from __future__ import annotations

from datetime import date
from decimal import Decimal

import pytest

from quartermaster import month_service, service
from quartermaster.models import Section


def _apply(db, month, entry_id, amount):
    """Record an applied amount against a month entry by posting."""
    return month_service.add_posting(
        db, month, entry_id, date.today(), Decimal(str(amount)), description="test"
    )


def _seed_budget(db):
    income = service.add_entry(db, Section.income, "Paycheck", Decimal("2500.00"))
    rent = service.add_entry(
        db, Section.fixed_bill, "Rent", Decimal("1200.00")
    )
    card_a = service.add_entry(
        db, Section.debt_minimum, "Card A", Decimal("40.00")
    )
    card_b = service.add_entry(
        db, Section.debt_minimum, "Card B", Decimal("60.00")
    )
    service.set_debt_target(db, card_a.id)
    return income, rent, card_a, card_b


def test_valid_year_month():
    assert month_service.valid_year_month("2026-04")
    assert month_service.valid_year_month("2026-12")
    assert not month_service.valid_year_month("2026-00")
    assert not month_service.valid_year_month("2026-13")
    assert not month_service.valid_year_month("26-04")
    assert not month_service.valid_year_month("2026/04")


def test_shift_year_month_rolls_years():
    assert month_service.shift_year_month("2026-12", 1) == "2027-01"
    assert month_service.shift_year_month("2026-01", -1) == "2025-12"
    assert month_service.shift_year_month("2026-04", 0) == "2026-04"
    assert month_service.shift_year_month("2026-04", 12) == "2027-04"


def test_create_month_snapshots_budget(db):
    income, rent, card_a, card_b = _seed_budget(db)
    month = month_service.create_month(db, "2026-04")
    assert month.year_month == "2026-04"
    assert len(month.entries) == 4
    by_source = {e.source_entry_id: e for e in month.entries}
    assert by_source[income.id].planned == Decimal("2500.00")
    assert by_source[income.id].origin_name == "Paycheck"
    assert by_source[income.id].origin_planned == Decimal("2500.00")
    assert by_source[income.id].applied == Decimal("0.00")
    assert by_source[rent.id].section == Section.fixed_bill
    assert month.target is not None
    assert month.target.entry is not None
    assert month.target.entry.source_entry_id == card_a.id


def test_create_month_idempotent(db):
    _seed_budget(db)
    first = month_service.create_month(db, "2026-04")
    second = month_service.create_month(db, "2026-04")
    assert first.id == second.id


def test_create_month_rejects_bad_year_month(db):
    with pytest.raises(ValueError):
        month_service.create_month(db, "2026-00")


def test_deviation_state_reflects_edits(db):
    _seed_budget(db)
    month = month_service.create_month(db, "2026-04")
    rent = next(e for e in month.entries if e.origin_name == "Rent")
    assert month_service.deviation_state(rent) == month_service.DeviationState.unchanged

    month_service.update_month_entry(
        db, month, rent.id, planned=Decimal("1300.00")
    )
    rent = next(e for e in month.entries if e.id == rent.id)
    assert month_service.deviation_state(rent) == month_service.DeviationState.edited


def test_added_row_is_new_in_month(db):
    _seed_budget(db)
    month = month_service.create_month(db, "2026-04")
    extra = month_service.add_month_entry(
        db, month, Section.other, "Surprise", Decimal("20.00")
    )
    assert extra.origin_name is None
    assert month_service.deviation_state(extra) == (
        month_service.DeviationState.new_in_month
    )


def test_applied_update_changes_totals(db):
    _seed_budget(db)
    month = month_service.create_month(db, "2026-04")
    rent = next(e for e in month.entries if e.origin_name == "Rent")
    _apply(db, month, rent.id, "1200.00")
    db.refresh(month)
    view = month_service.section_view(month, Section.fixed_bill, "Fixed")
    assert view.total_applied == Decimal("1200.00")
    assert view.total_planned == Decimal("1200.00")


def test_per_month_target_is_isolated(db):
    _seed_budget(db)
    april = month_service.create_month(db, "2026-04")
    may = month_service.create_month(db, "2026-05")
    april_b = next(
        e for e in april.entries
        if e.section == Section.debt_minimum and e.origin_name == "Card B"
    )
    month_service.set_month_target(db, april, april_b.id)
    april_target = month_service.get_month_target(db, april)
    may_target = month_service.get_month_target(db, may)
    assert april_target.entry is not None
    assert april_target.entry.origin_name == "Card B"
    assert may_target.entry is not None
    assert may_target.entry.origin_name == "Card A"


def test_delete_month_entry_returns_section(db):
    _seed_budget(db)
    month = month_service.create_month(db, "2026-04")
    rent = next(e for e in month.entries if e.origin_name == "Rent")
    result = month_service.delete_month_entry(db, month, rent.id)
    assert result == Section.fixed_bill
    db.refresh(month)
    remaining = [
        e for e in month.entries if e.section == Section.fixed_bill
    ]
    assert remaining == []


def test_budget_entry_deleted_after_snapshot_leaves_month_intact(db):
    _seed_budget(db)
    month = month_service.create_month(db, "2026-04")
    # remove budget-side rent; month-side rent should still render unchanged
    budget_rent = service.list_entries(db, Section.fixed_bill)[0]
    service.delete_entry(db, budget_rent.id)
    db.expire_all()
    month_rent = next(e for e in month.entries if e.origin_name == "Rent")
    assert month_rent.source_entry_id is None
    assert month_service.deviation_state(month_rent) == (
        month_service.DeviationState.unchanged
    )