import redis
import pickle
import sys

# load some django settings here some day


class StorageError(Exception):
    pass


def storage_error(typ):
    return type('Storage%sError' % typ.__name__, (typ, StorageError), {})


def raise_storage_error():
    typ, value, trace = sys.exc_info()

    raise storage_error(typ), value, trace


class Storage:
    key_prefix = 'sublab_monitor.'

    def __init__(self, app_prefix):
        self.key_prefix += '%s.' % app_prefix

        try:
            self.redis = redis.StrictRedis()
        except redis.RedisError:
            raise_storage_error()

    def key(self, key):
        return '%s%s' % (self.key_prefix, key)

    def get(self, key):
        lookup_key = self.key(key)

        try:
            entry = self.redis.get(lookup_key)
        except redis.RedisError:
            raise_storage_error()

        if entry is None:
            return None

        try:
            return pickle.loads(entry)
        except pickle.PickleError:
            raise_storage_error()

    def set(self, key, value):
        lookup_key = self.key(key)

        try:
            entry = pickle.dumps(value)
        except pickle.PickleError:
            raise_storage_error()

        try:
            self.redis.set(lookup_key, entry)
        except redis.RedisError:
            raise_storage_error()