import builtins
import hashlib

import pytest

from hasher import hash_file


def test_sha256_matches_hashlib(tmp_path):
    p = tmp_path / "f.bin"
    # Larger than the 64KB read chunk so the streaming loop iterates.
    data = b"hello world\n" * 10000
    p.write_bytes(data)
    assert hash_file(p, "sha256") == hashlib.sha256(data).hexdigest()


def test_default_algorithm_is_sha256(tmp_path):
    p = tmp_path / "f.bin"
    p.write_bytes(b"abc")
    assert hash_file(p) == hashlib.sha256(b"abc").hexdigest()


def test_blake3_produces_expected_digest(tmp_path):
    blake3 = pytest.importorskip("blake3")
    p = tmp_path / "f.bin"
    p.write_bytes(b"abc")
    assert hash_file(p, "blake3") == blake3.blake3(b"abc").hexdigest()


def test_blake3_missing_raises_importerror(tmp_path, monkeypatch):
    p = tmp_path / "f.bin"
    p.write_bytes(b"abc")
    real_import = builtins.__import__

    def fake_import(name, *args, **kwargs):
        if name == "blake3":
            raise ImportError("simulated missing blake3")
        return real_import(name, *args, **kwargs)

    monkeypatch.setattr(builtins, "__import__", fake_import)
    with pytest.raises(ImportError):
        hash_file(p, "blake3")