"""Utility functions and classes for the stix2 library."""
# HACK
from collections import Mapping
import copy
import datetime as dt
import json

from dateutil import parser
import pytz

from .exceptions import (InvalidValueError, RevokeError,
                         UnmodifiablePropertyError)

# Sentinel value for properties that should be set to the current time.
# We can't use the standard 'default' approach, since if there are multiple
# timestamps in a single object, the timestamps will vary by a few microseconds.
NOW = object()

# STIX object properties that cannot be modified
STIX_UNMOD_PROPERTIES = ["created", "created_by_ref", "id", "type"]


class STIXdatetime(dt.datetime):
    def __new__(cls, *args, **kwargs):
        precision = kwargs.pop('precision', None)
        if isinstance(args[0], dt.datetime):  # Allow passing in a datetime object
            dttm = args[0]
            args = (dttm.year, dttm.month, dttm.day, dttm.hour, dttm.minute,
                    dttm.second, dttm.microsecond, dttm.tzinfo)
        # self will be an instance of STIXdatetime, not dt.datetime
        self = dt.datetime.__new__(cls, *args, **kwargs)
        self.precision = precision
        return self

    def __repr__(self):
        return "'%s'" % format_datetime(self)


def deduplicate(stix_obj_list):
    """Deduplicate a list of STIX objects to a unique set.

    Reduces a set of STIX objects to unique set by looking
    at 'id' and 'modified' fields - as a unique object version
    is determined by the combination of those fields

    Note: Be aware, as can be seen in the implementation
    of deduplicate(),that if the "stix_obj_list" argument has
    multiple STIX objects of the same version, the last object
    version found in the list will be the one that is returned.

    Args:
        stix_obj_list (list): list of STIX objects (dicts)

    Returns:
        A list with a unique set of the passed list of STIX objects.

    """
    unique_objs = {}

    for obj in stix_obj_list:
        try:
            unique_objs[(obj['id'], obj['modified'])] = obj
        except KeyError:
            # Handle objects with no `modified` property, e.g. marking-definition
            unique_objs[(obj['id'], obj['created'])] = obj

    return list(unique_objs.values())


def get_timestamp():
    """Return a STIX timestamp of the current date and time."""
    return STIXdatetime.now(tz=pytz.UTC)


def format_datetime(dttm):
    """Convert a datetime object into a valid STIX timestamp string.

    1. Convert to timezone-aware
    2. Convert to UTC
    3. Format in ISO format
    4. Ensure correct precision
       a. Add subsecond value if non-zero and precision not defined
    5. Add "Z"

    """

    if dttm.tzinfo is None or dttm.tzinfo.utcoffset(dttm) is None:
        # dttm is timezone-naive; assume UTC
        zoned = pytz.utc.localize(dttm)
    else:
        zoned = dttm.astimezone(pytz.utc)
    ts = zoned.strftime("%Y-%m-%dT%H:%M:%S")
    ms = zoned.strftime("%f")
    precision = getattr(dttm, "precision", None)
    if precision == 'second':
        pass  # Alredy precise to the second
    elif precision == "millisecond":
        ts = ts + '.' + ms[:3]
    elif zoned.microsecond > 0:
        ts = ts + '.' + ms.rstrip("0")
    return ts + "Z"


def parse_into_datetime(value, precision=None):
    """Parse a value into a valid STIX timestamp object.
    """
    if isinstance(value, dt.date):
        if hasattr(value, 'hour'):
            ts = value
        else:
            # Add a time component
            ts = dt.datetime.combine(value, dt.time(0, 0, tzinfo=pytz.utc))
    else:
        # value isn't a date or datetime object so assume it's a string
        try:
            parsed = parser.parse(value)
        except (TypeError, ValueError):
            # Unknown format
            raise ValueError("must be a datetime object, date object, or "
                             "timestamp string in a recognizable format.")
        if parsed.tzinfo:
            ts = parsed.astimezone(pytz.utc)
        else:
            # Doesn't have timezone info in the string; assume UTC
            ts = pytz.utc.localize(parsed)

    # Ensure correct precision
    if not precision:
        return STIXdatetime(ts, precision=precision)
    ms = ts.microsecond
    if precision == 'second':
        ts = ts.replace(microsecond=0)
    elif precision == 'millisecond':
        ms_len = len(str(ms))
        if ms_len > 3:
            # Truncate to millisecond precision
            factor = 10 ** (ms_len - 3)
            ts = ts.replace(microsecond=(ts.microsecond // factor) * factor)
        else:
            ts = ts.replace(microsecond=0)
    return STIXdatetime(ts, precision=precision)


def get_dict(data):
    """Return data as a dictionary.

    Input can be a dictionary, string, or file-like object.
    """

    if type(data) is dict:
        return data
    else:
        try:
            return json.loads(data)
        except TypeError:
            pass
        try:
            return json.load(data)
        except AttributeError:
            pass
        try:
            return dict(data)
        except (ValueError, TypeError):
            raise ValueError("Cannot convert '%s' to dictionary." % str(data))


def find_property_index(obj, properties, tuple_to_find):
    """Recursively find the property in the object model, return the index
    according to the _properties OrderedDict. If it's a list look for
    individual objects.
    """
    from .base import _STIXBase
    try:
        if tuple_to_find[1] in obj._inner.values():
            return properties.index(tuple_to_find[0])
        raise ValueError
    except ValueError:
        for pv in obj._inner.values():
            if isinstance(pv, list):
                for item in pv:
                    if isinstance(item, _STIXBase):
                        val = find_property_index(item,
                                                  item.object_properties(),
                                                  tuple_to_find)
                        if val is not None:
                            return val
            elif isinstance(pv, dict):
                if pv.get(tuple_to_find[0]) is not None:
                    try:
                        return int(tuple_to_find[0])
                    except ValueError:
                        return len(tuple_to_find[0])
                for item in pv.values():
                    if isinstance(item, _STIXBase):
                        val = find_property_index(item,
                                                  item.object_properties(),
                                                  tuple_to_find)
                        if val is not None:
                            return val


def new_version(data, **kwargs):
    """Create a new version of a STIX object, by modifying properties and
    updating the ``modified`` property.
    """

    if not isinstance(data, Mapping):
        raise ValueError('cannot create new version of object of this type! '
                         'Try a dictionary or instance of an SDO or SRO class.')

    unchangable_properties = []
    if data.get("revoked"):
        raise RevokeError("new_version")
    try:
        new_obj_inner = copy.deepcopy(data._inner)
    except AttributeError:
        new_obj_inner = copy.deepcopy(data)
    properties_to_change = kwargs.keys()

    # Make sure certain properties aren't trying to change
    for prop in STIX_UNMOD_PROPERTIES:
        if prop in properties_to_change:
            unchangable_properties.append(prop)
    if unchangable_properties:
        raise UnmodifiablePropertyError(unchangable_properties)

    cls = type(data)
    if 'modified' not in kwargs:
        kwargs['modified'] = get_timestamp()
    elif 'modified' in data:
        old_modified_property = parse_into_datetime(data.get('modified'), precision='millisecond')
        new_modified_property = parse_into_datetime(kwargs['modified'], precision='millisecond')
        if new_modified_property <= old_modified_property:
            raise InvalidValueError(cls, 'modified',
                                    "The new modified datetime cannot be before than or equal to the current modified datetime."
                                    "It cannot be equal, as according to STIX 2 specification, objects that are different "
                                    "but have the same id and modified timestamp do not have defined consumer behavior.")
    new_obj_inner.update(kwargs)
    # Exclude properties with a value of 'None' in case data is not an instance of a _STIXBase subclass
    return cls(**{k: v for k, v in new_obj_inner.items() if v is not None})


def revoke(data):
    """Revoke a STIX object.

    Returns:
        A new version of the object with ``revoked`` set to ``True``.
    """
    if not isinstance(data, Mapping):
        raise ValueError('cannot revoke object of this type! Try a dictionary '
                         'or instance of an SDO or SRO class.')

    if data.get("revoked"):
        raise RevokeError("revoke")
    return new_version(data, revoked=True)


def get_class_hierarchy_names(obj):
    """Given an object, return the names of the class hierarchy."""
    names = []
    for cls in obj.__class__.__mro__:
        names.append(cls.__name__)
    return names


def remove_custom_stix(stix_obj):
    """remove any custom STIX objects or properties

    Args:
        stix_obj (dict OR python-stix obj): a single python-stix object
                                             or dict of a STIX object

    Returns:
        A new version of the object with any custom content removed
    """

    if stix_obj["type"].startswith("x-"):
        # if entire object is custom, discard
        return None

    custom_props = []
    for prop in stix_obj.items():
        if prop[0].startswith("x_"):
            # for every custom property, record it and set value to None
            # (so we can pass it to new_version() and it will be dropped)
            custom_props.append((prop[0], None))

    if custom_props:
        # obtain set of object properties that can be transferred
        # to a new object version. This is 1)custom props with their
        # values set to None, and 2)any properties left that are not
        # unmodifiable STIX properties or the "modified" property

        # set of properties that are not supplied to new_version()
        # to be used for updating properties. This includes unmodifiable
        # properties (properties that new_version() just re-uses from the
        # existing STIX object) and the "modified" property. We dont supply the
        # "modified" property so that new_version() creates a new datetime
        # value for this property
        non_supplied_props = STIX_UNMOD_PROPERTIES + ["modified"]

        props = [(prop, stix_obj[prop]) for prop in stix_obj if prop not in non_supplied_props]

        # add to set the custom properties we want to get rid of (with their value=None)
        props.extend(custom_props)

        return new_version(stix_obj, **(dict(props)))

    else:
        return stix_obj