"""Unit tests for the deterministic half of referral_service: code
generation, normalisation, and lookup helpers. DB-backed linkage logic
is exercised manually via the dev container."""
from __future__ import annotations

import pytest

from app.services.referral_service import (
    _ALPHABET,
    _CODE_LEN,
    generate_code,
    normalise_code,
)


# ---------------------------------------------------------------------------
# Code generation
# ---------------------------------------------------------------------------


def test_generate_code_length():
    code = generate_code()
    assert len(code) == _CODE_LEN


def test_generate_code_alphabet():
    """Every character must come from the unambiguous alphabet."""
    for _ in range(50):
        code = generate_code()
        for ch in code:
            assert ch in _ALPHABET, f"unexpected char {ch!r} in {code!r}"


def test_generate_code_no_ambiguous_chars():
    """0, O, 1, I, L are excluded to avoid dictation errors."""
    for _ in range(200):
        code = generate_code()
        assert not (set(code) & set("01IOL"))


def test_generate_code_diversity():
    """Two consecutive generations should almost never collide
    (sanity check on the RNG)."""
    a, b = generate_code(), generate_code()
    assert a != b


# ---------------------------------------------------------------------------
# normalise_code
# ---------------------------------------------------------------------------


def test_normalise_uppercases():
    assert normalise_code("abcdefgh") == "ABCDEFGH"


def test_normalise_strips_disallowed_chars():
    """Users may paste with spaces / dashes / quotes — strip those."""
    assert normalise_code(" ABCD-EFGH ") == "ABCDEFGH"
    assert normalise_code('"ABCDEFGH"') == "ABCDEFGH"


def test_normalise_rejects_wrong_length():
    """If too short / too long after cleaning, return None — bogus."""
    assert normalise_code("ABC") is None
    assert normalise_code("ABCDEFGHX") is None
    # Long enough but ambiguous chars stripped → still wrong length:
    assert normalise_code("ABCDEFG0") is None    # 0 stripped → 7 chars


def test_normalise_rejects_none_and_empty():
    assert normalise_code(None) is None
    assert normalise_code("") is None
    assert normalise_code("   ") is None


def test_normalise_preserves_valid_code():
    """A code that's already canonical should pass through unchanged."""
    code = generate_code()
    assert normalise_code(code) == code