models.py

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

from base.models import NamedBase
from species.models import SpeciesBase, Species


class Culture(NamedBase):
    species = models.ManyToManyField(Species, through='CultureSpecies')


class CultureBase(models.Model):
    """ Abstract base class for elements relating to culture. """

    class Meta:
        abstract = True
        verbose_name = _('culture')
        verbose_name_plural = _('cultures')

    culture = models.ForeignKey(Culture, on_delete=models.CASCADE)

    def __str__(self):
        return str(self.culture)


class CultureSpecies(CultureBase, SpeciesBase):
    ratio = models.FloatField(
        help_text=_('fraction, monoculture equivalent')
        # TODO: Validate value > 0.0 and <= 1.0
    )