from __future__ import annotations

import json
from datetime import UTC, date, datetime
from decimal import Decimal
from pathlib import Path

import pytest

from broker_sync.models import Account, AccountType, ActivityType
from broker_sync.providers.fidelity_planviewer import (
    ACCOUNT_ID,
    FidelityCreds,
    FidelityPlanViewerProvider,
    FidelityProviderConfigError,
    fidelity_holdings_to_snapshot,
    gains_offset_delta_activity,
)
from broker_sync.providers.parsers.fidelity import (
    FidelityHolding,
    parse_transactions_html,
    parse_valuation_json,
)

_FIXTURES = Path(__file__).parent.parent / "fixtures" / "fidelity"


def test_accounts_exposes_single_workplace_pension_account() -> None:
    prov = FidelityPlanViewerProvider(FidelityCreds(
        storage_state_path="/tmp/x", plan_id="META",
    ))
    assert prov.accounts() == [
        Account(
            id=ACCOUNT_ID,
            name="Fidelity UK Pension",
            account_type=AccountType.WORKPLACE_PENSION,
            currency="GBP",
            provider="fidelity-planviewer",
        ),
    ]


async def test_fetch_raises_without_storage_state() -> None:
    prov = FidelityPlanViewerProvider(FidelityCreds(
        storage_state_path="/tmp/does-not-exist-xyzzy.json", plan_id="META",
    ))
    with pytest.raises(FidelityProviderConfigError, match="storage_state"):
        async for _ in prov.fetch():
            pytest.fail("should have raised before yielding")


# -- parser tests against real (captured) fixture --


def test_parse_transactions_real_fixture() -> None:
    html = (_FIXTURES / "transactions-full.html").read_text()
    txs = parse_transactions_html(html)
    # Scheme has ~48 months + a couple of single premiums + 1 rebate;
    # Bulk Switches must be filtered out (zero-amount rows).
    assert 40 <= len(txs) <= 100
    # All dates are within the scheme's lifetime (2022-03 to today-ish).
    assert all(tx.date >= datetime(2022, 1, 1, tzinfo=UTC) for tx in txs)
    # Sum should match the header total on the page (£102,004.15 at
    # fixture time). Allow a £5 tolerance in case the page summary row
    # changes in future captures — the unit test primarily guards parsing
    # correctness, not drift in the fixture.
    total = sum((tx.amount for tx in txs), Decimal(0))
    assert abs(total - Decimal("102004.15")) < Decimal("5")


def test_parse_transactions_skips_bulk_switch() -> None:
    html = (_FIXTURES / "transactions-full.html").read_text()
    txs = parse_transactions_html(html)
    assert not any("bulk switch" in tx.tx_type.lower() for tx in txs)


def test_parse_transactions_external_id_deterministic() -> None:
    html = (_FIXTURES / "transactions-full.html").read_text()
    a = parse_transactions_html(html)
    b = parse_transactions_html(html)
    assert [tx.external_id for tx in a] == [tx.external_id for tx in b]
    assert all(tx.external_id.startswith("fidelity:tx:") for tx in a)


def test_parse_valuation_fixture() -> None:
    payload = json.loads((_FIXTURES / "valuation.json").read_text())
    holdings = parse_valuation_json(payload)
    assert len(holdings) >= 1
    h = holdings[0]
    assert h.fund_code == "KDOA"
    assert "Passive Global Equity" in h.fund_name
    assert h.currency == "GBP"
    assert h.units > 0
    assert h.unit_price > 0
    # Value ≈ units * price
    assert abs(h.total_value - h.units * h.unit_price) < Decimal("1")
    # Contribution-type breakdown must parse
    assert set(h.units_by_source.keys()) >= {"SASC", "ERXS"}


def test_holdings_to_snapshot_real_fixture() -> None:
    html = (_FIXTURES / "transactions-full.html").read_text()
    valuation = json.loads((_FIXTURES / "valuation.json").read_text())
    holdings = parse_valuation_json(valuation)
    total_contrib = sum((tx.amount for tx in parse_transactions_html(html)),
                        Decimal(0))

    snapshot = fidelity_holdings_to_snapshot(
        holdings=holdings,
        total_real_contribution=total_contrib,
        as_of=date(2026, 4, 18),
    )
    assert snapshot is not None
    assert snapshot.date == date(2026, 4, 18)
    assert snapshot.currency == "GBP"
    # Cost basis sums to the cash contributions (allocated by fund value share)
    sum_cost = sum((p.total_cost_basis for p in snapshot.positions), Decimal(0))
    assert abs(sum_cost - total_contrib) < Decimal("1")
    # Meta scheme had KDOA + LAFC + one other at fixture time; the
    # dominant fund must be KDOA.
    symbols = [p.symbol for p in snapshot.positions]
    assert "KDOA" in symbols
    kdoa = next(p for p in snapshot.positions if p.symbol == "KDOA")
    assert kdoa.quantity > 0
    # Proportional cost-basis allocation: KDOA holds nearly the whole pot
    # so it should get the lion's share of cost
    kdoa_share = kdoa.total_cost_basis / sum_cost
    assert kdoa_share > Decimal("0.9")
    # cashBalances zero — pension contributions flow straight into funds
    assert snapshot.cash_balances == {"GBP": Decimal(0)}


def test_holdings_to_snapshot_none_when_no_holdings() -> None:
    assert fidelity_holdings_to_snapshot(
        holdings=[], total_real_contribution=Decimal("100"),
        as_of=date(2026, 4, 18),
    ) is None


def test_provider_caches_holdings_for_cli_snapshot_push() -> None:
    """The CLI reads `last_holdings` after fetch() drains to push the
    manual snapshot. This guards the contract that fetch() populates the
    attribute even when no Activity is yielded (e.g., backfill window
    cut-off)."""
    prov = FidelityPlanViewerProvider(FidelityCreds(
        storage_state_path="/tmp/x", plan_id="META",
    ))
    # Pre-fetch state: empty
    assert prov.last_holdings == []
    assert prov.last_total_contribution == Decimal(0)


# -- delta-shaped gains offset (the monthly accumulation mechanism) --


def _holdings_summing_to(total: Decimal) -> list[FidelityHolding]:
    return [FidelityHolding(
        fund_code="KDOA", fund_name="Test", units=Decimal("100"),
        unit_price=total / Decimal("100"), currency="GBP", total_value=total,
        units_by_source={},
    )]


def test_gains_delta_emits_deposit_when_gain_exceeds_prior_offset() -> None:
    # pot £145k, real contrib £102k → current gain £43k; prior offset £35k
    # → delta = +£8k
    activity = gains_offset_delta_activity(
        holdings=_holdings_summing_to(Decimal("145000")),
        total_real_contribution=Decimal("102000"),
        prior_offset_cumulative=Decimal("35000"),
        as_of=datetime(2026, 5, 17, tzinfo=UTC),
    )
    assert activity is not None
    assert activity.activity_type == ActivityType.DEPOSIT
    assert activity.amount == Decimal("8000")
    assert activity.external_id == "fidelity:gains-delta:2026-05-17"
    assert "unrealised-gains-offset" in (activity.notes or "")


def test_gains_delta_emits_withdrawal_on_market_drop() -> None:
    # pot dropped: current gain £30k, prior offset £35k → delta = -£5k
    activity = gains_offset_delta_activity(
        holdings=_holdings_summing_to(Decimal("132000")),
        total_real_contribution=Decimal("102000"),
        prior_offset_cumulative=Decimal("35000"),
        as_of=datetime(2026, 5, 17, tzinfo=UTC),
    )
    assert activity is not None
    assert activity.activity_type == ActivityType.WITHDRAWAL
    assert activity.amount == Decimal("5000")


def test_gains_delta_suppressed_below_minimum() -> None:
    # delta ~£0.20, below the £0.50 min — skip emission to avoid noise.
    activity = gains_offset_delta_activity(
        holdings=_holdings_summing_to(Decimal("137000.20")),
        total_real_contribution=Decimal("102000"),
        prior_offset_cumulative=Decimal("35000"),
        as_of=datetime(2026, 5, 17, tzinfo=UTC),
    )
    assert activity is None


def test_gains_delta_none_when_no_holdings() -> None:
    assert gains_offset_delta_activity(
        holdings=[], total_real_contribution=Decimal("0"),
        prior_offset_cumulative=Decimal("0"),
        as_of=datetime(2026, 5, 17, tzinfo=UTC),
    ) is None