import uuid

from fastapi import APIRouter, Depends, Query, status
from sqlalchemy.ext.asyncio import AsyncSession

from app.auth.dependencies import get_current_user
from app.database import get_session
from app.models.user import User
from app.schemas.budget import BudgetCreate, BudgetResponse, BudgetUpdate
from app.services import budget_service
from app.utils import utcnow

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


def _current_month() -> str:
    now = utcnow()
    return f"{now.year}-{now.month:02d}"


@router.get("", response_model=list[BudgetResponse])
async def list_budgets(
    month: str = Query(default=None, description="Month YYYY-MM (defaults to current month)"),
    session: AsyncSession = Depends(get_session),
    current_user: User = Depends(get_current_user),
) -> list[BudgetResponse]:
    if month is None:
        month = _current_month()
    return await budget_service.list_budgets(session, current_user.id, month)


@router.post("", response_model=BudgetResponse, status_code=status.HTTP_201_CREATED)
async def create_budget(
    data: BudgetCreate,
    session: AsyncSession = Depends(get_session),
    current_user: User = Depends(get_current_user),
) -> BudgetResponse:
    return await budget_service.create_budget(session, current_user.id, data)


@router.put("/{budget_id}", response_model=BudgetResponse)
async def update_budget(
    budget_id: uuid.UUID,
    data: BudgetUpdate,
    session: AsyncSession = Depends(get_session),
    current_user: User = Depends(get_current_user),
) -> BudgetResponse:
    return await budget_service.update_budget(session, current_user.id, budget_id, data)


@router.delete("/{budget_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_budget(
    budget_id: uuid.UUID,
    session: AsyncSession = Depends(get_session),
    current_user: User = Depends(get_current_user),
) -> None:
    await budget_service.delete_budget(session, current_user.id, budget_id)


@router.post("/rollover", response_model=list[BudgetResponse], status_code=status.HTTP_201_CREATED)
async def rollover_budgets(
    month: str = Query(..., description="Target month YYYY-MM to copy budgets into"),
    session: AsyncSession = Depends(get_session),
    current_user: User = Depends(get_current_user),
) -> list[BudgetResponse]:
    """Copy budgets from month-1 into the given month (skips existing ones)."""
    return await budget_service.rollover_budgets(session, current_user.id, month)