import hashes, options
import fixedseq


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

  ColorStack* = FixedSeq[5, Color, int8]


proc `$`*(s: ColorStack): string =
  result.add("St@[")
  for i, color in s:
    result.add($color)
    if i < s.high:
      result.add(", ")
  result.add("]")


type
  Die* = tuple[color: Color, value: int]

  Tile* = enum
    tBackward = -1,
    tForward = 1

  Square* = object
    camels: ColorStack
    tile: Option[Tile]

  Board* = object
    squares*: array[1..16, Square]
    camels*: array[Color, range[1..16]]
    diceRolled*: array[Color, bool]
    leader*: Option[Color]
    gameOver*: bool
    initialized: bool


const allDice = @[cRed, cGreen, cBlue, cYellow, cPurple]


proc `[]`*[T](b: var Board, idx: T): var Square =
  b.squares[idx]


proc hash*(b: Board): Hash =
  var h: Hash = 0
  # there could be a tile anywhere so we have to check all squares
  for i, sq in b.squares:
    if sq.camels.len > 0 or sq.tile.isSome:
      h = h !& i
      if sq.tile.isSome:
        h = h !& int(sq.tile.get) * 10 # so it isn't confused with a camel
      else:
        for c in sq.camels.asInt:
          h = h !& c
  result = !$h


proc init*(b: var Board) =
  for sq in b.squares.mitems:
    sq.camels.initFixedSeq
  b.initialized = true


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 ""


proc setState*(b: var Board; 
              camels: openArray[tuple[c: Color, p: int]];
              tiles: openArray[tuple[t: Tile, p: int]]) =
  for (color, dest) in camels: # note that `camels` is ordered, as this determines stacking
    b[dest].camels.add(color)
    b.camels[color] = dest

  for (tile, dest) in tiles:
    b[dest].tile = some(tile)

  let leadCamel = b[max(b.camels)].camels[^1] # top camel in the last currently-occupied space
  b.leader = some(leadCamel)


proc resetDice*(b: var Board) =
  var d: array[Color, bool]
  b.diceRolled = d


proc advance*(b: var Board, die: Die) =
  let
    (color, roll) = die
    startPos = b.camels[color]
  var endPos = startPos + roll
  
  if endPos > 16: # camel has passed the finish line
    b.leader = some(b[startPos].camels[^1])
    b.gameOver = true
    return

  var prepend = false
  if b[endPos].tile.isSome: # adjust position (and possibly stacking) to account for tile
    let t = b[endPos].tile.get
    endPos += int(t)
    if t == tBackward: prepend = true

  let stackStart = b[startPos].camels.find(color)
  if prepend:
    b[startPos].camels.moveSubstackPre(b[endPos].camels, stackStart)
    let stackLen = b[startPos].camels.len - stackStart
    for i in 0 ..< stackLen:
      # we know how many camels we added to the bottom, so set the position for each of those
      b.camels[b[endPos].camels[i]] = endPos
  else:
    let dstPrevHigh = b[endPos].camels.high
    b[startPos].camels.moveSubstack(b[endPos].camels, stackStart)
    # the camels that have moved start immediately after the previous high camel
    for i in (dstPrevHigh + 1) .. b[endPos].camels.high:
      b.camels[b[endPos].camels[i]] = endPos
  
  # if we are stacking on or moving past the previous leader
  if endPos >= b.camels[b.leader.get]:
    b.leader = some(b[endPos].camels[^1])
  
  b.diceRolled[color] = true