# coding=utf-8
# --------------------------------------------------------------------------
# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License. See License.txt in the project root for
# license information.
# --------------------------------------------------------------------------
import base64
from json import JSONEncoder
from typing import Union, cast, Any
from datetime import datetime, date, time, timedelta
from datetime import timezone


__all__ = ["NULL", "CoreJSONEncoder"]


class _Null:
    """To create a Falsy object"""

    def __bool__(self) -> bool:
        return False


NULL = _Null()
"""
A falsy sentinel object which is supposed to be used to specify attributes
with no data. This gets serialized to `null` on the wire.
"""


def _timedelta_as_isostr(td: timedelta) -> str:
    """Converts a datetime.timedelta object into an ISO 8601 formatted string, e.g. 'P4DT12H30M05S'

    Function adapted from the Tin Can Python project: https://github.com/RusticiSoftware/TinCanPython

    :param td: The timedelta object to convert
    :type td: datetime.timedelta
    :return: An ISO 8601 formatted string representing the timedelta object
    :rtype: str
    """

    # Split seconds to larger units
    seconds = td.total_seconds()
    minutes, seconds = divmod(seconds, 60)
    hours, minutes = divmod(minutes, 60)
    days, hours = divmod(hours, 24)

    days, hours, minutes = list(map(int, (days, hours, minutes)))
    seconds = round(seconds, 6)

    # Build date
    date_str = ""
    if days:
        date_str = "%sD" % days

    # Build time
    time_str = "T"

    # Hours
    bigger_exists = date_str or hours
    if bigger_exists:
        time_str += "{:02}H".format(hours)

    # Minutes
    bigger_exists = bigger_exists or minutes
    if bigger_exists:
        time_str += "{:02}M".format(minutes)

    # Seconds
    try:
        if seconds.is_integer():
            seconds_string = "{:02}".format(int(seconds))
        else:
            # 9 chars long w/ leading 0, 6 digits after decimal
            seconds_string = "%09.6f" % seconds
            # Remove trailing zeros
            seconds_string = seconds_string.rstrip("0")
    except AttributeError:  # int.is_integer() raises
        seconds_string = "{:02}".format(seconds)

    time_str += "{}S".format(seconds_string)

    return "P" + date_str + time_str


def _datetime_as_isostr(dt: Union[datetime, date, time, timedelta]) -> str:
    """Converts a datetime.(datetime|date|time|timedelta) object into an ISO 8601 formatted string.

    :param dt: The datetime object to convert
    :type dt: datetime.datetime or datetime.date or datetime.time or datetime.timedelta
    :return: An ISO 8601 formatted string representing the datetime object
    :rtype: str
    """
    # First try datetime.datetime
    if hasattr(dt, "year") and hasattr(dt, "hour"):
        dt = cast(datetime, dt)
        # astimezone() fails for naive times in Python 2.7, so make make sure dt is aware (tzinfo is set)
        if not dt.tzinfo:
            iso_formatted = dt.replace(tzinfo=timezone.utc).isoformat()
        else:
            iso_formatted = dt.astimezone(timezone.utc).isoformat()
        # Replace the trailing "+00:00" UTC offset with "Z" (RFC 3339: https://www.ietf.org/rfc/rfc3339.txt)
        return iso_formatted.replace("+00:00", "Z")
    # Next try datetime.date or datetime.time
    try:
        dt = cast(Union[date, time], dt)
        return dt.isoformat()
    # Last, try datetime.timedelta
    except AttributeError:
        dt = cast(timedelta, dt)
        return _timedelta_as_isostr(dt)


class CoreJSONEncoder(JSONEncoder):
    """A JSON encoder that's capable of serializing datetime objects and bytes."""

    def default(self, o: Any) -> Any:
        if isinstance(o, (bytes, bytearray)):
            return base64.b64encode(o).decode()
        try:
            return _datetime_as_isostr(o)
        except AttributeError:
            pass
        return super(CoreJSONEncoder, self).default(o)
