from datetime import date
from decimal import Decimal
from fastapi import APIRouter, Depends, HTTPException, Query, status
from sqlalchemy import func
from sqlalchemy.orm import Session
from app.auth.dependencies import get_current_user
from app.database import get_db
from app.models.budget import Budget
from app.models.operation import Operation
from app.models.user import User
from app.schemas.budget import BudgetCreate, BudgetUpdate, BudgetOut

router = APIRouter(prefix="/budgets", tags=["budgets"])


def _compute_spent(db: Session, budget: Budget, current_user: User) -> Decimal:
    period_start = budget.start_date
    period_end = budget.end_date or date.today()
    total = db.query(func.sum(Operation.amount)).filter(
        Operation.user_id == current_user.id,
        Operation.category_id == budget.category_id,
        func.date(Operation.date) >= period_start,
        func.date(Operation.date) <= period_end,
        Operation.is_planned == False,
    ).scalar() or Decimal("0")
    return total


@router.get("", response_model=list[BudgetOut])
def list_budgets(db: Session = Depends(get_db), current_user: User = Depends(get_current_user)):
    budgets = db.query(Budget).filter(Budget.user_id == current_user.id).all()
    result = []
    for b in budgets:
        out = BudgetOut.model_validate(b)
        out.spent = _compute_spent(db, b, current_user)
        result.append(out)
    return result


@router.get("/{budget_id}", response_model=BudgetOut)
def get_budget(budget_id: int, db: Session = Depends(get_db), current_user: User = Depends(get_current_user)):
    obj = db.get(Budget, budget_id)
    if not obj or obj.user_id != current_user.id:
        raise HTTPException(status_code=404, detail="Budget not found")
    out = BudgetOut.model_validate(obj)
    out.spent = _compute_spent(db, obj, current_user)
    return out


@router.post("", response_model=BudgetOut, status_code=status.HTTP_201_CREATED)
def create_budget(body: BudgetCreate, db: Session = Depends(get_db), current_user: User = Depends(get_current_user)):
    obj = Budget(**body.model_dump(), user_id=current_user.id)
    db.add(obj)
    db.commit()
    db.refresh(obj)
    return BudgetOut.model_validate(obj)


@router.patch("/{budget_id}", response_model=BudgetOut)
def update_budget(
    budget_id: int, body: BudgetUpdate,
    db: Session = Depends(get_db), current_user: User = Depends(get_current_user)
):
    obj = db.get(Budget, budget_id)
    if not obj or obj.user_id != current_user.id:
        raise HTTPException(status_code=404, detail="Budget not found")
    for field, value in body.model_dump(exclude_none=True).items():
        setattr(obj, field, value)
    db.commit()
    db.refresh(obj)
    return BudgetOut.model_validate(obj)


@router.delete("/{budget_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_budget(budget_id: int, db: Session = Depends(get_db), current_user: User = Depends(get_current_user)):
    obj = db.get(Budget, budget_id)
    if not obj or obj.user_id != current_user.id:
        raise HTTPException(status_code=404, detail="Budget not found")
    db.delete(obj)
    db.commit()