"""
MeshBay Node — QUIC chunk client (MNP v2).

Drop-in replacement for ChunkClient with QUIC/UDP transport.
Same application-layer protocol: MNP handshake → stream requests.

Node identity verified via Ed25519 PK from hub (not TLS cert chain).
TLS cert is self-signed; we use CERT_NONE equivalent in QUIC config.
"""

import asyncio
import base64
import logging
import struct
from pathlib import Path

import blake3
import jwt
import msgpack
from aioquic.asyncio import connect, QuicConnectionProtocol
from aioquic.quic.configuration import QuicConfiguration
from aioquic.quic.events import QuicEvent, StreamDataReceived
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PublicKey

from meshbay_common import MNP_VERSION
from meshbay_common.crypto import (
    chunk_key as derive_chunk_key,
    decrypt_chunk,
    verify_chunk_signature,
)
from meshbay_common.protocol import MNP

log = logging.getLogger(__name__)

ALPN    = ["meshbay-mnp"]
MAX_MSG = 64 * 1024 * 1024


# ── Client-side protocol ──────────────────────────────────────────────────────

class _MNPClientProtocol(QuicConnectionProtocol):
    """
    Client-side QUIC protocol.
    Uses per-stream asyncio.Queue for received messages — no race conditions.
    """

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._bufs:   dict[int, bytearray]    = {}
        self._queues: dict[int, asyncio.Queue] = {}

    def _queue_for(self, stream_id: int) -> asyncio.Queue:
        if stream_id not in self._queues:
            self._queues[stream_id] = asyncio.Queue()
            self._bufs[stream_id]   = bytearray()
        return self._queues[stream_id]

    def quic_event_received(self, event: QuicEvent) -> None:
        if isinstance(event, StreamDataReceived):
            sid = event.stream_id
            q   = self._queue_for(sid)
            self._bufs[sid].extend(event.data)
            buf = self._bufs[sid]
            while len(buf) >= 4:
                length = struct.unpack(">I", buf[:4])[0]
                if length > MAX_MSG:
                    raise ValueError(f"Message too large: {length}")
                if len(buf) < 4 + length:
                    break
                msg_bytes = bytes(buf[4:4 + length])
                del buf[:4 + length]
                q.put_nowait(msgpack.unpackb(msg_bytes, raw=False))

    async def _recv(self, stream_id: int, timeout: float = 10.0) -> dict:
        q = self._queue_for(stream_id)
        return await asyncio.wait_for(q.get(), timeout=timeout)

    def _send(self, stream_id: int, obj: dict) -> None:
        data = msgpack.packb(obj, use_bin_type=True)
        payload = struct.pack(">I", len(data)) + data
        self._quic.send_stream_data(stream_id, payload)
        self.transmit()


# ── QuicChunkClient ───────────────────────────────────────────────────────────

class QuicChunkClient:
    """
    QUIC-based MNP client. Drop-in replacement for ChunkClient.

    Usage:
        async with QuicChunkClient(host, port, token, gek, pk_node_b64) as client:
            data = await client.fetch_chunk(file_id, chunk_index=0)
    """

    def __init__(
        self,
        host: str,
        port: int,
        jwt_token: str,
        gek: bytes,
        pk_node_b64: str,
    ):
        self._host      = host
        self._port      = port
        self._jwt_token = jwt_token
        self._gek       = gek
        self._pk_node   = Ed25519PublicKey.from_public_bytes(
            base64.b64decode(pk_node_b64))
        self._proto: _MNPClientProtocol | None = None
        self._cm        = None
        self._ctrl_stream = 0   # stream 0 = control/handshake

    async def __aenter__(self):
        await self.connect()
        return self

    async def __aexit__(self, *_):
        await self.close()

    async def connect(self) -> None:
        import ssl
        config = QuicConfiguration(
            is_client=True,
            alpn_protocols=ALPN,
            verify_mode=ssl.CERT_NONE,  # identity verified via Ed25519 at MNP layer
        )
        self._cm = connect(
            self._host, self._port,
            configuration=config,
            create_protocol=_MNPClientProtocol,
        )
        self._proto = await self._cm.__aenter__()

        # MNP handshake on stream 0
        self._proto._send(self._ctrl_stream, {
            "type":  MNP.HANDSHAKE,
            "v":     MNP_VERSION,
            "token": self._jwt_token,
        })
        ack = await self._proto._recv(self._ctrl_stream)
        if ack.get("type") != MNP.HANDSHAKE_ACK:
            raise ConnectionError(f"QUIC handshake rejected: {ack}")
        log.debug("QUIC connected to %s:%d", self._host, self._port)

    async def close(self) -> None:
        if self._cm:
            await self._cm.__aexit__(None, None, None)
            self._cm = None
            self._proto = None

    def _new_stream(self) -> int:
        """Open a new bidirectional QUIC stream for a request."""
        stream_id = self._proto._quic.get_next_available_stream_id(is_unidirectional=False)
        return stream_id

    async def fetch_index(self) -> bytes:
        """Request the Mesh Group Index."""
        sid = self._new_stream()
        self._proto._send(sid, {"type": MNP.INDEX_SYNC, "v": MNP_VERSION})
        msg = await self._proto._recv(sid)
        return base64.b64decode(msg["index_b64"])

    async def fetch_chunk(self, file_id: str, chunk_index: int) -> bytes:
        """Fetch, verify, and decrypt one chunk over QUIC."""
        sid = self._new_stream()
        self._proto._send(sid, {
            "type":        MNP.FILE_REQUEST,
            "v":           MNP_VERSION,
            "file_id":     file_id,
            "chunk_index": chunk_index,
        })
        msg = await self._proto._recv(sid, timeout=30.0)

        if msg.get("type") == "error":
            raise LookupError(msg.get("detail", "Unknown error"))

        ct        = base64.b64decode(msg["ct_b64"])
        nonce     = base64.b64decode(msg["nonce_b64"])
        ct_hash   = base64.b64decode(msg["ct_hash_b64"])
        pt_hash   = base64.b64decode(msg["pt_hash_b64"])
        sig       = base64.b64decode(msg["sig_b64"])
        file_hash = base64.b64decode(msg["file_hash_b64"])
        ci        = msg["chunk_index"]

        verify_chunk_signature(self._pk_node, ci, nonce, ct_hash, sig)

        if blake3.blake3(ct).digest() != ct_hash:
            raise ValueError("Ciphertext hash mismatch")

        ckey      = derive_chunk_key(self._gek, file_hash, ci)
        plaintext = decrypt_chunk(ckey, nonce, ct)

        if blake3.blake3(plaintext).digest() != pt_hash:
            raise ValueError("Plaintext hash mismatch after decryption")

        return plaintext