from urllib.parse import urlparse

from django.conf import settings
from django.core.cache import caches
from django.db import models
from django.templatetags.static import static
from django.test import RequestFactory
from django.utils import timezone
from django.utils.cache import _generate_cache_header_key
from django.utils.formats import date_format
from django.utils.html import format_html
from django.utils.translation import gettext_lazy as _
from django_hosts.resolvers import get_host, reverse, reverse_host
from docutils.core import publish_parts
from markdown import markdown
from markdown.extensions.toc import TocExtension, slugify as _md_title_slugify

BLOG_DOCUTILS_SETTINGS = {
    "doctitle_xform": False,
    "initial_header_level": 2,
    "id_prefix": "s-",
    "raw_enabled": False,
    "file_insertion_enabled": False,
}
BLOG_DOCUTILS_SETTINGS.update(getattr(settings, "BLOG_DOCUTILS_SETTINGS", {}))


def _md_slugify(value, separator):
    # matches the `id_prefix` setting of BLOG_DOCUTILS_SETTINGS
    return "s" + separator + _md_title_slugify(value, separator)


class EntryQuerySet(models.QuerySet):
    def published(self):
        return self.active().filter(pub_date__lte=timezone.now())

    def active(self):
        return self.filter(is_active=True)


class ContentFormat(models.TextChoices):
    REST = "reST", "reStructuredText"
    HTML = "html", "Raw HTML"
    MARKDOWN = "md", "Markdown"

    @classmethod
    def to_html(cls, fmt, source):
        """
        Convert the given source from the given format to HTML
        """
        if not fmt or fmt == cls.HTML:
            return source
        if fmt == cls.REST:
            return publish_parts(
                source=source,
                writer_name="html",
                settings_overrides=BLOG_DOCUTILS_SETTINGS,
            )["fragment"]
        if fmt == cls.MARKDOWN:
            return markdown(
                source,
                output_format="html",
                extensions=[
                    # baselevel is 1 unlike `initial_header_level` from
                    # BLOG_DOCUTILS_SETTINGS because rst always starts from heading
                    # level 1, but markdown can have specific heading levels so
                    # starting from 1 makes sense.
                    "tables",
                    TocExtension(baselevel=1, slugify=_md_slugify),
                ],
            )
        raise ValueError(f"Unsupported format {fmt}")

    def img(self, url, alt_text):
        """
        Generate the source code for an image in the current format
        """
        CF = type(self)
        return {
            CF.REST: f".. image:: {url}\n   :alt: {alt_text}",
            CF.HTML: format_html('<img src="{}" alt="{}">', url, alt_text),
            CF.MARKDOWN: f"![{alt_text}]({url})",
        }[self]


class ImageUpload(models.Model):
    """
    Make it easier to attach images to blog posts.
    """

    title = models.CharField(
        max_length=100, help_text="Not published anywhere, just used internally"
    )
    image = models.FileField(upload_to="blog/images/%Y/%m/")
    alt_text = models.TextField(
        help_text="Make the extra effort, it makes a difference 💖"
    )
    uploaded_on = models.DateTimeField(auto_now_add=True)
    uploaded_by = models.ForeignKey(
        "auth.User", null=True, editable=False, on_delete=models.SET_NULL
    )

    class Meta:
        ordering = ("-uploaded_on",)

    def __str__(self):
        return f"({self.uploaded_on.date()}) {self.title}"

    @property
    def full_url(self):
        """
        Return a full URL (scheme + hostname + path) to the image
        """
        p = urlparse(self.image.url)
        if p.netloc:
            return self.image.url
        host = get_host()
        hostname = reverse_host(host)
        return f"{host.scheme}{hostname}{host.port}{self.image.url}"


class Entry(models.Model):
    headline = models.CharField(max_length=200)
    slug = models.SlugField(unique_for_date="pub_date")
    is_active = models.BooleanField(
        help_text=_(
            "Tick to make this entry live (see also the publication date). "
            "Note that administrators (like yourself) are allowed to preview "
            "inactive entries whereas the general public aren't."
        ),
        default=False,
    )
    pub_date = models.DateTimeField(
        verbose_name=_("Publication date"),
        help_text=_(
            "For an entry to be published, it must be active and its "
            "publication date must be in the past."
        ),
    )
    content_format = models.CharField(choices=ContentFormat, max_length=50)
    summary = models.TextField()
    summary_html = models.TextField()
    body = models.TextField()
    body_html = models.TextField()
    author = models.CharField(max_length=100)
    social_media_card = models.ForeignKey(
        ImageUpload,
        on_delete=models.PROTECT,
        blank=True,
        null=True,
        help_text=_(
            "For maximum compatibility, the image should be < 5 MB "
            "and at least 1200x627 px."
        ),
    )

    objects = EntryQuerySet.as_manager()

    class Meta:
        db_table = "blog_entries"
        verbose_name_plural = "entries"
        ordering = ("-pub_date",)
        get_latest_by = "pub_date"

    def __str__(self):
        return self.headline

    def get_absolute_url(self):
        kwargs = {
            "year": self.pub_date.year,
            "month": self.pub_date.strftime("%b").lower(),
            "day": self.pub_date.strftime("%d").lower(),
            "slug": self.slug,
        }
        return reverse("weblog:entry", kwargs=kwargs, host="www")

    def is_published(self):
        """
        Return True if the entry is publicly accessible.
        """
        return self.is_active and self.pub_date <= timezone.now()

    is_published.boolean = True

    @property
    def pub_date_localized(self):
        return date_format(self.pub_date)

    @property
    def description(self):
        return _("Posted by {author} on {pub_date}").format(
            author=self.author, pub_date=self.pub_date_localized
        )

    def save(self, *args, **kwargs):
        self.summary_html = ContentFormat.to_html(self.content_format, self.summary)
        self.body_html = ContentFormat.to_html(self.content_format, self.body)
        super().save(*args, **kwargs)
        self.invalidate_cached_entry()

    def invalidate_cached_entry(self):
        url = urlparse(self.get_absolute_url())
        rf = RequestFactory(
            SERVER_NAME=url.netloc,
            HTTP_X_FORWARDED_PROTOCOL=url.scheme,
        )
        is_secure = url.scheme == "https"
        request = rf.get(url.path, secure=is_secure)
        request.LANGUAGE_CODE = settings.DEFAULT_LANGUAGE_CODE
        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
        cache_key = _generate_cache_header_key(
            settings.CACHE_MIDDLEWARE_KEY_PREFIX, request
        )
        cache.delete(cache_key)

    @property
    def opengraph_tags(self):
        tags = {
            "og:type": "article",
            "og:title": self.headline,
            "og:description": self.description,
            "og:article:published_time": self.pub_date.isoformat(),
            "og:article:author": self.author,
            "og:image": static("img/logos/django-logo-negative.png"),
            "og:image:alt": "Django logo",
            "og:url": self.get_absolute_url(),
            "og:site_name": "Django Project",
            "twitter:card": "summary",
            "twitter:creator": "djangoproject",
            "twitter:site": "djangoproject",
        }
        if card := self.social_media_card:
            tags |= {
                "og:image": card.full_url,
                "og:image:alt": card.alt_text,
            }

        return tags


class EventQuerySet(EntryQuerySet):
    def past(self):
        return self.filter(date__lte=timezone.now()).order_by("-date")

    def future(self):
        return self.filter(date__gte=timezone.now()).order_by("date")


class Event(models.Model):
    headline = models.CharField(max_length=200, null=False)
    external_url = models.URLField()
    date = models.DateField()
    location = models.CharField(max_length=100)
    is_active = models.BooleanField(
        help_text=_(
            "Tick to make this event live (see also the publication date). "
            "Note that administrators (like yourself) are allowed to preview "
            "inactive events whereas the general public aren't."
        ),
        default=False,
    )
    pub_date = models.DateTimeField(
        verbose_name=_("Publication date"),
        help_text=_(
            "For an event to be published, it must be active and its "
            "publication date must be in the past."
        ),
    )

    objects = EventQuerySet.as_manager()

    class Meta:
        ordering = ("-pub_date",)
        get_latest_by = "pub_date"

    def is_published(self):
        """
        Return True if the event is publicly accessible.
        """
        return self.is_active and self.pub_date <= timezone.now()

    is_published.boolean = True