def get_os_release():
    """Get all key-value pairs from /etc/os-release as a dict"""
    from collections import OrderedDict

    data = OrderedDict()
    if os.path.exists('/etc/os-release'):
        with open('/etc/os-release') as f:
            for line in f:
                try:
                    key, val = line.rstrip().split('=', 1)
                except ValueError:
                    continue
                data[key.strip()] = val.strip('"')
    return data

def release_dict_osr():
    """ Populate a dict with pertinent values from /etc/os-release """
    data = {}
    os_release = get_os_release()
    if 'ID' in os_release:
        data['DISTRIB_ID'] = os_release['ID']
    if 'VERSION_ID' in os_release:
        data['DISTRIB_RELEASE'] = os_release['VERSION_ID']

    return data

def release_dict_lsb():
    """ Return the output of lsb_release -ir as a dictionary """
    from subprocess import PIPE

    try:
        output, err = bb.process.run(['lsb_release', '-ir'], stderr=PIPE)
    except bb.process.CmdError as exc:
        return {}

    lsb_map = { 'Distributor ID': 'DISTRIB_ID',
                'Release': 'DISTRIB_RELEASE'}
    lsb_keys = lsb_map.keys()

    data = {}
    for line in output.splitlines():
        if line.startswith("-e"):
            line = line[3:]
        try:
            key, value = line.split(":\t", 1)
        except ValueError:
            continue
        if key in lsb_keys:
            data[lsb_map[key]] = value

    if len(data.keys()) != 2:
        return None

    return data

def release_dict_file():
    """ Try to gather release information manually when other methods fail """
    data = {}
    try:
        if os.path.exists('/etc/lsb-release'):
            data = {}
            with open('/etc/lsb-release') as f:
                for line in f:
                    key, value = line.split("=", 1)
                    data[key] = value.strip()
        elif os.path.exists('/etc/redhat-release'):
            data = {}
            with open('/etc/redhat-release') as f:
                distro = f.readline().strip()
            import re
            match = re.match(r'(.*) release (.*) \((.*)\)', distro)
            if match:
                data['DISTRIB_ID'] = match.group(1)
                data['DISTRIB_RELEASE'] = match.group(2)
        elif os.path.exists('/etc/SuSE-release'):
            data = {}
            data['DISTRIB_ID'] = 'SUSE LINUX'
            with open('/etc/SuSE-release') as f:
                for line in f:
                    if line.startswith('VERSION = '):
                        data['DISTRIB_RELEASE'] = line[10:].rstrip()
                        break

    except IOError:
        return {}
    return data

def distro_identifier(adjust_hook=None):
    """Return a distro identifier string based upon lsb_release -ri,
       with optional adjustment via a hook"""

    import re

    # Try /etc/os-release first, then the output of `lsb_release -ir` and
    # finally fall back on parsing various release files in order to determine
    # host distro name and version.
    distro_data = release_dict_osr()
    if not distro_data:
        distro_data = release_dict_lsb()
    if not distro_data:
        distro_data = release_dict_file()

    distro_id = distro_data.get('DISTRIB_ID', '')
    release = distro_data.get('DISTRIB_RELEASE', '')

    if adjust_hook:
        distro_id, release = adjust_hook(distro_id, release)
    if not distro_id:
        return "Unknown"
    # Filter out any non-alphanumerics
    distro_id = re.sub(r'\W', '', distro_id)

    if release:
        id_str = '{0}-{1}'.format(distro_id.lower(), release)
    else:
        id_str = distro_id
    return id_str.replace(' ','-').replace('/','-')
