from itertools import chain
from operator import attrgetter

from django.apps import apps
from django.db import models
from django.utils.translation import gettext_lazy as _

CAROUSEL_MODES = [
    ("off", _("Off")),
    ("latest", _("Latest Articles")),
    ("news", _("Latest News")),
    ("selected-articles", _("Selected Articles")),
    ("mixed", _("Latest Articles and News")),
    ("mixed-selected", _("Selected Articles and News")),
]


class Carousel(models.Model):
    mode = models.CharField(
        max_length=200,
        blank=False,
        null=False,
        default="Latest",
        choices=CAROUSEL_MODES,
    )
    enabled = True

    exclude = models.BooleanField(
        help_text=_(
            "If enabled, the selectors below will behave as an exclusion list",
        ),
        default=False,
    )

    latest_articles = models.BooleanField(
        default=False,
        help_text="The carousel will display the latest published articles",
    )

    # these fields contains a custom list of articles and article-like carousel objects for Mixed and News modes
    articles = models.ManyToManyField(
        "submission.Article",
        blank=True,
        null=True,
        related_name="articles",
    )

    latest_news = models.BooleanField(
        default=False,
        help_text="The carousel will display the latest published news items",
    )

    # a selected news field
    news_articles = models.ManyToManyField(
        "comms.NewsItem",
        blank=True,
    )

    # article and news limits
    article_limit = models.IntegerField(
        verbose_name="Maximum Number of Articles to Show",
        default=3,
    )
    news_limit = models.IntegerField(
        verbose_name="Maximum Number of News Items to Show",
        default=0,
    )
    issues = models.ManyToManyField(
        "journal.issue",
        verbose_name=_("Issues and Collections"),
        blank=True,
    )

    current_issue = models.BooleanField(
        default=False,
        help_text="Always include the current issue",
    )

    def get_items(self):
        import core.logic as core_logic

        Article = apps.get_model("submission", "Article")
        Issue = apps.get_model("journal", "Issue")
        NewsItem = apps.get_model("comms", "NewsItem")

        articles = Article.objects.none()
        news = NewsItem.objects.none()
        issues = Issue.objects.none()

        if self.latest_articles:
            if hasattr(self, "press"):
                articles |= core_logic.latest_articles(self, "press")
            elif hasattr(self, "journal"):
                articles |= core_logic.latest_articles(self, "journal")
            if self.article_limit > 0:
                articles = articles[: self.article_limit]

        if self.articles.exists():
            if self.exclude:
                articles = articles.exclude(id__in=self.articles.all().values("id"))
            else:
                articles = chain(self.articles.all(), articles)

        if self.latest_news:
            if hasattr(self, "press"):
                news |= core_logic.news_items(self, "press")
            elif hasattr(self, "journal"):
                news |= core_logic.news_items(self, "journal")
            if self.news_limit > 0:
                news = news[: self.news_limit]

        if self.news_articles.exists():
            if self.exclude:
                news = news.exclude(pk__in=self.news_articles.all().values("id"))
            else:
                news = chain(self.news_articles.all(), news)

        if self.issues.exists():
            if self.exclude:
                issues = issues.exclude(pk__in=self.issues.all().values("id"))
            else:
                issues = chain(self.issues.all(), issues)

        return sorted(
            chain(articles, news, issues),
            key=attrgetter("date_published"),
            reverse=True,
        )


class CarouselObject(models.Model):
    """
    This model is deprecated. Carousels are formed dynamically from selected items.

    A warning is not raised, since an early migration uses the model.
    """

    large_image_file = models.ForeignKey(
        "core.File", null=True, blank=True, on_delete=models.SET_NULL
    )
    url = models.CharField(max_length=5000, blank=True, null=True)
    title = models.CharField(max_length=300)
    index = models.IntegerField(default=1)
    articleID = models.ManyToManyField("submission.Article", null=True, blank=True)

    @property
    def local_url(self):
        return self.url