import random
import lxml.etree as etree
import libvirt
import string
import re


def is_kvm_available(xml):
    kvm_domains = get_xml_path(xml, "//domain/@type='kvm'")
    if kvm_domains > 0:
        return True
    else:
        return False


def randomMAC():
    """Generate a random MAC address."""
    # qemu MAC
    oui = [0x52, 0x54, 0x00]

    mac = oui + [random.randint(0x00, 0xff),
                 random.randint(0x00, 0xff),
                 random.randint(0x00, 0xff)]
    return ':'.join(map(lambda x: "%02x" % x, mac))


def randomUUID():
    """Generate a random UUID."""

    u = [random.randint(0, 255) for ignore in range(0, 16)]
    u[6] = (u[6] & 0x0F) | (4 << 4)
    u[8] = (u[8] & 0x3F) | (2 << 6)
    return "-".join(["%02x" * 4, "%02x" * 2, "%02x" * 2, "%02x" * 2,
                     "%02x" * 6]) % tuple(u)


def randomPasswd(length=12, alphabet=string.letters + string.digits):
    """Generate a random password"""
    return ''.join([random.choice(alphabet) for i in xrange(length)])


def get_max_vcpus(conn, type=None):
    """@param conn: libvirt connection to poll for max possible vcpus
       @type type: optional guest type (kvm, etc.)"""
    if type is None:
        type = conn.getType()
    try:
        m = conn.getMaxVcpus(type.lower())
    except libvirt.libvirtError:
        m = 32
    return m


def xml_escape(str):
    """Replaces chars ' " < > & with xml safe counterparts"""
    if str is None:
        return None

    str = str.replace("&", "&amp;")
    str = str.replace("'", "&apos;")
    str = str.replace("\"", "&quot;")
    str = str.replace("<", "&lt;")
    str = str.replace(">", "&gt;")
    return str


def compareMAC(p, q):
    """Compare two MAC addresses"""
    pa = p.split(":")
    qa = q.split(":")

    if len(pa) != len(qa):
        if p > q:
            return 1
        else:
            return -1

    for i in xrange(len(pa)):
        n = int(pa[i], 0x10) - int(qa[i], 0x10)
        if n > 0:
            return 1
        elif n < 0:
            return -1
    return 0


def get_xml_path(xml, path=None, func=None):
    """
    Return the content from the passed xml xpath, or return the result
    of a passed function (receives xpathContext as its only arg)
    """
    doc = None
    result = None

    doc = etree.fromstring(xml)
    if path:
        result = get_xpath(doc, path)
    elif func:
        result = func(doc)

    else:
        raise ValueError("'path' or 'func' is required.")
    return result


def get_xpath(doc, path):
    result = None

    ret = doc.xpath(path)
    if ret is not None:
        if type(ret) == list:
            if len(ret) >= 1:
                if hasattr(ret[0],'text'):
                    result = ret[0].text
                else:
                    result = ret[0]
        else:
            result = ret

    return result

def pretty_mem(val):
    val = int(val)
    if val > (10 * 1024 * 1024):
        return "%2.2f GB" % (val / (1024.0 * 1024.0))
    else:
        return "%2.0f MB" % (val / 1024.0)


def pretty_bytes(val):
    val = int(val)
    if val > (1024 * 1024 * 1024):
        return "%2.2f GB" % (val / (1024.0 * 1024.0 * 1024.0))
    else:
        return "%2.2f MB" % (val / (1024.0 * 1024.0))


def validate_uuid(val):
    if type(val) is not str:
        raise ValueError("UUID must be a string.")

    form = re.match("[a-fA-F0-9]{8}[-]([a-fA-F0-9]{4}[-]){3}[a-fA-F0-9]{12}$",
                    val)
    if form is None:
        form = re.match("[a-fA-F0-9]{32}$", val)
        if form is None:
            raise ValueError(
                  "UUID must be a 32-digit hexadecimal number. It may take "
                    "the form xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx or may "
                    "omit hyphens altogether.")

        else:   # UUID had no dashes, so add them in
            val = (val[0:8] + "-" + val[8:12] + "-" + val[12:16] +
                   "-" + val[16:20] + "-" + val[20:32])
    return val