// Core Part about an Interpreter for 
// the Brainf***++ language
//==============================================

object CW10a {  


// representation of Bf memory 

type Mem = Map[Int, Int]


// (1) Write a function that takes a file name as argument and
// and requests the corresponding file from disk. It Returns the
// content of the file as a String. If the file does not exists,
// the function should Return the empty string.

import io.Source
import scala.util._

def load_bff(name: String) : String = 
  Try(Source.fromFile(name)("ISO-8859-1").mkString).getOrElse("")


// (2) Complete the functions for safely reading  
// and writing brainf***++ memory. Safely read should
// Return the value stored in the Map for a given memory
// pointer, provided it exists; otherwise it Returns 0. The
// writing function generates a new Map with the
// same data, except at the given memory pointer the
// value v is stored.


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

def write(mem: Mem, mp: Int, v: Int) : Mem =
  mem.updated(mp, v)


// (3) Implement the two jumping instructions in the 
// brainf***++ language. In jumpRight, given a program and 
// a program counter move the program counter to the right 
// until after the *matching* ]-command. Similarly, 
// jumpLeft implements the move to the left to just after
// the *matching* [-command.

def jumpRight(prog: String, pc: Int, level: Int) : Int = {
  if (prog.length <= pc) pc 
  else (prog(pc), level) match {
    case (']', 0) => pc + 1
    case (']', l) => jumpRight(prog, pc + 1, l - 1)
    case ('[', l) => jumpRight(prog, pc + 1, l + 1)
    case (_, l) => jumpRight(prog, pc + 1, l)
  }
}

def jumpLeft(prog: String, pc: Int, level: Int) : Int = {
  if (pc < 0) pc 
  else (prog(pc), level) match {
    case ('[', 0) => pc + 1
    case ('[', l) => jumpLeft(prog, pc - 1, l - 1)
    case (']', l) => jumpLeft(prog, pc - 1, l + 1)
    case (_, l) => jumpLeft(prog, pc - 1, l)
  }
}

// test cases
//jumpRight("""--[..+>--].>.++""", 3, 0)         // => 10
//jumpLeft("""--[..+>--].>.++""", 8, 0)          // => 3
//jumpRight("""--[..[+>]--].>.++""", 3, 0)       // => 12
//jumpRight("""--[..[[-]+>[.]]--].>.++""", 3, 0) // => 18
//jumpRight("""--[..[[-]+>[.]]--.>.++""", 3, 0)  // => 22 (outside)
//jumpLeft("""[******]***""", 7, 0)              // => -1 (outside)

// (4) Complete the compute function that interprets (runs) a brainf***++
// program: the arguments are a program (represented as a string), a program 
// counter, a memory counter and a brainf***++ memory. It Returns the
// memory at the stage when the execution of the brainf***++ program
// finishes. The interpretation finishes once the program counter
// pc is pointing to something outside the program string.
// If the pc points to a character inside the program, the pc, 
// memory pointer and memory need to be updated according to 
// rules of the brainf***++ language. Then, recursively, the compute 
// function continues with the command at the new program
// counter. 
//
// Implement the run function that calls compute with the program
// counter and memory counter set to 0.

def compute(prog: String, pc: Int, mp: Int, mem: Mem) : Mem = {
  if (0 <= pc && pc < prog.length) { 
    val (new_pc, new_mp, new_mem) = prog(pc) match {
      case '>' => (pc + 1, mp + 1, mem)
      case '<' => (pc + 1, mp - 1, mem)
      case '+' => (pc + 1, mp, write(mem, mp, sread(mem, mp) + 1))
      case '-' => (pc + 1, mp, write(mem, mp, sread(mem, mp) - 1))
      case '.' => { print(sread(mem, mp).toChar); (pc + 1, mp, mem) }
      //case ',' => (pc + 1, mp, write(mem, mp, Console.in.read().toByte))
      //case ',' => (pc + 1, mp, write(mem, mp, scala.io.StdIn.readByte()))
      case '['  => 
	      if (sread(mem, mp) == 0) (jumpRight(prog, pc + 1, 0), mp, mem) else (pc + 1, mp, mem) 
      case ']'  => 
	      if (sread(mem, mp) != 0) (jumpLeft(prog, pc - 1, 0), mp, mem) else (pc + 1, mp, mem) 
 
      // new commands
      case '@' => (pc + 1, mp, write(mem, sread(mem, mp), sread(mem, mp - 1)))
      case '*' => (pc + 1, mp, write(mem, mp, sread(mem, mp) * sread(mem, mp -1)))
      case '#' => { println(s"${sread(mem, mp)}"); (pc + 1, mp, mem) }
      
      case _ => (pc + 1, mp, mem)
    }		     
    compute(prog, new_pc, new_mp, new_mem)	
  }
  else mem
}

def run(prog: String, m: Mem = Map()) = compute(prog, 0, 0, m)





// some sample bf/bf++-programs collected from the Internet
//==========================================================


// some contrived (small) programs
//---------------------------------

// clears the 0-cell
//run("[-]", Map(0 -> 100))    // Map will be 0 -> 0

// moves content of the 0-cell to 1-cell
//run("[->+<]", Map(0 -> 10))  // Map will be 0 -> 0, 1 -> 10


// copies content of the 0-cell to 2-cell and 4-cell
//run("[>>+>>+<<<<-]", Map(0 -> 42))    // Map(0 -> 0, 2 -> 42, 4 -> 42)


// prints out numbers 0 to 9
//run("""+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]""")

// bf++ program calculating the cube-function, 10 * 10 * 10 = 1000
//run("""++++++++++#>+***#""")           // Map(0 -> 10, 1 -> 1000)


// bf++ program copies 3 from 0-cell to to cells 1, 4, 5, 6 and 7
// (note that because of how the program wprks cell 1 will contain 7) 
//run("""+++>+@+@+@+@+@""")   // Map(0 -> 3, 1 -> 7, 4 -> 3, 5 -> 3, 6 -> 3, 7 -> 3)



// some more "useful" programs
//-----------------------------

// hello world program 1
//run("""++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++
//       ..+++.>>.<-.<.+++.------.--------.>>+.>++.""")

// hello world program 2
//run("""++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>+
//       +.<<+++++++++++++++.>.+++.------.--------.>+.>.""")

// hello world program 3
//run("""+++++++++[>++++++++>+++++++++++>+++++<<<-]>.>++.+++++++..
//       +++.>-.------------.<++++++++.--------.+++.------.--------.>+.""")

 
// draws the Sierpinski triangle
//run(load_bff("sierpinski.bf"))


//fibonacci numbers below 100
//run("""+++++++++++
//      >+>>>>++++++++++++++++++++++++++++++++++++++++++++
//      >++++++++++++++++++++++++++++++++<<<<<<[>[>>>>>>+>
//      +<<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-]<[>++++++++++[-
//      <-[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]>[<<[>>>+<<<
//      -]>>[-]]<<]>>>[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]
//      >[<<+>>[-]]<<<<<<<]>>>>>[+++++++++++++++++++++++++
//      +++++++++++++++++++++++.[-]]++++++++++<[->-<]>++++
//      ++++++++++++++++++++++++++++++++++++++++++++.[-]<<
//      <<<<<<<<<<[>>>+>+<<<<-]>>>>[<<<<+>>>>-]<-[>>.>.<<<
//      [-]]<<[>>+>+<<<-]>>>[<<<+>>>-]<<[<+>-]>[<+>-]<<<-]""")

//outputs the square numbers up to 10000
//run("""++++[>+++++<-]>[<+++++>-]+<+[>[>+>+<<-]++>>[<<+>>-]>>>[-]++>[-]+
//       >>>+[[-]++++++>>>]<<<[[<++++++++<++>>-]+<.<[>----<-]<]
//       <<[>>>>>[>>>[-]+++++++++<[>-<-]+++++++++>[-[<->-]+[<<<]]<[>+<-]>]<<-]<<-]""")


// calculates 2 to the power of 6 
//(example from a C-to-BF compiler at https://github.com/elikaski/BF-it)
//run(""">>[-]>[-]++>[-]++++++><<<>>>>[-]+><>[-]<<[-]>[>+<<+>-]>[<+>-]
//       <><[-]>[-]<<<[>>+>+<<<-]>>>[<<<+>>>-][-]><<>>[-]>[-]<<<[>>[-]
//       <[>+>+<<-]>[<+>-]+>[[-]<-<->>]<<<-]>>[<<+>>-]<<[[-]>[-]<<[>+>
//       +<<-]>>[<<+>>-][-]>[-]<<<<<[>>>>+>+<<<<<-]>>>>>[<<<<<+>>>>>-]
//       <<>>[-]>[-]<<<[>>>+<<<-]>>>[<<[<+>>+<-]>[<+>-]>-]<<<>[-]<<[-]
//       >[>+<<+>-]>[<+>-]<><[-]>[-]<<<[>>+>+<<<-]>>>-[<<<+>>>-]<[-]>[-]
//       <<<[>>+>+<<<-]>>>[<<<+>>>-][-]><<>>[-]>[-]<<<[>>[-]<[>+>+<<-]>
//       [<+>-]+>[[-]<-<->>]<<<-]>>[<<+>>-]<<][-]>[-]<<[>+>+<<-]>>[<<+>
//       >-]<<<<<[-]>>>>[<<<<+>>>>-]<<<<><>[-]<<[-]>[>+<<+>-]>[<+>-]<>
//       <[-]>[-]>[-]<<<[>>+>+<<<-]>>>[<<<+>>>-]<<>>[-]>[-]>[-]>[-]>[-]>
//       [-]>[-]>[-]>[-]>[-]<<<<<<<<<<>>++++++++++<<[->+>-[>+>>]>[+[-<+
//       >]>+>>]<<<<<<]>>[-]>>>++++++++++<[->-[>+>>]>[+[-<+>]>+>>]<<<<<
//       ]>[-]>>[>++++++[-<++++++++>]<.<<+>+>[-]]<[<[->-<]++++++[->++++
//       ++++<]>.[-]]<<++++++[-<++++++++>]<.[-]<<[-<+>]<<><<<""")



// a Mandelbrot set generator in brainf*** written by Erik Bosman
// (http://esoteric.sange.fi/brainfuck/utils/mandelbrot/)
//
//run(load_bff("mandelbrot.bf"))


// a benchmark program (counts down from 'Z' to 'A')
//
//run(load_bff("benchmark.bf"))

// calculates the Collatz series for numbers from 1 to 30
//
//run(load_bff("collatz.bf"))

}