Transform json file into the kotlin code that defines the same data structure

codegen.kt

package uk.gov.justice.digital.hmpps.createandvaryalicenceapi.service

import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
import com.fasterxml.jackson.module.kotlin.readValue
import uk.gov.justice.digital.hmpps.createandvaryalicenceapi.model.policy.LicencePolicy
import java.io.File
import java.nio.charset.StandardCharsets.UTF_8
import kotlin.reflect.full.memberProperties

val seenTypes = mutableSetOf<Class<*>>()

val policyMap = mapOf(
  "policyV2_1" to "src/main/resources/policy_conditions/policyV2.1.json",
  "policyV2" to "src/main/resources/policy_conditions/policyV2.json",
  "policyV1" to "src/main/resources/policy_conditions/policyV1.json",
)

fun main() {
  policyMap.forEach { (k, v) ->
   writePolicyFile(k, v)
  }
}

fun writePolicyFile(name: String, location: String) {
  val policyObj = getLicencePolicy(location)

  val policy = printValue(policyObj)

  var text = "package uk.gov.justice.digital.hmpps.createandvaryalicenceapi.service\n\n"
  seenTypes.forEach {
    text += "import ${it.canonicalName}\n"
  }
  text += "\n\nval $name = $policy"

  println(text)

  File("src/main/kotlin/uk/gov/justice/digital/hmpps/createandvaryalicenceapi/service/${name}.kt").writeText(
    text, UTF_8
  )
}

private fun getLicencePolicy(location: String): LicencePolicy {
  val stream = File(location).inputStream()
  return jacksonObjectMapper().readValue(stream)
}

private fun printValue(value: Any?, depth: Int = 0): String? = when {
  value == null -> null

  String::class.isInstance(value) -> if (value.toString().contains("\"")) "\"\"\"$value\"\"\"" else "\"$value\""

  Int::class.isInstance(value) -> value.toString()

  Boolean::class.isInstance(value) -> value.toString()

  java.util.List::class.java.isInstance(value) -> {
    var result = ""
    result += "listOf("
    (value as List<*>?)?.forEach {
      result += "${printValue(it!!, depth + 2)},\n"
    }
    result += depth.pad(")")
    result
  }

  value::class.java.packageName.startsWith("uk.gov") -> {
    seenTypes.add(value::class.java)
    val members = value::class.memberProperties
    var result = depth.pad("${value::class.simpleName!!}(\n")
    members.forEach {
      val fieldValue = it.call(value)
      val formattedValue = printValue(fieldValue, depth + 2)
      result += (depth + 2).pad("${it.name} = $formattedValue,\n")
    }
    result += depth.pad(")")
    result
  }

  else -> throw RuntimeException("${value::class} = unknown -> ${value::class.javaObjectType}\n")
}


fun Int.pad(v: String) = "${" ".repeat(this)} $v"