from tempfile import NamedTemporaryFile
import sys

import pytest

from ray.dashboard.modules.job.utils import file_tail_iterator


@pytest.fixture
def tmp():
    with NamedTemporaryFile() as f:
        yield f.name


class TestIterLine:
    def test_invalid_type(self):
        with pytest.raises(TypeError, match="path must be a string"):
            next(file_tail_iterator(1))

    def test_file_not_created(self, tmp):
        it = file_tail_iterator(tmp)
        assert next(it) is None
        f = open(tmp, "w")
        f.write("hi\n")
        f.flush()
        assert next(it) is not None

    def test_wait_for_newline(self, tmp):
        it = file_tail_iterator(tmp)
        assert next(it) is None

        f = open(tmp, "w")
        f.write("no_newline_yet")
        assert next(it) is None
        f.write("\n")
        f.flush()
        assert next(it) == "no_newline_yet\n"

    def test_multiple_lines(self, tmp):
        it = file_tail_iterator(tmp)
        assert next(it) is None

        f = open(tmp, "w")

        num_lines = 10
        for i in range(num_lines):
            s = f"{i}\n"
            f.write(s)
            f.flush()
            assert next(it) == s

        assert next(it) is None

    def test_batching(self, tmp):
        it = file_tail_iterator(tmp)
        assert next(it) is None

        f = open(tmp, "w")

        # Write lines in batches of 10, check that we get them back in batches.
        for _ in range(100):
            num_lines = 10
            for i in range(num_lines):
                f.write(f"{i}\n")
            f.flush()

            assert next(it) == "\n".join(str(i) for i in range(10)) + "\n"

        assert next(it) is None

    def test_delete_file(self):
        with NamedTemporaryFile() as tmp:
            it = file_tail_iterator(tmp.name)
            f = open(tmp.name, "w")

            assert next(it) is None

            f.write("hi\n")
            f.flush()

            assert next(it) == "hi\n"

        # Calls should continue returning None after file deleted.
        assert next(it) is None


if __name__ == "__main__":
    sys.exit(pytest.main(["-v", __file__]))