extraParseVlad

import Library._
import Untyped._

case class NotImplementedException(s: String) extends RuntimeException(s)
case class ParseOpException(s: String) extends ParseException(s)


object Parser {



  def constructBinding(bind: SExpr): LetBindExt = bind match {
    case SList(SSym(name) :: value :: Nil) => {
      if (ExprExt.reservedWords.contains(name)) throw new ParseOpException("Id cannot be reserved keyword")
      else LetBindExt(name, parse(value))
    }
    case _ =>  throw new ParseOpException("Invalid let-bind format")
  }

  def extractParams(params: List[SExpr]): List[String] = params match {
    case Nil => Nil
    case param :: t => {
      val hd = parse(param)
      hd match {
        case IdExt(name) => name :: extractParams(params.tail)
        case _ => throw new ParseOpException("Extract params error")
      }
    }
  }




  def parse(str: String): ExprExt = parse(Reader.read(str))

  def parse(sexpr: SExpr): ExprExt = sexpr match{

    case SNum(x) => NumExt(x)
    case SSym("nil") => NilExt()
    case SSym("true") => TrueExt()
    case SSym("false") => FalseExt()
    case SSym(name) => {
      if (ExprExt.reservedWords.contains(name)) throw new ParseOpException("Id cannot be reserved keyword")
      else IdExt(name)
    }


    case SList(list: List[SExpr]) => list match {

      case (SSym(symbol) :: left :: right :: Nil) if ExprExt.binOps.contains(symbol)  => BinOpExt(symbol, parse(left), parse(right))

      case (SSym(symbol) :: e :: Nil) if ExprExt.unOps.contains(symbol) => UnOpExt(symbol, parse(e))

      case SSym("if") :: c :: t :: e :: Nil => IfExt(parse(c), parse(t), parse(e))

      case SSym("let") :: SList(bindings) :: body :: Nil => {

        val letBindings: List[LetBindExt] = bindings.map(bind => constructBinding(bind))
        val letBindingsNames: List[String] = letBindings.map(bind => bind.name)


        if (letBindingsNames.size > 0 && letBindingsNames.toSet.size == letBindingsNames.size)
          LetExt(letBindings, parse(body))
        else throw new ParseOpException("A let expression can only bind a parameter name once")
      }

      case SSym("lambda") :: SList(params) :: body:: Nil => {
        val paramsNames: List[String] = extractParams(params)
        if (paramsNames.toSet.size == paramsNames.size)
          FdExt(paramsNames, parse(body))
        else throw new ParseOpException("A let expression can only bind a parameter name once")
      }

      case h :: t => AppExt(parse(h), t.map(parse)) // "App" case

      case _ =>  throw new ParseOpException("`e` does not evaluate to a function value")

    }





    case _ => throw new ParseOpException(s"Invalid type of SExpr: $sexpr")

  }
}