[SOLVED] CS {-

{-
Module: Game.

Functions used in the game loop to change the game state.
-}
module Game where

import Types
import Constants
import Action
import Board
import Player

{-
performAction and helpers.
-}

The current player is the first element in the players list.
currentPlayer :: [Player] -> Player
currentPlayer = head

The previous player is the last element in the players list.
previousPlayer :: [Player] -> Player
previousPlayer = last

The player that just played goes to the back of the list. Used to change turn.
rotatePlayers :: [Player] -> [Player]
rotatePlayers [] = []
rotatePlayers (p:ps) = ps ++ [p]

A step action is valid if the step is valid and no other player is in the target cell (canMove).
validStepAction :: Game -> Step -> Bool
validStepAction (Game b ps) s = (canMove (currentPlayer ps) ps s) && (validStep b s)

Generate all valid steps at a game state.
validSteps :: Game -> [Action]
validSteps g@(Game b ps) = map Move (filter (validStepAction g) steps)
where
steps = let p = currentPlayer ps in makeSteps (currentCell p) (adjacentCells p)

A wall action is valid if the wall is valid and player has walls remaining.
validWallAction :: Game -> Wall -> Bool
validWallAction (Game b ps) w = (hasWallsLeft (currentPlayer ps)) && (validWall b w)

Generate all valid walls at a game state.
validWalls :: Game -> [Action]
validWalls g = map Place (filter (validWallAction g) walls)
where
walls = concat [[wallRight c, wallTop c] | c<-[(i, j) | i<-allColumns, j<-allRows]]– Generate all valid actions at a game state.validActions :: Game -> [Action]
validActions g = (validSteps g) ++ (validWalls g)

Key function. Given a game and an action, checks the validity of the action and applies it to the
game, generating a new game.
performAction :: Game -> Action -> Maybe Game
performAction g@(Game b (p:ps)) (Move s)
|validStepAction g s =
Just (Game b (rotatePlayers ((movePlayer (nextTurn p) s):ps)))
| otherwise = Nothing
performAction g@(Game b (p:ps)) (Place w)
|validWallAction g w =
Just (Game (placeWall b w) (rotatePlayers ((useWall (nextTurn p)):ps)))
| otherwise = Nothing