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

import pytest

from app.parsers.base import ParserError
from app.parsers.csv_formats import detect_csv_format, parse_csv
from app.parsers.validate import balance_difference

FIXTURES = Path(__file__).parent / "fixtures"

FIXTURE_CASES = [
    ("DKB_2025.csv", "dkb_csv"),
    ("DKB_2026.csv", "dkb_csv"),
    ("VR_2025.csv", "vr_csv"),
    ("VR_2026.csv", "vr_csv"),
    ("HVB_2025.csv", "hvb_csv"),
    ("HVB_2026.csv", "hvb_csv"),
]


def _read_bytes(filename: str) -> bytes:
    return (FIXTURES / filename).read_bytes()


def _gebucht_count(raw: bytes) -> int:
    """Independently count 'Gebucht' rows without keeping/printing any row content."""
    # DKB is UTF-8 (with BOM); Status column is ASCII, safe to count on raw text.
    text = raw.decode("utf-8-sig")
    return text.count(';"Gebucht";')


@pytest.mark.parametrize("filename,fmt", FIXTURE_CASES)
def test_fixture_rowcount_and_ascending(filename, fmt):
    path = FIXTURES / filename
    if not path.exists():
        pytest.skip(f"Fixture {filename} fehlt")
    parsed = parse_csv(path)
    stmt = parsed.statement
    assert stmt.bank == fmt
    assert len(stmt.transactions) > 0
    dates = [t.booking_date for t in stmt.transactions]
    assert dates == sorted(dates), "Transaktionen muessen chronologisch aufsteigend sein"
    for t in stmt.transactions:
        assert isinstance(t.amount, Decimal)


@pytest.mark.parametrize("filename,fmt", [c for c in FIXTURE_CASES if c[1] == "vr_csv"])
def test_vr_fixture_balance_chain_and_anchor(filename, fmt):
    path = FIXTURES / filename
    if not path.exists():
        pytest.skip(f"Fixture {filename} fehlt")
    parsed = parse_csv(path)
    assert parsed.balance_checkable is True
    assert balance_difference(parsed.statement) == Decimal("0")
    assert parsed.anchor is not None
    anchor_date, anchor_balance = parsed.anchor
    assert isinstance(anchor_date, date)
    assert isinstance(anchor_balance, Decimal)


@pytest.mark.parametrize("filename,fmt", [c for c in FIXTURE_CASES if c[1] == "dkb_csv"])
def test_dkb_fixture_anchor_and_gebucht_filter(filename, fmt):
    path = FIXTURES / filename
    if not path.exists():
        pytest.skip(f"Fixture {filename} fehlt")
    raw = _read_bytes(filename)
    parsed = parse_csv(path)
    assert parsed.anchor is not None
    assert parsed.balance_checkable is False
    assert parsed.statement.opening_balance is None
    assert parsed.statement.closing_balance is None
    # Filtering: parsed transaction count must equal independently-counted
    # "Gebucht" data rows in the raw file (counts only, no content asserted).
    assert len(parsed.statement.transactions) == _gebucht_count(raw)
    for t in parsed.statement.transactions:
        assert t.counterparty != ""


@pytest.mark.parametrize("filename,fmt", [c for c in FIXTURE_CASES if c[1] == "hvb_csv"])
def test_hvb_fixture_no_balance_check(filename, fmt):
    path = FIXTURES / filename
    if not path.exists():
        pytest.skip(f"Fixture {filename} fehlt")
    parsed = parse_csv(path)
    assert parsed.balance_checkable is False
    assert parsed.anchor is None
    assert parsed.statement.opening_balance is None
    assert parsed.statement.closing_balance is None
    for t in parsed.statement.transactions:
        assert t.counterparty == ""


# ---------------------------------------------------------------------------
# Synthetic tests: minimal, fictitious CSVs constructed as bytes in-test.
# ---------------------------------------------------------------------------

def _dkb_row(booking, value, status, payer, payee, purpose, umsatztyp, iban, amount):
    return (
        f'"{booking}";"{value}";"{status}";"{payer}";"{payee}";'
        f'"{purpose}";"{umsatztyp}";"{iban}";"{amount}";"";"";""\r\n'
    )


def _build_dkb_csv() -> bytes:
    header = (
        '"Girokonto";"DE00123456780000000042"\r\n'
        '"Zeitraum:";"01.01.2025 - 31.01.2025"\r\n'
        '"Kontostand vom 31.01.2025:";"1.000,00\xa0€"\r\n'
        '""\r\n'
        '"Buchungsdatum";"Wertstellung";"Status";"Zahlungspflichtige*r";'
        '"Zahlungsempfänger*in";"Verwendungszweck";"Umsatztyp";"IBAN";"Betrag (€)";'
        '"Gläubiger-ID";"Mandatsreferenz";"Kundenreferenz"\r\n'
    )
    rows = (
        _dkb_row("15.01.25", "15.01.25", "Gebucht", "Max Muster", "Erika Beispiel",
                 "Testzweck A", "Ausgang", "DE00TESTIBAN1", "-10,00")
        + _dkb_row("10.01.25", "10.01.25", "Vorgemerkt", "Max Muster", "Erika Beispiel",
                    "Testzweck B (nicht gebucht)", "Ausgang", "DE00TESTIBAN1", "-99,00")
        + _dkb_row("05.01.25", "05.01.25", "Gebucht", "Erika Beispiel", "Max Muster",
                    "Testzweck C", "Eingang", "DE00TESTIBAN1", "50,00")
    )
    return (header + rows).encode("utf-8-sig")


def _build_vr_csv(saldi_consistent: bool = True) -> bytes:
    header = (
        "Bezeichnung Auftragskonto;IBAN Auftragskonto;BIC Auftragskonto;"
        "Bankname Auftragskonto;Buchungstag;Valutadatum;Name Zahlungsbeteiligter;"
        "IBAN Zahlungsbeteiligter;BIC (SWIFT-Code) Zahlungsbeteiligter;Buchungstext;"
        "Verwendungszweck;Betrag;Waehrung;Saldo nach Buchung;Bemerkung;"
        "Gekennzeichneter Umsatz;Glaeubiger ID;Mandatsreferenz\r\n"
    )
    # File order is descending (newest first), matches real format.
    saldo_newest = "120,00" if saldi_consistent else "999,00"
    rows = (
        "Testkonto;DE00TESTVR000000000001;GENODETEST;Test-Bank;15.01.2025;15.01.2025;"
        "Beispiel Gegenpartei;DE00GEGEN0001;GENODETEST;Buchung;Testzweck A;20,00;EUR;"
        f"{saldo_newest};;;;\r\n"
        "Testkonto;DE00TESTVR000000000001;GENODETEST;Test-Bank;05.01.2025;05.01.2025;"
        "Beispiel Gegenpartei 2;DE00GEGEN0002;GENODETEST;Buchung;Testzweck B;100,00;EUR;"
        "100,00;;;;\r\n"
    )
    return (header + rows).encode("utf-8-sig")


def _build_hvb_csv() -> bytes:
    header = "Kontonummer;Buchungsdatum;Valuta;Verwendungszweck;Betrag;Waehrung\r\n"
    rows = (
        "123456789;05.01.2025;05.01.2025;Testzweck mit Umlaut ä ö ü ß;-30,00;EUR\r\n"
        "123456789;15.01.2025;15.01.2025;Testzweck zwei;40,00;EUR\r\n"
    )
    return (header + rows).encode("utf-16")


def test_detect_dkb_csv():
    assert detect_csv_format(_build_dkb_csv()) == "dkb_csv"


def test_detect_vr_csv():
    assert detect_csv_format(_build_vr_csv()) == "vr_csv"


def test_detect_hvb_csv():
    assert detect_csv_format(_build_hvb_csv()) == "hvb_csv"


def test_detect_garbage_returns_none():
    assert detect_csv_format(b"this,is,not;a\nrecognised\tformat garbage 1234") is None


def test_dkb_synthetic_skips_non_gebucht_rows(tmp_path):
    p = tmp_path / "dkb_synth.csv"
    p.write_bytes(_build_dkb_csv())
    parsed = parse_csv(p)
    assert len(parsed.statement.transactions) == 2
    for t in parsed.statement.transactions:
        assert t.purpose != "" and "nicht gebucht" not in t.purpose


def test_dkb_synthetic_two_digit_year_parsed(tmp_path):
    p = tmp_path / "dkb_synth.csv"
    p.write_bytes(_build_dkb_csv())
    parsed = parse_csv(p)
    dates = [t.booking_date for t in parsed.statement.transactions]
    assert date(2025, 1, 5) in dates
    assert date(2025, 1, 15) in dates


def test_dkb_synthetic_anchor(tmp_path):
    p = tmp_path / "dkb_synth.csv"
    p.write_bytes(_build_dkb_csv())
    parsed = parse_csv(p)
    assert parsed.anchor == (date(2025, 1, 31), Decimal("1000.00"))
    assert parsed.balance_checkable is False


def test_vr_synthetic_balance_chain_ok(tmp_path):
    p = tmp_path / "vr_synth.csv"
    p.write_bytes(_build_vr_csv(saldi_consistent=True))
    parsed = parse_csv(p)
    assert parsed.balance_checkable is True
    assert balance_difference(parsed.statement) == Decimal("0")
    assert parsed.anchor == (date(2025, 1, 15), Decimal("120.00"))


def test_vr_synthetic_balance_chain_break_raises(tmp_path):
    p = tmp_path / "vr_synth_broken.csv"
    p.write_bytes(_build_vr_csv(saldi_consistent=False))
    with pytest.raises(ParserError):
        parse_csv(p)


def test_hvb_synthetic_utf16_decode(tmp_path):
    p = tmp_path / "hvb_synth.csv"
    p.write_bytes(_build_hvb_csv())
    parsed = parse_csv(p)
    stmt = parsed.statement
    assert len(stmt.transactions) == 2
    assert stmt.transactions[0].booking_date == date(2025, 1, 5)
    assert stmt.transactions[1].booking_date == date(2025, 1, 15)
    assert "ä" in stmt.transactions[0].purpose
    assert all(t.counterparty == "" for t in stmt.transactions)
    assert parsed.balance_checkable is False
    assert parsed.anchor is None


def test_parse_csv_unknown_format_raises(tmp_path):
    p = tmp_path / "garbage.csv"
    p.write_bytes(b"not,a;known\nformat\n")
    with pytest.raises(ParserError):
        parse_csv(p)


CSV_FILES = ["DKB_2025", "DKB_2026", "VR_2025", "VR_2026", "HVB_2025", "HVB_2026"]


@pytest.mark.parametrize("name", CSV_FILES)
def test_csv_expected_values(name):
    path = FIXTURES / f"{name}.csv"
    exp_path = FIXTURES / f"expected_csv_{name}.json"
    if not path.exists() or not exp_path.exists():
        pytest.skip("Fixture oder expected-Datei fehlt")
    result = parse_csv(path)
    exp = json.loads(exp_path.read_text())
    txs = result.statement.transactions
    assert len(txs) == exp["transaction_count"]
    for c in exp["spot_checks"]:
        t = txs[c["index"]]
        assert str(t.booking_date) == c["booking_date"]
        assert str(t.amount) == c["amount"]
        assert c["counterparty_contains"] in t.counterparty
        assert c["purpose_contains"] in t.purpose