"""Tests for the PRF -> HKDF -> Nostr key derivation."""

from __future__ import annotations

import pytest

from nostr_passkey.derivation import PRF_OUTPUT_BYTES, derive_nostr_key

PRF_A = bytes.fromhex("11" * 32)
PRF_B = bytes.fromhex("22" * 32)


def test_deterministic_for_same_inputs() -> None:
    a = derive_nostr_key(PRF_A, salt="alpha")
    b = derive_nostr_key(PRF_A, salt="alpha")
    assert a == b


def test_different_salts_produce_different_keys() -> None:
    a = derive_nostr_key(PRF_A, salt="alpha")
    b = derive_nostr_key(PRF_A, salt="beta")
    assert a.privkey_hex != b.privkey_hex
    assert a.npub != b.npub


def test_different_prf_outputs_produce_different_keys() -> None:
    a = derive_nostr_key(PRF_A, salt="alpha")
    b = derive_nostr_key(PRF_B, salt="alpha")
    assert a.privkey_hex != b.privkey_hex


def test_no_salt_differs_from_nonempty_salt() -> None:
    no_salt = derive_nostr_key(PRF_A)
    salted = derive_nostr_key(PRF_A, salt="x")
    assert no_salt.privkey_hex != salted.privkey_hex


def test_rejects_wrong_prf_length() -> None:
    with pytest.raises(ValueError):
        derive_nostr_key(b"too-short")
    with pytest.raises(ValueError):
        derive_nostr_key(bytes(PRF_OUTPUT_BYTES + 1))


def test_output_shapes() -> None:
    ident = derive_nostr_key(PRF_A)
    assert len(ident.privkey_hex) == 64  # 32 bytes hex
    assert len(ident.pubkey_hex) == 64   # x-only, 32 bytes hex
    assert ident.nsec.startswith("nsec1")
    assert ident.npub.startswith("npub1")