"""
Syndication feed generation library -- used for generating RSS, etc.

Sample usage:

>>> from django.utils import feedgenerator
>>> feed = feedgenerator.Rss201rev2Feed(
...     title="Poynter E-Media Tidbits",
...     link="http://www.poynter.org/column.asp?id=31",
...     description="A group Weblog by the sharpest minds in online media/journalism/publishing.",
...     language="en",
... )
>>> feed.add_item(
...     title="Hello",
...     link="http://www.holovaty.com/test/",
...     description="Testing."
... )
>>> with open('test.rss', 'w') as fp:
...     feed.write(fp, 'utf-8')

For definitions of the different versions of RSS, see:
http://web.archive.org/web/20110718035220/http://diveintomark.org/archives/2004/02/04/incompatible-rss
"""
import datetime
from urllib.parse import urlparse
from .xmlutils import SimplerXMLGenerator
from .encoding import force_text, iri_to_uri
from . import datetime_safe
from io import StringIO
from .timezone import is_aware

def rfc2822_date(date):
    # We can't use strftime() because it produces locale-dependent results, so
    # we have to map english month and day names manually
    months = ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec',)
    days = ('Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun')
    # Support datetime objects older than 1900
    date = datetime_safe.new_datetime(date)
    # We do this ourselves to be timezone aware, email.Utils is not tz aware.
    dow = days[date.weekday()]
    month = months[date.month - 1]
    time_str = date.strftime(f'{dow}, %d {month} %Y %H:%M:%S ')
    if is_aware(date):
        offset = date.tzinfo.utcoffset(date)
        timezone = (offset.days * 24 * 60) + (offset.seconds // 60)
        hour, minute = divmod(timezone, 60)
        return time_str + '%+03d%02d' % (hour, minute)
    else:
        return time_str + '-0000'

def rfc3339_date(date):
    # Support datetime objects older than 1900
    date = datetime_safe.new_datetime(date)
    time_str = date.strftime('%Y-%m-%dT%H:%M:%S')
    if is_aware(date):
        offset = date.tzinfo.utcoffset(date)
        timezone = (offset.days * 24 * 60) + (offset.seconds // 60)
        hour, minute = divmod(timezone, 60)
        return time_str + '%+03d:%02d' % (hour, minute)
    else:
        return time_str + 'Z'

def get_tag_uri(url, date):
    """
    Creates a TagURI.

    See http://web.archive.org/web/20110514113830/http://diveintomark.org/archives/2004/05/28/howto-atom-id
    """
    bits = urlparse(url)
    d = ''
    if date is not None:
        d = ',%s' % datetime_safe.new_datetime(date).strftime('%Y-%m-%d')
    fragment = ''
    if bits.fragment != '':
        fragment = '/%s' % (bits.fragment)
    return f'tag:{bits.hostname}{d}:{bits.path}{fragment}'

class SyndicationFeed:
    "Base class for all syndication feeds. Subclasses should provide write()"
    def __init__(self, title, link, description, language=None, author_email=None,
            author_name=None, author_link=None, subtitle=None, categories=None,
            feed_url=None, feed_copyright=None, feed_guid=None, ttl=None, **kwargs):
        to_unicode = lambda s: force_text(s, strings_only=True)
        if categories:
            categories = [force_text(c) for c in categories]
        if ttl is not None:
            # Force ints to unicode
            ttl = force_text(ttl)
        self.feed = {
            'title': to_unicode(title),
            'link': iri_to_uri(link),
            'description': to_unicode(description),
            'language': to_unicode(language),
            'author_email': to_unicode(author_email),
            'author_name': to_unicode(author_name),
            'author_link': iri_to_uri(author_link),
            'subtitle': to_unicode(subtitle),
            'categories': categories or (),
            'feed_url': iri_to_uri(feed_url),
            'feed_copyright': to_unicode(feed_copyright),
            'id': feed_guid or link,
            'ttl': ttl,
        }
        self.feed.update(kwargs)
        self.items = []

    def add_item(self, title, link, description, author_email=None,
        author_name=None, author_link=None, pubdate=None, comments=None,
        unique_id=None, enclosure=None, categories=(), item_copyright=None,
        ttl=None, content=None, updateddate=None, **kwargs):
        """
        Adds an item to the feed. All args are expected to be Python Unicode
        objects except pubdate and updateddate, which are datetime.datetime
        objects, and enclosure, which is an instance of the Enclosure class.
        """
        to_unicode = lambda s: force_text(s, strings_only=True)
        if categories:
            categories = [to_unicode(c) for c in categories]
        if ttl is not None:
            # Force ints to unicode
            ttl = force_text(ttl)
        item = {
            'title': to_unicode(title),
            'link': iri_to_uri(link),
            'description': to_unicode(description),
            'content': to_unicode(content),
            'author_email': to_unicode(author_email),
            'author_name': to_unicode(author_name),
            'author_link': iri_to_uri(author_link),
            'pubdate': pubdate,
            'updateddate': updateddate,
            'comments': to_unicode(comments),
            'unique_id': to_unicode(unique_id),
            'enclosure': enclosure,
            'categories': categories or (),
            'item_copyright': to_unicode(item_copyright),
            'ttl': ttl,
        }
        item.update(kwargs)
        self.items.append(item)

    def num_items(self):
        return len(self.items)

    def root_attributes(self):
        """
        Return extra attributes to place on the root (i.e. feed/channel) element.
        Called from write().
        """
        return {}

    def add_root_elements(self, handler):
        """
        Add elements in the root (i.e. feed/channel) element. Called
        from write().
        """
        pass

    def item_attributes(self, item):
        """
        Return extra attributes to place on each item (i.e. item/entry) element.
        """
        return {}

    def add_item_elements(self, handler, item):
        """
        Add elements on each item (i.e. item/entry) element.
        """
        pass

    def write(self, outfile, encoding):
        """
        Outputs the feed in the given encoding to outfile, which is a file-like
        object. Subclasses should override this.
        """
        raise NotImplementedError

    def writeString(self, encoding):
        """
        Returns the feed in the given encoding as a string.
        """
        s = StringIO()
        self.write(s, encoding)
        return s.getvalue()

    def latest_post_date(self):
        """
        Returns the latest item's pubdate or updateddate. If no item has either
        date, returns the current date/time.
        """
        updates = [i['pubdate'] for i in self.items if i['pubdate'] is not None]
        updates.extend(i['updateddate'] for i in self.items if i['updateddate'] is not None)
        if len(updates) > 0:
            updates.sort()
            return updates[-1]
        else:
            return datetime.datetime.now()

class Enclosure:
    "Represents an RSS enclosure"
    def __init__(self, url, length, mime_type):
        "All args are expected to be Python Unicode objects"
        self.length, self.mime_type = length, mime_type
        self.url = iri_to_uri(url)

class RssFeed(SyndicationFeed):
    mime_type = 'application/rss+xml; charset=utf-8'
    def write(self, outfile, encoding):
        handler = SimplerXMLGenerator(outfile, encoding)
        handler.startDocument()
        handler.startElement("rss", self.rss_attributes())
        handler.startElement("channel", self.root_attributes())
        self.add_root_elements(handler)
        self.write_items(handler)
        self.endChannelElement(handler)
        handler.endElement("rss")

    def rss_attributes(self):
        return {'version': self._version}

    def write_items(self, handler):
        for item in self.items:
            handler.startElement('item', self.item_attributes(item))
            self.add_item_elements(handler, item)
            handler.endElement("item")

    def add_root_elements(self, handler):
        # Required Elements as per the specification
        handler.addQuickElement("title", self.feed['title'])
        handler.addQuickElement("link", self.feed['link'])
        handler.addQuickElement("description", self.feed['description'])

        # Optional Channel Elements
        if self.feed['language'] is not None:
            handler.addQuickElement("language", self.feed['language'])
        for cat in self.feed['categories']:
            handler.addQuickElement("category", cat)
        if self.feed['feed_copyright'] is not None:
            handler.addQuickElement("copyright", self.feed['feed_copyright'])
        handler.addQuickElement("lastBuildDate", rfc2822_date(self.latest_post_date()))
        if self.feed['ttl'] is not None:
            handler.addQuickElement("ttl", self.feed['ttl'])

    def endChannelElement(self, handler):
        handler.endElement("channel")

class RssUserland091Feed(RssFeed):
    _version = "0.91"
    def add_item_elements(self, handler, item):
        handler.addQuickElement("title", item['title'])
        handler.addQuickElement("link", item['link'])
        if item['description'] is not None:
            handler.addQuickElement("description", item['description'])

class Rss201rev2Feed(RssFeed):
    # Spec: http://blogs.law.harvard.edu/tech/rss
    _version = "2.0"
    def add_item_elements(self, handler, item):
        handler.addQuickElement("title", item['title'])
        handler.addQuickElement("link", item['link'])
        if item['description'] is not None:
            handler.addQuickElement("description", item['description'])

        # Author information.
        if item["author_name"] and item["author_email"]:
            handler.addQuickElement("author", "%s (%s)" % \
                (item['author_email'], item['author_name']))
        elif item["author_email"]:
            handler.addQuickElement("author", item["author_email"])
        elif item["author_name"]:
            handler.addQuickElement("dc:creator", item["author_name"], {"xmlns:dc": "http://purl.org/dc/elements/1.1/"})

        if item['pubdate'] is not None:
            handler.addQuickElement("pubDate", rfc2822_date(item['pubdate']))
        if item['comments'] is not None:
            handler.addQuickElement("comments", item['comments'])
        if item['unique_id'] is not None:
            handler.addQuickElement("guid", item['unique_id'], attrs={'isPermaLink': 'false'})
        if item['ttl'] is not None:
            handler.addQuickElement("ttl", item['ttl'])

        # Enclosure.
        if item['enclosure'] is not None:
            handler.addQuickElement("enclosure", '',
                {"url": item['enclosure'].url, "length": item['enclosure'].length,
                    "type": item['enclosure'].mime_type})

        # Categories.
        for cat in item['categories']:
            handler.addQuickElement("category", cat)

class Atom1Feed(SyndicationFeed):
    # Spec: http://atompub.org/2005/07/11/draft-ietf-atompub-format-10.html
    mime_type = 'application/atom+xml; charset=utf-8'
    ns = "http://www.w3.org/2005/Atom"

    def write(self, outfile, encoding):
        handler = SimplerXMLGenerator(outfile, encoding)
        handler.startDocument()
        handler.startElement('feed', self.root_attributes())
        self.add_root_elements(handler)
        self.write_items(handler)
        handler.endElement("feed")

    def root_attributes(self):
        if self.feed['language'] is not None:
            return {"xmlns": self.ns, "xml:lang": self.feed['language']}
        else:
            return {"xmlns": self.ns}

    def add_root_elements(self, handler):
        handler.addQuickElement("title", self.feed['title'])
        handler.addQuickElement("link", "", {"rel": "alternate", "href": self.feed['link']})
        if self.feed['feed_url'] is not None:
            handler.addQuickElement("link", "", {"rel": "self", "href": self.feed['feed_url']})
        handler.addQuickElement("id", self.feed['id'])
        handler.addQuickElement("updated", rfc3339_date(self.latest_post_date()))
        if self.feed['author_name'] is not None:
            handler.startElement("author", {})
            handler.addQuickElement("name", self.feed['author_name'])
            if self.feed['author_email'] is not None:
                handler.addQuickElement("email", self.feed['author_email'])
            if self.feed['author_link'] is not None:
                handler.addQuickElement("uri", self.feed['author_link'])
            handler.endElement("author")
        # try to use description or subtitle if provided, subtitle has
        # precedence above description
        if self.feed['description'] is not None:
            handler.addQuickElement("subtitle", self.feed['description'])
        if self.feed['subtitle'] is not None:
            handler.addQuickElement("subtitle", self.feed['subtitle'])
        for cat in self.feed['categories']:
            handler.addQuickElement("category", "", {"term": cat})
        if self.feed['feed_copyright'] is not None:
            handler.addQuickElement("rights", self.feed['feed_copyright'])

    def write_items(self, handler):
        for item in self.items:
            handler.startElement("entry", self.item_attributes(item))
            self.add_item_elements(handler, item)
            handler.endElement("entry")

    def add_item_elements(self, handler, item):
        handler.addQuickElement("title", item['title'])
        handler.addQuickElement("link", "", {"href": item['link'], "rel": "alternate"})

        updateddate = datetime.datetime.now()
        if item['pubdate'] is not None:
            handler.addQuickElement("published", rfc3339_date(item['pubdate']))
            updateddate = item['pubdate']
        if item['updateddate'] is not None:
            updateddate = item['updateddate']
        handler.addQuickElement("updated", rfc3339_date(updateddate))

        # Author information.
        if item['author_name'] is not None:
            handler.startElement("author", {})
            handler.addQuickElement("name", item['author_name'])
            if item['author_email'] is not None:
                handler.addQuickElement("email", item['author_email'])
            if item['author_link'] is not None:
                handler.addQuickElement("uri", item['author_link'])
            handler.endElement("author")

        # Unique ID.
        if item['unique_id'] is not None:
            unique_id = item['unique_id']
        else:
            unique_id = get_tag_uri(item['link'], item['pubdate'])
        handler.addQuickElement("id", unique_id)

        # Summary.
        if item['description'] is not None:
            handler.addQuickElement("summary", item['description'], {"type": "html"})

        # Full content.
        if item['content'] is not None:
            handler.addQuickElement("content", item['content'], {"type": "html"})

        # Enclosure.
        if item['enclosure'] is not None:
            handler.addQuickElement("link", '',
                {"rel": "enclosure",
                 "href": item['enclosure'].url,
                 "length": item['enclosure'].length,
                 "type": item['enclosure'].mime_type})

        # Categories.
        for cat in item['categories']:
            handler.addQuickElement("category", "", {"term": cat})

        # Rights.
        if item['item_copyright'] is not None:
            handler.addQuickElement("rights", item['item_copyright'])

# This isolates the decision of what the system default is, so calling code can
# do "feedgenerator.DefaultFeed" instead of "feedgenerator.Rss201rev2Feed".
DefaultFeed = Rss201rev2Feed