import sqlite3
from decimal import Decimal
from pathlib import Path

from fin_hub.services.billing import build_billing_basis
from fin_hub.services.exchange import ingest_planning_evidence
from fin_hub.services.ledger import import_csv, record_engagement_price

CLIENT_KEY = "client:acme|app:portal|instance:prod-01"


def _seed_billing_ledger(tmp_path: Path):
    ledger = tmp_path / "ledger.db"
    direct = tmp_path / "direct.csv"
    direct.write_text(
        "product,amount,currency,invoice_date,environment,client_id,application_id,app_instance_id\n"
        "Dedicated service,20.00,EUR,2026-07-01,production,acme,portal,prod-01\n",
        encoding="utf-8",
    )
    shared = tmp_path / "shared.csv"
    shared.write_text(
        "product,amount,currency,invoice_date,environment\n"
        "Shared cluster,100.00,EUR,2026-07-01,production\n",
        encoding="utf-8",
    )
    import_csv(direct, "hosteurope", ledger_path=ledger)
    import_csv(shared, "hosteurope", ledger_path=ledger)
    with sqlite3.connect(ledger) as conn:
        shared_fact_id = conn.execute(
            "SELECT financial_fact_id FROM ledger_entries "
            "WHERE cost_attribution_key IS NULL"
        ).fetchone()[0]
    price = record_engagement_price(
        client_id="acme",
        application_id="portal",
        app_instance_id="prod-01",
        period_month="2026-07",
        amount="200.00",
        currency="EUR",
        source="agreement-v1",
        ledger_path=ledger,
    )
    allocation = {
        "schema_version": "0.1",
        "record_type": "allocation",
        "record_id": "allocation:shared:2026-07:v1",
        "revision_of": None,
        "resource_id": "resource:shared_cluster",
        "service_id": "shared-cluster",
        "workload_id": None,
        "tenant_id": None,
        "environment": "production",
        "cost_attribution_key": "platform:shared-cluster",
        "period_start": "2026-07-01",
        "period_end": "2026-07-31",
        "currency": "EUR",
        "source_evidence": ["resource-control:namespace-cpu-v1"],
        "created_at": "2026-08-11T10:00:00Z",
        "financial_fact_ids": [shared_fact_id],
        "method": "namespace-cpu-v1",
        "allocated_amount": "100.00",
        "shares": [{"target_key": CLIENT_KEY, "share": "0.80"}],
        "residual_share": "0.20",
    }
    ingest_planning_evidence(allocation, ledger_path=ledger)
    return ledger, direct, price, allocation


def test_billing_basis_combines_direct_and_allocated_cost_idempotently(tmp_path: Path):
    ledger, _direct, price, allocation = _seed_billing_ledger(tmp_path)

    first = build_billing_basis(ledger_path=ledger)
    second = build_billing_basis(ledger_path=ledger)

    assert first == second
    assert first.artifact_type == "billing_basis_report"
    assert "not an invoice" in first.disclaimer
    record = first.records[0]
    assert record.price_id == price.id
    assert record.revenue == Decimal("200.00")
    assert record.direct_cost == Decimal("20.00")
    assert record.allocated_cost == Decimal("80.00")
    assert record.total_cost == Decimal("100.00")
    assert record.margin == Decimal("100.00")
    assert record.allocation_ids == (allocation["record_id"],)
    assert record.financial_fact_ids
    assert "agreement-v1" in record.provenance
    assert first.exceptions[0].reason == "unattributed_allocation_residual"
    assert first.exceptions[0].amount == Decimal("20.00")


def test_billing_basis_id_changes_and_exposes_correction_and_price_revision(tmp_path: Path):
    ledger, direct, price, _allocation = _seed_billing_ledger(tmp_path)
    before = build_billing_basis(ledger_path=ledger).records[0]
    direct.write_text(
        "product,amount,currency,invoice_date,environment,client_id,application_id,app_instance_id\n"
        "Dedicated service,25.00,EUR,2026-07-01,production,acme,portal,prod-01\n",
        encoding="utf-8",
    )
    import_csv(direct, "hosteurope", ledger_path=ledger, force=True)
    revised_price = record_engagement_price(
        client_id="acme",
        application_id="portal",
        app_instance_id="prod-01",
        period_month="2026-07",
        amount="210.00",
        currency="EUR",
        source="agreement-v2",
        revision_of=price.id,
        ledger_path=ledger,
    )

    after = build_billing_basis(ledger_path=ledger).records[0]

    assert after.billing_basis_id != before.billing_basis_id
    assert after.price_id == revised_price.id
    assert after.price_revision_of == price.id
    assert after.financial_fact_corrections
    assert after.direct_cost == Decimal("25.00")
    assert after.margin == Decimal("105.00")


def test_client_cost_without_price_is_an_explicit_exception(tmp_path: Path):
    ledger = tmp_path / "ledger.db"
    source = tmp_path / "direct.csv"
    source.write_text(
        "product,amount,currency,invoice_date,client_id,application_id,app_instance_id\n"
        "Dedicated service,20.00,EUR,2026-07-01,acme,portal,prod-01\n",
        encoding="utf-8",
    )
    import_csv(source, "hosteurope", ledger_path=ledger)

    export = build_billing_basis(ledger_path=ledger)

    assert export.records == ()
    assert export.exceptions[0].reason == "missing_price_basis"
    assert export.exceptions[0].cost_attribution_key == CLIENT_KEY
    assert export.exceptions[0].amount == Decimal("20.00")