"""Verify actual rendered stages in the synthetic long-trial recordings.

Copies of H.264 packets alone are insufficient evidence that clients saw a
retry slate or a recovered channel. Compare decoded text pixels, not file names.
"""
import argparse
import json
from pathlib import Path
import subprocess


def pixels(ffmpeg, path, second=0):
    command = [ffmpeg, '-hide_banner', '-loglevel', 'error', '-nostdin', '-threads', '1', '-filter_threads', '1',
               '-ss', str(second), '-i', str(path), '-frames:v', '1', '-vf',
               'crop=1920:260:0:430,scale=640:86:flags=area', '-pix_fmt', 'gray', '-f', 'rawvideo', 'pipe:1']
    output = subprocess.run(command, capture_output=True, check=True, timeout=20).stdout
    if len(output) != 640 * 86:
        raise RuntimeError('Incomplete video frame')
    return output


def difference(first, second):
    return sum(abs(a-b) for a, b in zip(first, second)) / len(first)


def verify(root, ffmpeg):
    result = json.loads((root / 'result.json').read_text())
    if result['FailureSeconds'] != 75:
        raise ValueError('Use the long trial with the documented stage times')
    errors = {}
    for language in ('pl', 'en'):
        waiting = pixels(ffmpeg, root / (language + '-waiting-slate.ts'))
        retrying = pixels(ffmpeg, root / (language + '-retrying-slate.ts'))
        observed_waiting = pixels(ffmpeg, root / (language + '.mkv'), 1)
        observed_retrying = pixels(ffmpeg, root / (language + '.mkv'), 70)
        live = pixels(ffmpeg, root / (language + '.mkv'), 39)
        recovered = pixels(ffmpeg, root / (language + '.mkv'), 140)
        metrics = {'waiting_error': difference(waiting, observed_waiting),
                   'retrying_error': difference(retrying, observed_retrying),
                   'live_difference': difference(retrying, live),
                   'recovered_difference': difference(retrying, recovered)}
        assert metrics['waiting_error'] < 0.5 and metrics['retrying_error'] < 0.5, metrics
        assert metrics['live_difference'] > 15 and metrics['recovered_difference'] > 15, metrics
        other = 'en' if language == 'pl' else 'pl'
        assert difference(observed_retrying, pixels(ffmpeg, root / (other + '-retrying-slate.ts'))) > 2
        errors[language] = {key: round(value, 4) for key, value in metrics.items()}
    result.update(RenderedWaitingVerified=True, RenderedRetryingVerified=True, RenderedLiveRecoveryVerified=True,
                  RenderedPerViewerLanguageVerified=True, VisualErrorMetrics=errors)
    (root / 'result.json').write_text(json.dumps(result, indent=2) + '\n')
    print(json.dumps({'rendered_stages_verified': True, 'metrics': errors}))


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--output', type=Path, required=True)
    parser.add_argument('--ffmpeg', default='/usr/lib/jellyfin-ffmpeg/ffmpeg')
    args = parser.parse_args()
    verify(args.output, args.ffmpeg)