# # core/models.py  (all-in-one, flat style)
# from django.conf import settings
# from django.db import models
# from django.contrib.contenttypes.fields import GenericForeignKey
# from django.contrib.contenttypes.models import ContentType
# import uuid
#
# # =============================
# # Mixins & Tenant manager
# # =============================
# class TimeStampedModel(models.Model):
#     created_at = models.DateTimeField(auto_now_add=True, db_index=True)
#     updated_at = models.DateTimeField(auto_now=True, db_index=True)
#     class Meta:
#         abstract = True
#
# class UserStampedModel(models.Model):
#     created_by = models.ForeignKey(
#         settings.AUTH_USER_MODEL, null=True, blank=True,
#         on_delete=models.SET_NULL, related_name="%(class)s_created"
#     )
#     updated_by = models.ForeignKey(
#         settings.AUTH_USER_MODEL, null=True, blank=True,
#         on_delete=models.SET_NULL, related_name="%(class)s_updated"
#     )
#     class Meta:
#         abstract = True
#
# class ActiveModel(models.Model):
#     is_active = models.BooleanField(default=True, db_index=True)
#     class Meta:
#         abstract = True
#
# class TenantManager(models.Manager):
#     def for_tenant(self, tenant):
#         return super().get_queryset().filter(tenant=tenant)
#
# class TenantScopedModel(TimeStampedModel, UserStampedModel, ActiveModel):
#     tenant = models.ForeignKey("core.Tenant", on_delete=models.CASCADE, db_index=True)
#     objects = TenantManager()
#     class Meta:
#         abstract = True
#
# # =============================
# # Core primitives
# # =============================
# class Tenant(TimeStampedModel, ActiveModel):
#     code = models.SlugField(max_length=64, unique=True)
#     name = models.CharField(max_length=255)
#     status = models.CharField(max_length=32, default="active")  # active|suspended|closed
#     def __str__(self):
#         return f"{self.code} – {self.name}"
#
# class Facility(TenantScopedModel):
#     code = models.SlugField(max_length=64)
#     name = models.CharField(max_length=255)
#     facility_type = models.CharField(max_length=64, blank=True, default="")  # hospital|clinic|lab|...
#     address_line1 = models.CharField(max_length=255, blank=True, default="")
#     address_line2 = models.CharField(max_length=255, blank=True, default="")
#     city = models.CharField(max_length=120, blank=True, default="")
#     state = models.CharField(max_length=120, blank=True, default="")
#     postal_code = models.CharField(max_length=30, blank=True, default="")
#     country = models.CharField(max_length=2, blank=True, default="")  # ISO-3166-1 alpha-2
#
#     class Meta:
#         unique_together = [("tenant", "code")]
#         indexes = [
#             models.Index(fields=["tenant", "name"]),
#             models.Index(fields=["tenant", "facility_type"]),
#         ]
#
#     def __str__(self):
#         return f"{self.code} – {self.name}"
#
# class Patient(TenantScopedModel):
#     uuid = models.UUIDField(unique=True, editable=False, null=True, blank=True, default=uuid.uuid4)
#     given_name = models.CharField(max_length=120)
#     family_name = models.CharField(max_length=120, blank=True, default="")
#     birth_date = models.DateField(null=True, blank=True)
#     sex = models.CharField(max_length=16, blank=True, default="")  # male|female|other|unknown
#     primary_facility = models.ForeignKey("core.Facility", null=True, blank=True, on_delete=models.SET_NULL)
#
#     class Meta:
#         indexes = [
#             models.Index(fields=["tenant", "family_name", "given_name"]),
#             models.Index(fields=["tenant", "birth_date"]),
#         ]
#
#     def __str__(self):
#         return f"{self.family_name}, {self.given_name}".strip(", ")
#
# class IdentifierType(TenantScopedModel):
#     code = models.SlugField(max_length=64)
#     name = models.CharField(max_length=120)
#     issuer = models.CharField(max_length=120, blank=True, default="")  # e.g., MOH, facility code
#
#     class Meta:
#         unique_together = [("tenant", "code")]
#
#     def __str__(self):
#         return self.name
#
# class Identifier(TenantScopedModel):
#     patient = models.ForeignKey("core.Patient", on_delete=models.CASCADE, related_name="identifiers")
#     id_type = models.ForeignKey("core.IdentifierType", on_delete=models.PROTECT)
#     value = models.CharField(max_length=128)
#     is_primary = models.BooleanField(default=False)
#     period_start = models.DateField(null=True, blank=True)
#     period_end = models.DateField(null=True, blank=True)
#
#     class Meta:
#         unique_together = [("tenant", "id_type", "value")]
#         indexes = [
#             models.Index(fields=["tenant", "value"]),
#             models.Index(fields=["tenant", "patient"]),
#         ]
#
#     def __str__(self):
#         return f"{self.id_type.code}:{self.value}"
#
# class Practitioner(TenantScopedModel):
#     """Clinical identity; keep HR employment in hr.Employee and auth in accounts.User."""
#     user = models.ForeignKey("accounts.User", null=True, blank=True, on_delete=models.SET_NULL)
#     full_name = models.CharField(max_length=255)
#     license_id = models.CharField(max_length=80, blank=True, default="")
#     specialty = models.CharField(max_length=120, blank=True, default="")
#     npi = models.CharField(max_length=20, blank=True, default="")  # if relevant in your locale
#     active_from = models.DateField(null=True, blank=True)
#     active_to = models.DateField(null=True, blank=True)
#
#     class Meta:
#         indexes = [
#             models.Index(fields=["tenant", "full_name"]),
#         ]
#         unique_together = []  # add ("tenant","license_id") if licenses are unique
#
#     def __str__(self):
#         return self.full_name
#
# class Department(TenantScopedModel):
#     facility = models.ForeignKey("core.Facility", on_delete=models.PROTECT)
#     code = models.SlugField(max_length=64)
#     name = models.CharField(max_length=255)
#     class Meta:
#         unique_together = [("tenant", "facility", "code")]
#         indexes = [models.Index(fields=["tenant", "facility", "name"])]
#     def __str__(self):
#         return f"{self.facility.code}:{self.code}"
#
# class LocationNode(TenantScopedModel):
#     """Generic clinical location tree (building/floor/room/chair/etc.)."""
#     facility = models.ForeignKey("core.Facility", on_delete=models.PROTECT)
#     parent = models.ForeignKey("self", null=True, blank=True, on_delete=models.CASCADE, related_name="children")
#     code = models.SlugField(max_length=64)
#     name = models.CharField(max_length=255)
#     kind = models.CharField(max_length=32, default="room")  # building|floor|zone|room|chair|desk...
#     class Meta:
#         unique_together = [("tenant", "facility", "code")]
#         indexes = [models.Index(fields=["tenant", "facility", "kind"])]
#     def __str__(self):
#         return f"{self.facility.code}:{self.code}"
#
# class Encounter(TenantScopedModel):
#     class EncounterClass(models.TextChoices):
#         INPATIENT = "INPATIENT", "Inpatient"
#         OUTPATIENT = "OUTPATIENT", "Outpatient"
#         EMERGENCY = "EMERGENCY", "Emergency"
#         VIRTUAL = "VIRTUAL", "Virtual"
#
#     class EncounterStatus(models.TextChoices):
#         PLANNED = "PLANNED", "Planned"
#         IN_PROGRESS = "IN_PROGRESS", "In Progress"
#         FINISHED = "FINISHED", "Finished"
#         CANCELLED = "CANCELLED", "Cancelled"
#
#     patient = models.ForeignKey("core.Patient", on_delete=models.PROTECT, related_name="encounters")
#     facility = models.ForeignKey("core.Facility", on_delete=models.PROTECT, related_name="encounters")
#     encounter_class = models.CharField(max_length=20, choices=EncounterClass.choices)
#     status = models.CharField(max_length=20, choices=EncounterStatus.choices, default=EncounterStatus.PLANNED)
#     start_at = models.DateTimeField()
#     end_at = models.DateTimeField(null=True, blank=True)
#     attending = models.ForeignKey("core.Practitioner", null=True, blank=True, on_delete=models.SET_NULL, related_name="encounters_attending")
#     department = models.ForeignKey("core.Department", null=True, blank=True, on_delete=models.SET_NULL)
#     location_node = models.ForeignKey("core.LocationNode", null=True, blank=True, on_delete=models.SET_NULL)
#
#     class Meta:
#         indexes = [
#             models.Index(fields=["tenant", "patient", "start_at"]),
#             models.Index(fields=["tenant", "facility", "start_at"]),
#             models.Index(fields=["tenant", "encounter_class"]),
#             models.Index(fields=["tenant", "status"]),
#         ]
#
#     def __str__(self):
#         return f"{self.patient_id} @ {self.facility_id} ({self.encounter_class})"
#
# class Address(TenantScopedModel):
#     line1 = models.CharField(max_length=255, blank=True, default="")
#     line2 = models.CharField(max_length=255, blank=True, default="")
#     city = models.CharField(max_length=120, blank=True, default="")
#     state = models.CharField(max_length=120, blank=True, default="")
#     postal_code = models.CharField(max_length=30, blank=True, default="")
#     country = models.CharField(max_length=2, blank=True, default="")
#     def __str__(self):
#         return ", ".join(x for x in [self.line1, self.city, self.state] if x)
#
# class ContactPoint(TenantScopedModel):
#     system = models.CharField(max_length=20)  # phone|email
#     value = models.CharField(max_length=120)
#     use = models.CharField(max_length=20, blank=True, default="")  # home|work|mobile
#     preferred = models.BooleanField(default=False)
#     class Meta:
#         indexes = [models.Index(fields=["tenant", "system", "value"])]
#     def __str__(self):
#         return f"{self.system}:{self.value}"
#
# class PatientContact(TenantScopedModel):
#     patient = models.ForeignKey("core.Patient", on_delete=models.CASCADE, related_name="contacts")
#     name = models.CharField(max_length=255, blank=True, default="")
#     relationship = models.CharField(max_length=40, blank=True, default="")  # guardian|next-of-kin
#     address = models.ForeignKey("core.Address", null=True, blank=True, on_delete=models.SET_NULL)
#     phone = models.ForeignKey("core.ContactPoint", null=True, blank=True, on_delete=models.SET_NULL, related_name="pc_phone")
#     email = models.ForeignKey("core.ContactPoint", null=True, blank=True, on_delete=models.SET_NULL, related_name="pc_email")
#
# class Consent(TenantScopedModel):
#     patient = models.ForeignKey("core.Patient", on_delete=models.CASCADE, related_name="consents")
#     kind = models.CharField(max_length=40)  # treatment|surgery|disclosure|photo
#     given_at = models.DateTimeField()
#     revoked_at = models.DateTimeField(null=True, blank=True)
#     details = models.JSONField(null=True, blank=True)  # form id, signer, ip, scope, etc.
#     class Meta:
#         indexes = [models.Index(fields=["tenant", "patient", "kind", "given_at"])]
#
# class PatientMergeEvent(TenantScopedModel):
#     surviving = models.ForeignKey("core.Patient", on_delete=models.PROTECT, related_name="merges_surviving")
#     merged = models.ForeignKey("core.Patient", on_delete=models.PROTECT, related_name="merges_merged")
#     reason = models.CharField(max_length=120, blank=True, default="")
#     happened_at = models.DateTimeField(auto_now_add=True)
#
# class Coverage(TenantScopedModel):
#     """Patient's active insurance coverage (neutral, referenced by billing & insurance_approvals)."""
#     patient = models.ForeignKey("core.Patient", on_delete=models.CASCADE, related_name="coverages")
#     payer = models.ForeignKey("billing.Payer", on_delete=models.PROTECT)  # keep payer master in billing
#     member_id = models.CharField(max_length=64)
#     plan_name = models.CharField(max_length=120, blank=True, default="")
#     period_start = models.DateField(null=True, blank=True)
#     period_end = models.DateField(null=True, blank=True)
#     is_primary = models.BooleanField(default=True)
#     class Meta:
#         indexes = [models.Index(fields=["tenant", "patient", "is_primary"])]
#         unique_together = []  # consider ("tenant","patient","payer","member_id")
#
# class CareTeam(TenantScopedModel):
#     patient = models.ForeignKey("core.Patient", on_delete=models.CASCADE)
#     encounter = models.ForeignKey("core.Encounter", null=True, blank=True, on_delete=models.SET_NULL)
#
# class CareTeamMember(TenantScopedModel):
#     careteam = models.ForeignKey("core.CareTeam", on_delete=models.CASCADE, related_name="members")
#     practitioner = models.ForeignKey("core.Practitioner", on_delete=models.PROTECT)
#     role = models.CharField(max_length=40, blank=True, default="")  # attending|consultant|nurse
#     class Meta:
#         indexes = [models.Index(fields=["tenant", "role"])]]
#
# class Attachment(TenantScopedModel):
#     file = models.FileField(upload_to="attachments/%Y/%m/")
#     title = models.CharField(max_length=255, blank=True, default="")
#     content_type = models.CharField(max_length=120, blank=True, default="")
#     size_bytes = models.PositiveIntegerField(default=0)
#     patient = models.ForeignKey("core.Patient", null=True, blank=True, on_delete=models.SET_NULL, related_name="attachments")
#     encounter = models.ForeignKey("core.Encounter", null=True, blank=True, on_delete=models.SET_NULL, related_name="attachments")
#
#     class Meta:
#         indexes = [
#             models.Index(fields=["tenant", "patient"]),
#             models.Index(fields=["tenant", "encounter"]),
#         ]
#
#     def __str__(self):
#         return self.title or self.file.name
#
# class AuditEvent(TenantScopedModel):
#     action = models.CharField(max_length=32)  # create|update|delete|read|login|export|import|custom
#     actor = models.ForeignKey("accounts.User", null=True, blank=True, on_delete=models.SET_NULL, related_name="audit_events")
#     target_content_type = models.ForeignKey(ContentType, on_delete=models.SET_NULL, null=True, blank=True)
#     target_object_id = models.CharField(max_length=64, blank=True, default="")
#     target = GenericForeignKey("target_content_type", "target_object_id")
#     summary = models.CharField(max_length=255, blank=True, default="")
#     payload = models.JSONField(null=True, blank=True)  # optional diff/extra data
#     occurred_at = models.DateTimeField(auto_now_add=True)
#
#     class Meta:
#         indexes = [
#             models.Index(fields=["tenant", "action", "occurred_at"]),
#             models.Index(fields=["tenant", "target_content_type", "target_object_id"]),
#         ]
#
#     def __str__(self):
#         return f"[{self.action}] {self.summary or self.id}"