content: {-# LANGUAGE GADTSyntax #-}
  {-# LANGUAGE KindSignatures #-}
  {-# OPTIONS_GHC -Wno-deprecations -Wno-name-shadowing -Wno-star-is-type #-}
  
  {-
    Copyright 2020 The CodeWorld Authors. All rights reserved.
  
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at
  
        http://www.apache.org/licenses/LICENSE-2.0
  
    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
  -}
  
  module CodeWorld.App
    {-# WARNING "This is an experimental API.  It can change at any time." #-}
    ( Rule,
      eventRule,
      pictureRule,
      multiEventRule,
      multiPictureRule,
      subrule,
      rules,
      applicationOf,
      unsafeMultiApplicationOf,
    )
  where
  
  import CodeWorld
  import Data.List (foldl')
  import System.Random (StdGen)
  
  data Rule :: * -> * where
    EventRule :: (Int -> Event -> state -> state) -> Rule state
    PictureRule :: (Int -> state -> Picture) -> Rule state
    Rules :: [Rule state] -> Rule state
  
  eventRule :: (Event -> state -> state) -> Rule state
  eventRule = EventRule . const
  
  pictureRule :: (state -> Picture) -> Rule state
  pictureRule = PictureRule . const
  
  multiEventRule :: (Int -> Event -> state -> state) -> Rule state
  multiEventRule = EventRule
  
  multiPictureRule :: (Int -> state -> Picture) -> Rule state
  multiPictureRule = PictureRule
  
  subrule :: (a -> b) -> (b -> a -> a) -> Rule b -> Rule a
  subrule getter setter (EventRule event_b) = EventRule event_a
    where
      event_a k ev a = setter (event_b k ev (getter a)) a
  subrule getter _setter (PictureRule pic_b) = PictureRule pic_a
    where
      pic_a n = pic_b n . getter
  subrule getter setter (Rules rules) = Rules (map (subrule getter setter) rules)
  
  rules :: [Rule state] -> Rule state
  rules = Rules
  
  applicationOf :: world -> [Rule world] -> IO ()
  applicationOf w rules = activityOf w event picture
    where
      event ev = foldl' (.) id [f ev | f <- concatMap eventHandlers rules]
      picture w = pictures [pic w | pic <- concatMap pictureHandlers rules]
      eventHandlers (EventRule f) = [f 0]
      eventHandlers (Rules rs) = concatMap eventHandlers rs
      eventHandlers _ = []
      pictureHandlers (PictureRule f) = [f 0]
      pictureHandlers (Rules rs) = concatMap pictureHandlers rs
      pictureHandlers _ = []
  
  unsafeMultiApplicationOf :: Int -> (StdGen -> state) -> [Rule state] -> IO ()
  unsafeMultiApplicationOf n initial rules =
    unsafeGroupActivityOf n initial event picture
    where
      event k ev = foldl' (.) id [f k ev | f <- concatMap eventHandlers rules]
      picture k w = pictures [pic k w | pic <- concatMap pictureHandlers rules]
      eventHandlers (EventRule f) = [f]
      eventHandlers (Rules rs) = concatMap eventHandlers rs
      eventHandlers _ = []
      pictureHandlers (PictureRule f) = [f]
      pictureHandlers (Rules rs) = concatMap pictureHandlers rs
      pictureHandlers _ = []
  