"""Tests for the pure reconciliation functions.

These tests use lightweight stand-in objects (namedtuples) rather than
SQLAlchemy ORM instances, so the reconcile module has zero DB dependency.
"""

from __future__ import annotations

from dataclasses import dataclass
from datetime import date, datetime, timezone
from decimal import Decimal
from typing import Optional

import pytest

from cyclone import db, reconcile
from cyclone.db import (
    ActivityEvent,
    Batch,
    Claim,
    ClaimState,
    Match,
    Remittance,
)
from cyclone.reconcile import Match as ReconcileMatch


# --- Stand-in types -----------------------------------------------------------


@dataclass
class FakeClaim:
    id: str
    patient_control_number: str
    service_date_from: Optional[date]
    state: str = "submitted"
    matched_remittance_id: Optional[str] = None


@dataclass
class FakeRemit:
    id: str
    payer_claim_control_number: str
    service_date: Optional[date]
    is_reversal: bool = False


# --- match() ------------------------------------------------------------------


def test_match_same_pcn_within_window_matches():
    claims = [FakeClaim("CLM-1", "PCN-A", date(2026, 6, 1))]
    remits = [FakeRemit("CLP-1", "PCN-A", date(2026, 6, 2))]
    matches = reconcile.match(claims, remits, window_days=7)
    assert len(matches) == 1
    assert matches[0].claim.id == "CLM-1"
    assert matches[0].remittance.id == "CLP-1"
    assert matches[0].strategy == "auto"


def test_match_dates_outside_window_unmatched():
    claims = [FakeClaim("CLM-1", "PCN-A", date(2026, 6, 1))]
    remits = [FakeRemit("CLP-1", "PCN-A", date(2026, 7, 1))]  # 30d apart
    matches = reconcile.match(claims, remits, window_days=7)
    assert matches == []


def test_match_different_pcn_unmatched():
    claims = [FakeClaim("CLM-1", "PCN-A", date(2026, 6, 1))]
    remits = [FakeRemit("CLP-1", "PCN-B", date(2026, 6, 1))]
    matches = reconcile.match(claims, remits)
    assert matches == []


def test_match_multiple_claims_same_pcn_picks_closest_date():
    claims = [
        FakeClaim("CLM-1", "PCN-A", date(2026, 5, 1)),
        FakeClaim("CLM-2", "PCN-A", date(2026, 6, 1)),  # closer
    ]
    remits = [FakeRemit("CLP-1", "PCN-A", date(2026, 6, 2))]
    matches = reconcile.match(claims, remits)
    assert len(matches) == 1
    assert matches[0].claim.id == "CLM-2"


def test_match_multiple_remits_same_pcn_each_gets_own_claim():
    claims = [
        FakeClaim("CLM-1", "PCN-A", date(2026, 6, 1)),
        FakeClaim("CLM-2", "PCN-A", date(2026, 6, 15)),
    ]
    remits = [
        FakeRemit("CLP-1", "PCN-A", date(2026, 6, 2)),
        FakeRemit("CLP-2", "PCN-A", date(2026, 6, 16)),
    ]
    matches = reconcile.match(claims, remits)
    assert len(matches) == 2
    claim_ids = {m.claim.id for m in matches}
    assert claim_ids == {"CLM-1", "CLM-2"}


def test_match_skips_already_matched_claims():
    claims = [FakeClaim("CLM-1", "PCN-A", date(2026, 6, 1), matched_remittance_id="OLD")]
    remits = [FakeRemit("CLP-1", "PCN-A", date(2026, 6, 1))]
    matches = reconcile.match(claims, remits)
    assert matches == []


def test_match_falls_back_to_first_claim_when_no_service_date():
    """When the remit has no service_date, match the first claim for that PCN."""
    claims = [
        FakeClaim("CLM-1", "PCN-A", None),
        FakeClaim("CLM-2", "PCN-A", None),
    ]
    remits = [FakeRemit("CLP-1", "PCN-A", None)]
    matches = reconcile.match(claims, remits)
    assert len(matches) == 1
    assert matches[0].claim.id == "CLM-1"


def test_match_reversal_flag_propagates():
    claims = [FakeClaim("CLM-1", "PCN-A", date(2026, 6, 1))]
    remits = [FakeRemit("CLP-1", "PCN-A", date(2026, 6, 1), is_reversal=True)]
    matches = reconcile.match(claims, remits)
    assert matches[0].is_reversal is True


# ApplyIntent + apply_payment / apply_reversal / split_unmatched ----------------


def test_apply_payment_full_amount_returns_paid():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.SUBMITTED.value)
    remit = FakeRemit("CLP-1", "PCN-A", None)
    intent = reconcile.apply_payment(claim, remit, charge=Decimal("100"), paid=Decimal("100"))
    assert intent.new_state == ClaimState.PAID
    assert intent.activity_kind == "reconcile"
    assert intent.skipped is False


def test_apply_payment_partial_amount_returns_partial():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.SUBMITTED.value)
    remit = FakeRemit("CLP-1", "PCN-A", None)
    intent = reconcile.apply_payment(claim, remit, charge=Decimal("100"), paid=Decimal("60"))
    assert intent.new_state == ClaimState.PARTIAL


def test_apply_payment_zero_paid_returns_received():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.SUBMITTED.value)
    remit = FakeRemit("CLP-1", "PCN-A", None)
    intent = reconcile.apply_payment(claim, remit, charge=Decimal("100"), paid=Decimal("0"))
    assert intent.new_state == ClaimState.RECEIVED


def test_apply_payment_status_4_returns_denied():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.SUBMITTED.value)
    remit = FakeRemit("CLP-1", "PCN-A", None)
    intent = reconcile.apply_payment(claim, remit, charge=Decimal("100"), paid=Decimal("0"),
                                       status_code="4")
    assert intent.new_state == ClaimState.DENIED


def test_apply_payment_already_paid_is_noop():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.PAID.value)
    remit = FakeRemit("CLP-1", "PCN-A", None)
    intent = reconcile.apply_payment(claim, remit, charge=Decimal("100"), paid=Decimal("100"))
    assert intent.skipped is True
    assert intent.activity_kind == "invalid_state"
    assert intent.new_state is None


def test_apply_reversal_of_paid_returns_reversed_with_prior_state():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.PAID.value)
    remit = FakeRemit("CLP-1", "PCN-A", None, is_reversal=True)
    intent = reconcile.apply_reversal(claim, remit)
    assert intent.new_state == ClaimState.REVERSED
    assert intent.prior_claim_state == ClaimState.PAID
    assert intent.activity_kind == "reversal"
    assert intent.skipped is False


def test_apply_reversal_of_partial_works_same_way():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.PARTIAL.value)
    remit = FakeRemit("CLP-1", "PCN-A", None, is_reversal=True)
    intent = reconcile.apply_reversal(claim, remit)
    assert intent.new_state == ClaimState.REVERSED
    assert intent.prior_claim_state == ClaimState.PARTIAL


def test_apply_reversal_of_denied_is_noop():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.DENIED.value)
    remit = FakeRemit("CLP-1", "PCN-A", None, is_reversal=True)
    intent = reconcile.apply_reversal(claim, remit)
    assert intent.skipped is True
    assert intent.activity_kind == "reversal_skipped"


def test_apply_reversal_of_already_reversed_is_noop():
    claim = FakeClaim("CLM-1", "PCN-A", None, state=ClaimState.REVERSED.value)
    remit = FakeRemit("CLP-1", "PCN-A", None, is_reversal=True)
    intent = reconcile.apply_reversal(claim, remit)
    assert intent.skipped is True


def test_split_unmatched_partitions_by_match_set():
    claims = [FakeClaim("CLM-1", "A", None), FakeClaim("CLM-2", "B", None)]
    remits = [FakeRemit("CLP-1", "A", None), FakeRemit("CLP-2", "C", None)]
    matches = [ReconcileMatch(claim=claims[0], remittance=remits[0], strategy="auto", is_reversal=False)]
    unmatched_claims, unmatched_remits = reconcile.split_unmatched(claims, remits, matches)
    assert [c.id for c in unmatched_claims] == ["CLM-2"]
    assert [r.id for r in unmatched_remits] == ["CLP-2"]


# --- reconcile.run() integration tests ----------------------------------------


@pytest.fixture
def fixture_835(tmp_path, monkeypatch):
    """Set up a clean DB and return an empty helper for building remits."""
    monkeypatch.setenv("CYCLONE_DB_URL", f"sqlite:///{tmp_path}/reconcile.db")
    db._reset_for_tests()
    db.init_db()
    yield
    db._reset_for_tests()


def _make_batch(s, batch_id="b1", kind="835"):
    s.add(Batch(
        id=batch_id, kind=kind, input_filename="x",
        parsed_at=datetime(2026, 6, 19, tzinfo=timezone.utc),
    ))
    s.flush()


def _make_claim(s, claim_id="CLM-1", pcn="PCN-A", charge="100.00",
                service_date=None, state=ClaimState.SUBMITTED):
    s.add(Claim(
        id=claim_id, batch_id="b1", patient_control_number=pcn,
        service_date_from=service_date, charge_amount=Decimal(charge),
        state=state,
    ))
    s.flush()


def _make_remit(s, remit_id="CLP-1", pcn="PCN-A", status="1",
                charge="100.00", paid="100.00", service_date=None,
                is_reversal=False):
    rid = remit_id + ":b1xxxxxx"
    s.add(Remittance(
        id=rid, batch_id="b1", payer_claim_control_number=pcn,
        status_code=status, total_charge=Decimal(charge), total_paid=Decimal(paid),
        received_at=datetime(2026, 6, 19, tzinfo=timezone.utc),
        service_date=service_date, is_reversal=is_reversal,
    ))
    s.flush()
    return rid


def test_run_matches_and_updates_state(fixture_835):
    with db.SessionLocal()() as s:
        _make_batch(s)
        _make_claim(s, "CLM-1", "PCN-A", "100.00", date(2026, 6, 1))
        _make_remit(s, "CLP-1", "PCN-A", "1", "100.00", "100.00", date(2026, 6, 1))
        s.commit()

    with db.SessionLocal()() as s:
        from cyclone import reconcile
        result = reconcile.run(s, "b1")
        s.commit()

    assert result.matched == 1
    assert result.unmatched_remittances == 0
    assert result.unmatched_claims == 0

    with db.SessionLocal()() as s:
        claim = s.get(Claim, "CLM-1")
        assert claim.state == ClaimState.PAID
        assert claim.matched_remittance_id == "CLP-1:b1xxxxxx"


def test_run_orphan_remit_leaves_claim_unmatched(fixture_835):
    with db.SessionLocal()() as s:
        _make_batch(s)
        _make_claim(s, "CLM-1", "PCN-A", "100.00", date(2026, 6, 1))
        _make_remit(s, "CLP-2", "PCN-NEW", "1", "50.00", "50.00", date(2026, 6, 5))
        s.commit()

    with db.SessionLocal()() as s:
        from cyclone import reconcile
        result = reconcile.run(s, "b1")
        s.commit()

    assert result.matched == 0
    assert result.unmatched_remittances == 1
    # Spec-bug fix (T10): claim PCN-A does not match remit PCN-NEW, so the
    # claim stays in the unmatched bucket. Original spec asserted 0.
    assert result.unmatched_claims == 1


def test_run_reversal_flips_paid_to_reversed(fixture_835):
    with db.SessionLocal()() as s:
        _make_batch(s)
        # Spec-bug fix (T10): dates are 5 days apart so match() picks this claim
        # (default window_days=7). Original spec used 2026-06-01 vs 2026-06-10
        # (9 days, outside window) which produced no match.
        _make_claim(s, "CLM-1", "PCN-A", "100.00", date(2026, 6, 5),
                    state=ClaimState.PAID)
        # Match row already exists from prior reconcile.
        s.add(Match(
            claim_id="CLM-1", remittance_id="CLP-OLD:b1xxxxxx",
            strategy="auto", matched_at=datetime.now(timezone.utc),
            is_reversal=False,
        ))
        s.flush()
        _make_remit(s, "CLP-REV", "PCN-A", "22", "100.00", "-100.00",
                    date(2026, 6, 10), is_reversal=True)
        s.commit()

    with db.SessionLocal()() as s:
        from cyclone import reconcile
        result = reconcile.run(s, "b1")
        s.commit()

    assert result.matched == 1
    with db.SessionLocal()() as s:
        claim = s.get(Claim, "CLM-1")
        assert claim.state == ClaimState.REVERSED
        # Match rows: original + reversal.
        matches = s.query(Match).filter(Match.claim_id == "CLM-1").all()
        assert len(matches) == 2
        reversal_match = [m for m in matches if m.is_reversal][0]
        assert reversal_match.prior_claim_state == ClaimState.PAID


def test_run_reconcile_raise_in_session_leaves_prior_commits_alone(fixture_835):
    """A ``reconcile.run`` raise inside an open session does not damage
    previously-committed rows.

    The test seeds a batch + remit, commits them in one session, then
    calls ``reconcile.run`` in a fresh session with ``match`` monkey-
    patched to raise. The pre-existing rows must survive — they're on
    disk from the prior commit, separate from the rolling-back
    session. This pins the unit-level invariant that ``reconcile.run``
    itself never commits and never silently mutates rows outside the
    session it was given; it is the *caller's* responsibility (now
    ``CycloneStore.add`` per SP27 Task 10) to control the transaction
    boundary.
    """
    with db.SessionLocal()() as s:
        _make_batch(s)
        _make_remit(s, "CLP-1", "PCN-A", "1", "100.00", "100.00")
        s.commit()

    # Monkeypatch reconcile.match to raise.
    from cyclone import reconcile
    real_match = reconcile.match
    def boom(*a, **kw): raise RuntimeError("synthetic fault")
    reconcile.match = boom
    try:
        with db.SessionLocal()() as s:
            try:
                reconcile.run(s, "b1")
                s.commit()
            except RuntimeError:
                pass  # caller is responsible for catch; reconcile.run itself shouldn't raise
    finally:
        reconcile.match = real_match

    # Batch + remit still present.
    with db.SessionLocal()() as s:
        b = s.get(Batch, "b1")
        assert b is not None
        r = s.query(Remittance).first()
        assert r is not None