import json
import hashlib


class CloudLedger:
    _blocks = []

    @classmethod
    def anchor(cls, data: dict) -> str:
        payload = json.dumps(data, sort_keys=True).encode("utf-8")
        anchor_id = hashlib.sha256(payload).hexdigest()
        cls._blocks.append({"anchor_id": anchor_id, "data": data})
        return anchor_id

    @classmethod
    def latest(cls):
        if not cls._blocks:
            return None
        return cls._blocks[-1]