import logging
import subprocess
import tempfile
import unittest


class TestTail(unittest.TestCase):

    def setUp(self):
        self.log_file = tempfile.NamedTemporaryFile()
        self.logrotate_config = tempfile.NamedTemporaryFile()
        self.logrotate_config.write("""%s {
            copytruncate
            notifempty
            missingok
            rotate 1
            weekly
        }""" % self.log_file.name)
        self.logrotate_config.flush()
        self.logrotate_state_file = tempfile.NamedTemporaryFile()
        self.last_line = None

    def _trigger_logrotate(self):
        subprocess.check_call([
            'logrotate',
            '-v',  # Verbose logging
            '-f',  # Force the rotation even though the file isn't old
            # Create a state file that you have file permissions for
            '-s', self.logrotate_state_file.name,
            self.logrotate_config.name
        ])

    def test_logrotate_copytruncate(self):
        from collector.checks.utils import TailFile

        def line_parser(l):
            self.last_line = l

        tail = TailFile(logging.getLogger(), self.log_file.name, line_parser)
        self.assertEqual(tail._size, 0)

        # Write some data to the log file
        init_string = "hey there, I am a log\n"
        self.log_file.write(init_string)
        self.log_file.flush()

        # Consume from the tail
        gen = tail.tail(line_by_line=False, move_end=True)
        gen.next()

        # Verify that the tail consumed the data I wrote
        self.assertEqual(tail._size, len(init_string))

        try:
            # Trigger a copytruncate logrotation on the log file
            self._trigger_logrotate()

            # Write a new line to the log file
            new_string = "I am shorter\n"
            self.log_file.write(new_string)
            self.log_file.flush()

            # Verify that the tail recognized the logrotation
            gen.next()
            self.assertEqual(self.last_line, new_string[:-1], self.last_line)
        except OSError:
            "logrotate is not present"

if __name__ == '__main__':
    logging.getLogger().setLevel(logging.DEBUG)
    logging.getLogger().addHandler(logging.StreamHandler())
    unittest.main()