// A Transpiler for the Brainf*** language

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

import io.Source

import scala.util._

// loding a bf-file 

def load_bff(name: String) : String = 

  Try(Source.fromFile(name)("ISO-8859-1").mkString).getOrElse("")

// "splicing" a BF program counting occurrences

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

// generating "compound" c-instructions 

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

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

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

  case '+' => "(*ptr) += " + n.toString + ";"

  case '-' => "(*ptr) -= " + n.toString + ";"

  case '.' => "putchar(*ptr);" * n

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

  case '['  => "while(*ptr){" * n

  case ']'  => "}" * n

  case _ => ""

}

def instrs2(prog: String) : String =

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

def compile_str(prog: String) : String = {

  "#include <string.h>\n" ++

  "#include <stdio.h>\n" ++

  "char field[30000];\n" ++

  "char *ptr = &field[15000];" ++

  "int main()\n{\n" ++

  "memset(field, '\\0', 30000);\n" ++

  instrs2(prog) ++

  "\n return 0;\n}"

}

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

  val fw = new java.io.FileWriter(name + ".c") 

  val is = compile_str(prog)

  //println(is)

  fw.write(is) 

  fw.close()

}

import sys.process._

def compile_run(prog: String) = {

  compile("tmp", prog)

  "gcc -O0 -o tmp tmp.c".!

  "./tmp".!

  ()

}

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

  val start = System.nanoTime()

  for (i <- 0 until n) code

  val end = System.nanoTime()

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

}

// the mandelbrot program

val b0 = load_bff("mandelbrot.bf")

println(s"${time_needed(1, compile_run(b0))} secs")

// a benchmark program (counts down from 'Z' to 'A')

val b1 = """>++[<+++++++++++++>-]<[[>+>+<<-]>[<+>-]++++++++

            [>++++++++<-]>.[-]<<>++++++++++[>++++++++++[>++

            ++++++++[>++++++++++[>++++++++++[>++++++++++[>+

            +++++++++[-]<-]<-]<-]<-]<-]<-]<-]++++++++++."""

println(s"${time_needed(1, compile_run(b1))} secs")