SchemaValidationListener.scala

import SchemaValidationListener._
import org.everit.json.schema.Schema
import org.everit.json.schema.event.{CombinedSchemaMatchEvent, SchemaReferencedEvent, ValidationListener}

import scala.collection.mutable.ListBuffer
import scala.util.matching.Regex
import scala.collection.JavaConverters._

object SchemaValidationListener {

  case class SchemaReferenced(location: String, schemaId: String)

  val SchemaId = "schemaId"
  val schemaRefRe: Regex = "^\\{\"\\$ref\":\"([\\w\\/._-]+)\"\\}$".r(SchemaId)

  def extractSchemaReferenced(schema: String): Option[String] = {
    schemaRefRe
      .findFirstMatchIn(schema)
      .map(_.group(SchemaId))
  }
}

case class SchemaValidationListener() extends ValidationListener {

  val schemasReferencedMatching: ListBuffer[SchemaReferenced] = ListBuffer.empty

  override def schemaReferenced(event: SchemaReferencedEvent): Unit = {
    val subSchema: Schema = event.getReferredSchema
    val schemaReferenced = Option(subSchema.getId).getOrElse(subSchema.getSchemaLocation)
    val path = event.getPath.asScala.mkString("/")

    val reference = SchemaReferenced(path, schemaReferenced)
    schemasReferencedMatching.append(reference)
  }

  override def combinedSchemaMatch(event: CombinedSchemaMatchEvent): Unit = {
    val subSchema: Schema = event.getSubSchema
    val path = event.getPath.asScala.mkString("/")

    extractSchemaReferenced(subSchema.toString)
      .foreach { schemaId =>
        val reference = SchemaReferenced(path, schemaId)
        schemasReferencedMatching.append(reference)
      }
  }

}