"""Check serialized root entity IDs required for reproducible prefab replication."""
import re


def root_id(text):
    # Braces in resource strings and comments must not change object depth.
    tokens = re.findall(r'//[^\n]*|/\*[\s\S]*?\*/|"(?:\\.|[^"\\])*"|[{}]|\b\w+\b', text)
    tokens = [token for token in tokens if not token.startswith(('//', '/*'))]
    depth = 0
    identities = []
    for index, token in enumerate(tokens):
        if token == '{':
            depth += 1
        elif token == '}':
            depth -= 1
        elif token == 'ID' and depth == 1:
            identities.append(tokens[index + 1] if index + 1 < len(tokens) else '')
    if len(identities) != 1 or not re.fullmatch(r'"[A-F0-9]{16}"', identities[0]):
        raise ValueError('Prefab needs exactly one saved root entity ID')
    identity = identities[0][1:-1]
    if identity == '0000000000000000':
        raise ValueError('Prefab root entity ID must not be zero')
    return identity


def check_prefabs(paths):
    seen = {}
    for path in sorted(paths):
        try:
            identity = root_id(path.read_text())
        except ValueError as error:
            raise ValueError(f'{path}: {error}') from error
        if identity in seen:
            raise ValueError(f'Duplicate prefab root ID {identity}: {seen[identity]} and {path}')
        seen[identity] = path
    return len(seen)