module Game.Entities (Entities, Entity, mkEntities, updateAll, render, renderVisible, playerPosition) where

import Control.Monad
import Data.Bits (Bits (..))
import Data.Foldable (find, traverse_)
import Data.IORef
import Data.List (sort)
import qualified Game.Controller as C
import Game.Entities.Common
import Game.Entities.Const
import Game.Entities.Effect
import Game.Entities.Pickup
import Game.Entities.Player
import Game.Entities.Robot
import Game.Entities.Slime
import Game.Entities.Types
import qualified Game.Map as M
import qualified Game.Sprites as S
import qualified Game.State as GS
import SDL (($~))
import qualified SDL

mkEntities :: S.SpriteSheet -> M.Map -> IORef C.Controls -> IORef GS.State -> IO Entities
mkEntities sprites m controls stateRef = do
  player <- case find M.isPlayer (M.objects m) of
    Just (M.PlayerEntity x y) -> mkPlayer sprites x y controls (M.isBlocked m)
    _ -> error "No player entity in map"
  playerRef <- newIORef player
  entities <- traverse (toEntity playerRef) $ sort $ filter (not . M.isPlayer) (M.objects m)
  -- the entities list has always player first
  pure $ Entities sprites playerRef stateRef (player : entities)
  where
    toEntity :: IORef Entity -> M.Object -> IO Entity
    toEntity playerRef (M.SlimeEntity x y) = mkSlime sprites x y (collision playerRef 16) (M.isBlocked m)
    toEntity playerRef (M.RobotEntity x y) = mkRobot sprites x y (collision playerRef 24) (M.isBlocked m)
    toEntity playerRef (M.BatteryEntity x y) = mkBattery sprites x y (collision playerRef 16)
    toEntity _ (M.PlayerEntity _ _) = error "Player already processed"

-- | Return the player's entity position (x, y).
playerPosition :: Entities -> (Int, Int)
playerPosition (Entities _ _ _ entities) =
  (player.x, player.y)
  where
    player = head entities

updateAll :: Entities -> IO Entities
updateAll es = do
  -- update the player first (including the reference)
  updatedPlayer <- player.update player
  void $ writeIORef es.player updatedPlayer
  state <- readIORef stateRef
  -- update hit delay if the player was hit
  let playerWasHit = state.hitDelay > 0
  when playerWasHit (writeIORef stateRef state {GS.hitDelay = state.hitDelay - 1})
  -- then the other entities
  updated <- (updatedPlayer :) <$> traverse (updateFilter playerWasHit) others
  -- process actions
  updated' <- processActions updated (concatMap (\e -> e.actions) updated)
  -- clear actions, filter out destroyed entities, and add the new ones
  pure es {entities = map (\e -> e {actions = []}) (filter (\e -> not e.destroy) updated')}
  where
    stateRef = es.state
    player = head es.entities
    others = tail es.entities

    -- the actions can add new entities of modify existing ones
    processActions :: [Entity] -> [Action] -> IO [Entity]
    processActions ents (a : t) =
      case a of
        ActionAddDustEffect x y -> do
          effect <- mkEffect es.sprites x y "dust"
          processActions (ents ++ [effect]) t
        ActionAddBattery -> do
          stateRef $~ (\s -> s {GS.batteries = s.batteries + 1})
          processActions ents t
        ActionHitPlayer -> do
          s <- readIORef stateRef
          ents' <-
            if s.lives == 1
              then do
                writeIORef stateRef s {GS.lives = 0, GS.gameOverDelay = gameOverDelay}
                pure $ (head ents) {dir = Dying, gravity = gravityUp, frame = 0} : tail ents
              else do
                writeIORef stateRef s {GS.lives = s.lives - 1, GS.hitDelay = hitDelay}
                pure ents
          processActions ents' t
    processActions ents [] = pure ents

    -- Update entities skipping enemies if the player was hit.
    updateFilter :: Bool -> Entity -> IO Entity
    updateFilter False e = e.update e
    updateFilter True e
      | notEnemy e = e.update e
      | otherwise = pure e

    notEnemy :: Entity -> Bool
    notEnemy ent = case ent.typ of
      TypeEnemy -> False
      _ -> True

-- | Render only visible entities according to the provided viewport.
renderVisible :: SDL.Renderer -> Entities -> M.Viewport -> IO ()
renderVisible renderer (Entities sprites player state entities) v =
  render renderer (Entities sprites player state visible)
  where
    -- FIXME: entities should have size so we can be exact here and
    -- avoid the hardcoded size
    visible = filter (\e -> isVisible v e.x e.y 16 16) entities
    isVisible :: M.Viewport -> Int -> Int -> Int -> Int -> Bool
    isVisible (M.Viewport vx vy vw vh) x y w h =
      x < vx + vw && vx < x + w && y < vy + vh && vy < y + h

render :: SDL.Renderer -> Entities -> IO ()
render renderer es = do
  state <- readIORef es.state
  -- if the player was hit, make the enemies wiggle before unfreezing
  if state.hitDelay == 0 || state.hitDelay > hitDelay `div` 3
    then traverse_ renderOne others
    else traverse_ (renderWiggling ((.&.) 2 state.hitDelay)) others
  -- always render player last
  -- won't draw all the frames if the player was hit
  if testBit state.hitDelay 2 then pure () else renderOne player
  where
    player = head es.entities
    others = tail es.entities

    renderWiggling :: Int -> Entity -> IO ()
    renderWiggling m e = case e.typ of
      TypeEnemy -> renderOne e {x = e.x + m}
      _ -> renderOne e

    renderOne :: Entity -> IO ()
    renderOne e =
      S.render renderer e.sprite e.x e.y set e.frame
      where
        set = toSpriteSet e.dir