lib/RPGEngine/Input/ActionSelection.hs

@@ -68,8 +68,23 @@ pickUpItem id s@Playing{ level = level, player = player } = newState
 pickUpItem _ _ = Error "Something went wrong while picking up an item"
 
 -- Use an item
-useItem :: ItemId -> State -> State -- TODO
+-- Should receive a Playing state
-useItem _ s = s -- TODO
+useItem :: ItemId -> State -> State
+useItem iid s@Playing{ level = level, player = player} = newState
+    where newState = s{ level = newLevel, player = newPlayer }
+          -- Remove item from inventory if necessary
+          (Just usingItem) = find ((== iid) . itemId) $ inventory player
+          usedItem         = decreaseDurability usingItem
+          newInventory     = filter (/= usingItem) $ inventory player
+          newPlayer        = player{ inventory = putItemBack usedItem newInventory }
+          putItemBack Nothing inv     = inv
+          putItemBack (Just item) inv = item:inv
+          -- Remove entity if necessary
+          allEntities = entities level
+          entitiesWithUseItem = filter (any ((== UseItem iid) . snd) . entityActions) allEntities
+          attackedEntity = head entitiesWithUseItem
+          newLevel = level{ entities = filter (/= attackedEntity) $ entities level}
+useItem _ _ = Error "Something went wrong while using an item"
 
 -- Attack an entity using an item
 -- Should receive a Playing state
@@ -77,7 +92,7 @@ decreaseHp :: EntityId -> ItemId -> State -> State
 decreaseHp eid iid s@Playing{ level = level, player = player } = newState
     where newState = s{ level = newLevel, player = newPlayer }
           -- Change player
-          (Just usingItem) = find ((== iid) . itemId) (inventory player)
+          (Just usingItem) = find ((== iid) . itemId) $ inventory player
           usedItem         = decreaseDurability usingItem
           newInventory     = filter (/= usingItem) $ inventory player
           newPlayer = player{ inventory = putItemBack usedItem newInventory, playerHp = newHp }
@@ -89,7 +104,7 @@ decreaseHp eid iid s@Playing{ level = level, player = player } = newState
           (Just (Right attackedEntity)) = getWithId eid level
           newLevel = level{ entities = putEntityBack dealtWithEntity newEntities }
           newEntities = filter ((/= eid) . entityId) $ entities level
-          dealtWithEntity = decreaseHealth attackedEntity damageDealAmount 
+          dealtWithEntity = decreaseHealth attackedEntity damageDealAmount
           putEntityBack Nothing    list = list
           putEntityBack (Just ent) list = ent:list
           damageGetAmount = inverse (entityValue attackedEntity)

lib/RPGEngine/Input/Playing.hs

@@ -84,7 +84,7 @@ goToNextLevel s = s
 
 -- Move a player in a direction if possible.
 movePlayer :: Direction -> Game -> Game
-movePlayer dir g@Game{ state = s@Playing{ player = p@Player{ position = (x, y) }}} = newGame
+movePlayer dir g@Game{ state = s@Playing{ player = p@Player{ position = (x, y) }}} = tryForceInteraction newGame g
     where newGame   = g{ state = newState }
           newState  = s{ player   = newPlayer }
           newPlayer = p{ position = newCoord  }
@@ -93,6 +93,25 @@ movePlayer dir g@Game{ state = s@Playing{ player = p@Player{ position = (x, y) }
           (xD, yD)  = directionOffsets dir
 movePlayer _ g = g{ state = Error "something went wrong while moving the player" }
 
+-- TODO Clean this function
+-- Try to force an interaction. If there is an entity, you have to
+-- interact with it. If it is an item, the user should trigger this
+-- themselves. If forced, the player should not move to the new position.
+tryForceInteraction :: Game -> Game -> Game
+tryForceInteraction g@Game{ state = Playing { level = level, player = player }} fallBack@Game{ state = Playing{ player = firstPlayer }} = newGame triedInteraction
+    where newGame g@Game{ state = s@ActionSelection{ continue = c@Playing{ player = player}}} = g{ state = s{ continue = c{ player = playerWithRestorePos }}}
+          newGame g = g
+          playerWithRestorePos = (newPlayer triedInteraction){ position = position firstPlayer }
+          newPlayer Game{ state = ActionSelection{ continue = Playing{ player = player }}} = player
+          triedInteraction  | hasEntity (hasAt pos level) = interact g
+                            | otherwise = g
+          pos = position player
+          hasEntity (Just (Right entity)) = True
+          hasEntity _                     = False
+tryForceInteraction g _ = g{ state = Error "something went wrong while trying to force interaction"}
+
+-- If there is an interaction at the current position, go to 
+-- actionSelection state. Otherwise just continue the game.
 checkForInteraction :: Game -> Game
 checkForInteraction g@Game{ state = Playing{ level = level, player = player }} = newGame
     where newGame       | canInteract = interact g