Convert Spark2.2's UDAF to 3.0 Aggregator - scala

Question

I have a already written UDAF in scala using Spark2.4. Since our Databricks cluster was in 6.4 runtime whose support is no more there, we need to move to 7.3 LTS which have the long term support and uses Spark3. UDAF is deprecated in Spark3 and will be removed in future(most likely). So I am trying to convert a UDAF into Aggregator function
import org.apache.spark.sql.Row
import org.apache.spark.sql.expressions.{MutableAggregationBuffer, UserDefinedAggregateFunction}
import org.apache.spark.sql.types.{IntegerType,StringType, StructField, StructType, DataType}
object MaxCampaignIdAggregator extends UserDefinedAggregateFunction with java.io.Serializable{
override def inputSchema: StructType = new StructType()
.add("id", IntegerType, true)
.add("name", StringType, true)
def bufferSchema: StructType = new StructType()
.add("id", IntegerType, true)
.add("name", StringType, true)
// Returned Data Type .
def dataType: DataType = new StructType()
.add("id", IntegerType, true)
.add("name", StringType, true)
// Self-explaining
def deterministic: Boolean = true
// This function is called whenever key changes
def initialize(buffer: MutableAggregationBuffer) = {
buffer(0) = null
buffer(1) = null
}
// Iterate over each entry of a group
def update(buffer: MutableAggregationBuffer, inputRow: Row): Unit ={
val inputId = inputRow.getAs[Int](0)
val actualInputId = inputRow.get(0)
val inputName = inputRow.getString(1)
val bufferId = buffer.getAs[Int](0)
val actualBufferId = buffer.get(0)
val bufferName = buffer.getString(1)
if(actualBufferId == null){
buffer(0) = actualInputId
buffer(1) = inputName
}else if(actualInputId != null) {
if(inputId > bufferId){
buffer(0) = inputId
buffer(1) = inputName
}
}
}
// Merge two partial aggregates
def merge(buffer1: MutableAggregationBuffer, buffer2: Row) = {
val buffer1Id = buffer1.getAs[Int](0)
val actualbuffer1Id = buffer1.get(0)
val buffer1Name = buffer1.getString(1)
val buffer2Id = buffer2.getAs[Int](0)
val actualbuffer2Id = buffer2.get(0)
val buffer2Name = buffer2.getString(1)
if(actualbuffer1Id == null){
buffer1(0) = actualbuffer2Id
buffer1(1) = buffer2Name
}else if(actualbuffer2Id != null){
if(buffer2Id > buffer1Id){
buffer1(0) = buffer2Id
buffer1(1) = buffer2Name
}
}
}
// Called after all the entries are exhausted.
def evaluate(buffer: Row): Any = {
Row(buffer.get(0), buffer.getString(1))
}
}
After usage this give output as :
{"id": 1282, "name": "McCormick Christmas"}
{"id": 1305, "name": "McCormick Perfect Pinch"}
{"id": 1677, "name": "Viking Cruises Viking Cruises"}