"""
Proxy all /api/documents/* requests to doc-service:8001/documents/*.

Uses a module-level AsyncClient for connection pooling.
Strips hop-by-hop headers that must not be forwarded.
File downloads (/file endpoint) are streamed.
"""
import os

import httpx
from fastapi import APIRouter, Depends, HTTPException, Request
from fastapi.responses import StreamingResponse

from app.deps import get_current_user
from app.models.user import User

DOC_SERVICE_URL = os.environ.get("DOC_SERVICE_URL", "http://doc-service:8001")

# Module-level client — reused across requests for connection pooling
_client = httpx.AsyncClient(base_url=DOC_SERVICE_URL, timeout=120.0)

router = APIRouter()

_HOP_BY_HOP = frozenset(
    [
        "connection",
        "keep-alive",
        "proxy-authenticate",
        "proxy-authorization",
        "te",
        "trailers",
        "transfer-encoding",
        "upgrade",
        "host",
    ]
)


def _forward_headers(request: Request, user_id: str) -> dict:
    headers = {
        k: v
        for k, v in request.headers.items()
        if k.lower() not in _HOP_BY_HOP
    }
    headers["x-user-id"] = user_id
    return headers


@router.api_route("/{path:path}", methods=["GET", "POST", "PUT", "PATCH", "DELETE"])
async def proxy_documents(
    path: str,
    request: Request,
    current_user: User = Depends(get_current_user),
) -> StreamingResponse:
    url = f"/documents/{path}" if path else "/documents"
    headers = _forward_headers(request, str(current_user.id))

    # For multipart uploads, stream the body directly
    body = await request.body()

    try:
        response = await _client.request(
            method=request.method,
            url=url,
            headers=headers,
            content=body,
            params=dict(request.query_params),
        )
    except httpx.RequestError as exc:
        raise HTTPException(status_code=502, detail=f"doc-service unreachable: {exc}")

    # Strip hop-by-hop from response headers
    resp_headers = {
        k: v
        for k, v in response.headers.items()
        if k.lower() not in _HOP_BY_HOP
    }

    return StreamingResponse(
        content=iter([response.content]),
        status_code=response.status_code,
        headers=resp_headers,
        media_type=response.headers.get("content-type"),
    )