from datetime import datetime

from tortoise import Model, fields


class TimestampMixin:
    created_at: fields.Field[datetime] = fields.DatetimeField(auto_now_add=True)
    modified_at: fields.Field[datetime] = fields.DatetimeField(auto_now=True)


class Teilchen(TimestampMixin, Model):
    name: fields.Field[str] = fields.TextField()
    description: fields.Field[str] = fields.TextField()
    number: fields.Field[int] = fields.IntField()  # TODO: validate values >= 0

    tags: fields.ManyToManyRelation["Tag"] = fields.ManyToManyField(
        "models.Tag",
        through="models.TeilchenTag",
        related_name="teilchen",
        forward_key="tag_id",
        backward_key="teilchen_id",
    )


class Tag(TimestampMixin, Model):
    name: fields.Field[str] = fields.CharField(max_length=20)


class TeilchenTag(Model):
    teilchen: fields.ForeignKeyRelation[Teilchen] = fields.ForeignKeyField(
        "models.Teilchen"
    )
    tag: fields.ForeignKeyRelation[Tag] = fields.ForeignKeyField("models.Tag")
    weight: fields.Field[int] = fields.IntField()  # range? percentage?