#!/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_label = "mp4v"
fourcc = cv.VideoWriter_fourcc(*fourcc_label)

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):
    frame = np.zeros((height, width, 3), dtype=np.uint8)
    frame[:] = (34, 42, 58)

    progress = index / max(frame_count - 1, 1)
    center_x = int(70 + progress * (width - 140))
    center_y = height // 2
    color = (40, 180 + index % 60, 245)

    cv.circle(frame, (center_x, center_y), 42, color, -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,
    )
    cv.putText(
        frame,
        "OpenCV VideoWriter",
        (36, height - 34),
        cv.FONT_HERSHEY_SIMPLEX,
        0.85,
        (215, 230, 255),
        2,
        cv.LINE_AA,
    )

    writer.write(frame)

writer.release()

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

saved_frames = int(capture.get(cv.CAP_PROP_FRAME_COUNT))
saved_fps = capture.get(cv.CAP_PROP_FPS)
saved_width = int(capture.get(cv.CAP_PROP_FRAME_WIDTH))
saved_height = int(capture.get(cv.CAP_PROP_FRAME_HEIGHT))
ok, first_frame = capture.read()
capture.release()

if not ok or first_frame is None:
    raise SystemExit(f"Could not read first frame from: {output_path}")

size_kib = output_path.stat().st_size / 1024

print(f"wrote: {output_path}")
print(f"fourcc: {fourcc_label}")
print(f"frames written: {frame_count}")
print(f"frames read back: {saved_frames}")
print(f"fps: {saved_fps:.1f}")
print(f"size: {saved_width}x{saved_height}")
print(f"first frame: {first_frame.shape[1]}x{first_frame.shape[0]}x{first_frame.shape[2]}")
print(f"file size: {size_kib:.1f} KiB")