require "Vector"
local V = Vector

require "Primitives"
local P = Primitives

require "Operations"
local O = Operations

require "Textures"
local T = Textures

local eps = 0.01
local max_dist = 50
local bg_col = {1,0,1}

local function calculate_normal(sdf, l)
   local delta = 1e-3;
   return -V.new{sdf(l+V.x*delta).dist-sdf(l-V.x*delta).dist,
                 sdf(l+V.y*delta).dist-sdf(l-V.y*delta).dist,
                 sdf(l+V.z*delta).dist-sdf(l-V.z*delta).dist}/(2*delta)
end

local function march(location, ray_dir, sdf, count)
   local p = sdf(location)
   if p.dist < eps then
      return p.texture(location, ray_dir, calculate_normal(sdf, location-(ray_dir*eps)), count)
   elseif p.dist > max_dist then
      return bg_col
   else
      return march(location + ray_dir*p.dist,
                   ray_dir, sdf, count+1)
   end
end

local function render(scene, width, height, filename) 
   print("Rendering to file " .. filename .. "...")
   
   local f = io.open(filename, "w")
   f:write("P3 ", width, " ", height, " 255\n")

   local c = scene.camera
   local cam_dir = V.normalize(c.point_at - c.location)
   local right = V.normalize(c.right)
   local up = V.cross(right,cam_dir)
   local aspect = height/width;
   
   for y=1,height do

      if y % math.floor(height/10) == 0 then
         print(y/math.floor(height/10) * 10 .. "%")
      end

      local rayy = cam_dir + up*((y/height - 0.5)*c.fov*aspect)

      for x=1,width do
         local ray_dir = V.normalize(rayy + right*((x/width - 0.5)*c.fov))
         local col = march(c.location, ray_dir, scene.sdf, 0)
         col = {math.min(col[1]*255, 255),
                math.min(col[2]*255, 255),
                math.min(col[3]*255, 255)}

         f:write(math.floor(col[1]), " ", math.floor(col[2]), " ", math.floor(col[3]), " ")
      end
      f:write("\n")
   end
   f:write("\n")

   f:close()

   print("done")
end



local scene = {
   sdf = O.union(P.make_sphere(V.new{0,0,0}, 1,
                       -- T.make_count_texture()),
                               T.make_phong({V.new{2,-1,2}}, {0,1,0},
                                  1.0, 0.5, 100)),
                 P.make_sphere(V.new{1.5,0,1.0}, 0.5,
                               T.make_phong({V.new{2,-1,2}}, {0,0,1},
                                  1.0, 0.5, 100))),
                               
   camera = {location = V.new{0,-5,0},
             point_at = V.new{0,0,0},
             right = V.new{1,0,0},
             fov = 1}}

render(scene, 640, 480, "test.ppm")