import asyncio
import logging
import xml.etree.ElementTree as ET
from pathlib import PurePosixPath
from urllib.parse import unquote

import httpx
from fastapi import APIRouter, BackgroundTasks, Header, HTTPException, status
from pydantic import BaseModel, Field

from app.config import get_settings
from app.ingest.extractors import SUPPORTED_TYPES
from app.ingest.pipeline import process_file
from app.webhook.auth import verify_secret
from app.webhook.models import EventType


logger = logging.getLogger(__name__)
router = APIRouter()


# Limits parallel pipeline execution during a bulk import so we don't
# saturate Ollama/WebDAV with thousands of concurrent requests.
BULK_CONCURRENCY = 4
_bulk_semaphore = asyncio.Semaphore(BULK_CONCURRENCY)

# Amplification guard: one /bulk-import dispatches one BackgroundTask per
# matching file with no upper bound. Repeated calls (a misfiring Nextcloud
# flow, or an attacker holding the secret) would pile unbounded tasks. We
# track outstanding dispatched work and reject a new bulk while any is
# still draining — bulk runs are rare, so serialising them is acceptable.
_inflight = 0


async def _process_with_semaphore(file_path: str, event_type: EventType) -> None:
    global _inflight
    try:
        async with _bulk_semaphore:
            await process_file(file_path, event_type)
    finally:
        _inflight -= 1


class BulkRequest(BaseModel):
    path: str = Field(min_length=1)


PROPFIND_BODY = """<?xml version="1.0"?>
<d:propfind xmlns:d="DAV:"><d:prop><d:resourcetype/></d:prop></d:propfind>
"""

DAV_NS = {"d": "DAV:"}


async def list_files_recursive(base_url: str, user: str, password: str, path: str) -> list[str]:
    """PROPFIND with Depth: infinity. Returns relative file paths (no folders)."""
    base = base_url.rstrip("/")
    rel = path.strip("/")
    url = f"{base}/{rel}"

    async with httpx.AsyncClient(auth=(user, password), timeout=120.0) as client:
        response = await client.request(
            "PROPFIND",
            url,
            headers={"Depth": "infinity", "Content-Type": "application/xml"},
            content=PROPFIND_BODY,
        )
    if response.status_code not in (200, 207):
        raise RuntimeError(f"PROPFIND failed: status={response.status_code}")

    root = ET.fromstring(response.text)
    base_path_segment = PurePosixPath(httpx.URL(base).path).as_posix()  # "/remote.php/dav/files/u"
    out: list[str] = []
    for resp in root.findall("d:response", DAV_NS):
        href = resp.findtext("d:href", default="", namespaces=DAV_NS)
        decoded = unquote(href)
        # Strip the WebDAV base prefix → leaves "Documents/.../file.pdf"
        if decoded.startswith(base_path_segment):
            decoded = decoded[len(base_path_segment):]
        decoded = decoded.lstrip("/")
        if not decoded or decoded.endswith("/"):
            continue
        # Skip directory entries (those have <d:collection/> resourcetype)
        rt = resp.find("d:propstat/d:prop/d:resourcetype/d:collection", DAV_NS)
        if rt is not None:
            continue
        out.append(decoded)
    return out


@router.post("/bulk-import", status_code=status.HTTP_202_ACCEPTED)
async def bulk_import(
    body: BulkRequest,
    background: BackgroundTasks,
    x_webhook_secret: str | None = Header(default=None),
):
    global _inflight
    settings = get_settings()
    verify_secret(x_webhook_secret, settings.webhook_secret)

    if _inflight > 0:
        logger.warning(
            "bulk rejected: import already in progress",
            extra={"event": "bulk_rejected", "path": body.path, "inflight": _inflight},
        )
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail="a bulk import is already in progress",
        )

    try:
        files = await list_files_recursive(
            settings.nextcloud_webdav_url,
            settings.nextcloud_user,
            settings.nextcloud_app_password,
            body.path,
        )
    except (RuntimeError, httpx.HTTPError, ET.ParseError) as exc:
        logger.exception(
            "bulk listing failed",
            extra={"event": "bulk_listing_failed", "path": body.path, "error": str(exc)},
        )
        raise HTTPException(status_code=502, detail="webdav listing failed") from exc

    dispatched = 0
    for f in files:
        ext = PurePosixPath(f).suffix.lstrip(".").lower()
        if ext not in SUPPORTED_TYPES:
            continue
        _inflight += 1
        background.add_task(_process_with_semaphore, f, EventType.CREATED)
        dispatched += 1

    logger.info(
        "bulk dispatch",
        extra={"event": "bulk_dispatch", "path": body.path, "dispatched": dispatched, "total_listed": len(files)},
    )
    return {"status": "accepted", "dispatched": dispatched}