"""Resolve pinned shared frame/backing assets without copying them into a card proof."""
from pathlib import Path
import hashlib, json
ROOT = Path(__file__).resolve().parent

def digest(path):
    return hashlib.sha256(Path(path).read_bytes()).hexdigest()

def load_tier(tier, version=None):
    index = json.loads((ROOT / 'manifest.json').read_text())
    entry = index['tiers'][tier]
    version = version or entry['selectedVersion']
    if version not in entry['versions']:
        raise ValueError(f'Unknown tier revision: {tier}/{version}')
    directory = ROOT / tier / version
    manifest = json.loads((directory / 'manifest.json').read_text())
    for relative, record in manifest['files'].items():
        path = directory / relative
        if not path.is_file() or digest(path) != record['sha256']:
            raise ValueError(f'Shared layer missing or changed: {tier}/{version}/{relative}')
    return {
        'tier': tier, 'version': version, 'directory': directory,
        'manifestSHA256': digest(directory / 'manifest.json'),
        'layout': json.loads((directory / 'layout.json').read_text()),
        'reviewStatus': manifest['reviewStatus'],
        'assets': {name: directory / relative for name, relative in manifest['assets'].items()},
    }