module RPGEngine.Input.ActionSelection
( handleInputActionSelection
) where

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

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

------------------------------ 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 selection continue } = newGame
    where newGame = game{ state = execute selectedAction continue }
          selectedAction = Leave
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
pickUpItem :: ItemId -> State -> State
pickUpItem _ s = s -- TODO

-- 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