1 files changed, 171 insertions, 0 deletions
diff --git a/runtime/commonMain/src/kotlinx/serialization/json/internal/TreeJsonOutput.kt b/runtime/commonMain/src/kotlinx/serialization/json/internal/TreeJsonOutput.kt
new file mode 100644
index 00000000..1d11f1f9
--- /dev/null
+++ b/runtime/commonMain/src/kotlinx/serialization/json/internal/TreeJsonOutput.kt
@@ -0,0 +1,171 @@
+/*
+ * Copyright 2018 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package kotlinx.serialization.json.internal
+
+import kotlinx.serialization.*
+import kotlinx.serialization.internal.*
+import kotlinx.serialization.json.*
+import kotlinx.serialization.modules.*
+import kotlin.collections.set
+import kotlin.jvm.*
+
+internal fun <T> Json.writeJson(value: T, serializer: SerializationStrategy<T>): JsonElement {
+    lateinit var result: JsonElement
+    val encoder = JsonTreeOutput(this) { result = it }
+    encoder.encode(serializer, value)
+    return result
+}
+
+private sealed class AbstractJsonTreeOutput(
+    final override val json: Json,
+    val nodeConsumer: (JsonElement) -> Unit
+) : NamedValueEncoder(), JsonOutput {
+
+    final override val context: SerialModule
+        get() = json.context
+
+    @JvmField
+    protected val configuration = json.configuration
+
+    private var writePolymorphic = false
+
+    override fun encodeJson(element: JsonElement) {
+        encodeSerializableValue(JsonElementSerializer, element)
+    }
+
+    override fun shouldEncodeElementDefault(desc: SerialDescriptor, index: Int): Boolean = configuration.encodeDefaults
+    override fun composeName(parentName: String, childName: String): String = childName
+    abstract fun putElement(key: String, element: JsonElement)
+    abstract fun getCurrent(): JsonElement
+
+    override fun encodeTaggedNull(tag: String) = putElement(tag, JsonNull)
+
+    override fun encodeTaggedInt(tag: String, value: Int) = putElement(tag, JsonLiteral(value))
+    override fun encodeTaggedByte(tag: String, value: Byte) = putElement(tag, JsonLiteral(value))
+    override fun encodeTaggedShort(tag: String, value: Short) = putElement(tag, JsonLiteral(value))
+    override fun encodeTaggedLong(tag: String, value: Long) = putElement(tag, JsonLiteral(value))
+
+    override fun encodeTaggedFloat(tag: String, value: Float) {
+        if (configuration.strictMode && !value.isFinite()) {
+            throw JsonInvalidValueInStrictModeException(value)
+        }
+
+        putElement(tag, JsonLiteral(value))
+    }
+
+    override fun <T> encodeSerializableValue(serializer: SerializationStrategy<T>, value: T) {
+        encodePolymorphically(serializer, value) {
+            writePolymorphic = true
+        }
+    }
+
+    override fun encodeTaggedDouble(tag: String, value: Double) {
+        if (configuration.strictMode && !value.isFinite()) {
+            throw JsonInvalidValueInStrictModeException(value)
+        }
+
+        putElement(tag, JsonLiteral(value))
+    }
+
+    override fun encodeTaggedBoolean(tag: String, value: Boolean) = putElement(tag, JsonLiteral(value))
+    override fun encodeTaggedChar(tag: String, value: Char) = putElement(tag, JsonLiteral(value.toString()))
+    override fun encodeTaggedString(tag: String, value: String) = putElement(tag, JsonLiteral(value))
+    override fun encodeTaggedEnum(
+        tag: String,
+        enumDescription: EnumDescriptor,
+        ordinal: Int
+    ) = putElement(tag, JsonLiteral(enumDescription.getElementName(ordinal)))
+
+    override fun encodeTaggedValue(tag: String, value: Any) {
+        putElement(tag, JsonLiteral(value.toString()))
+    }
+
+    override fun beginStructure(desc: SerialDescriptor, vararg typeParams: KSerializer<*>): CompositeEncoder {
+        val consumer =
+            if (currentTagOrNull == null) nodeConsumer
+            else { node -> putElement(currentTag, node) }
+
+        val encoder = when (desc.kind) {
+            StructureKind.LIST, UnionKind.POLYMORPHIC -> JsonTreeListOutput(json, consumer)
+            StructureKind.MAP -> JsonTreeMapOutput(json, consumer)
+            else -> JsonTreeOutput(json, consumer)
+        }
+
+        if (writePolymorphic) {
+            writePolymorphic = false
+            encoder.putElement(configuration.classDiscriminator, JsonPrimitive(desc.name))
+        }
+
+        return encoder
+    }
+
+    override fun endEncode(desc: SerialDescriptor) {
+        nodeConsumer(getCurrent())
+    }
+}
+
+private open class JsonTreeOutput(json: Json, nodeConsumer: (JsonElement) -> Unit) :
+    AbstractJsonTreeOutput(json, nodeConsumer) {
+
+    protected val content: MutableMap<String, JsonElement> = linkedMapOf()
+
+    override fun putElement(key: String, element: JsonElement) {
+        content[key] = element
+    }
+
+    override fun getCurrent(): JsonElement = JsonObject(content)
+}
+
+private class JsonTreeMapOutput(json: Json, nodeConsumer: (JsonElement) -> Unit) : JsonTreeOutput(json, nodeConsumer) {
+    private lateinit var tag: String
+
+    override fun putElement(key: String, element: JsonElement) {
+        val idx = key.toInt()
+        if (idx % 2 == 0) { // writing key
+            check(element is JsonLiteral) { "Expected JsonLiteral, but has $element" }
+            tag = element.content
+        } else {
+            content[tag] = element
+        }
+    }
+
+    override fun getCurrent(): JsonElement {
+        return JsonObject(content)
+    }
+
+    override fun shouldWriteElement(desc: SerialDescriptor, tag: String, index: Int): Boolean = true
+}
+
+private class JsonTreeListOutput(json: Json, nodeConsumer: (JsonElement) -> Unit) :
+    AbstractJsonTreeOutput(json, nodeConsumer) {
+    private val array: ArrayList<JsonElement> = arrayListOf()
+
+    override fun shouldWriteElement(desc: SerialDescriptor, tag: String, index: Int): Boolean = true
+
+    override fun putElement(key: String, element: JsonElement) {
+        val idx = key.toInt()
+        array.add(idx, element)
+    }
+
+    override fun getCurrent(): JsonElement = JsonArray(array)
+}
+
+@Suppress("USELESS_CAST") // Contracts does not work in K/N
+internal inline fun <reified T : JsonElement> cast(obj: JsonElement): T {
+    check(obj is T) { "Expected ${T::class} but found ${obj::class}" }
+    return obj as T
+}