"""
Utility to backfill channel titles/names inside the Qdrant payloads.

Usage:
    python -m python_app.sync_qdrant_channels \
        --batch-size 512 \
        --max-batches 200 \
        --dry-run
"""

from __future__ import annotations

import argparse
import logging
from typing import Dict, Iterable, List, Optional, Set, Tuple
import time

import requests

from .config import CONFIG
from .search_app import _ensure_client

LOGGER = logging.getLogger(__name__)


def chunked(iterable: Iterable, size: int):
    chunk: List = []
    for item in iterable:
        chunk.append(item)
        if len(chunk) >= size:
            yield chunk
            chunk = []
    if chunk:
        yield chunk


def resolve_channels(channel_ids: Iterable[str]) -> Dict[str, str]:
    client = _ensure_client(CONFIG)
    ids = list(set(channel_ids))
    if not ids:
        return {}
    body = {
        "size": len(ids) * 2,
        "_source": ["channel_id", "channel_name"],
        "query": {"terms": {"channel_id.keyword": ids}},
    }
    response = client.search(index=CONFIG.elastic.index, body=body)
    resolved: Dict[str, str] = {}
    for hit in response.get("hits", {}).get("hits", []):
        source = hit.get("_source") or {}
        cid = source.get("channel_id")
        cname = source.get("channel_name")
        if cid and cname and cid not in resolved:
            resolved[cid] = cname
    return resolved


def upsert_channel_payload(
    qdrant_url: str,
    collection: str,
    channel_id: str,
    channel_name: str,
    *,
    dry_run: bool = False,
) -> bool:
    """Set channel_name/channel_title for all vectors with this channel_id."""
    payload = {"channel_name": channel_name, "channel_title": channel_name}
    body = {
        "payload": payload,
        "filter": {"must": [{"key": "channel_id", "match": {"value": channel_id}}]},
    }
    LOGGER.info("Updating channel_id=%s -> %s", channel_id, channel_name)
    if dry_run:
        return True
    resp = requests.post(
        f"{qdrant_url}/collections/{collection}/points/payload",
        json=body,
        timeout=120,
    )
    if resp.status_code >= 400:
        LOGGER.error("Failed to update %s: %s", channel_id, resp.text)
        return False
    return True


def scroll_missing_payloads(
    qdrant_url: str,
    collection: str,
    batch_size: int,
    *,
    max_points: Optional[int] = None,
) -> Iterable[List[Tuple[str, Dict[str, any]]]]:
    """Yield batches of (point_id, payload) missing channel names."""
    fetched = 0
    next_page = None
    while True:
        current_limit = batch_size
        while True:
            body = {
                "limit": current_limit,
                "with_payload": True,
                "filter": {"must": [{"is_empty": {"key": "channel_name"}}]},
            }
            if next_page:
                body["offset"] = next_page
            try:
                resp = requests.post(
                    f"{qdrant_url}/collections/{collection}/points/scroll",
                    json=body,
                    timeout=120,
                )
                resp.raise_for_status()
                break
            except requests.HTTPError as exc:
                LOGGER.warning(
                    "Scroll request failed at limit=%s: %s", current_limit, exc
                )
                if current_limit <= 5:
                    raise
                current_limit = max(5, current_limit // 2)
                LOGGER.info("Reducing scroll batch size to %s", current_limit)
                time.sleep(2)
            except requests.RequestException as exc:  # type: ignore[attr-defined]
                LOGGER.warning("Transient scroll error: %s", exc)
                time.sleep(2)
        payload = resp.json().get("result", {})
        points = payload.get("points", [])
        if not points:
            break
        batch: List[Tuple[str, Dict[str, any]]] = []
        for point in points:
            pid = point.get("id")
            p_payload = point.get("payload") or {}
            batch.append((pid, p_payload))
        yield batch
        fetched += len(points)
        if max_points and fetched >= max_points:
            break
        next_page = payload.get("next_page_offset")
        if not next_page:
            break


def main() -> None:
    logging.basicConfig(level=logging.INFO, format="%(levelname)s %(message)s")
    parser = argparse.ArgumentParser(
        description="Backfill missing channel_name/channel_title in Qdrant payloads"
    )
    parser.add_argument("--batch-size", type=int, default=512)
    parser.add_argument(
        "--max-points",
        type=int,
        default=None,
        help="Limit processing to the first N points for testing",
    )
    parser.add_argument("--dry-run", action="store_true")
    args = parser.parse_args()

    q_url = CONFIG.qdrant_url
    collection = CONFIG.qdrant_collection
    total_updates = 0

    for batch in scroll_missing_payloads(
        q_url, collection, args.batch_size, max_points=args.max_points
    ):
        channel_ids: Set[str] = set()
        for _, payload in batch:
            cid = payload.get("channel_id")
            if cid:
                channel_ids.add(str(cid))
        if not channel_ids:
            continue
        resolved = resolve_channels(channel_ids)
        if not resolved:
            LOGGER.warning("No channel names resolved for ids: %s", channel_ids)
            continue
        for cid, name in resolved.items():
            if upsert_channel_payload(
                q_url, collection, cid, name, dry_run=args.dry_run
            ):
                total_updates += 1
        LOGGER.info("Updated %s channel payloads so far", total_updates)

    LOGGER.info("Finished. Total channel updates attempted: %s", total_updates)


if __name__ == "__main__":
    main()