-- A framework for a Tetris program.
-- It allows an ellipse to be moved left and right, rotated, and dropped
-- using keyboard keys.  Thus it demonstrates animation.

-- by Scot Drysdale on 11/7/07, based on a verson by Chris Bailey-Kellogg

import Random
import DrawX
import Graphics.SOE.Gtk hiding (Region)
import qualified Graphics.SOE.Gtk as G (Region)
import PictureEX

dx = 1             -- Distance to move left or right when hit 'j' or 'l' key
columns = 10       -- Columns in the board
rows = 15          -- number of rows in the board
squareSize = 30    -- Square side length in pixels
winX = round (columns * squareSize)  -- Width of drawing window in pixels
winY = round (rows * squareSize)     -- Height of drawing window in pixels
speed = 500        -- speed/1000 is the number of seconds to move 1 unit in y.

-- Opens a buffered user window for animation using user coordinates.
-- Coordinates are min and max X, min and max Y in user coordinates
-- and width and height of the window in pixels.  Also widow title.
openUserWindowEx :: Float -> Float -> Float -> Float -> Int -> Int -> 
                  String -> IO UserWindow
openUserWindowEx uXmin uXmax uYmin uYmax winX winY title =
  do
    w <- openWindowEx title (Just (0,0)) (Just (winX,winY)) drawBufferedGraphic
    return (WinData w uXmin (uXmax - uXmin) uYmax (uYmax - uYmin) winX winY)
                  

main = runGraphics $
  do uw <- openUserWindowEx 0.5 (columns + 0.5) 0.5 (rows + 0.5) winX winY "Tetris"
     stime <- timeGetTime
     
     let new = do x <- randomRIO (1, columns)
                  let xRound = roundF x
                  stime <- timeGetTime
                  loop xRound stime (Shape (Ellipse 1 0.5))

         -- Loop to control the piece as it drops.  
         -- x is the current x coordinate, stime the starting time when piece
         -- was dropped.  Motion controlled by the time 
         loop      :: Float -> Word32 -> Region -> IO ()
         loop x stime piece  = 
           do clearWindow (win uw)
              time <- timeGetTime    -- Gets system time in milliseconds
              let y = rows + 1 - (intToFloat (time - stime))/speed
              drawPic uw (Region Blue (Translate (x, y) piece))
              e <- maybeGetWindowEvent (win uw)                      
              case e of Just Closed -> return ()
                        Just (Key 'q' True) -> closeWindow (win uw)
                        Just (Key 'j' True) -> loop (left x) stime piece
                        Just (Key 'k' True) -> loop x stime (rotateL piece)
                        Just (Key 'l' True) -> loop (right x) stime piece
                        Just (Key ' ' True) -> new  -- Drop the piece
                        _                   -> if y < 0   -- Off the bottom?
                                               then new
                                               else loop x stime piece                       
        in new

-- Round to integer, then convert back to float
roundF = (intToFloat . round)

-- Move left if there is space
left x   = if x-dx<1 then 1 else x-dx

-- Move right if there is space
right x  = if x+dx>columns then columns else x+dx

-- Rotate 90 degrees (so to the left)
rotateL (Shape (Ellipse r1 r2)) = Shape (Ellipse r2 r1)