import datetime as dt
from collections import defaultdict

from sqlalchemy import select
from sqlalchemy.orm import Session

from .config import settings
from .models import Article
from .textutil import topic_label as _topic_label


def build_clusters(session: Session) -> list[dict]:
    cutoff = dt.datetime.utcnow() - dt.timedelta(hours=settings.article_window_hours)
    rows = session.execute(
        select(Article)
        .where(Article.cluster_key.is_not(None))
        .where(Article.published_at >= cutoff)
        .order_by(Article.published_at.desc())
    ).scalars().all()

    groups: dict[str, list[Article]] = defaultdict(list)
    for article in rows:
        groups[article.cluster_key].append(article)

    clusters = []
    for key, articles in groups.items():
        lat = sum(a.lat for a in articles) / len(articles)
        lon = sum(a.lon for a in articles) / len(articles)
        sources = sorted({a.source for a in articles})
        clusters.append(
            {
                "cluster_key": key,
                "lat": lat,
                "lon": lon,
                "location_name": articles[0].location_name,
                "country": articles[0].country,
                "article_count": len(articles),
                "source_count": len(sources),
                "sources": sources,
                "topic": _topic_label([a.title for a in articles]),
                "latest_published_at": max(a.published_at for a in articles).isoformat(),
                "headline": articles[0].title,
                "article_ids": [a.id for a in articles],
            }
        )

    clusters.sort(key=lambda c: c["article_count"], reverse=True)
    return clusters