"""Outbound relay bridge for NAT-safe node HTTP requests."""

from __future__ import annotations

import base64
import json
import logging
import os
import threading
import time
import urllib.error
import urllib.request
from concurrent.futures import ThreadPoolExecutor
from dataclasses import dataclass

log = logging.getLogger(__name__)

DEFAULT_MAX_CONCURRENCY = 8


@dataclass(frozen=True)
class RelayBridgeInfo:
    peer_id: str
    relay_addr: str


def _make_envelope(topic: str, payload: dict, peer_id: str) -> dict:
    return {
        "topic": topic,
        "version": 1,
        "from_peer": peer_id,
        "timestamp": time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime()),
        "msg_id": f"{peer_id}-{time.time_ns():x}",
        "ttl": 1,
        "payload": payload,
    }


def _max_concurrency_from_env() -> int:
    try:
        value = int(os.environ.get("MESHNET_RELAY_CONCURRENCY", DEFAULT_MAX_CONCURRENCY))
    except (TypeError, ValueError):
        return DEFAULT_MAX_CONCURRENCY
    return max(1, value)


class RelayHttpBridge:
    """Connect outbound to a relay and proxy relay HTTP requests to localhost.

    Requests are dispatched on a bounded worker pool (US-037) so a node that is
    the head of one route can still serve per-token ``/forward`` hops of another.
    Streaming responses (``text/event-stream``) are forwarded as multiple chunk
    frames sharing one ``request_id`` (US-036); everything else stays a single
    frame for backward compatibility.
    """

    def __init__(
        self,
        relay_url: str,
        peer_id: str,
        local_base_url: str,
        advertised_addr: str,
        reconnect_interval: float = 3.0,
        max_concurrency: int | None = None,
    ) -> None:
        self.relay_url = relay_url.rstrip("/")
        self.peer_id = peer_id
        self.local_base_url = local_base_url.rstrip("/")
        self.advertised_addr = advertised_addr
        self.reconnect_interval = reconnect_interval
        self.max_concurrency = max(1, max_concurrency) if max_concurrency else _max_concurrency_from_env()
        self._running = False
        self._thread: threading.Thread | None = None
        self._connected = threading.Event()
        self._executor: ThreadPoolExecutor | None = None
        self._send_lock = threading.Lock()
        self._ws = None

    @property
    def relay_addr(self) -> str:
        base = self.relay_url
        if base.endswith("/ws"):
            base = base[:-3]
        return f"{base}/rpc/{self.peer_id}"

    def start(self) -> RelayBridgeInfo:
        self._running = True
        self._executor = ThreadPoolExecutor(
            max_workers=self.max_concurrency, thread_name_prefix="relay-http-worker"
        )
        self._thread = threading.Thread(target=self._run, daemon=True, name="relay-http-bridge")
        self._thread.start()
        return RelayBridgeInfo(peer_id=self.peer_id, relay_addr=self.relay_addr)

    def wait_connected(self, timeout: float = 5.0) -> bool:
        return self._connected.wait(timeout)

    def stop(self) -> None:
        self._running = False
        if self._thread:
            self._thread.join(timeout=3.0)
        if self._executor is not None:
            self._executor.shutdown(wait=False)

    def _run(self) -> None:
        import websockets.sync.client as wsc  # type: ignore[import]

        while self._running:
            try:
                with wsc.connect(self.relay_url, open_timeout=5) as ws:
                    self._ws = ws
                    self._connected.set()
                    ws.send(json.dumps(_make_envelope(
                        "peer-register",
                        {"peer_id": self.peer_id, "addr": self.advertised_addr},
                        self.peer_id,
                    )))
                    while self._running:
                        try:
                            raw = ws.recv(timeout=1)
                        except TimeoutError:
                            continue
                        try:
                            envelope = json.loads(raw)
                        except (TypeError, json.JSONDecodeError):
                            continue
                        if envelope.get("topic") != "relay-http-request":
                            continue
                        payload = envelope.get("payload", {})
                        if payload.get("target_peer") not in {None, self.peer_id}:
                            continue
                        if self._executor is None:
                            break
                        self._executor.submit(self._process_request, payload)
            except Exception as exc:
                self._connected.clear()
                self._ws = None
                if self._running:
                    log.debug("relay bridge disconnected: %s", exc)
                    time.sleep(self.reconnect_interval)
        self._ws = None

    def _send_response_frame(self, payload: dict) -> bool:
        """Send one relay-http-response frame; False if the socket is gone.

        The lock is held per frame so concurrent workers interleave whole
        frames on the shared WebSocket, never torn ones.
        """
        ws = self._ws
        if ws is None:
            return False
        message = json.dumps(_make_envelope("relay-http-response", payload, self.peer_id))
        try:
            with self._send_lock:
                ws.send(message)
            return True
        except Exception as exc:
            log.debug("relay bridge send failed (request orphaned): %s", exc)
            return False

    def _process_request(self, payload: dict) -> None:
        request_id = str(payload.get("request_id") or "")
        method = str(payload.get("method") or "POST").upper()
        path = str(payload.get("path") or "/")
        headers = payload.get("headers") if isinstance(payload.get("headers"), dict) else {}

        req_suffix = f" request_id={request_id}" if request_id else ""
        print(f"  [node] relay {method} {path}{req_suffix}", flush=True)

        # body_base64 carries binary data (e.g. bfloat16 activation tensors) safely.
        # Fallback to text "body" for backward-compat with non-binary requests.
        body_b64 = payload.get("body_base64")
        if body_b64:
            data = base64.b64decode(body_b64)
        else:
            body_text = payload.get("body") or ""
            data = body_text.encode() if isinstance(body_text, str) else bytes(body_text)

        url = f"{self.local_base_url}{path}"
        req = urllib.request.Request(url, data=data, headers=headers, method=method)
        try:
            with urllib.request.urlopen(req, timeout=300.0) as resp:
                resp_headers = dict(resp.headers)
                content_type = resp.headers.get("Content-Type", "")
                if "text/event-stream" in content_type:
                    self._stream_response(request_id, resp, resp_headers)
                    return
                resp_bytes = resp.read()
                # Forward all X-Meshnet-* headers so the caller can reconstruct the activation.
                is_binary = "octet-stream" in content_type
                result: dict = {
                    "request_id": request_id,
                    "status": resp.status,
                    "headers": resp_headers,
                }
                if is_binary:
                    result["body_base64"] = base64.b64encode(resp_bytes).decode()
                else:
                    result["body"] = resp_bytes.decode(errors="replace")
                self._send_response_frame(result)
        except urllib.error.HTTPError as exc:
            self._send_response_frame({
                "request_id": request_id,
                "status": exc.code,
                "headers": {"Content-Type": exc.headers.get("Content-Type", "application/json")},
                "body": exc.read().decode(errors="replace"),
            })
        except Exception as exc:
            self._send_response_frame({
                "request_id": request_id,
                "status": 503,
                "headers": {"Content-Type": "application/json"},
                "body": json.dumps({"error": f"relay bridge local request failed: {exc}"}),
            })

    def _stream_response(self, request_id: str, resp, resp_headers: dict) -> None:
        """Forward an SSE response as chunk frames, one per complete SSE event.

        Frame order: header frame (status + headers), chunk frames, done frame.
        A receiver that sees no ``stream`` key treats the frame as a complete
        legacy response, so non-streaming peers are unaffected.
        """
        sent = self._send_response_frame({
            "request_id": request_id,
            "status": resp.status,
            "headers": resp_headers,
            "stream": True,
            "done": False,
        })
        if not sent:
            return
        event_lines: list[str] = []
        for raw_line in resp:
            line = raw_line.decode(errors="replace")
            event_lines.append(line)
            if line.strip():
                continue
            # Blank line terminates one SSE event — flush it as a frame.
            if not self._send_response_frame({
                "request_id": request_id,
                "stream": True,
                "chunk": "".join(event_lines),
                "done": False,
            }):
                return
            event_lines = []
        if event_lines:
            if not self._send_response_frame({
                "request_id": request_id,
                "stream": True,
                "chunk": "".join(event_lines),
                "done": False,
            }):
                return
        self._send_response_frame({
            "request_id": request_id,
            "stream": True,
            "done": True,
        })


def peer_id_from_wallet(wallet_address: str) -> str:
    return wallet_address[:16] if len(wallet_address) >= 16 else wallet_address