// Main Part 5 about an Interpreter for 

// the Brainf*** language

object M5a {

// representation of BF memory 

// ADD YOUR CODE BELOW

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

// (1)

def load_bff(name: String) : String = {

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

}

// (2) 

def sread(mem: Mem, mp: Int) : Int = {

    Try(mem.apply(mp)).getOrElse(0)

}

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

    mem + (mp -> v)

// sread(Map(), 2) == 0

// sread(Map(2 -> 1), 2) == 1

// write(Map(), 1, 2) == Map(1 -> 2)

// write(Map(1 -> 0), 1, 2) == Map(1 -> 2)

// val current = sread(Map(2 -> 1), 2)

// write(Map(2 -> 1), 2, current+1)

// (3) 

def jumpRight(prog: String, pc: Int, level: Int) : Int = prog.toList.apply(pc) match{

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

    case ']' => level match {

        case 0 => pc+1

        case _ => if (pc+1 >= prog.length) prog.length else jumpRight(prog, pc+1, level-1)

    }

    case _ => if (pc+1 >= prog.length) prog.length else jumpRight(prog, pc+1, level)

def jumpLeft(prog: String, pc: Int, level: Int) : Int = prog.toList.apply(pc) match{

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

    case '[' => level match {

        case 0 => pc+1

        case _ => if (pc-1 < 0) -1 else jumpLeft(prog, pc-1, level-1)

    }

    case _ => if (pc-1 < 0) -1 else 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)

def compute(prog: String, pc: Int, mp: Int, mem: Mem) : Mem = (pc >= 0 && pc < prog.length) match {

    case false => mem

    case true => prog.toList.apply(pc) match{

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

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

        case '+' => {

            val current = sread(mem, mp)

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

        }

        case '-' => {

            val current = sread(mem, mp)

            compute(prog, pc+1, mp, write(mem, mp, current-1))

        }

        case '.' => {

            print(mem.apply(mp).toChar)

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

        }

        case '[' => {

            if (mem.apply(mp) == 0) compute(prog, jumpRight(prog, pc+1, 0), mp, mem)

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

        }

        case ']' => {

           if (mem.apply(mp) != 0) compute(prog, jumpLeft(prog, pc-1, 0), mp, mem)

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

        }

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

    }

}

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

    compute(prog, 0, 0, m)

}

// run("[-]", Map(0 -> 100)) == Map(0 -> 0)

// run("[->+<]", Map(0 -> 10)) == Map(0 -> 0, 1 -> 10)

// run("[>>+>>+<<<<-]", Map(0 -> 42)) == Map(0 -> 0, 2 -> 42, 4 -> 42)

// run("""+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]""") == Map(0 -> 0, 1 -> 58, 2 -> 32)

// (5)

def generate(msg: List[Char]) : String = msg match {

    case Nil => ""

    case c => "+"*c.head.toInt + ".[-]" + generate(msg.tail)

}

// generate("ABC".toList)

// run("+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.[-]", Map())

// some sample bf-programs collected from the Internet

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

// // 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("""+++++[->++++++++++<]>--<+++[->>++++++++++<<]>>++<<----------[+>.>.<+<]""")

// // 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

// 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"))

// This template code is subject to copyright 

// by King's College London, 2022. Do not 

// make the template code public in any shape 

// or form, and do not exchange it with other 

// students under any circumstance.