module RPGEngine.Data.Game
( isLegalMove
) where

import RPGEngine.Data
    ( Player(Player, position),
      Direction,
      Physical(Exit, Walkable, Entrance),
      State(Playing, level),
      Game(Game, state, player) )
import RPGEngine.Data.Level (findAt, directionOffsets)

------------------------------ Exported ------------------------------

-- Check if a move is legal by checking what is located at the new position.
isLegalMove :: Direction -> Game -> Bool
isLegalMove dir g@Game{ state = Playing { level = lvl }, player = p@Player{ position = (x, y) }} = legality
    where legality = physical `elem` [Walkable, Entrance, Exit]
          physical = findAt newPos lvl
          newPos   = (x + xD, y + yD)
          (xD, yD) = directionOffsets dir
isLegalMove _   _ = False