from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *

class Transition:
    def draw(self, texture_prev, texture_next, window_width, window_height, delta_time, transition_time, transition_duration):
        # Update alpha value for fade effect
        alpha = transition_time / transition_duration
        if alpha > 1.0:
            alpha = 1.0

        # Draw the first image
        self._draw_image(texture_prev, 3840, 2160, window_width, window_height, 1 - alpha)  # TODO instead of decreasing alpha, draw transparent letterboxes
        # Draw the second image (with transparency)
        self._draw_image(texture_next, 3840, 2160, window_width, window_height, alpha)

        return alpha >= 1.0  # Complete



    # Draw the image with blending enabled (to allow fade effect)
    def _draw_image(self, texture_id, img_width, img_height, window_width, window_height, alpha):
        if (not alpha): return

        glEnable(GL_BLEND)
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
        glBindTexture(GL_TEXTURE_2D, texture_id)
        glColor4f(1.0, 1.0, 1.0, alpha)  # Set alpha to control transparency

        # Calculate aspect ratio
        img_aspect = img_width / float(img_height)
        win_aspect = window_width / float(window_height)

        scaled_width = window_width
        scaled_height = window_height

        # Scale the image to fit inside the window while maintaining aspect ratio
        if img_aspect > win_aspect:
            # Image is wider than window, letterbox vertically
            scaled_height = window_width / img_aspect
        else:
            # Image is taller than window, letterbox horizontally
            scaled_width = window_height * img_aspect

        # Position the image so it is centered
        offset_x = (window_width - scaled_width) / 2
        offset_y = (window_height - scaled_height) / 2

        # Normalize coordinates to range from -1 to 1
        x1 = (offset_x / window_width ) * 2 - 1
        y1 = (offset_y / window_height) * 2 - 1
        x2 = ((offset_x + scaled_width ) / window_width ) * 2 - 1
        y2 = ((offset_y + scaled_height) / window_height) * 2 - 1

        # Draw the image in the center with scaling
        glBegin(GL_QUADS)
        glTexCoord2f(0, 0)
        glVertex2f(x1, y1)
        glTexCoord2f(1, 0)
        glVertex2f(x2, y1)
        glTexCoord2f(1, 1)
        glVertex2f(x2, y2)
        glTexCoord2f(0, 1)
        glVertex2f(x1, y2)
        glEnd()

        glDisable(GL_BLEND)