// A Small Compiler for the WHILE Language

// the abstract syntax trees

abstract class Stmt

abstract class AExp

abstract class BExp 

type Block = List[Stmt]

// statements

case object Skip extends Stmt

case class If(a: BExp, bl1: Block, bl2: Block) extends Stmt

case class While(b: BExp, bl: Block) extends Stmt

case class Assign(s: String, a: AExp) extends Stmt

case class AssignA(s: String, a1: AExp, a2: AExp) extends Stmt

// arithmetic expressions

case class Var(s: String) extends AExp

case class Num(i: Int) extends AExp

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

// boolean expressions

case object True extends BExp

case object False extends BExp

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

// compiler headers needed for the JVM

// (contains an init method, as well as methods for read and write)

val beginning = """

.class public XXX.XXX

.super java/lang/Object

.method public <init>()V

   aload_0

   invokenonvirtual java/lang/Object/<init>()V

   return

.end method

.method public static write(I)V 

    .limit locals 1 

    .limit stack 2 

    getstatic java/lang/System/out Ljava/io/PrintStream; 

    iload 0

    return 

.end method

.method public static main([Ljava/lang/String;)V

   .limit locals 200

   .limit stack 200

"""

val ending = """

   return

.end method

"""

// for generating new labels

var counter = -1

def Fresh(x: String) = {

  counter += 1

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

}

// environments and instructions

// arithmetic expression compilation

}

// boolean expression compilation

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

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

}

// statement compilation

  case Assign(x, a) => {

  } 

  case If(b, bl1, bl2) => {

    val if_else = Fresh("If_else")

    val if_end = Fresh("If_end")

    val (instrs1, env1) = compile_block(bl1, env)

    val (instrs2, env2) = compile_block(bl2, env1)

    (compile_bexp(b, env, if_else) ++

     instrs1 ++

     instrs2 ++

  }

  case While(b, bl) => {

    val loop_begin = Fresh("Loop_begin")

    val loop_end = Fresh("Loop_end")

    val (instrs1, env1) = compile_block(bl, env)

     compile_bexp(b, env, loop_end) ++

     instrs1 ++

  }

  case Write(x) => 

  case AssignA(s, a1, a2) => {

    val index = if (env.isDefinedAt(s)) env(s) else 

     compile_aexp(a1, env) ++

     compile_aexp(a2, env) ++

  } 

}

// compilation of a block (i.e. list of instructions)

  case s::bl => {

    val (instrs1, env1) = compile_stmt(s, env)

    val (instrs2, env2) = compile_block(bl, env1)

    (instrs1 ++ instrs2, env2)

  }

}

// main compilation function for blocks

def compile(bl: Block, class_name: String) : String = {

  val instructions = compile_block(bl, Map.empty)._1

  (beginning ++ instructions.mkString ++ ending).replaceAllLiterally("XXX", class_name)

}

//

//    java -jar jvm/jasmin-2.4/jasmin.jar fib.j

//

// and started with

//

//    java fib/fib

import scala.util._

import scala.sys.process._

import scala.io

def compile_tofile(bl: Block, class_name: String) = {

  val output = compile(bl, class_name)

  val fw = new java.io.FileWriter(class_name + ".j") 

  fw.write(output) 

  fw.close()

}

def compile_all(bl: Block, class_name: String) : Unit = {

  compile_tofile(bl, class_name)

  println("compiled ")

  val test = ("java -jar jvm/jasmin-2.4/jasmin.jar " + class_name + ".j").!!

  println("assembled ")

}

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 compile_run(bl: Block, class_name: String) : Unit = {

  println("Start compilation")

  compile_all(bl, class_name)

  println("Time: " + time_needed(1, ("java " + class_name + "/" + class_name).!))

}

//====================

// Parser Combinators

//====================

import scala.language.implicitConversions

import scala.language.reflectiveCalls

  def parse(ts: I): Set[(T, I)]

  def parse_all(ts: I) : Set[T] =

    for ((head, tail) <- parse(ts); if (tail.isEmpty)) yield head

}

  def parse(sb: I) = 

    for ((head1, tail1) <- p.parse(sb); 

         (head2, tail2) <- q.parse(tail1)) yield ((head1, head2), tail2)

}

  def parse(sb: I) = p.parse(sb) ++ q.parse(sb)   

}

  def parse(sb: I) = 

    for ((head, tail) <- p.parse(sb)) yield (f(head), tail)

}

import scala.util.matching.Regex

case class RegexParser(reg: Regex) extends Parser[String, String] {

  def parse(sb: String) = reg.findPrefixMatchOf(sb) match {

    case None => Set()

    case Some(m) => Set((m.matched, m.after.toString))  

  }

}

def StringParser(s: String) = RegexParser(Regex.quote(s).r)

implicit def string2parser(s : String) = StringParser(s)

  def | (q : => Parser[I, T]) = new AltParser[I, T](p, q)

  def ==>[S] (f: => T => S) = new FunParser[I, T, S](p, f)

  def ~[S] (q : => Parser[I, S]) = new SeqParser[I, T, S](p, q)

}

implicit def StringOps(s: String) = new {

  def | (q : => Parser[String, String]) = new AltParser[String, String](s, q)

  def | (r: String) = new AltParser[String, String](s, r)

  def ==>[S] (f: => String => S) = new FunParser[String, String, S](s, f)

  def ~[S](q : => Parser[String, S]) = 

    new SeqParser[String, String, S](s, q)

  def ~ (r: String) = 

    new SeqParser[String, String, String](s, r)

}

val NumParser = RegexParser("[0-9]+".r) ==> (s => s.toInt : Int)

val IdParser = RegexParser("[a-z][a-z,0-9]*".r)

// Grammar Rules

lazy val AExp: Parser[String, AExp] = 

  (Te ~ "+" ~ AExp) ==> { case ((x, _), z) => Aop("+", x, z):AExp } |

  (Te ~ "-" ~ AExp) ==> { case ((x, _), z) => Aop("-", x, z):AExp } | Te

lazy val Te: Parser[String, AExp] = 

  (Fa ~ "*" ~ Te) ==> { case ((x, _), z) => Aop("*", x, z):AExp } | Fa

lazy val Fa: Parser[String, AExp] = 

   ("(" ~ AExp ~ ")") ==> { case ((_, y), _) => y } | 

   (IdParser ~ "[" ~ AExp ~ "]") ==> { case (((x, _), y), _) => Ref(x, y) } |

   IdParser ==> Var | 

   NumParser ==> Num

// boolean expressions

lazy val BExp: Parser[String, BExp] = 

   (AExp ~ "=" ~ AExp) ==> { case ((x, y), z) => Bop("=", x, z):BExp } | 

   (AExp ~ "!=" ~ AExp) ==> { case ((x, y), z) => Bop("!=", x, z):BExp } | 

   (AExp ~ "<" ~ AExp) ==> { case ((x, y), z) => Bop("<", x, z):BExp } | 

   (AExp ~ ">" ~ AExp) ==> { case ((x, y), z) => Bop("<", z, x):BExp } | 

   ("true" ==> ((_) => True:BExp )) | 

   ("false" ==> ((_) => False:BExp )) |

   ("(" ~ BExp ~ ")") ==> { case ((x, y), z) => y}

lazy val Stmt: Parser[String, Stmt] =

   ("skip" ==> (_ => Skip: Stmt)) |

   (IdParser ~ ":=" ~ AExp) ==> { case ((x, y), z) => Assign(x, z): Stmt } |

   (IdParser ~ "[" ~ AExp ~ "]" ~ ":=" ~ AExp) ==> { 

     case (((((x, y), z), v), w), u) => AssignA(x, z, u): Stmt } |

   ("if" ~ BExp ~ "then" ~ Block ~ "else" ~ Block) ==>

    { case (((((x,y),z),u),v),w) => If(y, u, w): Stmt } |

   ("while" ~ BExp ~ "do" ~ Block) ==> { case (((x, y), z), w) => While(y, w) } |

   ("new" ~ IdParser ~ "[" ~ NumParser ~ "]") ==> { case ((((x, y), z), u), v) => Array(y, u) } |

   ("write" ~ IdParser) ==> { case (_, y) => Write(y) } 

lazy val Stmts: Parser[String, Block] =

  (Stmt ~ ";" ~ Stmts) ==> { case ((x, y), z) => x :: z : Block } |

  (Stmt ==> ((s) => List(s) : Block)) 

lazy val Block: Parser[String, Block] =

   ("{" ~ Stmts ~ "}") ==> { case ((x, y), z) => y} | 

   (Stmt ==> (s => List(s)))

val fib = """

   n := 10;

   minus1 := 0;

   minus2 := 1;

   temp:=0;

   while (n > 0) do {

     temp := minus2; 

     minus2 := minus1 + minus2;

     minus1 := temp;

     n := n - 1};

   result := minus2;

   write result

   """.replaceAll("\\s+", "")

val fib_prog = Stmts.parse_all(fib).toList

//compile_run(fib_prog.head, "fib")

// BF 

// simple instructions

def instr(c: Char) : String = c match {

  case '>' => "ptr := ptr + 1;"

  case '<' => "ptr := ptr - 1;"

  case '+' => "field[ptr] := field[ptr] + 1;"

  case '-' => "field[ptr] := field[ptr] - 1;"

  case '.' => "x := field[ptr]; write x;"

  //case ',' => "XXX" // "ptr = getchar();\n"

  case '['  => "while (field[ptr] != 0) do {"

  case ']'  => "skip};"

  case _ => ""

}

def instrs(prog: String) : String =

  prog.toList.map(instr).mkString

def splice(cs: List[Char], acc: List[(Char, Int)]) : List[(Char, Int)] = (cs, acc) match {

  case (Nil, acc) => acc

  case (c :: cs, Nil) => splice(cs, List((c, 1)))

  case (c :: cs, (d, n) :: acc) => 

    if (c == d) splice(cs, (c, n + 1) :: acc)

    else splice(cs, (c, 1) :: (d, n) :: acc)

}

def spl(s: String) = splice(s.toList, Nil).reverse

def instr2(c: Char, n: Int) : String = c match {

  case '>' => "ptr := ptr + " + n.toString + ";"

  case '<' => "ptr := ptr - " + n.toString + ";"

  case '+' => "field[ptr] := field[ptr] + " + n.toString + ";"

  case '-' => "field[ptr] := field[ptr] - " + n.toString + ";"

  case '.' => "x := field[ptr]; write x;" //* n

  //case ',' => "*ptr = getchar();\n" * n

  case '['  => "while (field[ptr] != 0) do {" * n 

  case ']'  => "skip};" * n

  case _ => ""

}

def instrs2(prog: String) : String =

  spl(prog).map{ case (c, n) => instr2(c, n) }.mkString

def bf_str(prog: String) : String = {

  "\n" ++

  //"new field[30000];\n" ++

  "ptr := 15000;" ++

  "skip"

}

def bf_run(prog: String, name: String) = {

  println("BF processing start")

  val bf_string = bf_str(prog).replaceAll("\\s", "")

  println(s"BF parsing start (string length ${bf_string.length})")

  val bf_prog = Stmts.parse_all(bf_string).toList.head

  compile_run(Array("field", 30000) :: bf_prog, name)

}