import os
import hashlib
import json
from cryptography.hazmat.primitives.asymmetric import ed25519
from cryptography.hazmat.primitives import serialization
from typing import Dict, Any

class BifrostBridge:
    """
    Bifrost Bridge: The secure signing layer for the Akasha Subchain.
    Utilizes Ed25519 (to match Bifrost's Rust dalek implementation).
    """
    def __init__(self, key_path: str = "bifrost_node.key"):
        self.key_path = key_path
        self.private_key, self.public_key = self._load_or_generate_keys()

    def _load_or_generate_keys(self):
        if os.path.exists(self.key_path):
            with open(self.key_path, "rb") as f:
                private_bytes = f.read()
            private_key = ed25519.Ed25519PrivateKey.from_private_bytes(private_bytes)
        else:
            private_key = ed25519.Ed25519PrivateKey.generate()
            private_bytes = private_key.private_bytes(
                encoding=serialization.Encoding.Raw,
                format=serialization.PrivateFormat.Raw,
                encryption_algorithm=serialization.NoEncryption()
            )
            with open(self.key_path, "wb") as f:
                f.write(private_bytes)
        
        public_key = private_key.public_key()
        return private_key, public_key

    def get_public_key_hex(self) -> str:
        public_bytes = self.public_key.public_bytes(
            encoding=serialization.Encoding.Raw,
            format=serialization.PublicFormat.Raw
        )
        return public_bytes.hex()

    def sign_batch(self, batch_metadata: Dict[str, Any]) -> str:
        """
        Signs the batch metadata to create a Bifrost-Verified NanoBatch.
        Matches the message format in bifrost/src/nanochain.rs
        """
        # Canonical message format: nanochain_id + batch_index + merkle_root
        msg = f"{batch_metadata['nanochain_id']}{batch_metadata['batch_index']}{batch_metadata['root']}".encode('utf-8')
        signature = self.private_key.sign(msg)
        
        # Simulated Post-Quantum Layer (Spy-Level Security)
        # In a real PQ scenario, we would also sign with Kyber/Dilithium
        pq_sim_hash = hashlib.sha3_512(signature + b"PQ_SALT").hexdigest()
        
        return f"{signature.hex()}:{pq_sim_hash[:32]}"

    def encrypt_artifact(self, content: str) -> str:
        """
        Simulates the Zero-Trust encryption from the Bifrost core.
        In production, this would use ChaCha20Poly1305.
        """
        # Placeholder for Chacha20Poly1305 from cryptography.hazmat
        return hashlib.sha256(content.encode()).hexdigest() # Mocked
