cup/main.nim

import algorithm, options, sequtils, sugar


type
  Color = enum
    cRed, cGreen, cBlue, cYellow, cPurple

  Tile = enum
    tForward = -1,
    tBackward = 1

  Square = object
    camels: seq[Color]
    tile: Option[Tile]

  Die = tuple[color: Color, value: range[1..3]]

  Board = object
    squares: array[1..16, Square]
    camels: array[Color, range[1..16]]
    leader: Color


proc `[]`(b: var Board, idx: range[1..16]): var Square =
  b.squares[idx]


proc display(b: Board, start, stop: int) =
  for i in start..stop:
    let sq = b.squares[i]
    let lead = $i & ": "
    if sq.tile.isSome:
      echo lead, sq.tile.get
    else:
      echo lead, sq.camels
  echo "\n"


proc preRoll(b: var Board) =
  let colors = [cGreen, cYellow, cPurple, cBlue, cRed]
  var rolls = [range[1..16]3, 2, 3, 2, 1]

  for (color, roll) in zip(colors, rolls):
    let dest = roll + 1
    b[dest].camels.add(color)
    b.camels[color] = dest


proc advance(b: var Board, die: Die) =
  let
    (color, roll) = die
    startPos = b.camels[color]
  var prepend = false
  var endPos = startPos + roll
  if b[endPos].tile.isSome:
    endPos += int(b[endPos].tile.get)
    if b[endPos].tile.get == tBackward: prepend = true # if moving backward, we will prepend camel to the seq

  for i, c in b[startPos].camels:
    if c == color:
      let subStack = b[startPos].camels[i .. ^1]
      if prepend:
        b[endPos].camels.insert(subStack)
      else:
        b[endPos].camels.add(subStack)

      b[startPos].camels[i .. ^1] = @[]
      for moved in subStack:
        b.camels[moved] = endPos
      b.leader = b[b.camels.max][^1] # top camel in the last currently-occupied space

    break # breaking the outer loop here, not the inner


iterator allPermutations[T](x: seq[T]): seq[T] =
  # returns all permutations of a given array. Order is wonky but we don't care.
  var workingCopy = x
  yield workingCopy
  while workingCopy.nextPermutation: # this mutates workingCopy
    yield workingCopy
  workingCopy = x
  while workingCopy.prevPermutation:
    yield workingCopy


var b: Board
b.display(1, 5)
b.preRoll
let c = b.dup(advance((cRed, range[1..3]3)))
b.display(1, 5)
c.display(1, 5)