module Exercise08 where

import Data.Bits
import Data.List
import System.Random (mkStdGen, randoms, randomIO, Random)
import Data.Maybe


{- 
Rules
The game is played by two players: Player +1 (Virus) and Player -1 (Antibodies).
• The game takes place on an n*m cell grid, where n, m >= 2
• Initially, each cell is empty
• In each turn, a player can either claim an empty cell by placing an orb in it or place
another orb in a cell that player already owns
• A player cannot place orbs in cells claimed by the opponent
• A cell is filled when it contains at least the same number of orbs as orthogonally adjacent
cells
• When a cell is filled, the virus/antibodies overflow and attack the orthogonally adjacent
cells, moving one orb into each neighbour and converting existing orbs into their own kind.
• The game ends when either viruses or antibodies reach their goal of eliminating all orbs
of the enemy.


[[1,2,-1],[2,0,0],[0,-1,1]]

[ 1, 2,-1]
[ 2, 0, 0]
[ 0,-1, 1]

--> player +1 puts orb at (0, 1)

[ 1, 3,-1]
[ 2, 0, 0]
[ 0,-1, 1]

[ 2, 0, 2]
[ 2, 1, 0]
[ 0,-1, 1]

[ 0, 2, 0]
[ 3, 1, 1]
[ 0,-1, 1]

[ 1, 2, 0]
[ 0, 2, 1]
[ 1,-1, 1]

[ 1, 2, 0]
[ 0, 2, 1]
[ 1,-1, 1]
-}


-- Player is either 1 or -1
type Player = Int

-- A field is just an Int value where the absolute gives the number of pieces on the field
-- and the sign corresponds to the player
-- e.g. -3 would mean there are three blobs in this field of player -1
type Field = Int

type Row = [Field]
type Column = [Field]
-- boards are rectangles represented as a list of rows
type Board = [Row]

-- A position on the board is represented as (row, column)
-- (0,0) is the top left corner, coordinate values increase towards the bottom right
type Pos = (Int, Int)

-- A size represented as (height,width)
type Size = (Int, Int)

-- A strategy takes the player who's move it is, optionally takes a list of double values
-- to allow for probabilistic strategies, takes the current board and gives back the position
-- of the move the player should do
type Strategy = [Double] -> Player -> Board -> Pos
-- A stateful strategy can additionally pass some object between invocations
type StatefulStrategyFunc a = a -> [Double] -> Player -> Board -> (Pos, a)
-- first value is the state object to pass to the first invocation of each game
type StatefulStrategy a = (a, StatefulStrategyFunc a)

defaultSize :: (Int, Int)
defaultSize = (9,6)

-- Some useful helper functions
row :: Board -> Int -> Row
row = (!!)

column :: Board -> Int -> Column
column = row . transpose

width :: Board -> Int
width (x : _) = length x
width _       = 0

height :: Board -> Int
height = length

size :: Board -> Size
size b = (height b, width b)

getCell :: Pos -> Board -> Field
getCell (y, x) b = b !! y !! x

setCell :: Board -> Pos -> Int -> Board
setCell b (y, x) i = [[if r==y && c==x then i else getCell (r, c) b | c <- xs] | r <- ys] 
  where
    ys = [0 .. height b - 1]
    xs = [0 .. width b - 1]

-- pretty print a single cell
showCell :: Field -> String
showCell c = "- +" !! succ (signum c) : show (abs c)

-- pretty print the given board
showBoard :: Board -> String
showBoard = unlines . map (unwords . map showCell)

-- print a board to the console
printBoard :: Board -> IO ()
printBoard = putStr . showBoard

-- check if a position is on a board of the given size
isValidPos :: Size -> Pos -> Bool
isValidPos (r, c) (y, x) = y >= 0 && y < r && x >= 0 && x < c

{- x.1 -}

-- Check if the given player can put an orb on the given position
canPlaceOrb :: Player -> Pos -> Board -> Bool
canPlaceOrb p pos b
  | not $ isValidPos (size b) pos = False
  | otherwise = cell == 0 || ((p > 0 && cell > 0) || (p < 0 && cell < 0))
    where
      cell = getCell pos b

-- Check if the given player has won the game,
-- you can assume that the opponent has made at least one move before
hasWon :: Player -> Board -> Bool
hasWon p b
  | p == -1 = all ((==True) . all (<=0)) b
  | otherwise = all ((==True) . all (>=0)) b

-- the list of neighbors of a cell
neighbors :: Size -> Pos -> [Pos]
neighbors size (y, x) = [p | p <- [(y+1, x), (y-1, x), (y, x+1), (y, x-1)], isValidPos size p]

-- update a single position on the board
-- f: function that modifies the number of orbs in the cell
-- p: player to whom the updated cell should belong
updatePos :: (Int -> Int) -> Player -> Pos -> Board -> Board
updatePos f p pos b = setCell b pos newVal
  where
    newVal = p * f (abs (getCell pos b))

{- x.2 -}

-- place an orb for the given player in the given cell
putOrb :: Player -> Pos -> Board -> Board
putOrb p pos b
  | abs (getCell pos b) == length ns - 1 && not (hasWon p b) = overflow p pos newB ns
  | otherwise = newB
    where
      newB = updatePos (+1) p pos b
      ns = neighbors (size b) pos


overflow :: Player -> Pos -> Board -> [Pos] -> Board
overflow p pos b [y, z] = putOrb p y (putOrb p z (updatePos (+ (-1 * 2)) p pos b))
overflow p pos b [x, y, z] = putOrb p x (putOrb p y (putOrb p z (updatePos (+ (-1 * 3)) p pos b)))
overflow p pos b [w, x, y, z] = putOrb p w (putOrb p x (putOrb p y (putOrb p z (updatePos (+ (-1 * 4)) p pos b))))


{- x.3 -}

{-
type Strategy = [Double] -> Player -> Board -> Pos

type StatefulStrategyFunc a = a -> [Double] -> Player -> Board -> (Pos, a)

type StatefulStrategy a = (a, StatefulStrategyFunc a)
-}

{-WETT-}
-- Your strategy
strategy :: Strategy
strategy xs p b = candidates !! fromJust (elemIndex (maximum evals) evals)
  where
    candidates = candidateMoves p b
    evals = map (eval1 p b) candidates

candidateMoves :: Player -> Board -> [Pos]
candidateMoves p b = concat [[(y, x) | y <- [0 .. height b - 1], canPlaceOrb p (y, x) b] | x <- [0 .. width b - 1]]

eval :: Player -> Board -> Pos -> Int
eval p b pos = p * sum (map sum (putOrb p pos b))

eval1 :: Player -> Board -> Pos -> Int
eval1 p b pos = p * sum (map sum enemyMove)
  where
    p' = negate p
    firstMove = putOrb p pos b
    enemyMove = putOrb p' (enemyStrategy [] p' firstMove) firstMove

evalN :: Player -> Board -> Pos -> Int -> Int
evalN p b pos 0 = p * sum (map sum b)
evalN p b pos n = evalN p enemyMove (strategy [] p enemyMove) (n-1)
  where
    p' = negate p
    myMove = putOrb p pos b
    enemyMove = putOrb p' (enemyStrategy [] p' myMove) myMove

enemyStrategy :: Strategy
enemyStrategy xs p b = candidates !! fromJust (elemIndex (maximum evals) evals)
  where
    candidates = candidateMoves p b
    evals = map (eval p b) candidates

-- adds state to a strategy that doesn't use it
wrapStrategy :: Strategy -> StatefulStrategy Int
wrapStrategy strat = (0, \s r p b -> (strat r p b, succ s))

-- the actual strategy submissions
-- if you want to use state modify this instead of strategy
-- additionally you may change the Int in this type declaration to any type that is usefully for your strategy
strategyState :: StatefulStrategy Int
strategyState = wrapStrategy strategy
{-TTEW-}

-- Simulate a game between two strategies on a board of the given size and
-- returns the state of the board before each move together with the player that won the game
play :: [Int] -> Size -> StatefulStrategy a -> StatefulStrategy b -> [(Board, Pos)]
play rss (r, c) (isa, sa) (isb, sb) = go rss isa sa isb sb 1 0 (replicate r (replicate c 0))
  where
    -- type signature is necessary, inferred type is wrong!
    go :: [Int] -> a -> StatefulStrategyFunc a -> b -> StatefulStrategyFunc b -> Player -> Int -> Board -> [(Board, Pos)]
    go (rs:rss) stc sc stn sn p n b
      | won       = []
      | valid     = (b, m) : go rss stn sn st' sc (-p) (succ n) (putOrb p m b)
      | otherwise = []
      where
        won      = n > 1 && hasWon (-p) b
        (m, st') = sc stc (mkRandoms rs) p b
        valid    = isValidPos (size b) m && canPlaceOrb p m b

-- Play a game and print it to the console
playAndPrint :: Size -> StatefulStrategy a -> StatefulStrategy b -> IO ()
playAndPrint size sa sb = do
  seed <- randomIO
  -- let seed = 42
  let moves = play (mkRandoms seed) size sa sb
  putStr $
    unlines (zipWith showState moves $ cycle ['+', '-']) ++ "\n" ++
    (case length moves `mod` 2 of { 1 -> "Winner: +"; 0 -> "Winner: -" }) ++ "\n" ++
    "View at https://vmnipkow16.in.tum.de/christmas2020/embed.html#i" ++ base64 (1 : t size ++ concatMap (t . snd) moves) ++ "\n"
  where
    showState (b, pos) p = showBoard b ++ p : " places at " ++ show pos ++ "\n"
    t (a, b) = [a, b]

mkRandoms :: Random a => Int -> [a]
mkRandoms = randoms . mkStdGen

base64 :: [Int] -> String
base64 xs = case xs of
  []            -> ""
  [a]           -> f1 a : f2 a 0 : "=="
  [a, b]        -> f1 a : f2 a b : f3 b 0 : "="
  a : b : c : d -> f1 a : f2 a b : f3 b c : f4 c : base64 d
  where
    alphabet = (!!) "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    f1 a     = alphabet $ shiftR a 2
    f2 a b   = alphabet $ shiftL (a .&. 3 ) 4 .|. shiftR b 4
    f3 b c   = alphabet $ shiftL (b .&. 15) 2 .|. shiftR c 6
    f4 c     = alphabet $ c .&. 63