module OrbitPointOfView where

import Graphics.Rendering.OpenGL
import Graphics.UI.GLUT  as GLUT

import StateUtil
import Data.IORef

setPointOfView pPos = do
  (alpha,beta,r) <- get pPos
  let
   (x,y,z)    = calculatePointOfView alpha beta r
   (x2,y2,z2) = calculatePointOfView ((alpha+90)`mod` 360) beta r  
  lookAt (Vertex3 x y z) (Vertex3 0 0 0) (Vector3 x2 y2 z2)

calculatePointOfView  alp bet r = 
  let alpha =  fromIntegral alp*2*pi/fromIntegral 360
      beta  =  fromIntegral bet*2*pi/fromIntegral 360
      y = r * cos alpha
      u = r * sin alpha
      x = u * cos beta
      z = u * sin beta
  in (x,y,z)

keyForPos pPos (Char '+')         = modPos pPos (id,id,\x->x-0.1)
keyForPos pPos (Char '-')         = modPos pPos (id,id,(+)0.1)
keyForPos pPos (SpecialKey KeyLeft) = modPos pPos (id,(+)359,id)
keyForPos pPos (SpecialKey KeyRight)= modPos pPos (id,(+)1,id)
keyForPos pPos (SpecialKey KeyUp)   = modPos pPos ((+)1,id,id)
keyForPos pPos (SpecialKey KeyDown) = modPos pPos ((+)359,id,id)
keyForPos  _  _                     = return ()

modPos pPos (ffst,fsnd,ftrd) = do
  (alpha,beta,r) <- get pPos
  pPos $= (ffst alpha `mod` 360,fsnd beta `mod` 360,ftrd r) 
  postRedisplay Nothing

reshape screenSize@(Size w h) = do
  viewport $= ((Position 0 0), screenSize)
  matrixMode $= Projection 
  loadIdentity
  let near   = 0.001
      far    = 40
      fov    = 90
      ang    = (fov*pi)/(360)
      top    = near / ( cos(ang) / sin(ang) )
      aspect = fromIntegral(w)/fromIntegral(h)
      right = top*aspect
  frustum (-right) right (-top) top near far
  matrixMode $= Modelview 0