"""Fetch a hash-pinned independent LGPL reference from its named upstream.

The public teaching package contains our caller, not a copy of this library.
"""
from pathlib import Path
import argparse
import hashlib
import json
import urllib.parse
import urllib.request


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--manifest', type=Path, default=Path(__file__).with_name('reference-sources.json'))
    parser.add_argument('--output', type=Path, required=True)
    arguments = parser.parse_args()
    manifest = json.loads(arguments.manifest.read_text())
    arguments.output.mkdir(parents=True, exist_ok=True)
    receipt = {'commit': manifest['commit'], 'license': 'LGPL-3.0, retained in downloaded LICENSE', 'files': []}
    for item in manifest['files']:
        if item['path'] == 'setup.py':
            continue
        url = urllib.parse.urlsplit(item['url'])
        if url.scheme != 'https' or url.hostname != 'raw.githubusercontent.com' or not url.path.startswith('/valboz/VBBinaryLensing/' + manifest['commit'] + '/'):
            raise ValueError('Unexpected reference origin')
        destination = arguments.output / Path(item['path']).name
        mode = 'verified local cache; no HTTP'
        status = None
        if destination.exists():
            data = destination.read_bytes()
        else:
            request = urllib.request.Request(item['url'], headers={'User-Agent': 'SandboxPhysics-Public-Tutorial/1.0'})
            with urllib.request.urlopen(request, timeout=30) as response:
                status = response.status
                if status != 200:
                    raise ValueError('Unexpected reference response')
                data = response.read(item['bytes'] + 1)
            mode = 'anonymous upstream HTTP'
        if len(data) != item['bytes'] or hashlib.sha256(data).hexdigest() != item['sha256']:
            raise ValueError('Reference changed; refuse silently updated input: ' + item['path'])
        if not destination.exists():
            destination.write_bytes(data)
        receipt['files'].append({'name': destination.name, 'url': item['url'], 'mode': mode, 'status': status, 'bytes': len(data), 'sha256': item['sha256']})
    (arguments.output / 'download-receipt.json').write_text(json.dumps(receipt, indent=2) + '\n')
    print('PASS:', len(receipt['files']), 'hash-pinned independent reference files')


if __name__ == '__main__': main()