from datetime import date

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

from app.auth.dependencies import get_current_user
from app.database import get_session
from app.models.transaction import Transaction, TransactionType
from app.models.user import User
from app.schemas.history import HistoryResponse, MonthSummary
from app.utils import utcnow

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


@router.get("", response_model=HistoryResponse)
async def get_history(
    year: int = Query(default=None, description="Year (defaults to current year)"),
    session: AsyncSession = Depends(get_session),
    current_user: User = Depends(get_current_user),
) -> HistoryResponse:
    if year is None:
        year = utcnow().year

    months: list[MonthSummary] = []
    for mon in range(1, 13):
        start = date(year, mon, 1)
        if mon == 12:
            end = date(year + 1, 1, 1)
        else:
            end = date(year, mon + 1, 1)

        result = await session.execute(
            select(
                func.coalesce(
                    func.sum(
                        func.case(
                            (Transaction.type == TransactionType.income, Transaction.amount_cents),
                            else_=0,
                        )
                    ),
                    0,
                ).label("income"),
                func.coalesce(
                    func.sum(
                        func.case(
                            (Transaction.type == TransactionType.expense, Transaction.amount_cents),
                            else_=0,
                        )
                    ),
                    0,
                ).label("expense"),
                func.count(Transaction.id).label("count"),
            ).where(
                Transaction.user_id == current_user.id,
                Transaction.deleted_at.is_(None),
                Transaction.transaction_date >= start,
                Transaction.transaction_date < end,
            )
        )
        row = result.one()
        months.append(
            MonthSummary(
                month=f"{year}-{mon:02d}",
                income_cents=row.income,
                expense_cents=row.expense,
                balance_cents=row.income - row.expense,
                transaction_count=row.count,
            )
        )

    return HistoryResponse(year=year, months=months)