Synnefo

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from synnefo.util import units

from django.core.management import CommandError

from django.db.models import Q

OP_MAP = [

    ("!=", lambda x: ~x, ""),

    (">=", lambda x: x, "__gte"),

    ("=>", lambda x: x, "__gte"),

    (">", lambda x: x, "__gt"),

    ("<=", lambda x: x, "__lte"),

    ("=<", lambda x: x, "__lte"),

    ("<", lambda x: x, "__lt"),

    ("=", lambda x: x, ""),

    ]

def parse_filter(exp):

    for s, prepend, op in OP_MAP:

        key, sep, value = exp.partition(s)

        if s == sep:

            return key, prepend, op, value

    raise CommandError("Could not parse filter.")

def make_query(flt, handlers):

    key, prepend, opstr, value = parse_filter(flt)

    try:

        (dbkey, parse) = handlers[key]

        return prepend(Q(**{dbkey+opstr: parse(value)}))

    except KeyError:

        return None

def parse_with_unit(value):

    try:

        return units.parse(value)

    except units.ParseError:

        raise CommandError("Failed to parse value, should be an integer, "

                           "possibly followed by a unit, or 'inf'.")