#!/usr/bin/python

import mock

# subp returns basically stdout and stderr of invoking the command
#
##
## I'm trying to write and test a 'lsb_release()' function
## which returns basically what lsb_release --<codename|release> would do
## i'd like to cache the result for future calls, and
## am doing that via use of a global
##
## since the 'util' module is only opened once, the cache of __lsb_release
## is working correctly, and my tests are not able to wrap
## calls to the 'lsb_release' command. since the result gets cached.
##
## Note, though that using 'reset_lsb()' works as expected.

__lsb_release = None

def reset_lsb():
    global __lsb_release
    __lsb_release = None


def lsb_release(field="codename"):
    fields = ('description', 'release', 'codename', 'id')
    if field not in fields:
        raise ValueError("Invalid field: %s. Must be one of %s" %
                         (field, ','.join(fields)))

    global __lsb_release
    if __lsb_release is None:
        data = {}
        for k in fields:
            try:
                out, err = subp(['lsb_release', '--short', '--%s' % k], 
                                capture=True)
                data[k] = out.strip()
            except ProcessExecutionError as e:
                LOG.warn("Unable to get lsb_release/%s: %s", k, e)
                data[k] = "UNAVAILABLE"
        __lsb_release = data
    return __lsb_release

## test classes 
class TestLsbRelease(TestCase):
    @mock.patch("curtin.util.subp")
    def test_expected(self, mock_subp):
        ### HELP ####
        ## This works
        util.__reset_lsb()
        ## This does not.  The __lsb_release doesn't get set to None
        ## and the cached value from the other run is used.
        #util.__lsb_release = None

        rdata = {'id': 'Ubuntu', 'description': 'Ubuntu 14.04.3 LTS',
                 'codename': 'trusty', 'release': '14.04'}
        def fake_subp(cmd, capture=False):
            if cmd[0:2] == ["lsb_release", "--short"]:
                field = cmd[2].replace("--", "")
                return (rdata[field], "")
            return mock.DEFAULT
    
        mock_subp.side_effect = fake_subp
        found = util.lsb_release()
        mock_subp.assert_called_with(['lsb_release', '--short', '--id'],
                                          capture=True)
        self.assertEqual(found, rdata)

    @mock.patch("curtin.util.subp")
    def test_unavailable(self, mock_subp):
        util.__lsb_release = None

        def doraise(*args, **kwargs):
            raise util.ProcessExecutionError("bar")
        mock_subp.side_effect = doraise

        expected = {k: "UNAVAILABLE" for k in
                    ('id', 'description', 'codename', 'release')}
        self.assertEqual(util.lsb_release(), expected)