import hashlib
import json
import time
from typing import List, Dict, Any

class Ledger:
    """Cadeia de registros imutável (Append-only Hash-chain)"""
    def __init__(self):
        self.chain: List[Dict[str, Any]] = []
        self._initialize_genesis()

    def _initialize_genesis(self):
        genesis_entry = {
            "index": 0,
            "timestamp": time.time(),
            "data": "Genesis Block - MatVerse Truth Engine",
            "previous_hash": "0" * 64
        }
        genesis_entry["hash"] = self._calculate_hash(genesis_entry)
        self.chain.append(genesis_entry)

    def _calculate_hash(self, entry: Dict[str, Any]) -> str:
        content = f"{entry['index']}{entry['timestamp']}{json.dumps(entry['data'])}{entry['previous_hash']}"
        return hashlib.sha256(content.encode()).hexdigest()

    def append(self, data: Any) -> str:
        previous_entry = self.chain[-1]
        new_entry = {
            "index": len(self.chain),
            "timestamp": time.time(),
            "data": data,
            "previous_hash": previous_entry["hash"]
        }
        new_entry["hash"] = self._calculate_hash(new_entry)
        self.chain.append(new_entry)
        return new_entry["hash"]

    def verify(self) -> bool:
        for i in range(1, len(self.chain)):
            current = self.chain[i]
            previous = self.chain[i-1]
            if current["previous_hash"] != previous["hash"]:
                return False
            if current["hash"] != self._calculate_hash(current):
                return False
        return True

    def get_last_hash(self) -> str:
        return self.chain[-1]["hash"]