#!/usr/bin/env python3
from pathlib import Path

import cv2 as cv
import numpy as np


output_path = Path("output/generated-motion.mp4")
width, height = 640, 360
fps = 24.0
frame_count = 72
fourcc = cv.VideoWriter_fourcc(*"mp4v")


def make_frame(index):
    frame = np.full((height, width, 3), (34, 42, 58), dtype=np.uint8)
    progress = index / max(frame_count - 1, 1)
    center = (int(70 + progress * (width - 140)), height // 2)

    cv.circle(frame, center, 42, (40, 210, 245), -1)
    cv.putText(
        frame,
        f"Frame {index + 1:02d}/{frame_count}",
        (36, 62),
        cv.FONT_HERSHEY_SIMPLEX,
        1.1,
        (245, 245, 245),
        2,
        cv.LINE_AA,
    )
    return frame


output_path.parent.mkdir(parents=True, exist_ok=True)
writer = cv.VideoWriter(str(output_path), fourcc, fps, (width, height))

if not writer.isOpened():
    raise SystemExit(f"Could not open VideoWriter for: {output_path}")

for index in range(frame_count):
    writer.write(make_frame(index))

writer.release()

capture = cv.VideoCapture(str(output_path))
if not capture.isOpened():
    raise SystemExit(f"Could not reopen video: {output_path}")

decoded_width = int(capture.get(cv.CAP_PROP_FRAME_WIDTH))
decoded_height = int(capture.get(cv.CAP_PROP_FRAME_HEIGHT))
decoded_fps = capture.get(cv.CAP_PROP_FPS)
decoded_frames = 0

while True:
    ok, frame = capture.read()
    if not ok:
        break
    decoded_frames += 1

capture.release()

if decoded_frames != frame_count:
    raise SystemExit(f"Decoded {decoded_frames} of {frame_count} frames")
if (decoded_width, decoded_height) != (width, height):
    raise SystemExit(
        f"Decoded size {decoded_width}x{decoded_height}, expected {width}x{height}"
    )
if abs(decoded_fps - fps) > 0.01:
    raise SystemExit(f"Decoded FPS {decoded_fps:.2f}, expected {fps:.2f}")

print(f"wrote: {output_path}")
print(f"frames decoded: {decoded_frames}/{frame_count}")
print(f"fps decoded: {decoded_fps:.1f}")
print(f"size decoded: {decoded_width}x{decoded_height}")