serializers) serializers += serializer
+
+				// Save polymorphic value
+				if (property.originalName == polymorphicProperty) {
+					require(polymorphicPropertyValue == null) { "Polymorphic property value already set" }
+					requireNotNull(property.defaultValue) { "Default value must be set for polymorphic property" }
+
+					polymorphicPropertyValue = when (property.defaultValue) {
+						is DefaultValue.String -> property.defaultValue.value
+						is DefaultValue.EnumMember -> property.defaultValue.serialName
+
+						else -> error("Polymorphic property value is of invalid type ${property.defaultValue}")
+					}
+				}
 			}
 		}.build()
 
@@ -76,12 +119,30 @@ class ObjectModelBuilder(
 		// Create class
 		return TypeSpec.classBuilder(data.name.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL))
 			.apply {
+				data.interfaces.forEach { interfaceName ->
+					addSuperinterface(
+						ClassName(
+							Packages.MODEL,
+							interfaceName.toPascalCase(from = CaseFormat.CAPITALIZED_CAMEL)
+						)
+					)
+				}
+
 				modifiers += KModifier.DATA
 				descriptionBuilder.build(DescriptionType.MODEL, data.description)?.let {
 					addKdoc("%L", it)
 				}
 				if (data.deprecated) addAnnotation(deprecatedAnnotationSpecBuilder.build(Strings.DEPRECATED_CLASS))
 				addAnnotation(AnnotationSpec.builder(Types.SERIALIZABLE).build())
+
+				if (polymorphicProperty != null) {
+					addAnnotation(
+						AnnotationSpec.builder(Types.SERIAL_NAME).addMember(
+							"%S",
+							requireNotNull(polymorphicPropertyValue) { "Polymorphic property value is missing" }
+						).build()
+					)
+				}
 			}
 			.primaryConstructor(constructor)
 			.addProperties(properties)

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/model/RequestModelBuilder.kt

@@ -1,23 +1,26 @@
 package org.jellyfin.openapi.builder.model
 
 import net.pearx.kasechange.toPascalCase
-import org.jellyfin.openapi.builder.Builder
+import org.jellyfin.openapi.builder.ContextBuilder
 import org.jellyfin.openapi.constants.Packages
 import org.jellyfin.openapi.constants.Strings
 import org.jellyfin.openapi.model.ApiServiceOperation
 import org.jellyfin.openapi.model.DefaultValue
+import org.jellyfin.openapi.model.GeneratorContext
 import org.jellyfin.openapi.model.JellyFile
 import org.jellyfin.openapi.model.ObjectApiModel
 import org.jellyfin.openapi.model.ObjectApiModelProperty
 
 class RequestModelBuilder(
 	private val objectModelBuilder: ObjectModelBuilder,
-) : Builder<ApiServiceOperation, JellyFile> {
-	override fun build(data: ApiServiceOperation): JellyFile = objectModelBuilder.build(
+) : ContextBuilder<ApiServiceOperation, JellyFile> {
+	override fun build(context: GeneratorContext, data: ApiServiceOperation): JellyFile = objectModelBuilder.build(
+		context,
 		ObjectApiModel(
 			data.name.toPascalCase() + Strings.MODEL_REQUEST_SUFFIX,
 			data.description,
 			false,
+			emptySet(),
 			(data.pathParameters + data.queryParameters).map { parameter ->
 				ObjectApiModelProperty(
 					name = parameter.name,

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/openapi/OpenApiDefaultValueBuilder.kt

@@ -34,7 +34,8 @@ class OpenApiDefaultValueBuilder : ContextBuilder<Schema<Any>, DefaultValue?> {
 
 		return DefaultValue.EnumMember(
 			enumType = ClassName(Packages.MODEL, model.name),
-			memberName = schemaDefault.toScreamingSnakeCase(from = CaseFormat.CAPITALIZED_CAMEL)
+			memberName = schemaDefault.toScreamingSnakeCase(from = CaseFormat.CAPITALIZED_CAMEL),
+			serialName = schemaDefault,
 		)
 	}
 

openapi-generator/src/main/kotlin/org/jellyfin/openapi/builder/openapi/OpenApiModelBuilder.kt

@@ -9,6 +9,8 @@ import org.jellyfin.openapi.model.ApiModel
 import org.jellyfin.openapi.model.EmptyApiModel
 import org.jellyfin.openapi.model.EnumApiModel
 import org.jellyfin.openapi.model.GeneratorContext
+import org.jellyfin.openapi.model.InterfaceApiModel
+import org.jellyfin.openapi.model.InterfaceApiModelProperty
 import org.jellyfin.openapi.model.ObjectApiModel
 import org.jellyfin.openapi.model.ObjectApiModelProperty
 
@@ -16,42 +18,102 @@ class OpenApiModelBuilder(
 	private val openApiTypeBuilder: OpenApiTypeBuilder,
 	private val openApiDefaultValueBuilder: OpenApiDefaultValueBuilder,
 ) : ContextBuilder<Schema<Any>, ApiModel> {
-	override fun build(context: GeneratorContext, data: Schema<Any>): ApiModel = when {
-		// Object
-		data.type == "object" -> when (data.properties.isNullOrEmpty()) {
-			// No properties use the empty model
-			true -> EmptyApiModel(
-				data.name,
-				data.description,
-				data.deprecated == true
-			)
-			// Otherwise use the object model
-			false -> ObjectApiModel(
-				data.name,
-				data.description,
-				data.deprecated == true,
-				data.properties.map { (originalName, property) ->
-					val name = originalName.toCamelCase(from = CaseFormat.CAPITALIZED_CAMEL)
-					ObjectApiModelProperty(
-						name = name,
-						originalName = originalName,
-						defaultValue = openApiDefaultValueBuilder.build(context, property),
-						type = openApiTypeBuilder.build(ModelTypePath(data.name, name), property),
-						description = property.description,
-						deprecated = property.deprecated == true
+	override fun build(context: GeneratorContext, data: Schema<Any>): ApiModel {
+		return when {
+			// Object
+			data.type == "object" -> when {
+				// When properties set, use the object model
+				!data.properties.isNullOrEmpty() -> buildObjectModel(context, data)
+				// When oneOf set, use the interface model
+				!data.oneOf.isNullOrEmpty() -> buildInterfaceModel(context, data)
+				// Otherwise use the empty model
+				else -> buildEmptyModel(data)
+			}
+			// Enum
+			data.enum.isNotEmpty() -> buildEnumModel(data)
+
+			// Unknown type
+			else -> throw NotImplementedError("Unknown top-level type: ${data.type} for ${data.name}")
+		}
+	}
+
+	private fun buildInterfaceModel(context: GeneratorContext, data: Schema<Any>): InterfaceApiModel {
+		val referencedModels = data.oneOf.mapNotNull { it.`$ref`?.let(context::getOrGenerateModel) }
+		var sharedProperties: Set<InterfaceApiModelProperty>? = null
+
+		for ((index, model) in referencedModels.withIndex()) {
+			// Add interface to referenced model
+			context.addModelInterface(model, data.name)
+
+			// Only search for shared properties if the lookup didn't fail before this iteration
+			if (sharedProperties == null && index != 0) continue
+
+			// Find properties of current model
+			val modelProperties = when (model) {
+				is ObjectApiModel -> model.properties.map {
+					InterfaceApiModelProperty(
+						name = it.name,
+						originalName = it.originalName,
+						type = it.type,
+						description = it.description,
+						deprecated = it.deprecated,
 					)
 				}.toSet()
-			)
-		}
-		// Enum
-		data.enum.isNotEmpty() -> EnumApiModel(
-			data.name,
-			data.description,
-			data.deprecated == true,
-			data.enum.orEmpty().map { it.toString() }.toSet()
-		)
+				is InterfaceApiModel -> model.properties
+				else -> null
+			}
 
-		// Unknown type
-		else -> throw NotImplementedError("Unknown top-level type: ${data.type} for ${data.name}")
+			// Search for shared properties between previous and current iteration
+			sharedProperties = when {
+				// Unsupported model type
+				modelProperties == null -> null
+				// First iteration
+				sharedProperties == null -> modelProperties
+				// Compare with existing properties
+				else -> sharedProperties.filter { a -> modelProperties.any { b -> a.typeMatches(b) } }.toSet()
+			}
+		}
+
+		return InterfaceApiModel(
+			name = data.name,
+			description = data.description,
+			deprecated = data.deprecated == true,
+			interfaces = emptySet(),
+			polymorphicDiscriminator = data.discriminator?.propertyName,
+			properties = sharedProperties.orEmpty(),
+		)
 	}
+
+	private fun buildEmptyModel(data: Schema<Any>) = EmptyApiModel(
+		name = data.name,
+		description = data.description,
+		deprecated = data.deprecated == true,
+		interfaces = emptySet(),
+	)
+
+	private fun buildObjectModel(context: GeneratorContext, data: Schema<Any>) = ObjectApiModel(
+		name = data.name,
+		description = data.description,
+		deprecated = data.deprecated == true,
+		interfaces = emptySet(),
+		properties = data.properties.map { (originalName, property) ->
+			val name = originalName.toCamelCase(from = CaseFormat.CAPITALIZED_CAMEL)
+			ObjectApiModelProperty(
+				name = name,
+				originalName = originalName,
+				defaultValue = openApiDefaultValueBuilder.build(context, property),
+				type = openApiTypeBuilder.build(ModelTypePath(data.name, name), property),
+				description = property.description,
+				deprecated = property.deprecated == true,
+			)
+		}.toSet()
+	)
+
+	private fun buildEnumModel(data: Schema<Any>) = EnumApiModel(
+		name = data.name,
+		description = data.description,
+		deprecated = data.deprecated == true,
+		interfaces = emptySet(),
+		constants = data.enum.orEmpty().map { it.toString() }.toSet(),
+	)
 }

openapi-generator/src/main/kotlin/org/jellyfin/openapi/constants/Types.kt

@@ -33,4 +33,5 @@ object Types {
 	val SERIALIZABLE = ClassName("kotlinx.serialization", "Serializable")
 	val SERIAL_NAME = ClassName("kotlinx.serialization", "SerialName")
 	val USE_SERIALIZERs = ClassName("kotlinx.serialization", "UseSerializers")
+	val JSON_DISCRIMINATOR = ClassName("kotlinx.serialization.json", "JsonClassDiscriminator")
 }

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/ApiModel.kt

@@ -4,4 +4,5 @@ interface ApiModel {
 	val name: String
 	val description: String?
 	val deprecated: Boolean
+	val interfaces: Set<String>
 }

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/DefaultValue.kt

@@ -12,7 +12,11 @@ sealed interface DefaultValue {
 	@JvmInline
 	value class Boolean(val value: kotlin.Boolean) : DefaultValue
 
-	data class EnumMember(val enumType: TypeName, val memberName: kotlin.String) : DefaultValue
+	data class EnumMember(
+		val enumType: TypeName,
+		val memberName: kotlin.String,
+		val serialName: kotlin.String,
+	) : DefaultValue
 
 	/**
 	 * Custom value builder used in hooks.

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/EmptyApiModel.kt

@@ -3,5 +3,6 @@ package org.jellyfin.openapi.model
 data class EmptyApiModel(
 	override val name: String,
 	override val description: String?,
-	override val deprecated: Boolean
+	override val deprecated: Boolean,
+	override val interfaces: Set<String>,
 ) : ApiModel

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/EnumApiModel.kt

@@ -4,5 +4,6 @@ data class EnumApiModel(
 	override val name: String,
 	override val description: String?,
 	override val deprecated: Boolean,
-	val constants: Set<String>
+	override val interfaces: Set<String>,
+	val constants: Set<String>,
 ) : ApiModel

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/GeneratorContext.kt

@@ -7,6 +7,7 @@ import io.swagger.v3.oas.models.media.Schema
 import io.swagger.v3.parser.core.models.SwaggerParseResult
 import net.pearx.kasechange.CaseFormat
 import net.pearx.kasechange.toPascalCase
+import org.jellyfin.openapi.OpenApiGeneratorError
 import org.jellyfin.openapi.builder.openapi.OpenApiModelBuilder
 
 class GeneratorContext(
@@ -36,6 +37,18 @@ class GeneratorContext(
 		}
 	}
 
+	fun addModelInterface(model: ApiModel, interfaceName: String) {
+		val interfaces = model.interfaces + interfaceName
+		_models[model.name] = when (model) {
+			is EmptyApiModel -> model.copy(interfaces = interfaces)
+			is EnumApiModel -> model.copy(interfaces = interfaces)
+			is InterfaceApiModel -> model.copy(interfaces = interfaces)
+			is ObjectApiModel -> model.copy(interfaces = interfaces)
+
+			else -> throw OpenApiGeneratorError("Unknown model class ${model::class.qualifiedName}")
+		}
+	}
+
 	operator fun plusAssign(service: ApiService) {
 		_apiServices.add(service)
 	}

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/InterfaceApiModel.kt

@@ -0,0 +1,10 @@
+package org.jellyfin.openapi.model
+
+data class InterfaceApiModel(
+	override val name: String,
+	override val description: String?,
+	override val deprecated: Boolean,
+	override val interfaces: Set<String>,
+	val polymorphicDiscriminator: String?,
+	val properties: Set<InterfaceApiModelProperty>,
+) : ApiModel

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/InterfaceApiModelProperty.kt

@@ -0,0 +1,14 @@
+package org.jellyfin.openapi.model
+
+import com.squareup.kotlinpoet.TypeName
+
+data class InterfaceApiModelProperty(
+	val name: String,
+	val originalName: String,
+	val type: TypeName,
+	val description: String?,
+	val deprecated: Boolean,
+) {
+	fun typeMatches(other: InterfaceApiModelProperty): Boolean =
+		other === this || (name == other.name && originalName == other.originalName && type == other.type)
+}

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/ObjectApiModel.kt

@@ -4,5 +4,6 @@ data class ObjectApiModel(
 	override val name: String,
 	override val description: String?,
 	override val deprecated: Boolean,
-	val properties: Set<ObjectApiModelProperty>
+	override val interfaces: Set<String>,
+	val properties: Set<ObjectApiModelProperty>,
 ) : ApiModel

openapi-generator/src/main/kotlin/org/jellyfin/openapi/model/ObjectApiModelProperty.kt

@@ -8,5 +8,5 @@ data class ObjectApiModelProperty(
 	val defaultValue: DefaultValue?,
 	val type: TypeName,
 	val description: String?,
-	val deprecated: Boolean
+	val deprecated: Boolean,
 )