import operator
import os
import subprocess
import sys

from xml.dom import minidom

scripts_dir = os.path.dirname(__file__)
base_dir = os.path.dirname(scripts_dir)

_cached_dname, _cached_dversion = None, None

def _pipe_lower(args) :
    out, err = subprocess.Popen(args,
                                stdout=subprocess.PIPE).communicate()
    return out.strip().lower()

def get_distribution():
    global _cached_dname, _cached_dversion

    if _cached_dname :
      return _cached_dname, _cached_dversion

    if 'SJH_DISTRIBUTION' in os.environ:
        _cached_dname, _cached_dversion = os.environ['SJH_DISTRIBUTION'].split('-')
        return _cached_dname, _cached_dversion

    try:
        _cached_dname = _pipe_lower(['lsb_release', '-is'])
        _cached_dversion = _pipe_lower(['lsb_release', '-rs'])

    except OSError:
        pass

    return _cached_dname, _cached_dversion

def check_package(package):
    name, version = get_distribution()
    if name in ['fedora', 'mandrivalinux']:
        ret = subprocess.call(['rpm', '--quiet', '-q', package])
        return ret == 0
    elif name in ['ubuntu', 'debian']:
        cmd = ["dpkg-query", "-f='${status}'", "-W", package]
        out, err = subprocess.Popen(cmd, stdout=subprocess.PIPE).communicate()
        return out.find('install ok installed') != -1

    return None

def _check_suffix(name, suffixes) :
  """
  Returns a list of all matching suffixes for <name>.
  """
  return [name for suffix in suffixes if name.endswith(suffix)]

_unstable_names = {
    'debian': 'unstable',
    'fedora': 'rawhide',
    'mandrivalinux': 'cooker',
    'ubuntu': 'unstable',
}
def _parse_dependencies(dname, dversion):
    if not (dname and dversion):
        return []

    suffixes = ['alldistros.xml', '%s-allversions.xml' % (dname,),
                '%s-%s.xml' % (dname, dversion)]

    dirname = os.path.join(base_dir, 'config', 'sysdeps')
    filenames = [os.path.join(dirname, fname)
        for fname in os.listdir(dirname)
        if _check_suffix(fname, suffixes)]

    # check whether we have a file matching the exact distro version
    if not [name for name in filenames if name.endswith(suffixes[-1])] :
        # will break for unknown distros, but that's fine
        # (=> bug report => add support for distro)
        uversion = _unstable_names[dname]
        if (dversion == uversion) :
            # no config for unstable
            return []

        sys.stderr.write("Warning: unknown distro version, automatic fallback to %s.\n" % (uversion,))
        return _parse_dependencies(dname, uversion)


    return [minidom.parse(fname)
            for fname in filenames if os.path.exists(fname)]

_cached_packages = None
def get_packages():
    global _cached_packages

    if _cached_packages is not None :
        return _cached_packages

    dname, dversion = get_distribution()
    documents = _parse_dependencies(dname, dversion)
    _cached_packages = []

    if not documents :
        return _cached_packages

    roots = [doc.childNodes[0] for doc in documents]

    for node in reduce(operator.add, [root.childNodes for root in roots]) :
        if node.nodeType == node.ELEMENT_NODE:
            if node.nodeName == 'package':
                name = node.getAttribute('name')
                if node.hasAttribute('source'):
                    source = node.getAttribute('source')
                else:
                    source = None

                _cached_packages.append((name, source))

    return _cached_packages