"""Review business logic."""
from sqlalchemy.exc import IntegrityError
from app.extensions import db
from app.models.review import Review


class ReviewError(ValueError):
    pass


def create_review(listing, author, rating: int, body: str | None = None):
    """Leave a review for a seller. Listing must be sold. Returns Review."""
    from app.models.enums import ListingStatus
    if listing.status != ListingStatus.sold:
        raise ReviewError("can only review sold listings")
    if listing.user_id == author.id:
        raise ReviewError("cannot review your own listing")
    if rating not in range(1, 6):
        raise ReviewError("rating must be 1–5")

    review = Review(
        listing_id=listing.id,
        author_id=author.id,
        seller_id=listing.user_id,
        rating=rating,
        body=(body or "").strip() or None,
    )
    db.session.add(review)
    try:
        db.session.commit()
    except IntegrityError:
        db.session.rollback()
        raise ReviewError("you have already reviewed this listing")
    return review


def seller_rating(user_id) -> dict:
    """Return avg rating and count for a seller."""
    from app.extensions import db
    result = (db.session.query(
        db.func.round(db.func.avg(Review.rating), 1).label("avg"),
        db.func.count(Review.id).label("count"))
        .filter(Review.seller_id == user_id)
        .first())
    return {
        "avg": float(result.avg) if result.avg else None,
        "count": result.count or 0,
    }