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Json/Protobuf convertor macros for ScalaPB

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package scalapb_json

import scalapb.{GeneratedMessage, GeneratedMessageCompanion}
import scala.quoted.*

object ProtoMacros {
  implicit class ScalaPBMessageOps[A <: GeneratedMessage](
    private val companion: GeneratedMessageCompanion[A]
  ) extends AnyVal {
    inline def fromTextFormat(textFormat: String): A =
      ${ fromTextFormatImpl('textFormat, 'companion, debug = false) }

    inline def fromTextFormatDebug(textFormat: String): A =
      ${ fromTextFormatImpl('textFormat, 'companion, debug = true) }
  }

  private[scalapb_json] def getJavaClass(scalaName: String): Either[String, Class[?]] = {
    Class.forName(scalaName + "$").getMethods.filter { method =>
      // https://github.com/scalapb/ScalaPB/blob/v0.11.9/scalapb-runtime/src/main/scala/scalapb/GeneratedMessageCompanion.scala#L161
      method.getName == "toJavaProto" && method.getReturnType != classOf[Object]
    } match {
      case Array(method) =>
        Right(method.getReturnType)
      case other =>
        Left(s"Could not found Java class ${scalaName} ${other.mkString(" ")}")
    }
  }

  private def fromTextFormatImpl[A <: GeneratedMessage: Type](
    textFormat: Expr[String],
    companion: Expr[GeneratedMessageCompanion[A]],
    debug: Boolean
  )(using quote: Quotes): Expr[A] = {
    import quote.reflect.*
    textFormat.value match {
      case Some(str) =>
        val typeName = Type.show[A]
        val javaClass = getJavaClass(typeName).left.map(report.errorAndAbort(_)).merge
        val builder = javaClass
          .getMethod("newBuilder")
          .invoke(null)
          .asInstanceOf[com.google.protobuf.Message.Builder]
        com.google.protobuf.TextFormat.getParser.merge(str, builder)
        val result = builder.build().toString
        if (debug) {
          report.info(result)
        }
        '{ ${ companion }.fromAscii(${ textFormat }) }
      case None =>
        report.errorAndAbort("expect String literal")
    }
  }

}