from decimal import Decimal
from pathlib import Path

import pytest

from payslip_ingest.parsers.p60 import P60ParserError, parse_p60

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


def _load(name: str) -> str:
    return (FIXTURES / name).read_text(encoding="utf-8")


def test_parses_meta_uk_p60_2024_25() -> None:
    result = parse_p60(_load("meta_uk_p60_2024_25.txt"))

    assert result.tax_year == "2024/25"
    assert result.employer == "Facebook UK Limited"
    assert result.employer_paye_ref == "120/FA12345"
    assert result.gross_pay == Decimal("232630.34")
    assert result.income_tax == Decimal("95820.11")
    assert result.national_insurance == Decimal("5172.40")
    assert result.student_loan == Decimal("0.00")
    assert result.tax_code == "1257L"


def test_parse_p60_raises_on_non_p60_text() -> None:
    with pytest.raises(P60ParserError, match="does not look like a P60"):
        parse_p60("Payslip for March 2025\nGross: £1000\n")


def test_parse_p60_raises_on_empty_text() -> None:
    with pytest.raises(P60ParserError):
        parse_p60("")


def test_parse_p60_raises_without_tax_year_anchor() -> None:
    with pytest.raises(P60ParserError, match="Tax year"):
        parse_p60("P60\nSome other content without the required anchor\n")


def test_parse_p60_handles_old_facebook_uk_ltd_spelling() -> None:
    """Pre-2022 P60s list the employer as `Facebook UK Ltd` (no `Limited`)."""
    text = _load("meta_uk_p60_2024_25.txt").replace("Facebook UK Limited", "Facebook UK Ltd")
    result = parse_p60(text)
    assert result.employer == "Facebook UK Ltd"


def test_parse_p60_student_loan_missing_is_none() -> None:
    """P60s for years without student-loan deductions omit that line entirely."""
    text = _load("meta_uk_p60_2024_25.txt")
    # Strip the Student Loan line (simulating a year pre-loan).
    stripped = "\n".join(line for line in text.splitlines() if "Student Loan" not in line)
    result = parse_p60(stripped)
    assert result.student_loan is None


def test_parse_p60_tax_code_missing_is_none() -> None:
    """Some historical P60s may not print a `Final tax code` line."""
    text = _load("meta_uk_p60_2024_25.txt").replace("Final tax code", "XXX")
    result = parse_p60(text)
    assert result.tax_code is None


def test_parse_p60_sums_ni_across_letter_bands() -> None:
    """Employees who cross NI letter bands mid-year get one row per letter."""
    text = _load("meta_uk_p60_2024_25.txt")
    # Append a second NI letter row — same shape as the A row in the fixture.
    extra = "C                  £6,396.00       £47,268.00            £1,000.00\n"
    augmented = text + "\n" + extra
    result = parse_p60(augmented)
    # 5172.40 (letter A, in fixture) + 1000.00 (letter C, appended)
    assert result.national_insurance == Decimal("6172.40")