# Copyright (C) 2009 Canonical
#
# Authors:
#  Michael Vogt
#
# 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; version 3.
#
# 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

import dbus
import gc
import gettext
from gi.repository import GObject
from gi.repository import GLib
from gi.repository import Gio
import logging
import math
import os
import re
import tempfile
import traceback
import time
import xml.sax.saxutils
import errno

# py3 compat
try:
    from urllib.parse import urlsplit
    urlsplit  # pyflakes
except ImportError:
    from urlparse import urlsplit

from enums import Icons, APP_INSTALL_PATH_DELIMITER
from paths import (
    SOFTWARE_CENTER_CACHE_DIR,
    OEM_CHANNEL_DESCRIPTOR,
)

from config import get_config

from gettext import gettext as _

# define additional entities for the unescape method, needed
# because only '&', '<', and '>' are included by default
ESCAPE_ENTITIES = {"'": "'",
                   '"': '"'}

LOG = logging.getLogger(__name__)


class UnimplementedError(Exception):
    pass


class ExecutionTime(object):
    """
    Helper that can be used in with statements to have a simple
    measure of the timing of a particular block of code, e.g.
    with ExecutinTime("db flush"):
        db.flush()
    """
    def __init__(self, info="", with_traceback=False,
                 suppress_less_than_n_seconds=0.1):
        self.info = info
        self.with_traceback = with_traceback
        self.suppress_less_than_n_seconds = suppress_less_than_n_seconds

    def __enter__(self):
        self.now = time.time()

    def __exit__(self, type, value, stack):
        time_spend = time.time() - self.now
        if time_spend < self.suppress_less_than_n_seconds:
            return
        logger = logging.getLogger("softwarecenter.performance")
        logger.debug("%s: %s" % (self.info, time_spend))
        if self.with_traceback:
            log_traceback("populate model from query: '%s' (threaded: %s)")


class TraceActiveObjectTypes(object):
    """ A context manager that tracks what and how many new object types
        are added in the context block.

    Note that due to the gc.collect() call this is slow and should not
    be used in production code, but its very useful inside e.g. tests
    """

    def __init__(self, info):
        self.info = info
        self._known_obj_ids = set()

    def __enter__(self):
        gc.collect()
        for obj in gc.get_objects():
            self._known_obj_ids.add(id(obj))

    def __exit__(self, atype, value, stack):
        # ensure we start clean
        gc.collect()
        new_obj_types = {}
        for obj in gc.get_objects():
            if id(obj) in self._known_obj_ids:
                continue
            self._known_obj_ids.add(id(obj))
            if not type(obj) in new_obj_types:
                new_obj_types[type(obj)] = 0
            new_obj_types[type(obj)] += 1
        print "+++ new types after '%s':" % self.info
        #print new_obj_types
        for v in sorted(new_obj_types, key=new_obj_types.get):
            print v, new_obj_types[v]
        print "/+++\n"


class TraceMemoryUsage(object):
    """Trace amount of memory used by the app using /proc/$$/statm"""

    def __init__(self, info):
        self.info = info

    def __enter__(self):
        self.resident = self._get_mem_from_proc()["resident"]
        self.data = self._get_mem_from_proc()["data"]

    def __exit__(self, atype, value, stack):
        now_resident = self._get_mem_from_proc()["resident"] - self.resident
        now_data = self._get_mem_from_proc()["data"] - self.data
        print "++++ MEMORY DELTA for '%s': res: %s data: %s (%s %s)\n" % (
            self.info,
            # assume page size of 4k here
            get_nice_size(now_resident * 4 * 1024),
            get_nice_size(now_data * 4 * 1024),
            now_resident, now_data)

    def _get_mem_from_proc(self):
        with open("/proc/%i/statm" % os.getpid()) as f:
            size, resident, share, text, lib, data, dt = f.readline().split()
        return {'resident': int(resident),
                'data': int(data),
                }


def utf8(s):
    """
    Takes a string or unicode object and returns a utf-8 encoded
    string, errors are ignored
    """
    if s is None:
        return None
    if isinstance(s, unicode):
        return s.encode("utf-8", "ignore")
    return unicode(s, "utf8", "ignore").encode("utf8")


def log_traceback(info):
    """
    Helper that can be used as a debug helper to show what called
    the code at this place. Logs to softwarecenter.traceback
    """
    logger = logging.getLogger("softwarecenter.traceback")
    logger.debug("%s: %s" % (info, "".join(traceback.format_stack())))


def wait_for_apt_cache_ready(f):
    """ decorator that ensures that self.cache is ready using a
        gtk idle_add - needs a cache as argument
    """
    def wrapper(*args, **kwargs):
        self = args[0]
        # check if the cache is ready and
        window = None
        if hasattr(self, "app_view"):
            window = self.app_view.get_window()
        if not self.cache.ready:
            if window:
                window.set_cursor(self.busy_cursor)
            GLib.timeout_add(500, lambda: wrapper(*args, **kwargs))
            return False
        # cache ready now
        if window:
            window.set_cursor(None)
        f(*args, **kwargs)
        return False
    return wrapper


def capitalize_first_word(string):
    """ this takes a package synopsis and uppercases the first word's
        first letter
    """
    if len(string) > 1 and string[0].isalpha() and not string[0].isupper():
        return string[0].capitalize() + string[1:]
    return string


def normalize_package_description(desc):
    """ this takes a package description and normalizes it
        so that all unneeded \n are stripped away and all
        enumerations are at the start of the line and start with a "*"
        E.g.:
        Some potentially very long paragraph that is in a single line.
        A new paragraph.
        A list:
        * item1
        * item2 that may again be very very long
    """

    def get_indent(part, whitespace=" "):
        i = 0
        for i, char in enumerate(part):
            if char != whitespace:
                break
        return i

    def maybe_add_space(prefix):
        if not (prefix.endswith("\n") or prefix.endswith(" ")):
            return " "
        else:
            return ""

    BULLETS = ('- ', '* ', 'o ')
    norm_description = ""
    in_blist = False
    # process it
    for i, part in enumerate(desc.split("\n")):
        indent = get_indent(part)
        part = part.strip()

        # explicit newline
        if not part:
            norm_description += '\n'
            continue
        # check if in a enumeration
        if part[:2] in BULLETS:
            in_blist = True
            norm_description += "\n" + indent * ' ' + "* " + part[2:]
        elif in_blist and indent > 0:
            norm_description += " " + part
        elif part.endswith('.') or part.endswith(':'):
            if in_blist:
                in_blist = False
                norm_description += '\n'
            norm_description += maybe_add_space(norm_description) + part + '\n'
        else:
            in_blist = False
            norm_description += maybe_add_space(norm_description) + part
    return norm_description.strip()


def get_title_from_html(html):
    """ takes a html string and returns the document title,
        if the document has no title it uses the first h1
        (but only if that has no further html tags)

        returns "" if it can't find anything or can't parse the html
    """
    import xml.etree.ElementTree
    try:
        root = xml.etree.ElementTree.fromstring(html)
    except Exception as e:
        logging.warn("failed to parse: '%s' (%s)" % (html, e))
        return ""
    title = root.findall(".//title")
    if title:
        text = title[0].text
        return text
    all_h1 = root.findall(".//h1")
    if all_h1:
        h1 = all_h1[0]
        # we don't support any sub html in the h1 when
        if len(h1) == 0:
            return h1.text
    return ""


def htmlize_package_description(desc):
    html = ""
    inside_li = False
    for part in normalize_package_description(desc).split("\n"):
        stripped_part = part.strip()
        if not stripped_part:
            continue
        if stripped_part.startswith("* "):
            if not inside_li:
                html += "<ul>"
                inside_li = True
            html += '<li>%s</li>' % stripped_part[2:]
        else:
            if inside_li:
                html += "</ul>"
            html += '<p tabindex="0">%s</p>' % part
            inside_li = False
    if inside_li:
        html += "</ul>"
    return html


def get_http_proxy_string_from_libproxy(url):
    """Helper that uses libproxy to get the http proxy for the given url """
    import libproxy
    pf = libproxy.ProxyFactory()
    proxies = pf.getProxies(url)
    # FIXME: how to deal with multiple proxies?
    proxy = proxies[0]
    if proxy == "direct://":
        return ""
    else:
        return proxy


def get_http_proxy_string_from_gsettings():
    """Helper that gets the http proxy from gsettings

    May raise a exception if there is no schema for the proxy
    (e.g. on non-gnome systems)

    Returns: string with http://auth:pw@proxy:port/, None
    """
    # check if this is actually available and usable. if not
    # well ... it segfaults (thanks pygi)
    schemas = ["org.gnome.system.proxy", "org.gnome.system.proxy.http"]
    for schema in schemas:
        if not schema in Gio.Settings.list_schemas():
            raise ValueError("no schema '%s'" % schema)

    # Check to see if proxy mode is set to none before checking for host
    # (LP: #982567)
    psettings = Gio.Settings.new("org.gnome.system.proxy")
    if "none" in psettings.get_string("mode"):
        return None

    # If proxy mode isn't "none" check to see if host and port is set
    settings = Gio.Settings.new("org.gnome.system.proxy.http")
    if settings.get_string("host"):
        authentication = ""
        if settings.get_boolean("use-authentication"):
            user = settings.get_string("authentication-user")
            password = settings.get_string("authentication-password")
            authentication = "%s:%s@" % (user, password)
        host = settings.get_string("host")
        port = settings.get_int("port")
        # strip leading http (if there is one)
        if host.startswith("http://"):
            host = host[len("http://"):]
        http_proxy = "http://%s%s:%s/" % (authentication, host, port)
        if host:
            return http_proxy
    # no proxy
    return None


def encode_for_xml(unicode_data, encoding="ascii"):
    """ encode a given string for xml """
    return unicode_data.encode(encoding, 'xmlcharrefreplace')


def decode_xml_char_reference(s):
    """ takes a string like
        'Search&#x2026;'
        and converts it to
        'Search...'
    """
    p = re.compile("\&\#x(\d\d\d\d);")
    return p.sub(r"\u\1", s).decode("unicode-escape")


def unescape(text):
    """
    unescapes the given text
    """
    return xml.sax.saxutils.unescape(text, ESCAPE_ENTITIES)


def uri_to_filename(uri):
    try:
        import apt_pkg
        return apt_pkg.uri_to_filename(uri)
    except ImportError:
        p1 = re.compile("http://[^/]+/")
        uri = re.sub(p1, "", uri)
        return uri.replace("/", "_")


def human_readable_name_from_ppa_uri(ppa_uri):
    """ takes a PPA uri and returns a human readable name for it """
    name = urlsplit(ppa_uri).path
    if name.endswith("/ubuntu"):
        return name[0:-len("/ubuntu")]
    return name


def sources_filename_from_ppa_entry(entry):
    """
    takes a PPA SourceEntry and returns a filename suitable for sources.list.d
    """
    import apt_pkg
    name = "%s.list" % apt_pkg.uri_to_filename(entry.uri)
    return name


def obfuscate_private_ppa_details(text):
    """
    hides any private PPA details that may be found in the given text
    """
    result = text
    s = text.split()
    for item in s:
        if "private-ppa.launchpad.net" in item:
            url_parts = urlsplit(item)
            if url_parts.username:
                result = result.replace(url_parts.username, "hidden")
            if url_parts.password:
                result = result.replace(url_parts.password, "hidden")
    return result


def release_filename_in_lists_from_deb_line(debline):
    """
    takes a debline and returns the filename of the Release file
    in /var/lib/apt/lists
    """
    import aptsources.sourceslist
    entry = aptsources.sourceslist.SourceEntry(debline)
    name = "%s_dists_%s_Release" % (uri_to_filename(entry.uri), entry.dist)
    return name


def is_dbus_service_running(service_name):
    running = False
    try:
        bus = dbus.SessionBus()
        running = bus.name_has_owner(service_name)
    except:
        LOG.exception("could not check for dbus service %s" % service_name)
    return running


def is_gnome_shell_running():
    return is_dbus_service_running("org.gnome.Shell")


def is_unity_running():
    """
    return True if Unity is currently running
    """
    return is_dbus_service_running("com.canonical.Unity")


def get_icon_from_theme(icons, iconname=None, iconsize=Icons.APP_ICON_SIZE,
                        missingicon=Icons.MISSING_APP):
    """
    return the icon in the theme that corresponds to the given iconname
    """
    if not iconname:
        iconname = missingicon
    try:
        icon = icons.load_icon(iconname, iconsize, 0)
    except Exception as e:
        LOG.warning(
            utf8("could not load icon '%s', displaying missing "
                 "icon instead: %s ") % (utf8(iconname), utf8(e.message)))
        icon = icons.load_icon(missingicon, iconsize, 0)
    return icon


def get_file_path_from_iconname(icons, iconname=None,
                                iconsize=Icons.APP_ICON_SIZE):
    """
    return the file path of the icon in the theme that corresponds to the
    given iconname, or None if it cannot be determined
    """
    if not iconname or not icons.has_icon(iconname):
        iconname = Icons.MISSING_APP
    try:
        icon_info = icons.lookup_icon(iconname, iconsize, 0)
    except Exception:
        icon_info = icons.lookup_icon(Icons.MISSING_APP, iconsize, 0)
    if icon_info is not None:
        icon_file_path = icon_info.get_filename()
        return icon_file_path


def convert_desktop_file_to_installed_location(app_install_data_file_path,
                                               pkgname):
    """ returns the installed desktop file path that corresponds to the
        given app-install-data file path, and will also check directly for
        the desktop file that corresponds to a given pkgname.
    """
    if app_install_data_file_path and pkgname:
        # "normal" case
        installed_desktop_file_path = app_install_data_file_path.replace(
            "app-install/desktop/" + pkgname + ":", "applications/")
        if os.path.exists(installed_desktop_file_path):
            return installed_desktop_file_path
        # next, try case where a subdirectory is encoded in the app-install
        # desktop filename, e.g. kde4_soundkonverter.desktop
        installed_desktop_file_path = installed_desktop_file_path.replace(
            APP_INSTALL_PATH_DELIMITER, "/")
        if os.path.exists(installed_desktop_file_path):
            return installed_desktop_file_path
    # lastly, just try checking directly for the desktop file based on the
    # pkgname itself for the case of for-purchase items, etc.
    if pkgname:
        datadirs = GLib.get_system_data_dirs()
        for dir in datadirs:
            path = "%s/applications/%s.desktop" % (dir, pkgname)
            if os.path.exists(path):
                return path

        # files in the extras archive have their desktop filenames prepended
        # by "extras-", so we check for that also (LP: #1012877)
        for dir in datadirs:
            path = "%s/applications/extras-%s.desktop" % (dir, pkgname)
            if os.path.exists(path):
                return path
    LOG.warn("Could not determine the installed desktop file path for "
             "app-install desktop file: '%s'" % app_install_data_file_path)
    return ""

def get_desktop_id(desktop_file):
    """ Gets a desktop-id from a .desktop file path"""
    datadirs = [(i if i[-1] == '/' else i+'/') + 'applications/' for i in \
                GLib.get_system_data_dirs() + [GLib.get_user_data_dir()]]

    for dir in datadirs:
        if desktop_file.startswith(dir):
            return desktop_file[len(dir):].replace('/', '-')

    return desktop_file

def clear_token_from_ubuntu_sso_sync(appname):
    """ send a dbus signal to the com.ubuntu.sso service to clear
        the credentials for the given appname, e.g. _("Ubuntu Software Center")
        and wait for it to finish (or 2s)
    """
    from ubuntu_sso import (
        DBUS_BUS_NAME,
        DBUS_CREDENTIALS_IFACE,
        DBUS_CREDENTIALS_PATH,
    )
    # clean
    loop = GLib.MainLoop()
    bus = dbus.SessionBus()
    obj = bus.get_object(bus_name=DBUS_BUS_NAME,
                         object_path=DBUS_CREDENTIALS_PATH,
                         follow_name_owner_changes=True)
    proxy = dbus.Interface(object=obj,
                           dbus_interface=DBUS_CREDENTIALS_IFACE)
    proxy.connect_to_signal("CredentialsCleared", loop.quit)
    proxy.connect_to_signal("CredentialsNotFound", loop.quit)
    proxy.connect_to_signal("CredentialsError", loop.quit)
    proxy.clear_credentials(appname, {})
    # ensure we don't hang forever here
    GLib.timeout_add_seconds(2, loop.quit)
    # run the mainloop until the credentials are clear
    loop.run()


def get_nice_date_string(cur_t):
    """ return a "nice" human readable date, like "2 minutes ago"  """
    import datetime

    dt = datetime.datetime.utcnow() - cur_t
    days = dt.days
    secs = dt.seconds

    if days < 1:
        if secs < 120:   # less than 2 minute ago
            s = _('a few minutes ago')   # don't be fussy

        elif secs < 3600:   # less than an hour ago
            s = gettext.ngettext("%(min)i minute ago",
                                 "%(min)i minutes ago",
                                 (secs / 60)) % {'min': (secs / 60)}

        else:   # less than a day ago
            s = gettext.ngettext("%(hours)i hour ago",
                                 "%(hours)i hours ago",
                                 (secs / 3600)) % {'hours': (secs / 3600)}
    elif days <= 5:  # less than a week ago
        s = gettext.ngettext("%(days)i day ago",
                             "%(days)i days ago",
                             days) % {'days': days}
    else:   # any timedelta greater than 5 days old
        # YYYY-MM-DD
        s = cur_t.isoformat().split('T')[0]
    return s


def _get_from_desktop_file(desktop_file, key):
    import ConfigParser
    config = ConfigParser.ConfigParser()
    config.read(desktop_file)
    try:
        return config.get("Desktop Entry", key)
    except ConfigParser.NoOptionError:
        return None


def get_exec_line_from_desktop(desktop_file):
    return _get_from_desktop_file(desktop_file, "Exec")


def is_no_display_desktop_file(desktop_file):
    nd = _get_from_desktop_file(desktop_file, "NoDisplay")
    # desktop spec says the booleans are always either "true" or "false"
    if nd == "true":
        return True
    return False


def get_nice_size(n_bytes):
    nice_size = lambda s: [
        (s % 1024 ** i and "%.1f" % (s / 1024.0 ** i) or
         str(s / 1024 ** i)) + x.strip() for i, x in enumerate(' KMGTPEZY')
        if s < 1024 ** (i + 1) or i == 8][0]
    return nice_size(n_bytes)


def save_person_to_config(username):
    """ save the specified username value for Ubuntu SSO to the config file
    """
    # FIXME: ideally this would be stored in ubuntu-sso-client
    #        but it doesn't, so we store it here
    curr_name = get_person_from_config()
    if curr_name != username:
        config = get_config()
        config.reviews_username = username
        # refresh usefulness cache in the background once we know
        # the person
        from backend.reviews import UsefulnessCache
        UsefulnessCache(True)
    return


def get_person_from_config():
    """ get the username value for Ubuntu SSO from the config file
    """
    cfg = get_config()
    return cfg.reviews_username


def pnormaldist(qn):
    """
    Inverse normal distribution, based on the Ruby statistics2.pnormaldist
    """
    b = [1.570796288, 0.03706987906, -0.8364353589e-3,
         -0.2250947176e-3, 0.6841218299e-5, 0.5824238515e-5,
         -0.104527497e-5, 0.8360937017e-7, -0.3231081277e-8,
         0.3657763036e-10, 0.6936233982e-12]

    if qn < 0 or qn > 1:
        raise ValueError("qn must be between 0.0 and 1.0")
    if qn == 0.5:
        return 0.0

    w1 = qn
    if qn > 0.5:
        w1 = 1.0 - w1
    w3 = -math.log(4.0 * w1 * (1.0 - w1))
    w1 = b[0]
    for i in range(1, 11):
        w1 = w1 + (b[i] * math.pow(w3, i))

    if qn > 0.5:
        return math.sqrt(w1 * w3)
    else:
        return -math.sqrt(w1 * w3)


def wilson_score(pos, n, power=0.2):
    if n == 0:
        return 0
    z = pnormaldist(1 - power / 2)
    phat = 1.0 * pos / n
    return (phat + z * z / (2 * n) - z * math.sqrt(
            (phat * (1 - phat) + z * z / (4 * n)) / n)) / (1 + z * z / n)


def calc_dr(ratings, power=0.1):
    '''Calculate the dampened rating for an app given its collective ratings'''
    if not len(ratings) == 5:
        raise AttributeError('ratings argument must be a list of 5 integers')

    tot_ratings = 0
    for i in range(0, 5):
        tot_ratings = ratings[i] + tot_ratings

    sum_scores = 0.0
    for i in range(0, 5):
        ws = wilson_score(ratings[i], tot_ratings, power)
        sum_scores = sum_scores + float((i + 1) - 3) * ws
    return sum_scores + 3


# we need this because some iconnames have already split off the extension
# (the desktop file standard suggests this) but still have a "." in the name.
# From other sources we get icons with a full extension so a simple splitext()
# is not good enough
def split_icon_ext(iconname):
    """ return the basename of a icon if it matches a known icon
        extension like tiff, gif, jpg, svg, png, xpm, ico
    """
    SUPPORTED_EXTENSIONS = [".tiff", ".tif", ".gif", ".jpg", ".jpeg", ".svg",
                            ".png", ".xpm", ".ico"]
    basename, ext = os.path.splitext(iconname)
    if ext.lower() in SUPPORTED_EXTENSIONS:
        return basename
    return iconname


def mangle_paths_if_running_in_local_checkout():
    import softwarecenter.paths
    # we are running in a local checkout, make life as easy as possible
    # for this
    if os.path.exists("./data/ui/gtk3/SoftwareCenter.ui"):
        logging.getLogger("softwarecenter").info(
            "Using data (UI, xapian) from current dir")
        # set pythonpath for the various helpers
        if os.environ.get("PYTHONPATH", ""):
            os.environ["PYTHONPATH"] = os.path.abspath(".") + ":" +\
                os.environ.get("PYTHONPATH", "")
        else:
            os.environ["PYTHONPATH"] = os.path.abspath(".")
        datadir = "./data"
        xapian_base_path = datadir
        # set new global datadir
        softwarecenter.paths.datadir = datadir
        softwarecenter.paths.XAPIAN_BASE_PATH = xapian_base_path
        # also alter the app-install path
        path = "./build/share/app-install/desktop/software-center.menu"
        if os.path.exists(path):
            softwarecenter.paths.APP_INSTALL_PATH = './build/share/app-install'
            logging.warn("using local APP_INSTALL_PATH: %s" %
                         softwarecenter.paths.APP_INSTALL_PATH)
    else:
        datadir = softwarecenter.paths.datadir
        xapian_base_path = softwarecenter.paths.XAPIAN_BASE_PATH
    return (datadir, xapian_base_path)


def get_uuid():
    import uuid
    return str(uuid.uuid4())


def get_recommender_uuid():
    """ the recommender service requires a UUID that does not contain
        dashes
    """
    return get_uuid().replace("-", "")


def get_lock(path):
    """ return a lock that can be released with release_lock on success
        and -1 on failure
    """
    try:
        import apt_pkg
        return apt_pkg.get_lock(path, False)
    except ImportError:
        # implement me on non-apt system, I wish python had this in the stdlib
        pass


def release_lock(lock):
    """ release a lock acquired with get_lock """
    os.close(lock)


def make_string_from_list(base_str, item_list):
    """ This function takes a list of items and builds a nice human readable
        string with it of the form. Note that the base string needs a "%s".
        Example return:
          The base string with the list items a,b and c in it.
        Note that base_str needs to be a ngettext string already, so the
        example usage is:
         l = ["foo", "bar"]
         base_str = ngettext("This list: %s.", "This list: %s", len(l))
         s = make_string_from_list(base_string, l)
    """
    list_str = item_list[0]
    if len(item_list) > 1:
        # TRANSLATORS: this is a generic list delimit char, e.g. "foo, bar"
        list_str = _(", ").join(item_list[:-1])
        # TRANSLATORS: this is the last part of a list, e.g. "foo, bar and baz"
        list_str = _("%s and %s") % (list_str,
                                     item_list[-1])
    s = base_str % list_str
    return s


def ensure_file_writable_and_delete_if_not(file_path):
    """ This function checks for writeable access to a file and attempts to
        remove it if it is found to indeed be set as unwriteable
    """
    if os.path.exists(file_path) and not os.access(file_path, os.W_OK):
        try:
            LOG.warn("encountered non-writeable file, attempting to fix "
                     "by deleting: %s" % file_path)
            os.remove(file_path)
        except Exception as e:
            LOG.exception("failed to fix non-writeable file '%s': %s",
                          file_path, e)


def safe_makedirs(dir_path):
    """ This function can be used in place of a straight os.makedirs to
        handle the possibility of a race condition when more than one
        process may potentially be creating the same directory. It will
        not fail if two processes try to create the same dir at the same
        time
    """
    # avoid throwing an OSError, see for example LP: #743003
    if not os.path.exists(dir_path):
        try:
            os.makedirs(dir_path)
        except OSError as e:
            if e.errno == errno.EEXIST:
                # it seems that another process has already created this
                # directory in the meantime, that's ok
                pass
            else:
                # the error is due to something else, so we want to raise it
                raise


def get_oem_channel_descriptor(path=OEM_CHANNEL_DESCRIPTOR):
    """Return the ubuntu distribution channel descriptor or a empty string """
    if not os.path.exists(path):
        return ""
    with open(path) as f:
        for line in filter(lambda l: not l.startswith("#"), f):
            return line.strip()


class SimpleFileDownloader(GObject.GObject):

    LOG = logging.getLogger("softwarecenter.simplefiledownloader")

    __gsignals__ = {
        "file-url-reachable": (GObject.SIGNAL_RUN_LAST,
                               GObject.TYPE_NONE,
                               (bool,),),

        "file-download-complete": (GObject.SIGNAL_RUN_LAST,
                                   GObject.TYPE_NONE,
                                   (str,),),

        "error": (GObject.SIGNAL_RUN_LAST,
                  GObject.TYPE_NONE,
                  (GObject.TYPE_PYOBJECT,
                   GObject.TYPE_PYOBJECT,),),
    }

    def __init__(self):
        GObject.GObject.__init__(self)
        self.tmpdir = None
        self._cancellable = None

    def download_file(self, url, dest_file_path=None, use_cache=False,
                      simple_quoting_for_webkit=False):
        """ Download a url and emit the file-download-complete
            once the file is there. Note that calling this twice
            will cancel the previous pending operation.
            If dest_file_path is given, download to that specific
            local filename.
            If use_cache is given it will not use a tempdir, but
            instead a permanent cache dir - no etag or timestamp
            checks are performed.
        """
        self.LOG.debug(
            "download_file: %s %s %s" % (url, dest_file_path, use_cache))

        # cancel anything pending to avoid race conditions
        # like bug #839462
        if self._cancellable:
            self._cancellable.cancel()
            self._cancellable.reset()
        else:
            self._cancellable = Gio.Cancellable()

        # no need to cache file urls and no need to really download
        # them, its enough to adjust the dest_file_path
        if url.startswith("file:"):
            dest_file_path = url[len("file:"):]
            use_cache = False

        # if the cache is used, we use that as the dest_file_path
        if use_cache:
            cache_path = os.path.join(
                SOFTWARE_CENTER_CACHE_DIR, "download-cache")
            if not os.path.exists(cache_path):
                os.makedirs(cache_path)
            dest_file_path = os.path.join(cache_path, uri_to_filename(url))
            if simple_quoting_for_webkit:
                dest_file_path = dest_file_path.replace("%", "")
                dest_file_path = dest_file_path.replace("?", "")

        # no cache and no dest_file_path, use tempdir
        if dest_file_path is None:
            if self.tmpdir is None:
                self.tmpdir = tempfile.mkdtemp(prefix="software-center-")
            dest_file_path = os.path.join(self.tmpdir, uri_to_filename(url))

        self.url = url
        self.dest_file_path = dest_file_path

        # FIXME: we actually need to do etag based checking here to see
        #        if the source needs refreshing
        if os.path.exists(self.dest_file_path):
            self.emit('file-url-reachable', True)
            self.emit("file-download-complete", self.dest_file_path)
            return

        f = Gio.File.new_for_uri(url)
        # first check if the url is reachable
        f.query_info_async(Gio.FILE_ATTRIBUTE_STANDARD_SIZE, 0, 0,
                           self._cancellable,
                           self._check_url_reachable_and_then_download_cb,
                           url)

    def _ensure_correct_url(self, want_url):
        """This function will ensure that the url we requested to download
           earlier matches that is now downloaded.
        """
        # this function is needed as there is a race condition when the
        # operation is finished but the signal is not delivered yet (it's
        # still in the gtk event loop). in this case there is nothing to
        # self._cancel but self.url/self.dest_file_path will still point to
        # the wrong file
        if self.url != want_url:
            self.LOG.warn(
                "url changed from '%s' to '%s'" % (want_url, self.url))
            return False
        return True

    def _check_url_reachable_and_then_download_cb(self, f, result, want_url):
        self.LOG.debug("_check_url_reachable_and_then_download_cb: %s" % f)
        if not self._ensure_correct_url(want_url):
            return
        # normal operation
        try:
            info = f.query_info_finish(result)
            etag = info.get_etag()
            self.emit('file-url-reachable', True)
            self.LOG.debug("file reachable %s %s %s" % (self.url,
                                                        info,
                                                        etag))
            # url is reachable, now download the file
            f.load_contents_async(
                self._cancellable, self._file_download_complete_cb, want_url)
        except GObject.GError as e:
            self.LOG.debug("file *not* reachable %s" % self.url)
            self.emit('file-url-reachable', False)
            self.emit('error', GObject.GError, e)
        del f

    def _file_download_complete_cb(self, f, result, want_url):
        self.LOG.debug("file download completed %s" % self.dest_file_path)
        if not self._ensure_correct_url(want_url):
            return
        # The result from the download is actually a tuple with three
        # elements (content, size, etag?)
        # The first element is the actual content so let's grab that
        try:
            res, content, etag = f.load_contents_finish(result)
        except Exception as e:
            # I witnessed a strange error[1], so make the loader robust in this
            # situation
            # 1. content = f.load_contents_finish(result)[0]
            #    Gio.Error: DBus error org.freedesktop.DBus.Error.NoReply
            self.LOG.debug(e)
            self.emit('error', Exception, e)
            return
        # write out the data
        outputfile = open(self.dest_file_path, "w")
        outputfile.write(content)
        outputfile.close()
        self.emit('file-download-complete', self.dest_file_path)


# those helpers are packaging-system specific
from softwarecenter.db.pkginfo import get_pkg_info
# do not call get_pkg_info here, since package switch may not have been set
# instead use an anonymous function delay
upstream_version_compare = lambda v1, v2: \
    get_pkg_info().upstream_version_compare(v1, v2)
upstream_version = lambda v: get_pkg_info().upstream_version(v)
version_compare = lambda v1, v2: get_pkg_info().version_compare(v1, v2)

if __name__ == "__main__":
    s = decode_xml_char_reference('Search&#x2026;')
    print(s)
    print(type(s))
    print(unicode(s))