program main
   use iso_c_binding
   use raylib
   implicit none

   integer(c_int) :: screen_width = 800
   integer(c_int) :: screen_height = 450

   type(camera3d), target :: camera
   type(vector3) :: npc_position
   type(vector3) :: player_position
   real(c_float) :: npc_dir

   !
   ! implement a login and logout screen
   ! https://www.raylib.com/examples/core/loader.html?name=core_basic_screen_manager
   ! https://www.raylib.com/examples/text/loader.html?name=text_input_box
   !

   call init_window(screen_width, screen_height, "fortran client : raylib"//c_null_char)

   player_position = vector3( 0.0_c_float, 1.0_c_float, 2.0_c_float )
   npc_position = vector3( -4.0_c_float, 1.0_c_float, 0.0_c_float )
   npc_dir = 0.1_c_float

   camera%position = vector3(0.0_c_float, 10.0_c_float, 10.0_c_float) !Camera position
   camera%target = vector3(0.0_c_float, 0.0_c_float, 0.0_c_float) !Camera looking at point
   camera%up = vector3(0.0_c_float, 1.0_c_float, 0.0_c_float) !Camera up vector(rotation towards target)
   camera%fovy = 45.0_c_float !Camera field - of - view Y
   camera%projection = CAMERA_PERSPECTIVE !Camera projection type

   call set_target_fps(60_c_int)

   !Main game loop
   do while (.not. window_should_close()) ! Detect window close button or ESC key

      if (is_key_down(KEY_RIGHT)) then 
         player_position%x = player_position%x + 0.2_c_float
      else if (is_key_down(KEY_LEFT)) then 
         player_position%x = player_position%x - 0.2_c_float
      else if (is_key_down(KEY_DOWN)) then
         player_position%z = player_position%z + 0.2_c_float
      else if (is_key_down(KEY_UP)) then
         player_position%z = player_position%z - 0.2_c_float
      end if

      camera%position%x = player_position%x
      camera%position%y = player_position%y + 10.0_c_float
      camera%position%z = player_position%z + 10.0_c_float
      camera%target%x = player_position%x
      camera%target%y = player_position%y
      camera%target%z = player_position%z

      if (npc_position%x < -10) then
         npc_dir = 0.1_c_float
      else if (npc_position%x > 10) then
         npc_dir = -0.1_c_float
      end if
      npc_position%x = npc_position%x + npc_dir

      !
      ! implement a user input for texting
      ! https://www.raylib.com/examples/text/loader.html?name=text_input_box
      !

      call begin_drawing()
         call clear_background(RAYWHITE)

         call begin_mode_3d(camera)
            ! Draw floor
            call draw_grid(30_c_int, 1.0_c_float)

            ! Draw user & others text over them
            ! https://www.raylib.com/examples/text/loader.html?name=text_draw_3d

            !Draw npc cube
            call draw_cube(npc_position, 0.5_c_float, 0.5_c_float, 0.5_c_float, GRAY)
            call draw_cube_wires(npc_position, 0.5_c_float, 0.5_c_float, 0.5_c_float, DARKGRAY)

            !Draw player cube
            call draw_cube(player_position, 0.5_c_float, 0.5_c_float, 0.5_c_float, PURPLE)
            call draw_cube_wires(player_position, 0.5_c_float, 0.5_c_float, 0.5_c_float, DARKPURPLE)
         call end_mode_3d()
      call end_drawing()

   end do

   call close_window() !Close window and OpenGL context

contains

end program main