"""
Transactions router — paginated transaction history with filtering.
"""
from typing import Optional
from fastapi import APIRouter, Depends, Query
from sqlalchemy.orm import Session
from sqlalchemy import desc

from app.database.database import get_db
from app.database.models import User, Account, Transaction

router = APIRouter(prefix="/api/transactions", tags=["Transactions"])

def _resolve_user(db: Session, user_id: Optional[str]) -> str:
    if user_id:
        return user_id
    user = db.query(User).first()
    if not user:
        from fastapi import HTTPException
        raise HTTPException(status_code=404, detail="No users found.")
    return user.id

@router.get("/")
def get_transactions(
    user_id: Optional[str] = None,
    page: int = Query(default=1, ge=1),
    limit: int = Query(default=20, ge=1, le=100),
    category: Optional[str] = None,
    type: Optional[str] = None,
    db: Session = Depends(get_db),
):
    uid = _resolve_user(db, user_id)
    account_ids = [a.id for a in db.query(Account).filter(Account.user_id == uid).all()]

    query = db.query(Transaction).filter(Transaction.account_id.in_(account_ids))
    if category:
        query = query.filter(Transaction.category == category)
    if type:
        query = query.filter(Transaction.type == type)

    total = query.count()
    transactions = query.order_by(desc(Transaction.timestamp)).offset((page - 1) * limit).limit(limit).all()

    return {
        "transactions": [
            {
                "id": t.id,
                "merchant": t.merchant or "Unknown",
                "category": t.category or "Other",
                "amount": t.amount if t.type == "credit" else -abs(t.amount),
                "type": t.type,
                "timestamp": t.timestamp.isoformat() if t.timestamp else None,
                "tags": t.tags or [],
            }
            for t in transactions
        ],
        "total": total,
        "page": page,
        "pages": (total + limit - 1) // limit,
    }