// A Small Compiler for a Simple Functional Language

// (includes an external lexer and parser)

//

// call with 

//

//     scala fun.scala fact

//

//     scala fun.scala defs

//

// this will generate a .j file and run the jasmin

// assembler (installed at jvm/jasmin-2.4/jasmin.jar)

// it runs the resulting JVM file twice for timing 

// purposes.

import java.io._  

import scala.util._

import scala.sys.process._

// Abstract syntax trees for the Fun language

abstract class Exp extends Serializable 

abstract class BExp extends Serializable 

abstract class Decl extends Serializable 

case class Def(name: String, args: List[String], body: Exp) extends Decl

case class Main(e: Exp) extends Decl

case class Call(name: String, args: List[Exp]) extends Exp

case class If(a: BExp, e1: Exp, e2: Exp) extends Exp

case class Write(e: Exp) extends Exp

case class Var(s: String) extends Exp

case class Num(i: Int) extends Exp

case class Aop(o: String, a1: Exp, a2: Exp) extends Exp

case class Sequence(e1: Exp, e2: Exp) extends Exp

case class Bop(o: String, a1: Exp, a2: Exp) extends BExp

// compiler - built-in functions 

// copied from http://www.ceng.metu.edu.tr/courses/ceng444/link/jvm-cpm.html

//

// for generating new labels

var counter = -1

def Fresh(x: String) = {

  counter += 1

  x ++ "_" ++ counter.toString()

}

// Abstract syntax trees for the Fun language

abstract class KExp

case class KVar(s: String) extends KExp

case class KNum(i: Int) extends KExp

case class KAop(o: String, x1: String, x2: String) extends KExp

case class KCall(o: String, vrs: List[String]) extends KExp

case class KLet(x: String, e1: KExp, e2: KExp) extends KExp {

  override def toString = s"let $x = $e1 in \n$e2" 

}

def K(e: Exp) : KExp = e match {

  case Var(s) => KVar(s) 

  case Num(i) => KNum(i)

  case Aop(o, a1, a2) => {

    val x1 = Fresh("tmp")

    val x2 = Fresh("tmp") 

    KLet(x1, K(a1), KLet(x2, K(a2), KAop(o, x1, x2)))

  } 

  case Call(name: String, args: List[Exp]) => {

    def aux(as: List[(String, KExp)]) : KExp = as match {

      case Nil => KCall(name, args_new.map(_._1))

      case (x, a)::rest => KLet(x, a, aux(rest))

    }

    aux(args_new)

  }

}

def Denest(e: KExp) : KExp = e match {

  case KLet(xt, e1, e2) => {

    def insert(e: KExp) : KExp = e match {

      case KLet(yt, e3, e4) => KLet(yt, e3, insert(e4))

      case e => KLet(xt, e, Denest(e2))

    }

    insert(Denest(e1))  

  }

  case _ => e

}

println(K(e))

println(Denest(K(e)))

// convenient string interpolations 

// for instructions, labels and methods

import scala.language.implicitConversions

import scala.language.reflectiveCalls

implicit def sring_inters(sc: StringContext) = new {

    def i(args: Any*): String = "   " ++ sc.s(args:_*) ++ "\n"

    def l(args: Any*): String = sc.s(args:_*) ++ ":\n"

    def m(args: Any*): String = sc.s(args:_*) ++ "\n"

}

type Env = Map[String, Int]

  }

  }

  }

  case Call(name, args) => {

    val is = "I" * args.length

    args.map(a => compile_exp(a, env)).mkString ++

    i"invokestatic XXX/XXX/$name($is)I"

  }

  case Sequence(a1, a2) => {

    compile_exp(a1, env) ++ i"pop" ++ compile_exp(a2, env)

  }

  case Write(a1) => {

    compile_exp(a1, env) ++

    i"dup" ++

    i"invokestatic XXX/XXX/write(I)V"

  }

  */

}

// compile boolean expressions

def compile_bexp(b: BExp, env : Env, jmp: String) : String = b match {

  case Bop("==", a1, a2) => 

    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpne $jmp"

  case Bop("!=", a1, a2) => 

    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpeq $jmp"

  case Bop("<", a1, a2) => 

    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpge $jmp"

  case Bop("<=", a1, a2) => 

    compile_exp(a1, env) ++ compile_exp(a2, env) ++ i"if_icmpgt $jmp"

}

// compile function for declarations and main

def compile_decl(d: Decl) : String = d match {

  }

  }

}

// main compiler functions

def time_needed[T](i: Int, code: => T) = {

  val start = System.nanoTime()

  for (j <- 1 to i) code

  val end = System.nanoTime()

  (end - start)/(i * 1.0e9)

}

def deserialise[T](fname: String) : Try[T] = {

  import scala.util.Using

  Using(new ObjectInputStream(new FileInputStream(fname))) {

    in => in.readObject.asInstanceOf[T]

  }

}

def compile(class_name: String) : String = {

  val ast = deserialise[List[Decl]](class_name ++ ".prs").getOrElse(Nil) 

}

def compile_to_file(class_name: String) = {

  val output = compile(class_name)

  scala.tools.nsc.io.File(s"${class_name}.j").writeAll(output)

}

def compile_and_run(class_name: String) : Unit = {

  compile_to_file(class_name)

  (s"java -jar jvm/jasmin-2.4/jasmin.jar ${class_name}.j").!!

  println("Time: " + time_needed(2, (s"java ${class_name}/${class_name}").!))

}

// some examples of .fun files

//compile_to_file("fact")

//compile_and_run("fact")

//compile_and_run("defs")

}