from __future__ import annotations

from datetime import UTC, date, datetime
from decimal import Decimal

from broker_sync.models import AccountType, Activity, ActivityType
from broker_sync.providers.imap import (
    _IE_GIA_ACCOUNT_ID,
    _IE_ISA_ACCOUNT_ID,
    _split_ie_by_isa_cap,
    _uk_tax_year_start,
)


def _buy(on: datetime, qty: str, price: str) -> Activity:
    return Activity(
        external_id=f"invest-engine:{on.isoformat()}|{qty}|{price}",
        account_id=_IE_ISA_ACCOUNT_ID,
        account_type=AccountType.ISA,
        date=on,
        activity_type=ActivityType.BUY,
        currency="GBP",
        symbol="VUAG",
        quantity=Decimal(qty),
        unit_price=Decimal(price),
    )


def test_uk_tax_year_start_before_april_6_rolls_back() -> None:
    assert _uk_tax_year_start(datetime(2025, 4, 5, tzinfo=UTC)) == date(2024, 4, 6)
    assert _uk_tax_year_start(datetime(2025, 4, 6, tzinfo=UTC)) == date(2025, 4, 6)
    assert _uk_tax_year_start(datetime(2025, 1, 15, tzinfo=UTC)) == date(2024, 4, 6)
    assert _uk_tax_year_start(datetime(2024, 4, 7, tzinfo=UTC)) == date(2024, 4, 6)


def test_single_tax_year_under_cap_stays_isa() -> None:
    acts = [
        _buy(datetime(2024, 5, 1, tzinfo=UTC), "100", "50"),  # £5000
        _buy(datetime(2024, 8, 1, tzinfo=UTC), "100", "80"),  # £8000
    ]
    routed = _split_ie_by_isa_cap(acts)
    assert all(a.account_id == _IE_ISA_ACCOUNT_ID for a in routed)
    assert all(a.account_type is AccountType.ISA for a in routed)


def test_overflow_past_cap_flips_to_gia() -> None:
    acts = [
        _buy(datetime(2024, 5, 1, tzinfo=UTC), "100", "80"),   # £8,000
        # +£12,000 → £20,000 total; prev £8k < cap → ISA
        _buy(datetime(2024, 6, 1, tzinfo=UTC), "150", "80"),
        _buy(datetime(2024, 7, 1, tzinfo=UTC), "10", "80"),    # prev £20,000 ≥ cap → GIA
        _buy(datetime(2024, 8, 1, tzinfo=UTC), "10", "80"),    # GIA
    ]
    routed = _split_ie_by_isa_cap(acts)
    assert routed[0].account_id == _IE_ISA_ACCOUNT_ID
    assert routed[1].account_id == _IE_ISA_ACCOUNT_ID
    assert routed[2].account_id == _IE_GIA_ACCOUNT_ID
    assert routed[2].account_type is AccountType.GIA
    assert routed[3].account_id == _IE_GIA_ACCOUNT_ID


def test_tax_year_boundary_resets_cap() -> None:
    acts = [
        # 2023-24 tax year: £20k in ISA, plus one in GIA
        _buy(datetime(2023, 5, 1, tzinfo=UTC), "400", "50"),   # £20,000 → ISA (prev 0 < cap)
        _buy(datetime(2024, 1, 1, tzinfo=UTC), "100", "50"),   # GIA (prev 20k)
        # 2024-25 tax year starts 2024-04-06 — cap resets
        _buy(datetime(2024, 5, 1, tzinfo=UTC), "100", "50"),   # ISA (prev 0 for new year)
    ]
    routed = _split_ie_by_isa_cap(acts)
    assert routed[0].account_id == _IE_ISA_ACCOUNT_ID
    assert routed[1].account_id == _IE_GIA_ACCOUNT_ID
    assert routed[2].account_id == _IE_ISA_ACCOUNT_ID


def test_out_of_order_activities_sorted_before_cap_applied() -> None:
    acts = [
        _buy(datetime(2024, 8, 1, tzinfo=UTC), "10", "80"),    # later date but given first
        _buy(datetime(2024, 5, 1, tzinfo=UTC), "250", "80"),   # earlier, £20,000 → ISA
    ]
    routed = _split_ie_by_isa_cap(acts)
    by_date = {a.date: a for a in routed}
    assert by_date[datetime(2024, 5, 1, tzinfo=UTC)].account_id == _IE_ISA_ACCOUNT_ID
    assert by_date[datetime(2024, 8, 1, tzinfo=UTC)].account_id == _IE_GIA_ACCOUNT_ID


def test_non_ie_activities_passed_through_unchanged() -> None:
    schwab_act = Activity(
        external_id="schwab:abc",
        account_id="schwab-workplace",
        account_type=AccountType.GIA,
        date=datetime(2024, 5, 1, tzinfo=UTC),
        activity_type=ActivityType.SELL,
        currency="USD",
        symbol="META",
        quantity=Decimal("10"),
        unit_price=Decimal("500"),
    )
    routed = _split_ie_by_isa_cap([schwab_act])
    assert routed[0].account_id == "schwab-workplace"
    assert routed[0].account_type is AccountType.GIA