import re
import datetime

class Snapshot(object):
    """
    Snapshot class we use to convert zfs list string to proper object we can use to analyze replicas.
    """
    def __init__(self, snapshot_string):
        """
        We compile some regexes at init so we can use them quickly later.
        We keep tuples of data returned by zfs list command. We do this because it returns Tab-Seperated Data
        :param snapshot_string: string to parse into Snapshot() class object
        """
        self.snapshot_string = snapshot_string
        self.re_split_tabs = re.compile(r'\t+')
        self.re_name = re.compile(r"[^/]+$")
        self.re_zvol = re.compile(r"^.*[\\/]")
        self.snapshot_tuple = self.parse_string_to_table()
        self.disk_name = self.get_snapshot_name().split("@")[0]

    def __repr__(self):
        return self.get_snapshot_name()

    def get_snapshot_string(self):
        return self.snapshot_string

    def parse_string_to_table(self):
        """
        We split Tab-Seperaed data returned by zfs list to tuples so we can use it without hassle.
        :return: Tuple containing name, ctime, used_size, ref_size of snapshot
        """
        array = re.split(self.re_split_tabs, self.snapshot_string)
        return tuple(array)

    def get_snapshot_name(self):
        """
        We grab the name only from tuple
        :return: Whole name of the snapshot as str()
        """
        name_str = self.snapshot_tuple[0]
        name = next(self.re_name.finditer(name_str))
        return name.group()

    def get_snapshot_zvol(self):
        """
        We grab the zvol only from tuple
        :return: Zvol where replica is being kept - as str()
        """
        name_str = self.snapshot_tuple[0]
        zvol = next(self.re_zvol.finditer(name_str))
        return zvol.group()

    def get_snapshot_creation_time(self):
        """
        We grab the epoch time from the data in the tuple
        :return: UTC Human-Readable Date of creation of the snapshot
        """
        time_epoch = int(self.snapshot_tuple[1])
        return str(datetime.datetime.utcfromtimestamp(time_epoch))

    def get_snapshot_creation_time_epoch(self):
        """
        We will probably also make use of the epoch time
        :return: Epoch time straight from tuple
        """
        return int(self.snapshot_tuple[1])

    def get_snapshot_used_size(self, human_readable = True):
        """
        We grab used size of the snapshot
        :param human_readable: For backend we want it in Bytes. But we want the user to quickly see how big snapshot is.
        :return: Used Size of the snapshot Human-Readable or not
        """
        used_str = self.snapshot_tuple[2]
        if human_readable:
            return self.sizeof_fmt(int(used_str))
        else: return int(used_str)

    def get_snapshot_referenced_size(self, human_readable = True):
        """
         We grab referenced size of the snapshot
         :param human_readable: For backend we want it in Bytes. But we want the user to quickly see how big snapshot is.
         :return: Referenced Size of the snapshot Human-Readable or not
         """
        referenced_str = self.snapshot_tuple[3]
        if human_readable:
            return self.sizeof_fmt(int(referenced_str))
        else:
            return int(referenced_str)

    def get_disk_name(self):
        return self.disk_name

    @staticmethod
    def sizeof_fmt(num, suffix='B'):
        """
        Function taken from stackexchange. Used to make size in Bytes Human-readable
        :param num: Bytes value we want to convert
        :param suffix: suffix we want to add to SI Prefix like Ki, Gi etc. E.g. B for GiB
        :return: Human-Readable size string
        """
    ## FIXME WOW taken from stack but it's too fucking slow. Probably because of division. Have to profile
        for unit in ['','Ki','Mi','Gi','Ti','Pi','Ei','Zi']:
            if abs(num) < 1024.0:
                return "%3.1f%s%s" % (num, unit, suffix)
            num /= 1024.0
        return "%.1f%s%s" % (num, 'Yi', suffix)