"""Commands and queries for monthly budgets (R2, R7)."""

from __future__ import annotations

from ..errors import NotFoundError, ValidationError
from ..money import Money
from ..models import INCOME, Budget, clean_name
from ..repository import Repository

__all__ = ["BudgetService"]


class BudgetService:
    """Owns budget rules: positivity, expense-only, replace/delete semantics."""

    def __init__(self, repo: Repository) -> None:
        self._repo = repo

    # -- commands ----------------------------------------------------------

    def set_budget(self, category: str, amount: Money) -> Budget:
        clean = clean_name(category, "category")
        if not amount.is_positive:
            raise ValidationError("budget must be greater than zero")
        ref = self._repo.find_category(clean)
        if ref is None:
            raise NotFoundError(f"unknown category {clean!r}")
        category_id, stored_name, kind = ref
        if kind == INCOME:
            raise ValidationError(
                f"budgets apply to expense categories only "
                f"({stored_name!r} is income)"
            )
        self._repo.set_budget(category_id, amount.cents)
        return Budget(category=stored_name, amount=amount)

    def delete_budget(self, category: str) -> Budget:
        """Remove the budget for *category*; returns the deleted budget."""
        clean = clean_name(category, "category")
        ref = self._repo.find_category(clean)
        if ref is None:
            raise NotFoundError(f"unknown category {clean!r}")
        category_id, stored_name, _kind = ref
        cents = self._repo.get_budget(category_id)
        if cents is None:
            raise NotFoundError(f"no budget set for {stored_name!r}")
        self._repo.delete_budget(category_id)
        return Budget(category=stored_name, amount=Money(cents=cents))

    # -- queries -----------------------------------------------------------

    def list_budgets(self) -> list[Budget]:
        return [
            Budget(category=row["category"], amount=Money(cents=row["amount_cents"]))
            for row in self._repo.list_budgets()
        ]