Create constants for translation files

build.gradle

buildscript {
    repositories {
        mavenCentral()
        gradlePluginPortal()
    }
}

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.9.10'
}

repositories {
    mavenCentral()
}

dependencies {
    implementation('com.squareup:javapoet:1.13.0')
}

GenerateStrings.kt

abstract class GenerateStrings : DefaultTask() {

    @get:InputDirectory
    abstract val propertiesDir: DirectoryProperty

    @get:OutputDirectory
    abstract val destination: DirectoryProperty

    init {
        destination.convention(project.layout.buildDirectory.dir("generated/sources/strings"))
    }

    @TaskAction
    fun run() {
        val propertiesDir = propertiesDir.asFile.get()
        val propertiesFiles = propertiesDir.walkTopDown()
            .filter { it.isFile && it.extension == "properties" && !it.name.contains("_", ignoreCase = true) }
        val stringsSpec = TypeSpec.classBuilder("R")
            .addAnnotation(AnnotationSpec.builder(SuppressWarnings::class.java).addMember("value", "\$S", "unused").build())
            .addMethod(MethodSpec.constructorBuilder().addModifiers(Modifier.PRIVATE).build())
            .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
            .apply {
                for (propertiesFile in propertiesFiles) {
                    addType(
                        TypeSpec.classBuilder( propertiesFile.getName().replace(".properties", ""))
                            .addMethod(MethodSpec.constructorBuilder().addModifiers(Modifier.PRIVATE).build())
                            .addModifiers(Modifier.PUBLIC, Modifier.FINAL, Modifier.STATIC)
                            .apply {
                                val properties = Properties().apply { load(propertiesFile.reader()) }
                                for (propertyName in properties.propertyNames()) {
                                    addField(FieldSpec.builder(
                                        String::class.java, propertyName.toString(), Modifier.PUBLIC, Modifier.STATIC, Modifier.FINAL
                                    ).initializer("\$S", propertyName.toString())
                                        .build())
                                }
                            }
                            .build()
                    )
                }
            }
            .build()
        val outputFile = destination.asFile.get().resolve("com/pkmngen/game/R.java")
        if (!outputFile.exists()) {
            outputFile.getParentFile().mkdirs()
        }
        outputFile.writer().use {
            JavaFile.builder("com.pkmngen.game", stringsSpec).build()
                .writeTo(it)
        }
    }
}