# OpenGL example using SDL2

import sdl2
import opengl/opengl
import opengl/glu

# Initialize SDL
discard SDL_Init(INIT_EVERYTHING)

var
    window = CreateWindow("SDL Skeleton", 100, 100, 640, 480, SDL_WINDOW_OPENGL or SDL_WINDOW_RESIZABLE)
    context = window.GL_CreateContext()

# Initialize OpenGL
proc Init_OpenGL() =
    loadExtensions()
    glClearColor(0.0, 0.0, 0.0, 1.0)                  # Set background color to black and opaque
    glClearDepth(1.0)                                 # Set background depth to farthest
    glEnable(GL_DEPTH_TEST)                           # Enable depth testing for z-culling
    glDepthFunc(GL_LEQUAL)                            # Set the type of depth-test
    glShadeModel(GL_SMOOTH)                           # Enable smooth shading
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST) # Nice perspective corrections

proc reshape(pos_x :float, pos_y :float) =
    # TODO: use real width and height instead of constant values
    glViewport(0, 0, 640, 480)                        # Set the viewport to cover the new window
    glMatrixMode(GL_PROJECTION)                       # To operate on the Projection matrix
    glLoadIdentity()                                  # Reset
    # gluPerspective(40.0, 640 / 480, 0.1, 100.0)     # Enable perspective projection with fovy, aspect, zNear and zFar
    gluPerspective(pos_y, 640 / 480, 0.1, 100.0)

proc render() =
    glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT) # Clear color and depth buffers
    glMatrixMode(GL_MODELVIEW)                          # To operate on model-view matrix
    glLoadIdentity()                 # Reset the model-view matrix
    glTranslatef(1.5, 0.0, -7.0)     # Move right and into the screen

    # Render a cube consisting of 6 quads
    # Each quad consists of 2 triangles
    # Each triangle consists of 3 vertices

    glBegin(GL_TRIANGLES)        # Begin drawing of triangles

    # Top face (y = 1.0f)
    glColor3f(0.0, 1.0, 0.0)     # Green
    glVertex3f( 1.0, 1.0, -1.0)
    glVertex3f(-1.0, 1.0, -1.0)
    glVertex3f(-1.0, 1.0,  1.0)
    glVertex3f( 1.0, 1.0,  1.0)
    glVertex3f( 1.0, 1.0, -1.0)
    glVertex3f(-1.0, 1.0,  1.0)

    # Bottom face (y = -1.0f)
    glColor3f(1.0, 0.5, 0.0)     # Orange
    glVertex3f( 1.0, -1.0,  1.0)
    glVertex3f(-1.0, -1.0,  1.0)
    glVertex3f(-1.0, -1.0, -1.0)
    glVertex3f( 1.0, -1.0, -1.0)
    glVertex3f( 1.0, -1.0,  1.0)
    glVertex3f(-1.0, -1.0, -1.0)

    # Front face  (z = 1.0f)
    glColor3f(1.0, 0.0, 0.0)     # Red
    glVertex3f( 1.0,  1.0, 1.0)
    glVertex3f(-1.0,  1.0, 1.0)
    glVertex3f(-1.0, -1.0, 1.0)
    glVertex3f( 1.0, -1.0, 1.0)
    glVertex3f( 1.0,  1.0, 1.0)
    glVertex3f(-1.0, -1.0, 1.0)

    # Back face (z = -1.0f)
    glColor3f(1.0, 1.0, 0.0)     # Yellow
    glVertex3f( 1.0, -1.0, -1.0)
    glVertex3f(-1.0, -1.0, -1.0)
    glVertex3f(-1.0,  1.0, -1.0)
    glVertex3f( 1.0,  1.0, -1.0)
    glVertex3f( 1.0, -1.0, -1.0)
    glVertex3f(-1.0,  1.0, -1.0)

    # Left face (x = -1.0f)
    glColor3f(0.0, 0.0, 1.0)     # Blue
    glVertex3f(-1.0,  1.0,  1.0)
    glVertex3f(-1.0,  1.0, -1.0)
    glVertex3f(-1.0, -1.0, -1.0)
    glVertex3f(-1.0, -1.0,  1.0)
    glVertex3f(-1.0,  1.0,  1.0)
    glVertex3f(-1.0, -1.0, -1.0)

    # Right face (x = 1.0f)
    glColor3f(1.0, 0.0, 1.0)    # Magenta
    glVertex3f(1.0,  1.0, -1.0)
    glVertex3f(1.0,  1.0,  1.0)
    glVertex3f(1.0, -1.0,  1.0)
    glVertex3f(1.0, -1.0, -1.0)
    glVertex3f(1.0,  1.0, -1.0)
    glVertex3f(1.0, -1.0,  1.0)

    glEnd()  # End of drawing

    window.GL_SwapWindow() # Swap the front and back frame buffers (double buffering)




const
    RELEASED    = 0
    PRESSED     = 1

let
    MAXFRAMERATE: uint32 = 20 # milli seconds

var
    frametime   :uint32
    evt         :TEvent
    runGame     :bool = true
    position    :float = 20
    key_state   :ptr array[0 .. SDL_NUM_SCANCODES.int, uint8]
    tmp         :cstring

# Framerate limiter
proc limitFramerate() =
    var now = GetTicks()
    if frametime > now:
        Delay(frametime - now)
    frametime = frametime + MAXFRAMERATE

#Initialize OpenGL
Init_OpenGL()

#### ERROR
tmp = cast[cstring](glGetString(GL_SHADING_LANGUAGE_VERSION))
echo(tmp)

# Main loop
while runGame:
    while PollEvent(evt):
        if evt.kind == QuitEvent:
            runGame = false
            break
        if evt.kind == WindowEvent:
            reshape(pos_x=0.0, pos_y=position)

    #Checking the keyboard state
    key_state = GetKeyboardState()
    if key_state[SDL_SCANCODE_UP.ord] == PRESSED:
        reshape(pos_x=0.0, pos_y=position)
        if position < 100:
            position += 1
    elif key_state[SDL_SCANCODE_DOWN.ord] == PRESSED:
        reshape(pos_x=0.0, pos_y=position)
        if position > 10:
            position -= 1
    elif key_state[SDL_SCANCODE_ESCAPE.ord] == PRESSED:
        rungame = false
    render()
    limitFramerate()

destroy window