// 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._

import java.io.FileNotFoundException

import scala.annotation.tailrec

def load_bff(name: String) : String = {

    try {

        val bff = io.Source.fromFile(name).getLines().mkString(" ")

        bff

    }

    catch {

        case ex: FileNotFoundException =>

        val bff = ""

        bff

    }

}

// (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 = {

    val newMem = mem + (mp -> v)

    newMem

}

// (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.

@tailrec

def jumpRight(prog: String, pc: Int, level: Int) : Int = {

    if (pc > prog.length-1) pc

    else {

        prog(pc) match{

            case '[' => jumpRight(prog, pc+1, level+1)

            case ']' => if (level == 0) pc+1

                        else jumpRight(prog, pc+1, level-1)

            case _ => jumpRight(prog, pc+1, level)

        }

    }

}

@tailrec

def jumpLeft(prog: String, pc: Int, level: Int) : Int = {

    if (pc < 0) pc 

    else {

        prog(pc) match{

            case ']' => jumpLeft(prog, pc-1, level+1)

            case '[' => if (level == 0) pc+1

                        else jumpLeft(prog, pc-1, level-1)

            case _ => jumpLeft(prog, pc-1, level)

        }

    }

}

// testcases

//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.

@tailrec

def compute(prog: String, pc: Int, mp: Int, mem: Mem) : Mem = {

    if (pc > prog.length-1) mem

    else {

        prog(pc) match{

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

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

            case '+' => compute(prog, pc+1, mp,write(mem,mp,sread(mem,mp)+1))

            case '-' => compute(prog, pc+1, mp,write(mem,mp,sread(mem,mp)-1))

            case '.' => print(sread(mem,mp).toChar)

                        compute(prog, pc+1, mp, mem)

            case '[' => if (sread(mem,mp) == 0) compute(prog,jumpRight(prog,pc+1,0),mp,mem)

                        else compute(prog,pc+1,mp,mem)

            case ']' => if (sread(mem,mp) != 0) compute(prog,jumpLeft(prog,pc-1,0),mp,mem)

                        else compute(prog,pc+1,mp,mem)

            case '*' => compute(prog, pc+1,mp, write(mem,mp,sread(mem,mp)*sread(mem,mp-1)))

            case '@' => compute(prog,pc+1,mp, write(mem,sread(mem,mp),sread(mem,mp-1)))

            case '#' => print(sread(mem,mp))

                        compute(prog,pc+1, mp, mem)

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

        }

    }

}

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

    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"))

}