module RPGEngine.Input.ActionSelection
( handleInputActionSelection
) where

import RPGEngine.Input.Core (InputHandler, handleKey, composeInputHandlers, ListSelector (selection))

import RPGEngine.Data (Game (..), State (..), Direction (..), Action (..), ItemId, EntityId, Level (..), Player (inventory))
import Graphics.Gloss.Interface.IO.Game (Key(SpecialKey), SpecialKey (KeyUp, KeyDown))
import Graphics.Gloss.Interface.IO.Interact
    ( SpecialKey(..), KeyState(..) )
import RPGEngine.Data.Level (getWithId)

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

handleInputActionSelection :: InputHandler Game
handleInputActionSelection = composeInputHandlers [
    handleKey (SpecialKey KeySpace) Down selectAction,

    handleKey (SpecialKey KeyUp)    Down $ moveSelector North,
    handleKey (SpecialKey KeyDown)  Down $ moveSelector South
    ]

----------------------------------------------------------------------

selectAction :: Game -> Game
selectAction game@Game{ state = ActionSelection list selector continue } = newGame
    where newGame = game{ state = execute selectedAction continue }
          selectedAction = list !! index
          index = selection selector
selectAction g = g

-- TODO Lift this code from LevelSelection
-- Move the selector either up or down
moveSelector :: Direction -> Game -> Game
moveSelector dir game@Game{ state = state@(ActionSelection list selector _) } = newGame
    where newGame      = game{ state = newState }
          newState     = state{ selector = newSelector }
          newSelector  | constraint = selector{ selection = newSelection }
                       | otherwise = selector
          constraint   = 0 <= newSelection && newSelection < length list
          newSelection = selection selector + diff
          diff         | dir == North = -1
                       | dir == South =  1
                       | otherwise    =  0
moveSelector _ g = g{ state = Error "Something went wrong while moving the selector up or down"}

------------------------------ Actions -------------------------------

execute :: Action -> State -> State
execute (RetrieveItem id     ) s = pickUpItem id s
execute (UseItem      id     ) s = useItem id s
execute (DecreaseHp   eid iid) s = decreaseHp eid iid s
execute (IncreasePlayerHp iid) s = increasePlayerHp iid s
execute _ s = s

-- Pick up the item with itemId and put it in the players inventory
-- Should receive a Playing state
pickUpItem :: ItemId -> State -> State
pickUpItem id s@Playing{ level = level, player = player } = newState
    where (Just (Left pickedUpItem)) = getWithId id level
          newState     = s{ level = newLevel, player = newPlayer }
          newLevel     = level{ items = filteredItems }
          filteredItems = filter (/= pickedUpItem) $ items level
          newPlayer     = player{ inventory = newInventory }
          newInventory  = pickedUpItem:inventory player
pickUpItem _ _ = Error "Something went wrong while picking up an item"

-- Use an item on the player
useItem :: ItemId -> State -> State -- TODO
useItem _ s = s -- TODO

-- Attack an entity using an item
decreaseHp :: EntityId -> ItemId -> State -> State
decreaseHp _ _ s = s
-- TODO DecreaseHp of monster
-- TODO Check if monster is dead
-- TODO Entity attack player
-- TODO Decrease durability of item
-- TODO Break item if durability below zero

-- Heal a bit
increasePlayerHp :: ItemId -> State -> State
increasePlayerHp _ s = s
-- TODO Increase playerHp
-- TODO Decrease durability of item
-- TODO Remove item if durability below zero