from datetime import date, timedelta

from fastapi import Depends
from fastapi import APIRouter
from sqlalchemy import desc, or_, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.core.dependencies import get_optional_user
from app.database import get_db
from app.models import Bill, BillBrief, Follow, TrendScore
from app.models.user import User
from app.schemas.schemas import BillSchema

router = APIRouter()


async def _get_trending(db: AsyncSession) -> list[dict]:
    # Try progressively wider windows so stale scores still surface results
    for days_back in (1, 3, 7, 30):
        trending_result = await db.execute(
            select(Bill)
            .options(selectinload(Bill.sponsor), selectinload(Bill.briefs), selectinload(Bill.trend_scores))
            .join(TrendScore, Bill.bill_id == TrendScore.bill_id)
            .where(TrendScore.score_date >= date.today() - timedelta(days=days_back))
            .order_by(desc(TrendScore.composite_score))
            .limit(10)
        )
        trending_bills = trending_result.scalars().unique().all()
        if trending_bills:
            return [_serialize_bill(b) for b in trending_bills]
    return []


def _serialize_bill(bill: Bill) -> dict:
    b = BillSchema.model_validate(bill)
    if bill.briefs:
        b.latest_brief = bill.briefs[0]
    if bill.trend_scores:
        b.latest_trend = bill.trend_scores[0]
    return b.model_dump()


@router.get("")
async def get_dashboard(
    db: AsyncSession = Depends(get_db),
    current_user: User | None = Depends(get_optional_user),
):
    trending = await _get_trending(db)

    if current_user is None:
        return {"feed": [], "trending": trending, "follows": {"bills": 0, "members": 0, "topics": 0}}

    # Load follows for the current user
    follows_result = await db.execute(
        select(Follow).where(Follow.user_id == current_user.id)
    )
    follows = follows_result.scalars().all()

    followed_bill_ids = [f.follow_value for f in follows if f.follow_type == "bill"]
    followed_member_ids = [f.follow_value for f in follows if f.follow_type == "member"]
    followed_topics = [f.follow_value for f in follows if f.follow_type == "topic"]

    feed_bills: list[Bill] = []
    seen_ids: set[str] = set()

    # 1. Directly followed bills
    if followed_bill_ids:
        result = await db.execute(
            select(Bill)
            .options(selectinload(Bill.sponsor), selectinload(Bill.briefs), selectinload(Bill.trend_scores))
            .where(Bill.bill_id.in_(followed_bill_ids))
            .order_by(desc(Bill.latest_action_date))
            .limit(20)
        )
        for bill in result.scalars().all():
            if bill.bill_id not in seen_ids:
                feed_bills.append(bill)
                seen_ids.add(bill.bill_id)

    # 2. Bills from followed members
    if followed_member_ids:
        result = await db.execute(
            select(Bill)
            .options(selectinload(Bill.sponsor), selectinload(Bill.briefs), selectinload(Bill.trend_scores))
            .where(Bill.sponsor_id.in_(followed_member_ids))
            .order_by(desc(Bill.latest_action_date))
            .limit(20)
        )
        for bill in result.scalars().all():
            if bill.bill_id not in seen_ids:
                feed_bills.append(bill)
                seen_ids.add(bill.bill_id)

    # 3. Bills matching followed topics (single query with OR across all topics)
    if followed_topics:
        result = await db.execute(
            select(Bill)
            .options(selectinload(Bill.sponsor), selectinload(Bill.briefs), selectinload(Bill.trend_scores))
            .join(BillBrief, Bill.bill_id == BillBrief.bill_id)
            .where(or_(*[BillBrief.topic_tags.contains([t]) for t in followed_topics]))
            .order_by(desc(Bill.latest_action_date))
            .limit(20)
        )
        for bill in result.scalars().all():
            if bill.bill_id not in seen_ids:
                feed_bills.append(bill)
                seen_ids.add(bill.bill_id)

    # Sort feed by latest action date
    feed_bills.sort(key=lambda b: b.latest_action_date or date.min, reverse=True)

    return {
        "feed": [_serialize_bill(b) for b in feed_bills[:50]],
        "trending": trending,
        "follows": {
            "bills": len(followed_bill_ids),
            "members": len(followed_member_ids),
            "topics": len(followed_topics),
        },
    }