module Main where

import Linear

import Data.Matrix as M
import Data.List as L
import Data.Maybe

import Control.Monad
import Control.Monad.Loops
import Control.Concurrent
import Control.Concurrent.Timer
import Control.Concurrent.Suspend.Lifted
import Control.Concurrent.MVar
import Control.DeepSeq

import System.IO
import System.Console.ANSI as CA
import System.Console.Terminal.Size as TS

-- import Debug.Trace as T

import qualified Map
import Types

delay :: Delay
delay = msDelay (fromIntegral msdelay)

msdelay :: Int
msdelay = 100

step :: V2 Double
step = V2 0 0.5

rotStep :: Double
rotStep = 0.174533

fov :: Double
fov = pi / 2

main :: IO ()
main = do
  hSetBuffering stdin NoBuffering
  hideCursor
  state <- newMVar (State (V2 10 3) 0 False "")
  c <- newMVar Nothing
  whileM_ (not <$> stop <$> readMVar state) $ do
    CA.clearScreen
    takeMVar c
    char <- getKey
    putMVar c char
    modifyMVar_ state (\s -> if (not (stop s))
      then
        withMVar c (\char -> handleInput char s)
      else
        return s)
    outputs <- withMVar state draw
    withMVar state (\s -> when (not (stop s)) $ do
      let output = L.intercalate "\n"
            ( outputs
            ++ [show char]
            ++ [show (pos s) ++ " " ++ show (rot s)]
            )
      deepseq output (putStr output)
      )
    -- threadDelay msdelay
  showCursor

handleInput :: Maybe Char -> State -> IO State
handleInput Nothing state = return state
handleInput (Just char) state = do
  let npos delta = if not (doesCollide (pos state + delta))
        then pos state + delta
        else pos state
      nstate = case char of
        'w' -> state
          { pos = npos (step `rotVec` rot state) }
        's' -> state
          { pos = npos (- step `rotVec` rot state) }
        'd' -> state
          { rot = rot state + rotStep }
        'a' -> state
          { rot = rot state - rotStep }
        '\ESC' -> state
          { stop = True }
        _ -> state
  return nstate

draw :: State -> IO [String]
draw state@(State pos@(V2 x y) rot _ _) = do
  (Just (Window h w)) <- TS.size
  let dims@(dw, dh) = (min 160 w, min 60 h) -- if w >= h then (w, w `div` 2) else (w, h)
      output = map
        (\mh -> map (\mw -> drawPixel dims (mw, mh)) [1 .. fromIntegral dw])
        [1 .. fromIntegral dh - 2]
  return output
  where
    drawPixel (w, h) (ddw, ddh) =
      let rayLength = castRay (fromIntegral w) (fromIntegral h) ddw ddh
      in getPixel (fromMaybe 11 rayLength)
    castRay w h ddw ddh =
      let iter = [0, 0.05 .. 10]
          collPos a = (pos + (V2 0 (a * cos (- fov / 2 + ddh * fov / h))
            `rotVec` (rot - fov / 2 + ddw * fov / w)))
      in foldl (\acc a ->
          if isNothing acc
          then
            if doesCollide (collPos a)
            then Just a
            else acc
          else acc
        ) Nothing iter
    getPixel l
      | l <= 3    = '█'
      | l <= 4.5  = '▓'
      | l <= 6    = '▒'
      | l <= 9    = '░'
      | otherwise = ' '

doesCollide :: V2 Double -> Bool
doesCollide (V2 x y) =
  let tile = safeGet (floor x) (floor y) Map.map
  in case tile of
    Nothing  -> True
    Just '#' -> True
    _        -> False

rotVec (V2 x y) rad = V2 nx ny
  where
    nx = x * cos rad + y * sin rad
    ny = x * sin rad - y * cos rad

getKey :: IO (Maybe Char)
getKey = do
  charMVar <- newEmptyMVar
  tid <- forkIO (forkGetChar charMVar)
  threadDelay (msdelay `div` 5)
  empty <- isEmptyMVar charMVar
  if (not empty)
  then do
    killThread tid
    Just <$> takeMVar charMVar
  else do
    killThread tid
    return Nothing
  where
    forkGetChar mvar = do
      hSetEcho stdin False
      cs <- (: []) <$> hGetChar stdin
      hSetEcho stdin True
      when (not (null cs)) $ do
        _ <- putMVar mvar (head cs)
        return ()