from unittest.mock import Mock

from fenrirscreenreader.screenDriver.vcsaDriver import driver as VcsaDriver


class BulkReadFailure:
    def __init__(self, chunks):
        self.chunks = iter(chunks)
        self.readline_calls = 0

    def seek(self, offset):
        assert offset == 0

    def read(self):
        raise OSError(22, "Invalid argument")

    def readline(self, size):
        assert size == 1
        self.readline_calls += 1
        if self.readline_calls > 3:
            raise RuntimeError("read continued after EOF")
        return next(self.chunks)


class TransientInvalidArgumentRead:
    def __init__(self, payload):
        self.payload = payload
        self.read_calls = 0
        self.readline_calls = 0

    def seek(self, offset):
        assert offset == 0

    def read(self):
        self.read_calls += 1
        if self.read_calls == 1:
            raise OSError(22, "Invalid argument")
        return self.payload

    def readline(self, size):
        self.readline_calls += 1
        return b""


def build_vcsa_driver():
    vcsa_driver = VcsaDriver.__new__(VcsaDriver)
    vcsa_driver.env = {
        "runtime": {
            "DebugManager": Mock(),
        }
    }
    vcsa_driver.read_retry_delay = 0
    return vcsa_driver


def test_vcsa_read_fallback_stops_at_eof():
    vcsa_driver = build_vcsa_driver()
    screen_file = BulkReadFailure([b"a", b"b", b""])

    assert vcsa_driver.read_file(screen_file) == b"ab"
    assert screen_file.readline_calls == 3


def test_vcsa_read_retries_transient_invalid_argument():
    vcsa_driver = build_vcsa_driver()
    screen_file = TransientInvalidArgumentRead(b"\x01\x02\x00\x00x")

    assert vcsa_driver.read_file(screen_file) == b"\x01\x02\x00\x00x"
    assert screen_file.read_calls == 2
    assert screen_file.readline_calls == 0