"""TDD red tests for S1 crypto (QUALITY-125, SETTINGS-20/25)."""
import base64
import os
import tempfile

import pytest

from backend import crypto


def _valid_key_b64() -> str:
    # 32 raw bytes base64
    raw = b"0123456789abcdef0123456789abcdef"  # exactly 32
    return base64.b64encode(raw).decode()


def test_crypto_roundtrip_encrypt_decrypt(monkeypatch):
    """Given: valid SLAB_AES_KEY; When: encrypt then decrypt; Then: original value (QUALITY-125)."""
    key_b64 = _valid_key_b64()
    monkeypatch.setenv("SLAB_AES_KEY", key_b64)
    plaintext = "my-secret-app-password-123"
    ct_b64 = crypto.encrypt(plaintext)
    assert isinstance(ct_b64, str)
    recovered = crypto.decrypt(ct_b64)
    assert recovered == plaintext


def test_crypto_decrypt_tampered_raises_clean_error(monkeypatch):
    """Given: valid key; When: tamper the blob (flip a byte); Then: raises detectable error, no crash, no raw leak."""
    key_b64 = _valid_key_b64()
    monkeypatch.setenv("SLAB_AES_KEY", key_b64)
    plaintext = "secret"
    ct_b64 = crypto.encrypt(plaintext)
    # tamper: flip last byte
    blob = bytearray(base64.b64decode(ct_b64))
    blob[-1] ^= 0xFF
    tampered_b64 = base64.b64encode(blob).decode()
    with pytest.raises(Exception) as exc:  # will be specific like InvalidTag or our wrapper
        crypto.decrypt(tampered_b64)
    # must not contain the raw blob or secret
    msg = str(exc.value).lower()
    assert "secret" not in msg
    assert plaintext not in msg
    # detectable, e.g. contains "decrypt" or "tag" or "corrupt"
    assert any(k in msg for k in ("decrypt", "tag", "invalid", "corrupt", "fail"))


def test_crypto_missing_key_raises(monkeypatch):
    """Given: no SLAB_AES_KEY; When: encrypt; Then: clear runtime error."""
    monkeypatch.delenv("SLAB_AES_KEY", raising=False)
    with pytest.raises(RuntimeError, match="SLAB_AES_KEY"):
        crypto.encrypt("x")