from django.db import models
from mainapp.models import Satellite, Polarization, get_default_polarization
from django.db.models import F, ExpressionWrapper
from django.db.models.functions import Abs

class Transponders(models.Model):
    name = models.CharField(max_length=30, null=True, blank=True, verbose_name="Название транспондера")
    downlink = models.FloatField(blank=True, null=True, verbose_name="Downlink")
    frequency_range = models.FloatField(blank=True, null=True, verbose_name="Полоса")
    uplink = models.FloatField(blank=True, null=True, verbose_name="Uplink")
    zone_name = models.CharField(max_length=255, blank=True, null=True, verbose_name="Название зоны")
    polarization = models.ForeignKey(
        Polarization, default=get_default_polarization, on_delete=models.SET_DEFAULT, related_name="tran_polarizations", null=True, blank=True, verbose_name="Поляризация"
    )
    sat_id = models.ForeignKey(Satellite, on_delete=models.PROTECT, related_name="tran_satellite", verbose_name="Спутник")
    transfer =models.GeneratedField(
        expression=ExpressionWrapper(
            Abs(F('downlink') - F('uplink')),
            output_field=models.FloatField()
        ),
        output_field=models.FloatField(),
        db_persist=True,
        null=True, blank=True, verbose_name="Перенос"
    )

    def __str__(self):
        return self.name
    
    class Meta:
        verbose_name = "Транспондер"
        verbose_name_plural = "Транспондеры"