from django.db import models
from django.utils.html import escape
from django.utils.translation import gettext_lazy as _
from shortuuid.django_fields import ShortUUIDField

from moku.constants import Verbs
from moku.models.recipe import RecipeStep
from moku.validators import validate_emoji


def post_image_filename(instance, _):
    """Returns the filename that post images should be saved to."""
    return f"posts/{instance.created_by.username}__{instance.uuid}.webp"


class PostManager(models.Manager):
    """Manages post objects more efficiently by pre-fetching recipes and their steps."""

    def get_queryset(self):
        return (
            super()
            .get_queryset()
            .select_related("created_by")
            .prefetch_related(
                models.Prefetch(
                    "recipe__steps", queryset=RecipeStep.objects.order_by("order")
                )
            )
            .order_by("-created_at")
        )


class Post(models.Model):
    """Represents a single post on the site."""

    uuid = ShortUUIDField(
        verbose_name=_("unique id"),
        max_length=22,
        length=22,
        help_text=_("the unique id that identifies this post."),
    )
    emoji = models.CharField(
        verbose_name=_("emoji"),
        max_length=8,
        validators=[validate_emoji],
        help_text=_("an emoji to accompany your post!"),
    )
    verb = models.CharField(
        verbose_name=_("verb"),
        max_length=32,
        choices=Verbs.CHOICES,
        help_text=_("how should we best phrase this entry?"),
    )
    food = models.CharField(
        verbose_name=_("food"), max_length=128, help_text=_("what did you eat?")
    )
    image = models.ImageField(
        verbose_name=_("image"),
        blank=True,
        upload_to=post_image_filename,
        help_text=_("here you can upload a picture of what you ate!"),
    )
    recipe = models.ForeignKey(
        "Recipe",
        verbose_name=_("recipe"),
        blank=True,
        null=True,
        related_name="+",
        on_delete=models.SET_NULL,
        help_text=_("the recipe for what you ate, if you have one."),
    )
    created_by = models.ForeignKey(
        "User",
        related_name="posts",
        db_index=True,
        db_column="created_by_user_id",
        on_delete=models.CASCADE,
    )
    created_at = models.DateTimeField(
        auto_now_add=True, help_text=_("when this post was created.")
    )
    updated_at = models.DateTimeField(
        auto_now=True, help_text=_("when this post was last updated.")
    )

    objects = PostManager()

    def __str__(self):
        return f"{self.text} on {self.created_at}"

    @property
    def text(self):
        """
        The text of the post, with the post's chosen verb hydrated with food and user
        information.
        """
        return self.get_verb_display() % {
            "user": (
                f'<a href="{self.created_by.get_absolute_url()}">'
                f"@{self.created_by.username}</a>"
            ),
            "food": escape(self.food),
        }