block7.from

django.db import models
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.fields import GenericForeignKey

LEAD_MODEL = models.Q(app_label='lead_manager', model='Lead')
AGENT_MODEL = models.Q(app_label='lead_manager', model='Agent')
communicating_parties = LEAD_MODEL | AGENT_MODEL

class Message(models.Model):
    body = models.TextField()

    sender_type = models.ForeignKey(
        ContentType, 
        limit_choices_to=communicating_parties,
        null=True, blank=True, on_delete=models.SET_NULL, related_name="sent_messages"
    ) 
    sender_id = models.PositiveIntegerField(null=True, blank=True, db_index=True)
    sender = GenericForeignKey(ct_field='sender_type', fk_field='sender_id')

    receiver_type = models.ForeignKey(
        ContentType, 
        limit_choices_to=communicating_parties,
        null=True, blank=True, on_delete=models.SET_NULL, related_name="received_messages"
    )
    receiver_id = models.PositiveIntegerField(null=True, blank=True, db_index=True)
    receiver = GenericForeignKey(ct_field='receiver_type', fk_field='receiver_id')

    date_created = models.DateTimeField(auto_now_add=True)
    message_key = models.CharField(null=True, blank=True, max_length=50)
    is_delivered = models.BooleanField(default=False)

    def __str__(self):
        return "Message (%s) from %s to %s" % (self.id, self.sender, self.receiver)