// Main Part 5 about a "Compiler" for the Brainf*** language

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

// DEBUGGING INFORMATION FOR COMPILERS!!!

//

// Compiler, even real ones, are fiendishly difficult to get

// to produce correct code. One way to debug them is to run

// example programs ``unoptimised''; and then optimised. Does

// the optimised version still produce the same result?

// for timing purposes

import scala.io.Source

// ADD YOUR CODE BELOW

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

def sread(mem: Mem, mp: Int) : Int = mem.getOrElse(mp, 0)

def write(mem: Mem, mp: Int, v: Int) : Mem = mem + (mp -> v)

// (6)

def empty_stack(len : Int, st : List[Int]) : Map[Int, Int] = st match {

  case Nil => Map()

  case n :: tail => empty_stack(len, tail) + (n -> len)

}

def jtable_helper(pg : List[Char], st : List[Int] = List(), index : Int = 0) : Map[Int, Int] = pg match {

  case Nil => empty_stack(pg.length, st)

  case '[' :: tail => jtable_helper(tail, index :: st, index + 1)

  case ']' :: tail => st match {

    case Nil => jtable_helper(tail, st, index + 1) + (index -> -1)

    case n :: stail => jtable_helper(tail, stail, index + 1) + (n -> (index + 1)) + (index -> (n + 1))

  }

  case _ :: tail => jtable_helper(tail, st, index + 1)

}

def jtable(pg: String) : Map[Int, Int] = jtable_helper(pg.toList)

//

def compute2(prog: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = 

    if (pc < 0 || pc >= prog.length) mem else prog.charAt(pc) match {

        case '>' => compute2(prog, tb, pc+1, mp+1, mem)

        case '<' => compute2(prog, tb, pc+1, mp-1, mem)

        case '+' => compute2(prog, tb, pc+1, mp, mem + (mp -> (sread(mem, mp) + 1)))

        case '-' => compute2(prog, tb, pc+1, mp, mem + (mp -> (sread(mem, mp) - 1)))

        case '.' => print(sread(mem, mp).toChar); compute2(prog, tb, pc+1, mp, mem)

        case '[' => if (sread(mem, mp) == 0) compute2(prog, tb, tb.getOrElse(pc, -2), mp, mem)

                    else compute2(prog, tb, pc+1, mp, mem)

        case ']' => if (sread(mem, mp) == 0) compute2(prog, tb, pc+1, mp, mem)

                    else compute2(prog, tb, tb.getOrElse(pc, -2), mp, mem)

        case _ => compute2(prog, tb, pc+1, mp, mem)

def run2(prog: String, m: Mem = Map()) = compute2(prog, jtable(prog), 0, 0, m)

// time_needed(1, run2(load_bff("benchmark.bf")))

// time_needed(1, run2(load_bff("sierpinski.bf")))

// (7) 

def optimise(s: String) : String =

  s.filter(List('>', '<', '+', '-', '[', ']', '.').contains(_)).replaceAllLiterally("[-]", "0")

def compute3(prog: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = 

  if (pc < 0 || pc >= prog.length) mem else prog.charAt(pc) match {

        case '>' => compute3(prog, tb, pc+1, mp+1, mem)

        case '<' => compute3(prog, tb, pc+1, mp-1, mem)

        case '+' => compute3(prog, tb, pc+1, mp, mem + (mp -> (sread(mem, mp) + 1)))

        case '-' => compute3(prog, tb, pc+1, mp, mem + (mp -> (sread(mem, mp) - 1)))

        case '.' => print(sread(mem, mp).toChar); compute3(prog, tb, pc+1, mp, mem)

        case '[' => if (sread(mem, mp) == 0) compute3(prog, tb, tb.getOrElse(pc, -2), mp, mem)

                    else compute3(prog, tb, pc+1, mp, mem)

        case ']' => if (sread(mem, mp) == 0) compute3(prog, tb, pc+1, mp, mem)

                    else compute3(prog, tb, tb.getOrElse(pc, -2), mp, mem)

        case '0' => compute3(prog, tb, pc+1, mp, mem + (mp -> 0))

        case _ => compute3(prog, tb, pc+1, mp, mem)

def run3(prog: String, m: Mem = Map()) = 

  val optimized = optimise(prog)

  compute3(optimized, jtable(optimized), 0, 0, m)

// testcases

//

// optimise(load_bff("benchmark.bf"))          // should have inserted 0's

// optimise(load_bff("mandelbrot.bf")).length  // => 11205 // this is wrong, it's 11203!

// 

// time_needed(1, run3(load_bff("benchmark.bf")))

// (8)

def combine_helper(c : String, s : String) : String =

  val temp1 = s.replaceAllLiterally(c*26, c ++ "Z").replaceAllLiterally(c*25, c ++ "Y").replaceAllLiterally(c*24, c ++ "X").replaceAllLiterally(c*23, c ++ "W")

  val temp2 = temp1.replaceAllLiterally(c*22, c ++ "V").replaceAllLiterally(c*21, c ++ "U").replaceAllLiterally(c*20, c ++ "T").replaceAllLiterally(c*19, c ++ "S")

  val temp3 = temp2.replaceAllLiterally(c*18, c ++ "R").replaceAllLiterally(c*17, c ++ "Q").replaceAllLiterally(c*16, c ++ "P").replaceAllLiterally(c*15, c ++ "O")

  val temp4 = temp3.replaceAllLiterally(c*14, c ++ "N").replaceAllLiterally(c*13, c ++ "M").replaceAllLiterally(c*12, c ++ "L").replaceAllLiterally(c*11, c ++ "K")

  val temp5 = temp4.replaceAllLiterally(c*10, c ++ "J").replaceAllLiterally(c*9, c ++ "I").replaceAllLiterally(c*8, c ++ "H").replaceAllLiterally(c*7, c ++ "G")

  val temp6 = temp5.replaceAllLiterally(c*6, c ++ "F").replaceAllLiterally(c*5, c ++ "E").replaceAllLiterally(c*4, c ++ "D").replaceAllLiterally(c*3, c ++ "C")

  val temp7 = temp6.replaceAllLiterally(c*2, c ++ "B").replaceAllLiterally(c ++ ">", c ++ "A>").replaceAllLiterally(c ++ "<", c ++ "A<")

  val temp8 = temp7.replaceAllLiterally(c ++ "+", c ++ "A+").replaceAllLiterally(c ++ "-", c ++ "A-").replaceAllLiterally(c ++ "[", c ++ "A[")

  temp8.replaceAllLiterally(c ++ "]", c ++ "A]").replaceAllLiterally(c ++ ".", c ++ "A.").replaceAllLiterally(c ++ "0", c ++ "A0")

def combine(s: String) : String = 

  val temp1 = combine_helper(">", s)

  val temp2 = combine_helper("<", temp1)

  val temp3 = combine_helper("+", temp2)

  val temp4 = combine_helper("-", temp3)

  temp4

// testcase

// combine(load_bff("benchmark.bf"))

def compute4(prog: String, tb: Map[Int, Int], pc: Int, mp: Int, mem: Mem) : Mem = if (pc < 0 || pc >= prog.length) mem else prog.charAt(pc) match {

  case '>' => val n = (prog.charAt(pc+1).toInt - 64)

              compute4(prog, tb, pc+1, mp+n, mem)

  case '<' => val n = (prog.charAt(pc+1).toInt - 64)

              compute4(prog, tb, pc+1, mp-n, mem)

  case '+' => val n = (prog.charAt(pc+1).toInt - 64)

              compute4(prog, tb, pc+1, mp, mem + (mp -> (sread(mem, mp) + n)))

  case '-' => val n = (prog.charAt(pc+1).toInt - 64)

              compute4(prog, tb, pc+1, mp, mem + (mp -> (sread(mem, mp) - n)))

  case '.' => print(sread(mem, mp).toChar); compute4(prog, tb, pc+1, mp, mem)

  case '[' => if (sread(mem, mp) == 0) compute4(prog, tb, tb.getOrElse(pc, -2), mp, mem)

              else compute4(prog, tb, pc+1, mp, mem)

  case ']' => if (sread(mem, mp) == 0) compute4(prog, tb, pc+1, mp, mem)

              else compute4(prog, tb, tb.getOrElse(pc, -2), mp, mem)

  case '0' => compute4(prog, tb, pc+1, mp, mem + (mp -> 0))

  case _ => compute4(prog, tb, pc+1, mp, mem)

// should call first optimise and then combine on the input string

//

def run4(prog: String, m: Mem = Map()) = 

  val optimized = combine(optimise(prog))

  compute4(optimized, jtable(optimized), 0, 0, m)

// testcases

// combine(optimise(load_bff("benchmark.bf"))) // => """>A+B[<A+M>A-A]<A[[....."""

// testcases (they should now run much faster)

// time_needed(1, run4(load_bff("benchmark.bf")))

// time_needed(1, run4(load_bff("sierpinski.bf"))) 

// time_needed(1, run4(load_bff("mandelbrot.bf")))