"""
Referrals models for the Tenhal Multidisciplinary Healthcare Platform.

This module handles inter-discipline and external referrals.
"""

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

from core.models import (
    UUIDPrimaryKeyMixin,
    TimeStampedMixin,
    TenantOwnedMixin,
)


class Referral(UUIDPrimaryKeyMixin, TimeStampedMixin, TenantOwnedMixin):
    """
    Inter-discipline and external referrals.
    Tracks referrals between clinics and to external providers.
    """
    
    class Discipline(models.TextChoices):
        MEDICAL = 'MEDICAL', _('Medical')
        NURSING = 'NURSING', _('Nursing')
        OT = 'OT', _('Occupational Therapy')
        SLP = 'SLP', _('Speech-Language Pathology')
        ABA = 'ABA', _('Applied Behavior Analysis')
        EXTERNAL = 'EXTERNAL', _('External Provider')
    
    class Urgency(models.TextChoices):
        ROUTINE = 'ROUTINE', _('Routine')
        URGENT = 'URGENT', _('Urgent')
        EMERGENCY = 'EMERGENCY', _('Emergency')
    
    class Status(models.TextChoices):
        PENDING = 'PENDING', _('Pending')
        ACCEPTED = 'ACCEPTED', _('Accepted')
        REJECTED = 'REJECTED', _('Rejected')
        COMPLETED = 'COMPLETED', _('Completed')
        CANCELLED = 'CANCELLED', _('Cancelled')
    
    # Core Relationships
    patient = models.ForeignKey(
        'core.Patient',
        on_delete=models.CASCADE,
        related_name='referrals',
        verbose_name=_("Patient")
    )
    
    # From (Source)
    from_clinic = models.ForeignKey(
        'core.Clinic',
        on_delete=models.CASCADE,
        related_name='referrals_from',
        verbose_name=_("From Clinic")
    )
    from_discipline = models.CharField(
        max_length=20,
        choices=Discipline.choices,
        verbose_name=_("From Discipline")
    )
    from_provider = models.ForeignKey(
        'core.User',
        on_delete=models.SET_NULL,
        null=True,
        related_name='referrals_made',
        verbose_name=_("From Provider")
    )
    
    # To (Destination) - Internal or External
    to_clinic = models.ForeignKey(
        'core.Clinic',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='referrals_to',
        verbose_name=_("To Clinic")
    )
    to_discipline = models.CharField(
        max_length=20,
        choices=Discipline.choices,
        blank=True,
        verbose_name=_("To Discipline")
    )
    to_provider = models.ForeignKey(
        'core.User',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='referrals_received',
        verbose_name=_("To Provider")
    )
    external_provider_name = models.CharField(
        max_length=200,
        blank=True,
        help_text=_("Name of external provider if referral is external"),
        verbose_name=_("External Provider Name")
    )
    external_provider_contact = models.CharField(
        max_length=200,
        blank=True,
        verbose_name=_("External Provider Contact")
    )
    
    # Referral Details
    reason = models.TextField(
        verbose_name=_("Reason for Referral")
    )
    urgency = models.CharField(
        max_length=20,
        choices=Urgency.choices,
        default=Urgency.ROUTINE,
        verbose_name=_("Urgency")
    )
    status = models.CharField(
        max_length=20,
        choices=Status.choices,
        default=Status.PENDING,
        verbose_name=_("Status")
    )
    
    # Timestamps
    responded_at = models.DateTimeField(
        null=True,
        blank=True,
        verbose_name=_("Responded At")
    )
    completed_at = models.DateTimeField(
        null=True,
        blank=True,
        verbose_name=_("Completed At")
    )
    
    # Additional Information
    notes = models.TextField(
        blank=True,
        verbose_name=_("Notes")
    )
    response_notes = models.TextField(
        blank=True,
        verbose_name=_("Response Notes")
    )
    
    # Attachments (clinical documents, reports, etc.)
    clinical_summary = models.TextField(
        blank=True,
        help_text=_("Summary of clinical findings to share with receiving provider"),
        verbose_name=_("Clinical Summary")
    )
    
    class Meta:
        verbose_name = _("Referral")
        verbose_name_plural = _("Referrals")
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['patient', 'status']),
            models.Index(fields=['from_clinic', 'created_at']),
            models.Index(fields=['to_clinic', 'status']),
            models.Index(fields=['status', 'urgency']),
            models.Index(fields=['tenant', 'created_at']),
        ]
    
    def __str__(self):
        if self.to_clinic:
            return f"Referral: {self.from_clinic.name_en} → {self.to_clinic.name_en} - {self.patient}"
        else:
            return f"Referral: {self.from_clinic.name_en} → {self.external_provider_name} - {self.patient}"
    
    @property
    def is_internal(self):
        """Check if referral is internal (within the same facility)."""
        return self.to_clinic is not None
    
    @property
    def is_external(self):
        """Check if referral is external."""
        return self.to_clinic is None and bool(self.external_provider_name)
    
    @property
    def is_pending(self):
        """Check if referral is pending."""
        return self.status == self.Status.PENDING
    
    @property
    def response_time(self):
        """Calculate response time in hours."""
        if self.responded_at:
            delta = self.responded_at - self.created_at
            return round(delta.total_seconds() / 3600, 2)
        return None


class ReferralAutoRule(UUIDPrimaryKeyMixin, TimeStampedMixin, TenantOwnedMixin):
    """
    Automatic referral rules based on diagnoses or conditions.
    E.g., ASD diagnosis → auto-suggest referral to Pediatrician
    """
    
    name = models.CharField(
        max_length=200,
        verbose_name=_("Rule Name")
    )
    description = models.TextField(
        blank=True,
        verbose_name=_("Description")
    )
    
    # Trigger Conditions
    trigger_clinic = models.ForeignKey(
        'core.Clinic',
        on_delete=models.CASCADE,
        related_name='referral_auto_rules',
        verbose_name=_("Trigger Clinic")
    )
    trigger_keywords = models.JSONField(
        default=list,
        help_text=_("Keywords in diagnosis/assessment that trigger this rule"),
        verbose_name=_("Trigger Keywords")
    )
    
    # Target
    target_clinic = models.ForeignKey(
        'core.Clinic',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='referral_auto_rules_target',
        verbose_name=_("Target Clinic")
    )
    target_external_provider = models.CharField(
        max_length=200,
        blank=True,
        verbose_name=_("Target External Provider")
    )
    
    # Rule Configuration
    urgency = models.CharField(
        max_length=20,
        choices=Referral.Urgency.choices,
        default=Referral.Urgency.ROUTINE,
        verbose_name=_("Default Urgency")
    )
    auto_create = models.BooleanField(
        default=False,
        help_text=_("Automatically create referral (vs. just suggest)"),
        verbose_name=_("Auto Create")
    )
    is_active = models.BooleanField(
        default=True,
        verbose_name=_("Is Active")
    )
    
    class Meta:
        verbose_name = _("Referral Auto Rule")
        verbose_name_plural = _("Referral Auto Rules")
        ordering = ['trigger_clinic', 'name']
    
    def __str__(self):
        return f"{self.name} - {self.trigger_clinic.name_en}"