ASTNormalizer.scala

// ASTNormalizer.scala

package backend

import scala.annotation.tailrec

object ASTNormalizer:
  private def expandComposite(
      exprs: List[AwkMapExpr]
  ): List[AwkMapExpr] =
    exprs match {
      case h :: tail =>
        h match {
          case CompositeMap(innerExpr) =>
            innerExpr ::: exprs
          case _ =>
            h :: expandComposite(tail)
        }
      case Nil =>
        Nil
    }

  private def mergeProjections(
      exprs: List[AwkMapExpr]
  ): List[AwkMapExpr] =
    exprs match {
      case MapExpr(l1) :: MapExpr(l2) :: tail =>
        val m1 = Map(l1.idx.zipWithIndex.map(x => ((x._2 + 1) -> x._1)): _*)
        MapExpr(
          Projection(l2.idx.map(prj => m1(prj)): _*)
        ) :: tail
      case h :: tail =>
        h :: mergeProjections(tail)
      case Nil =>
        Nil
    }

  @tailrec
  private def normalizeList(
      exprs: List[AwkMapExpr]
  ): List[AwkMapExpr] =
    val result =
      expandComposite.andThen(mergeProjections)(exprs)
    if (result != exprs)
      normalizeList(result)
    else
      result

  def normalize(awkRootExpr: AwkQueryAST) = AwkQueryAST(
    awkRootExpr.fileNameOrPath,
    normalizeList(awkRootExpr.mapFilterExpr.toList): _*
  )