build.gradle.kts

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

group = "com.zhelenskiy"
version = "1.0"

fun generateClassSerializers() = buildString {
    operator fun String.unaryPlus() = appendLine(this)

    val tab = "    "
    val generateIndices = 0u..64u

    fun generateClassSerializerByPropertiesCount(n: UInt) {
        +"open class ClassKSerializer$n<${(listOf("T") + (1u..n).map { "R$it" }).joinToString(", ")}>("
        +"${tab}private val descriptorName: String,"
        for (i in 1u..n) {
            +"${tab}private val serializerPart$i: Property<T, R$i>,"
        }
        +"${tab}private val build: (${(1u..n).joinToString(", ") { "R$it" }}) -> T,"
        +") : KSerializer<T> {"

        +"${tab}final override val descriptor: SerialDescriptor = buildClassSerialDescriptor(descriptorName) {"
        for (i in 1u..n) {
            +"${tab}${tab}element(serializerPart${i}.name, serializerPart${i}.serializer.descriptor)"
        }
        +"${tab}}"

        +""

        +"${tab}final override fun serialize(encoder: Encoder, value: T) = encoder.encodeStructure(descriptor) {"
        for (i in 1u..n) {
            +"${tab}${tab}encodeSerializableElement(descriptor, ${i - 1u}, serializerPart${i}.serializer, serializerPart${i}.generator(value))"
        }
        +"${tab}}"

        +""

        if (n > 0u) {
            +"${tab}@OptIn(ExperimentalSerializationApi::class)"
        }
        +"${tab}final override fun deserialize(decoder: Decoder): T = decoder.decodeStructure(descriptor) {"
        if (n == 0u) {
            +"${tab}${tab}build()"
        } else {
            +"${tab}${tab}if (decodeSequentially()) {"
            +"${tab}${tab}${tab}build("
            for (i in 1u..n) {
                +"${tab}${tab}${tab}${tab}decodeSerializableElement(descriptor, ${i - 1u}, serializerPart${i}.serializer),"
            }
            +"${tab}${tab}${tab})"
            +"${tab}${tab}} else {"
            for (i in 1u..n) {
                +"${tab}${tab}${tab}var value$i: R$i? = null"
            }
            +"${tab}${tab}${tab}while (true) {"
            +"${tab}${tab}${tab}${tab}when (val index = decodeElementIndex(descriptor)) {"
            for (i in 1u..n) {
                +"${tab}${tab}${tab}${tab}${tab}${i - 1u} -> value$i = decodeSerializableElement(descriptor, ${i - 1u}, serializerPart${i}.serializer)"
            }
            +"${tab}${tab}${tab}${tab}${tab}CompositeDecoder.DECODE_DONE -> break"
            +"${tab}${tab}${tab}${tab}${tab}else -> error(\"Unexpected index: \$index\")"
            +"${tab}${tab}${tab}${tab}}"
            +"${tab}${tab}${tab}}"
            +"${tab}${tab}${tab}return@decodeStructure build("
            for (i in 1u..n) {
                +"${tab}${tab}${tab}${tab}value${i} ?: error(\"Absent field: \${serializerPart${i}.name}\"),"
            }
            +"${tab}${tab}${tab})"
            +"${tab}${tab}}"
        }
        +"${tab}}"

        +"}"

        +""

        +"fun <${(listOf("T") + (1u..n).map { "R$it" }).joinToString(", ")}> classSerializer("
        +"${tab}descriptorName: String,"
        for (i in 1u..n) {
            +"${tab}serializerPart$i: Property<T, R$i>,"
        }
        +"${tab}build: (${(1u..n).joinToString(", ") { "R$it" }}) -> T,"
        +") : KSerializer<T> = ClassKSerializer$n("
        +"${tab}descriptorName,"
        for (i in 1u..n) {
            +"${tab}serializerPart$i,"
        }
        +"${tab}build,"
        +")"
    }
    +"@file:Suppress(\"DuplicatedCode\")"
    +""
    +"package com.zhelenskiy.serialization"
    +""
    +"import kotlinx.serialization.ExperimentalSerializationApi"
    +"import kotlinx.serialization.KSerializer"
    +"import kotlinx.serialization.descriptors.SerialDescriptor"
    +"import kotlinx.serialization.descriptors.buildClassSerialDescriptor"
    +"import kotlinx.serialization.encoding.CompositeDecoder"
    +"import kotlinx.serialization.encoding.Decoder"
    +"import kotlinx.serialization.encoding.Encoder"
    +"import kotlinx.serialization.encoding.decodeStructure"
    +"import kotlinx.serialization.encoding.encodeStructure"
    +"import kotlinx.serialization.serializer"
    +"import kotlin.reflect.KProperty1"
    +""
    +"// This file is generated by a :generateClassSerializers task in build.gradle.kts"
    +""
    +""
    +"data class Property<T, R>("
    +"${tab}val name: String,"
    +"${tab}val serializer: KSerializer<R>,"
    +"${tab}val generator: (T) -> R,"
    +") {"
    +"${tab}constructor(property: KProperty1<T, R>, serializer: KSerializer<R>) : this(property.name, serializer, property)"
    +"${tab}companion object {"
    +"${tab}${tab}inline operator fun <T, reified R> invoke(name: String, noinline generator: (T) -> R): Property<T, R> ="
    +"${tab}${tab}${tab}Property(name, serializer<R>(), generator)"
    +""
    +"${tab}${tab}inline operator fun <T, reified R> invoke(property: KProperty1<T, R>): Property<T, R> ="
    +"${tab}${tab}${tab}Property(property, serializer<R>())"
    +"${tab}}"
    +"}"
    for (n in generateIndices) {
        +""
        generateClassSerializerByPropertiesCount(n)
    }
}

fun File.withCreatedParentDirectories() = apply { parentFile?.mkdirs() }

tasks.register("generateClassSerializers") {
    val sourceFile = generateClassSerializers()
    projectDir.resolve("src/com/zhelenskiy/serialization/ClassSerializer.kt").withCreatedParentDirectories().writeText(sourceFile)
}

tasks.withType<KotlinCompile> {
    dependsOn(":generateClassSerializers")
}

publishing {
    repositories {
        maven {
            url = uri("https://maven.pkg.github.com/zhelenskiy/kotlinx-serialization-builder")
            credentials {
                username = System.getenv("GITHUB_ACTOR")
                password = System.getenv("GITHUB_TOKEN")
            }
        }
    }
}