// Some more interesting testcases for the 

// WHILE compiler with arrays, it includes: 

//

//  - a small parser for WHILE programs

//

//  - transpiles BF programs into WHILE programs

//    and then compiles and runs them

//

//  - the power-example is the Mandelbrot set:

//       

//       * 65k for the transpiled WHILE program 

//       * parsing uses around 30 secs using fastparse

//       * the jasmin assembly file is 236k

//       * the resulting Java program takes about 20 secs 

//

//

// Call with scala-cli:

//

//

// Scala-cli is another REPL for scala. Unfortunately

// fastparse used in this file is not yet supported

// under ammonite.

// compile_arrays.sc (no peephole optimisations)

// compile_arrays2.sc (peephole optimisations applied)

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

  val start = System.nanoTime()

  for (j <- 2 to i) code

  val result = code

  val end = System.nanoTime()

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

}

// for BF we have to change the write library-function,

// because in BF integers are written out as characters

val beginning = """

.class public XXX.XXX

.super java/lang/Object

.method public static write(I)V 

    .limit locals 1 

    .limit stack 2 

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

    iload 0

    i2c                                           ; Int => Char

    invokevirtual java/io/PrintStream/print(C)V   ; println(I)V => print(C)V    

    return 

.end method

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

   .limit locals 200

   .limit stack 200

; COMPILED CODE STARTS   

"""

// modified main compilation function for blocks

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

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

  (beginning ++ instructions ++ ending).replace("XXX", class_name)

}

// post 2.5.0 ammonite

def compile_to_file(bl: Block, class_name: String) : Unit = 

  os.write.over(os.pwd / s"$class_name.j", compile(bl, class_name))  

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

  println(s"Start of compilation")

  compile_to_file(bl, class_name)

  println(s"generated $class_name.j file")

  val (jasmin_time, _) = 

    time_needed(1, os.proc("java", "-jar", "jasmin.jar", s"$class_name.j").call())

  println(s"generated $class_name.class file (in $jasmin_time secs).")

  val (running_time, output) = 

    time_needed(1, os.proc("java", s"${class_name}/${class_name}").call(stdout = os.Inherit, stdin = os.Inherit).out.text())

  println(output)

  println(s"done (in $running_time secs).")

}

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

// Grammar Rules for WHILE with arrays

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

def lowercase [$ : P] = P( CharIn("a-z") )

def uppercase[$ : P]  = P( CharIn("A-Z") )

def letter[$ : P]     = P( lowercase | uppercase )

def digit [$ : P]     = P( CharIn("0-9") )

def Number[$ : P]: P[Int] =  P( digit.rep(1) ).!.map(_.toInt)

def Ident[$ : P]: P[String] = P( letter ~ (letter | digit | "_").rep ).!

// arithmetic expressions

def AExp[$ : P]: P[AExp] = 

  P(  P(Te ~ "+" ~ AExp).map{ case (l, r) => Aop("+", l, r)} 

    | P(Te ~ "-" ~ AExp).map{ case (l, r) => Aop("-", l, r)}

    | Te )

def Te[$ : P]: P[AExp] = 

  P(  P(Fa ~ "*" ~ Te).map{ case (l, r) => Aop("*", l, r)} 

    | Fa )   

def Fa[$ : P]: P[AExp] = 

  P( "(" ~ AExp ~ ")" 

     | P (Ident ~ "[" ~ AExp ~ "]").map{Ref(_, _)}

     | P(Number).map{Num(_)} 

     | P(Ident).map{Var(_)} )

// boolean expressions

def BExp[$ : P]: P[BExp] = 

  P(  P(AExp ~ "=" ~ AExp).map{ case (x, z) => Bop("=", x, z)} 

    | P(AExp ~ "!=" ~ AExp).map{ case (x, z) => Bop("!=", x, z)}  

    | P(AExp ~ "<" ~ AExp).map{ case (x, z) => Bop("<", x, z)}  

    | P(AExp ~ ">" ~ AExp).map{ case (x, z) => Bop("<", z, x)}  

    | P("true").map{ _ => True} 

    | P("false").map{ _ => False} 

    | "(" ~ BExp ~ ")" )

// statements and blocks

def Stmt[$ : P]: P[Stmt] =

  P(  P("skip").map( _ => Skip) 

    | P(Ident ~ ":=" ~ AExp).map{Assign(_, _)} 

    | P(Ident ~ "[" ~ AExp ~ "]" ~ ":=" ~ AExp).map{AssignA(_, _, _)} 

    | P("if" ~ BExp ~ "then" ~ Block ~ "else" ~ Block).map{If(_, _, _)} 

    | P("while" ~ BExp ~ "do" ~ Block).map{While(_, _)} 

    | P("new(" ~ Ident ~ "[" ~ Number ~ "])").map{ArrayDef(_, _)} 

    | P("write(" ~ Ident ~ ")").map{Write(_)} ) 

def Stmts[$ : P]: P[Block] =

  P(  P(Stmt ~ ";" ~ Stmts).map{ case (x, z) => x :: z } 

    | P(Stmt).map{s => List(s)} ) 

def Block[$ : P]: P[Block] =

  P(  "{" ~ Stmts ~ "}" 

    | P(Stmt).map(s => List(s)) )

// some test cases for the parser

//println(fastparse.parse("(1 + (2 + 5)) + 4", AExp(_)).get)

//println(fastparse.parse("1 + 2 + 3 + 45", AExp(_)))

//println(fastparse.parse("1 + 2 * 3", AExp(_)))

//println(fastparse.parse("x + 2 * 3", AExp(_)))

//println(fastparse.parse("x2 := 5 + a", Stmts(_)))

//println(fastparse.parse("x2 := 5 + a[3+a]", Stmts(_)))

//println(fastparse.parse("a[x2+3] := 5 + a[3+a]", Stmts(_)))

//println(fastparse.parse("{x := 5; y := 8}", Block(_)))

//println(fastparse.parse("if (false) then {x := 5} else {x := 10}", Block(_)))

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)

   """

//println(fastparse.parse(fib, Stmts(_)).get.value)

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

// BF transpiler into WHILE with arrays

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

// simple BF instructions translation

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

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

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

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

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

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

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

  case ']'  => "skip};"

  case _ => ""

}

def instrs(prog: String) : String =

  prog.toList.map(instr).mkString

// Note: Unfortunately, the transpiled mandelbrot.bf program 

// is so large that it does not fit inside the limitations of 

// what the JVM imposes on methods (only 64K of instructions).

// Therefore some optimisations are first applied to 

// BF programs before WHILE programs are created. The

// optimisations are 

//  

//  - replacing BF-loops of the form [-] with a new 0-instruction 

//  - combining single increment/decrement instructions

//

// The size of the resulting .j-file is 270K.

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 '>' => s"ptr := ptr + $n;"

  case '<' => s"ptr := ptr - $n;"

  case '0' => s"mem[ptr] := 0;"

  case '+' => s"mem[ptr] := mem[ptr] + $n;"

  case '-' => s"mem[ptr] := mem[ptr] - $n;"

  case '.' => s"x := mem[ptr]; write(x);" 

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

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

  case _ => ""

}

def instrs2(prog: String) : String =

  spl(prog.replaceAll("""\[-\]""", "0")).map{ case (c, n) => instr2(c, n) }.mkString

// adding the "header" to the BF program

def bf_str(prog: String) : String = {

  "new(mem[30000]);" ++

  "ptr := 15000;" ++

  instrs2(prog) ++

  "skip"

}

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

  println(s"BF pre-processing of $name")

  val bf_string = bf_str(prog)

  println(s"BF parsing (program length ${bf_string.length} characters)")

  val (time, bf_prog) = 

  println(s"BF generated WHILE program (needed $time secs for parsing)")

  compile_and_run(bf_prog, name)

}

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

//@doc(" Benchmark 'Z' to 'A'.")

//@main

def bfc0() = bf_run(read(pwd / "benchmark.bf"), "bench")

//@doc(" Sierpinski triangle.")

//@main

def bfc1() = bf_run(read(pwd / "sierpinski.bf"), "sier")

// Hello World

val bf2 = """++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]

      >>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++."""

//@doc(" Hello world.")

//@main

def bfc2() = bf_run(bf2, "hello")

// Fibonacci 

val bf3 = """+++++++++++

      >+>>>>++++++++++++++++++++++++++++++++++++++++++++

      >++++++++++++++++++++++++++++++++<<<<<<[>[>>>>>>+>

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

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

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

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

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

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

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

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

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

//@doc(" Fibonacci numbers.")

//@main

def bfc3() = bf_run(bf3, "fibs")

// Mandelbrot Set

//----------------

//

// Note: Parsing of the generated WHILE program (around 60K in size)

// takes approximately 10 minutes to parse with our parser combinators,

// and approximately 30 seconds with Ammonite's fastparse.

//@doc(" Mandelbrot set.")

//@main

def bfc4() = bf_run(read(pwd / "mandelbrot.bf"), "mandelbrot")

// this unfortunately hits the capacity of the JVM, even with optimisations

//@doc(" Collatz series up to 30.")

//@main

//def bfc5() = bf_run(read(pwd / "collatz.bf"), "coll")

// this unfortunately hits the capacity of the JVM, even with optimisations

//@doc(" Towers of Hanoi.")

//@main

//def bfc6() = bf_run(read(pwd / "hanoi.bf"), "hanoi")

//

//@doc(" All benchmarks.")

//@main

def all() = { bfc0(); bfc1(); bfc2(); bfc3(); bfc4() } 

//all()

bfc4()

// old way to run it with Ammonite

//

// Call with (X being 0,1,..,4)

//

//  amm compile_bfc.sc all

//  amm compile_bfc.sc bfcX

//

//

// load the compiler

//import $file.compile_arrays2

//import compile_arrays2._ 

//

// load fastparse

//import $ivy.`com.lihaoyi::fastparse:3.0.2`