# Copyright (C) 2009, 2011 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Tests for OS Locks."""


from .. import (
    debug,
    errors,
    lock,
    tests,
    )
from .scenarios import load_tests_apply_scenarios


load_tests = load_tests_apply_scenarios


class TestOSLock(tests.TestCaseInTempDir):

    scenarios = [(
        name, {
            'write_lock': write_lock,
            'read_lock': read_lock})
        for name, write_lock, read_lock in lock._lock_classes]

    read_lock = None
    write_lock = None

    def setUp(self):
        super(TestOSLock, self).setUp()
        self.build_tree(['a-lock-file'])

    def test_create_read_lock(self):
        r_lock = self.read_lock('a-lock-file')
        r_lock.unlock()

    def test_create_write_lock(self):
        w_lock = self.write_lock('a-lock-file')
        w_lock.unlock()

    def test_read_locks_share(self):
        r_lock = self.read_lock('a-lock-file')
        try:
            lock2 = self.read_lock('a-lock-file')
            lock2.unlock()
        finally:
            r_lock.unlock()

    def test_write_locks_are_exclusive(self):
        w_lock = self.write_lock('a-lock-file')
        try:
            self.assertRaises(errors.LockContention,
                              self.write_lock, 'a-lock-file')
        finally:
            w_lock.unlock()

    def test_read_locks_block_write_locks(self):
        r_lock = self.read_lock('a-lock-file')
        try:
            if lock.have_fcntl and self.write_lock is lock._fcntl_WriteLock:
                # With -Dlock, fcntl locks are properly exclusive
                debug.debug_flags.add('strict_locks')
                self.assertRaises(errors.LockContention,
                                  self.write_lock, 'a-lock-file')
                # But not without it
                debug.debug_flags.remove('strict_locks')
                try:
                    w_lock = self.write_lock('a-lock-file')
                except errors.LockContention:
                    self.fail('Unexpected success. fcntl read locks'
                              ' do not usually block write locks')
                else:
                    w_lock.unlock()
                    self.knownFailure('fcntl read locks don\'t'
                                      ' block write locks without -Dlock')
            else:
                self.assertRaises(errors.LockContention,
                                  self.write_lock, 'a-lock-file')
        finally:
            r_lock.unlock()

    def test_write_locks_block_read_lock(self):
        w_lock = self.write_lock('a-lock-file')
        try:
            if lock.have_fcntl and self.read_lock is lock._fcntl_ReadLock:
                # With -Dlock, fcntl locks are properly exclusive
                debug.debug_flags.add('strict_locks')
                self.assertRaises(errors.LockContention,
                                  self.read_lock, 'a-lock-file')
                # But not without it
                debug.debug_flags.remove('strict_locks')
                try:
                    r_lock = self.read_lock('a-lock-file')
                except errors.LockContention:
                    self.fail('Unexpected success. fcntl write locks'
                              ' do not usually block read locks')
                else:
                    r_lock.unlock()
                    self.knownFailure('fcntl write locks don\'t'
                                      ' block read locks without -Dlock')
            else:
                self.assertRaises(errors.LockContention,
                                  self.read_lock, 'a-lock-file')
        finally:
            w_lock.unlock()


    def test_temporary_write_lock(self):
        r_lock = self.read_lock('a-lock-file')
        try:
            status, w_lock = r_lock.temporary_write_lock()
            self.assertTrue(status)
            # This should block another write lock
            try:
                self.assertRaises(errors.LockContention,
                                  self.write_lock, 'a-lock-file')
            finally:
                r_lock = w_lock.restore_read_lock()
            # We should be able to take a read lock now
            r_lock2 = self.read_lock('a-lock-file')
            r_lock2.unlock()
        finally:
            r_lock.unlock()

    def test_temporary_write_lock_fails(self):
        r_lock = self.read_lock('a-lock-file')
        try:
            r_lock2 = self.read_lock('a-lock-file')
            try:
                status, w_lock = r_lock.temporary_write_lock()
                self.assertFalse(status)
                # Taking out the lock requires unlocking and locking again, so
                # we have to replace the original object
                r_lock = w_lock
            finally:
                r_lock2.unlock()
            # We should be able to take a read lock now
            r_lock2 = self.read_lock('a-lock-file')
            r_lock2.unlock()
        finally:
            r_lock.unlock()
