"""PoC: prove that a non-headless Chromium under a virtual display (Xvfb) can
render a live/animated page and that we can capture it as frames.

This de-risks the hardest unknown of decision #1 (watch the real Discord screen
share by capturing a real client's rendered pixels) BEFORE touching Discord.

Run under a virtual display:

    xvfb-run -a --server-args="-screen 0 1280x720x24" \
        .venv/bin/python poc/capture_xvfb.py

Success = frames are non-blank AND change over time (proving live rendering +
capture actually work on this headless server).
"""

from __future__ import annotations

import hashlib
import pathlib
import sys
import time

from playwright.sync_api import sync_playwright

HERE = pathlib.Path(__file__).parent
PAGE = (HERE / "test_page.html").resolve()
OUT = HERE / "frames"
N = 6
INTERVAL = 0.4


def main() -> int:
    OUT.mkdir(exist_ok=True)
    hashes: list[str] = []
    sizes: list[int] = []

    with sync_playwright() as p:
        browser = p.chromium.launch(
            channel="chrome",  # use system google-chrome, no browser download
            headless=False,    # WebRTC/video needs a real (virtual) display
            args=["--no-sandbox", "--disable-gpu", "--autoplay-policy=no-user-gesture-required"],
        )
        page = browser.new_page(viewport={"width": 1280, "height": 720})
        page.goto(PAGE.as_uri())
        page.wait_for_timeout(500)

        for i in range(N):
            png = page.screenshot()  # captures the rendered virtual screen
            f = OUT / f"frame_{i:02d}.png"
            f.write_bytes(png)
            h = hashlib.sha256(png).hexdigest()[:12]
            hashes.append(h)
            sizes.append(len(png))
            print(f"  frame {i}: {len(png):>7} bytes  sha={h}")
            time.sleep(INTERVAL)

        browser.close()

    distinct = len(set(hashes))
    min_size = min(sizes)
    print(f"\n{N} frames, {distinct} distinct, min size {min_size} bytes")

    # A blank/black 1280x720 PNG compresses to a few KB; a real rendered scene is
    # much larger. Require non-trivial size and that the scene actually moved.
    ok_nonblank = min_size > 8_000
    ok_changing = distinct >= 3
    if ok_nonblank and ok_changing:
        print("PoC PASS: Xvfb + Chromium rendered a live scene and we captured changing, non-blank frames.")
        return 0
    print(f"PoC FAIL: nonblank={ok_nonblank} changing={ok_changing}")
    return 1


if __name__ == "__main__":
    sys.exit(main())