import os
import stat
import tempfile
import unittest

from atomic_write import atomic_write, atomic_write_text, atomic_write_bytes


class TestAtomicWrite(unittest.TestCase):
    def setUp(self):
        self.d = tempfile.mkdtemp()
        self.p = os.path.join(self.d, "out.txt")

    def test_basic_text(self):
        with atomic_write(self.p) as f:
            f.write("hello world")
        with open(self.p) as f:
            self.assertEqual(f.read(), "hello world")

    def test_bytes(self):
        atomic_write_bytes(self.p, b"\x00\x01\x02")
        with open(self.p, "rb") as f:
            self.assertEqual(f.read(), b"\x00\x01\x02")

    def test_text_helper(self):
        atomic_write_text(self.p, "abc")
        with open(self.p) as f:
            self.assertEqual(f.read(), "abc")

    def test_no_partial_on_exception(self):
        # pre-existing content must survive a failed write
        with open(self.p, "w") as f:
            f.write("ORIGINAL")
        try:
            with atomic_write(self.p) as f:
                f.write("PARTIAL")
                raise RuntimeError("boom")
        except RuntimeError:
            pass
        with open(self.p) as f:
            self.assertEqual(f.read(), "ORIGINAL")

    def test_no_temp_leftover_on_exception(self):
        try:
            with atomic_write(self.p) as f:
                f.write("x")
                raise ValueError("x")
        except ValueError:
            pass
        leftovers = [n for n in os.listdir(self.d) if n.startswith(".atomic_")]
        self.assertEqual(leftovers, [])

    def test_preserves_mode(self):
        with open(self.p, "w") as f:
            f.write("x")
        os.chmod(self.p, 0o600)
        with atomic_write(self.p) as f:
            f.write("y")
        self.assertEqual(stat.S_IMODE(os.stat(self.p).st_mode), 0o600)

    def test_overwrite_replaces(self):
        atomic_write_text(self.p, "first")
        atomic_write_text(self.p, "second")
        with open(self.p) as f:
            self.assertEqual(f.read(), "second")

    def test_creates_parent_dir(self):
        p = os.path.join(self.d, "sub", "deep", "f.txt")
        atomic_write_text(p, "nested")
        with open(p) as f:
            self.assertEqual(f.read(), "nested")

    def test_rejects_bad_mode(self):
        with self.assertRaises(ValueError):
            with atomic_write(self.p, mode="a"):
                pass

    def test_empty_write(self):
        atomic_write_text(self.p, "")
        self.assertTrue(os.path.exists(self.p))
        with open(self.p) as f:
            self.assertEqual(f.read(), "")


if __name__ == "__main__":
    unittest.main(verbosity=2)