import lxml.etree as ET
from lxml import etree
from lxml.builder import ElementMaker
from lxml.etree import Element


class SafeElementMaker:
    """
    Wraps ElementMaker to silently drop None values
    """

    def __init__(self, **kwargs):
        self._maker = ElementMaker(**kwargs)

    def __getattr__(self, tag):
        def safe_element(*children, **attrib):
            valid_children = [
                child
                for child in children
                if child is not None and (not isinstance(child, str) or child.strip())
            ]
            if valid_children or attrib:
                if isinstance(tag, str):
                    return self._maker.__getattr__(tag)(*valid_children, **attrib)
                elif issubclass(tag, Element):
                    return tag(*valid_children, **attrib)

        return safe_element


nsmap = {
    "content": "http://purl.org/rss/1.0/modules/content/",
    "media": "http://search.yahoo.com/mrss/",
    "itunes": "http://www.itunes.com/dtds/podcast-1.0.dtd",
    "dc": "http://purl.org/dc/elements/1.1/",
    "atom": "http://www.w3.org/2005/Atom",
}

CONTENT = SafeElementMaker(nsmap={None: nsmap["content"]}, namespace=nsmap["content"])
MEDIA = SafeElementMaker(nsmap={None: nsmap["media"]}, namespace=nsmap["media"])
ITUNES = SafeElementMaker(nsmap={None: nsmap["itunes"]}, namespace=nsmap["itunes"])
DC = SafeElementMaker(nsmap={None: nsmap["dc"]}, namespace=nsmap["dc"])
ATOM = SafeElementMaker(nsmap={None: nsmap["atom"]}, namespace=nsmap["atom"])
E: ElementMaker = SafeElementMaker(nsmap=nsmap)
CDATA = ET.CDATA

from datetime import datetime
from time import mktime


def rss():
    return E.rss({"version": "2.0"})


def parse_pubdate(date_str):
    try:
        return datetime.strptime(date_str, "%a, %d %b %Y %H:%M:%S %z")
    except ValueError:
        return datetime.min


def sort_rss(root):
    channel = root.find("channel")
    items = list(channel.findall("item"))
    for item in items:
        channel.remove(item)

    items.sort(
        key=lambda x: parse_pubdate(
            x.find("pubDate").text if x.find("pubDate") is not None else ""
        ),
        reverse=True,
    )

    for item in items:
        channel.append(item)
    return root


def serialize(root):
    # root = sort_rss(root)
    return etree.tostring(
        root, encoding="utf-8", xml_declaration=True, pretty_print=True
    )


def date_format(d):
    if d:
        return d.strftime("%a, %d %b %Y %H:%M:%S %z")


def to_datetime(struct_time):
    if struct_time:
        return datetime.fromtimestamp(mktime(struct_time))


def normalize_date(struct_time):
    return date_format(to_datetime(struct_time))