"""
Pharmacy app models for hospital management system.
Provides medication management, prescription processing, and pharmacy operations.
"""

import uuid
from django.db import models
from django.core.validators import RegexValidator, MinValueValidator, MaxValueValidator
from django.utils import timezone
from django.conf import settings
from django.contrib.contenttypes.fields import GenericRelation
from datetime import timedelta, datetime, date
from decimal import Decimal
import json


class Medication(models.Model):
    """
    Medication model for drug database and formulary management.
    """
    class ControlledSubstanceSchedule(models.TextChoices):
        CI = 'CI', 'Schedule I'
        CII = 'CII', 'Schedule II'
        CIII = 'CIII', 'Schedule III'
        CIV = 'CIV', 'Schedule IV'
        CV = 'CV', 'Schedule V'
        NON = 'NON', 'Non-Controlled'


    class DosageForm(models.TextChoices):
        TABLET = 'TABLET', 'Tablet'
        CAPSULE = 'CAPSULE', 'Capsule'
        LIQUID = 'LIQUID', 'Liquid'
        INJECTION = 'INJECTION', 'Injection'
        TOPICAL = 'TOPICAL', 'Topical'
        INHALER = 'INHALER', 'Inhaler'
        PATCH = 'PATCH', 'Patch'
        SUPPOSITORY = 'SUPPOSITORY', 'Suppository'
        CREAM = 'CREAM', 'Cream'
        OINTMENT = 'OINTMENT', 'Ointment'
        DROPS = 'DROPS', 'Drops'
        SPRAY = 'SPRAY', 'Spray'
        OTHER = 'OTHER', 'Other'

    class UnitOfMeasure(models.TextChoices):
        MG = 'MG', 'Milligrams'
        G = 'G', 'Grams'
        MCG = 'MCG', 'Micrograms'
        ML = 'ML', 'Milliliters'
        L = 'L', 'Liters'
        UNITS = 'UNITS', 'Units'
        IU = 'IU', 'International Units'
        MEQ = 'MEQ', 'Milliequivalents'
        PERCENT = 'PERCENT', 'Percent'
        OTHER = 'OTHER', 'Other'


    class FormularyStatus(models.TextChoices):
        PREFERRED = 'PREFERRED', 'Preferred'
        NON_PREFERRED = 'NON_PREFERRED', 'Non-Preferred'
        RESTRICTED = 'RESTRICTED', 'Restricted'
        NOT_COVERED = 'NOT_COVERED', 'Not Covered'
        PRIOR_AUTH = 'PRIOR_AUTH', 'Prior Authorization Required'

    # Tenant relationship
    tenant = models.ForeignKey(
        'core.Tenant',
        on_delete=models.CASCADE,
        related_name='medications',
        help_text='Organization tenant'
    )
    
    # Medication Information
    medication_id = models.UUIDField(
        default=uuid.uuid4,
        unique=True,
        editable=False,
        help_text='Unique medication identifier'
    )
    
    # Drug Identification
    generic_name = models.CharField(
        max_length=200,
        help_text='Generic drug name'
    )
    brand_name = models.CharField(
        max_length=200,
        blank=True,
        null=True,
        help_text='Brand/trade name'
    )
    
    # NDC and Coding
    ndc_number = models.CharField(
        max_length=20,
        blank=True,
        null=True,
        validators=[RegexValidator(r'^\d{4,5}-\d{3,4}-\d{1,2}$')],
        help_text='National Drug Code (NDC) number'
    )
    rxcui = models.CharField(
        max_length=20,
        blank=True,
        null=True,
        help_text='RxNorm Concept Unique Identifier'
    )
    
    # Drug Classification
    drug_class = models.CharField(
        max_length=100,
        help_text='Therapeutic drug class'
    )
    controlled_substance_schedule = models.CharField(
        max_length=5,
        choices=ControlledSubstanceSchedule.choices,
        default=ControlledSubstanceSchedule.NON,
        help_text='DEA controlled substance schedule'
    )
    
    # Formulation
    dosage_form = models.CharField(
        max_length=50,
        choices=DosageForm.choices,
        help_text='Dosage form'
    )
    strength = models.CharField(
        max_length=50,
        help_text='Drug strength (e.g., 500mg, 10mg/ml)'
    )
    unit_of_measure = models.CharField(
        max_length=20,
        choices=UnitOfMeasure.choices,
        help_text='Unit of measure'
    )
    
    # Clinical Information
    indications = models.TextField(
        help_text='Clinical indications'
    )
    contraindications = models.TextField(
        blank=True,
        null=True,
        help_text='Contraindications'
    )
    side_effects = models.TextField(
        blank=True,
        null=True,
        help_text='Common side effects'
    )
    warnings = models.TextField(
        blank=True,
        null=True,
        help_text='Warnings and precautions'
    )
    
    # Dosing Information
    adult_dose_range = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        help_text='Adult dosing range'
    )
    pediatric_dose_range = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        help_text='Pediatric dosing range'
    )
    max_daily_dose = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        help_text='Maximum daily dose'
    )
    
    # Administration
    routes_of_administration = models.JSONField(
        default=list,
        help_text='Routes of administration'
    )
    administration_instructions = models.TextField(
        blank=True,
        null=True,
        help_text='Administration instructions'
    )
    
    # Storage and Handling
    storage_requirements = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        help_text='Storage requirements'
    )
    special_handling = models.TextField(
        blank=True,
        null=True,
        help_text='Special handling requirements'
    )
    
    # Formulary Status
    formulary_status = models.CharField(
        max_length=20,
        choices=FormularyStatus.choices,
        default=FormularyStatus.PREFERRED,
        help_text='Formulary status'
    )
    
    # Availability
    is_active = models.BooleanField(
        default=True,
        help_text='Medication is active and available'
    )
    is_available = models.BooleanField(
        default=True,
        help_text='Currently available in inventory'
    )
    
    # Pricing
    unit_cost = models.DecimalField(
        max_digits=10,
        decimal_places=2,
        blank=True,
        null=True,
        help_text='Cost per unit'
    )
    awp = models.DecimalField(
        max_digits=10,
        decimal_places=2,
        blank=True,
        null=True,
        help_text='Average Wholesale Price'
    )
    
    # Manufacturer Information
    manufacturer = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        help_text='Manufacturer name'
    )
    manufacturer_ndc = models.CharField(
        max_length=20,
        blank=True,
        null=True,
        help_text='Manufacturer NDC'
    )
    
    # Metadata
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='created_medications',
        help_text='User who created the medication record'
    )
    
    class Meta:
        db_table = 'pharmacy_medication'
        verbose_name = 'Medication'
        verbose_name_plural = 'Medications'
        ordering = ['generic_name']
        indexes = [
            models.Index(fields=['tenant', 'is_active']),
            models.Index(fields=['generic_name']),
            models.Index(fields=['brand_name']),
            models.Index(fields=['ndc_number']),
            models.Index(fields=['drug_class']),
            models.Index(fields=['controlled_substance_schedule']),
        ]
        unique_together = ['tenant', 'ndc_number']
    
    def __str__(self):
        if self.brand_name:
            return f"{self.generic_name} ({self.brand_name}) {self.strength}"
        return f"{self.generic_name} {self.strength}"
    
    @property
    def is_controlled_substance(self):
        """
        Check if medication is a controlled substance.
        """
        return self.controlled_substance_schedule != 'NON'
    
    @property
    def display_name(self):
        """
        Get display name for medication.
        """
        return str(self)


class Prescription(models.Model):
    """
    Prescription model for electronic prescription management.
    """

    class QuantityUnit(models.TextChoices):
        TABLETS = 'TABLETS', 'Tablets'
        CAPSULES = 'CAPSULES', 'Capsules'
        ML = 'ML', 'Milliliters'
        GRAMS = 'GRAMS', 'Grams'
        UNITS = 'UNITS', 'Units'
        PATCHES = 'PATCHES', 'Patches'
        INHALERS = 'INHALERS', 'Inhalers'
        BOTTLES = 'BOTTLES', 'Bottles'
        TUBES = 'TUBES', 'Tubes'
        VIALS = 'VIALS', 'Vials'
        OTHER = 'OTHER', 'Other'

    class PrescriptionStatus(models.TextChoices):
        PENDING = 'PENDING', 'Pending'
        ACTIVE = 'ACTIVE', 'Active'
        DISPENSED = 'DISPENSED', 'Dispensed'
        PARTIALLY_DISPENSED = 'PARTIALLY_DISPENSED', 'Partially Dispensed'
        COMPLETED = 'COMPLETED', 'Completed'
        CANCELLED = 'CANCELLED', 'Cancelled'
        EXPIRED = 'EXPIRED', 'Expired'
        ON_HOLD = 'ON_HOLD', 'On Hold'
        TRANSFERRED = 'TRANSFERRED', 'Transferred'
        DRAFT = 'DRAFT', 'Draft'

    # Tenant relationship
    tenant = models.ForeignKey(
        'core.Tenant',
        on_delete=models.CASCADE,
        related_name='prescriptions',
        help_text='Organization tenant'
    )
    
    # Prescription Information
    prescription_id = models.UUIDField(
        default=uuid.uuid4,
        unique=True,
        editable=False,
        help_text='Unique prescription identifier'
    )
    prescription_number = models.CharField(
        max_length=20,
        unique=True,
        help_text='Prescription number'
    )
    
    # Patient and Provider
    patient = models.ForeignKey(
        'patients.PatientProfile',
        on_delete=models.CASCADE,
        related_name='prescriptions',
        help_text='Patient'
    )
    prescriber = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='prescribed_medications',
        help_text='Prescribing provider'
    )
    
    # Medication
    medication = models.ForeignKey(
        Medication,
        on_delete=models.CASCADE,
        related_name='prescriptions',
        help_text='Prescribed medication'
    )
    
    # Prescription Details
    quantity_prescribed = models.PositiveIntegerField(
        help_text='Quantity prescribed'
    )
    quantity_unit = models.CharField(
        max_length=20,
        choices=QuantityUnit.choices,
        help_text='Unit of quantity'
    )
    
    # Dosing Instructions
    dosage_instructions = models.TextField(
        help_text='Dosing instructions (SIG)'
    )
    frequency = models.CharField(
        max_length=50,
        help_text='Frequency of administration'
    )
    duration = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        help_text='Duration of therapy'
    )
    
    # Refills
    refills_authorized = models.PositiveIntegerField(
        default=0,
        help_text='Number of refills authorized'
    )
    refills_remaining = models.PositiveIntegerField(
        default=0,
        help_text='Number of refills remaining'
    )
    
    # Dates
    date_prescribed = models.DateTimeField(
        default=timezone.now,
        help_text='Date and time prescribed'
    )
    date_written = models.DateField(
        help_text='Date written on prescription'
    )
    expiration_date = models.DateField(
        blank=True,
        null=True,
        help_text='Prescription expiration date'
    )
    
    # Status
    status = models.CharField(
        max_length=20,
        choices=PrescriptionStatus.choices,
        default=PrescriptionStatus.PENDING,
        help_text='Prescription status'
    )
    
    # Clinical Information
    indication = models.CharField(
        max_length=200,
        blank=True,
        null=True,
        help_text='Indication for prescription'
    )
    diagnosis_code = models.CharField(
        max_length=20,
        blank=True,
        null=True,
        help_text='ICD-10 diagnosis code'
    )
    
    # Special Instructions
    pharmacy_notes = models.TextField(
        blank=True,
        null=True,
        help_text='Notes for pharmacy'
    )
    patient_instructions = models.TextField(
        blank=True,
        null=True,
        help_text='Patient instructions'
    )
    
    # Prior Authorization
    prior_authorization_required = models.BooleanField(
        default=False,
        help_text='Prior authorization required'
    )
    prior_authorization_number = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        help_text='Prior authorization number'
    )
    prior_authorization_expiry = models.DateField(
        blank=True,
        null=True,
        help_text='Prior authorization expiry date'
    )
    
    # Generic Substitution
    generic_substitution_allowed = models.BooleanField(
        default=True,
        help_text='Generic substitution allowed'
    )
    dispense_as_written = models.BooleanField(
        default=False,
        help_text='Dispense as written (DAW)'
    )
    
    # Electronic Prescription
    electronic_prescription = models.BooleanField(
        default=True,
        help_text='Electronic prescription'
    )
    e_prescription_id = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        help_text='Electronic prescription ID'
    )
    
    # Related Information
    encounter = models.ForeignKey(
        'emr.Encounter',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='prescriptions',
        help_text='Related encounter'
    )
    
    # Verification
    verified = models.BooleanField(
        default=False,
        help_text='Prescription has been verified'
    )
    verified_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='verified_prescriptions',
        help_text='Pharmacist who verified prescription'
    )
    verified_datetime = models.DateTimeField(
        blank=True,
        null=True,
        help_text='Date and time of verification'
    )
    
    # Insurance Approval Integration
    approval_requests = GenericRelation(
        'insurance_approvals.InsuranceApprovalRequest',
        content_type_field='content_type',
        object_id_field='object_id',
        related_query_name='prescription'
    )
    
    # Metadata
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        db_table = 'pharmacy_prescription'
        verbose_name = 'Prescription'
        verbose_name_plural = 'Prescriptions'
        ordering = ['-date_prescribed']
        indexes = [
            models.Index(fields=['tenant', 'status']),
            models.Index(fields=['patient', 'status']),
            models.Index(fields=['prescriber']),
            models.Index(fields=['medication']),
            models.Index(fields=['date_prescribed']),
            models.Index(fields=['prescription_number']),
        ]
    
    def __str__(self):
        return f"{self.prescription_number} - {self.patient.get_full_name()} - {self.medication.display_name}"
    
    def save(self, *args, **kwargs):
        """
        Generate prescription number if not provided.
        """
        if not self.prescription_number:
            # Generate prescription number (simple implementation)
            last_rx = Prescription.objects.filter(tenant=self.tenant).order_by('-id').first()
            if last_rx:
                last_number = int(last_rx.prescription_number.split('-')[-1])
                self.prescription_number = f"RX-{self.tenant.id}-{last_number + 1:06d}"
            else:
                self.prescription_number = f"RX-{self.tenant.id}-000001"
        
        # Set expiration date if not provided
        if not self.expiration_date:
            if self.medication.is_controlled_substance:
                # Controlled substances expire in 6 months
                self.expiration_date = self.date_written + timedelta(days=180)
            else:
                # Non-controlled substances expire in 1 year
                self.expiration_date = self.date_written + timedelta(days=365)
        
        # Set refills remaining
        if self.refills_remaining == 0 and self.refills_authorized > 0:
            self.refills_remaining = self.refills_authorized
        
        super().save(*args, **kwargs)
    
    @property
    def is_expired(self):
        """
        Check if prescription is expired.
        """
        return timezone.now().date() > self.expiration_date
    
    @property
    def days_until_expiry(self):
        """
        Calculate days until expiry.
        """
        if self.expiration_date:
            return (self.expiration_date - timezone.now().date()).days
        return None
    
    def has_valid_approval(self):
        """
        Check if prescription has a valid insurance approval.
        """
        from django.utils import timezone
        return self.approval_requests.filter(
            status__in=['APPROVED', 'PARTIALLY_APPROVED'],
            expiration_date__gte=timezone.now().date()
        ).exists()
    
    def get_active_approval(self):
        """
        Get the active insurance approval for this prescription.
        """
        from django.utils import timezone
        return self.approval_requests.filter(
            status__in=['APPROVED', 'PARTIALLY_APPROVED'],
            expiration_date__gte=timezone.now().date()
        ).first()
    
    def requires_approval(self):
        """
        Check if prescription requires insurance approval.
        Returns True if patient has insurance and no valid approval exists.
        Also checks if prior authorization is required.
        """
        if not self.patient.insurance_info.exists():
            return False
        
        # Check if prior authorization is explicitly required
        if self.prior_authorization_required and not self.prior_authorization_number:
            return True
        
        # Check if medication requires approval based on formulary status
        if self.medication.formulary_status in ['RESTRICTED', 'PRIOR_AUTH']:
            return not self.has_valid_approval()
        
        return False
    
    @property
    def approval_status(self):
        """
        Get current approval status for display.
        """
        if not self.patient.insurance_info.exists():
            return 'NO_INSURANCE'
        
        # Check prior authorization
        if self.prior_authorization_required:
            if self.prior_authorization_number:
                # Check if prior auth is expired
                if self.prior_authorization_expiry and self.prior_authorization_expiry < timezone.now().date():
                    return 'PRIOR_AUTH_EXPIRED'
                return 'PRIOR_AUTH_APPROVED'
            return 'PRIOR_AUTH_REQUIRED'
        
        # Check approval requests
        latest_approval = self.approval_requests.order_by('-created_at').first()
        if not latest_approval:
            if self.medication.formulary_status in ['RESTRICTED', 'PRIOR_AUTH']:
                return 'APPROVAL_REQUIRED'
            return 'NO_APPROVAL_NEEDED'
        
        if self.has_valid_approval():
            return 'APPROVED'
        
        return latest_approval.status


class MedicationInventoryItem(models.Model):
    """
    Bridge model linking medications to centralized inventory system.
    This model provides medication-specific metadata for inventory items.
    """
    
    # Tenant relationship
    tenant = models.ForeignKey(
        'core.Tenant',
        on_delete=models.CASCADE,
        related_name='medication_inventory_items',
        help_text='Organization tenant'
    )
    
    # Medication relationship
    medication = models.ForeignKey(
        Medication,
        on_delete=models.CASCADE,
        related_name='medication_inventory_items',
        help_text='Related medication'
    )
    
    # Centralized inventory item relationship
    inventory_item = models.ForeignKey(
        'inventory.InventoryItem',
        on_delete=models.CASCADE,
        related_name='medication_inventory_items',
        help_text='Centralized inventory item'
    )
    
    # Medication-specific information
    medication_inventory_id = models.UUIDField(
        default=uuid.uuid4,
        unique=True,
        editable=False,
        help_text='Unique medication inventory identifier'
    )
    
    # Pharmacy-specific fields
    formulary_tier = models.CharField(
        max_length=20,
        blank=True,
        null=True,
        help_text='Formulary tier for this medication'
    )
    
    therapeutic_equivalent = models.BooleanField(
        default=False,
        help_text='Therapeutic equivalent available'
    )
    
    auto_substitution_allowed = models.BooleanField(
        default=True,
        help_text='Automatic substitution allowed'
    )
    
    pharmacy_notes = models.TextField(
        blank=True,
        null=True,
        help_text='Pharmacy-specific notes'
    )
    
    # Dispensing information
    max_dispense_quantity = models.PositiveIntegerField(
        blank=True,
        null=True,
        help_text='Maximum quantity that can be dispensed at once'
    )
    
    requires_counseling = models.BooleanField(
        default=False,
        help_text='Requires patient counseling'
    )
    
    requires_id_verification = models.BooleanField(
        default=False,
        help_text='Requires ID verification for pickup'
    )
    
    # Metadata
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='created_medication_inventory_items',
        help_text='User who created the medication inventory item'
    )
    
    class Meta:
        db_table = 'pharmacy_medication_inventory_item'
        verbose_name = 'Medication Inventory Item'
        verbose_name_plural = 'Medication Inventory Items'
        ordering = ['medication__generic_name']
        indexes = [
            models.Index(fields=['tenant', 'medication']),
            models.Index(fields=['inventory_item']),
            models.Index(fields=['medication']),
        ]
        unique_together = ['tenant', 'medication', 'inventory_item']
    
    def __str__(self):
        return f"{self.medication.display_name} -> {self.inventory_item.item_name}"
    
    @property
    def current_stock(self):
        """
        Get current stock from related inventory stocks.
        """
        return sum(
            stock.quantity_on_hand 
            for stock in self.inventory_item.inventory_stocks.filter(
                quality_status='GOOD'
            )
        )
    
    @property
    def available_stock(self):
        """
        Get available stock from related inventory stocks.
        """
        return sum(
            stock.quantity_available 
            for stock in self.inventory_item.inventory_stocks.filter(
                quality_status='GOOD'
            )
        )
    
    @property
    def needs_reorder(self):
        """
        Check if medication needs reordering.
        """
        return self.current_stock <= self.inventory_item.reorder_point


# Legacy alias for backward compatibility during migration
InventoryItem = MedicationInventoryItem


class DispenseRecord(models.Model):
    """
    Dispense record model for tracking medication dispensing.
    """
    class DispenseStatus(models.TextChoices):
        DISPENSED = 'DISPENSED', 'Dispensed'
        PICKED_UP = 'PICKED_UP', 'Picked Up'
        RETURNED = 'RETURNED', 'Returned'
        CANCELLED = 'CANCELLED', 'Cancelled'

    # Prescription relationship
    prescription = models.ForeignKey(
        Prescription,
        on_delete=models.CASCADE,
        related_name='dispense_records',
        help_text='Related prescription'
    )
    
    # Inventory stock from centralized system
    inventory_stock = models.ForeignKey(
        'inventory.InventoryStock',
        on_delete=models.CASCADE,
        related_name='dispense_records',
        help_text='Inventory stock dispensed from'
    )
    
    # Dispense Information
    dispense_id = models.UUIDField(
        default=uuid.uuid4,
        unique=True,
        editable=False,
        help_text='Unique dispense identifier'
    )
    
    # Quantity
    quantity_dispensed = models.PositiveIntegerField(
        help_text='Quantity dispensed'
    )
    quantity_remaining = models.PositiveIntegerField(
        help_text='Quantity remaining on prescription'
    )
    
    # Dates
    date_dispensed = models.DateTimeField(
        default=timezone.now,
        help_text='Date and time dispensed'
    )
    
    # Staff
    dispensed_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='dispensed_medications',
        help_text='Pharmacist who dispensed medication'
    )
    verified_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='verified_dispenses',
        help_text='Pharmacist who verified dispense'
    )
    
    # Pricing
    unit_price = models.DecimalField(
        max_digits=10,
        decimal_places=2,
        help_text='Price per unit'
    )
    total_price = models.DecimalField(
        max_digits=10,
        decimal_places=2,
        help_text='Total price'
    )
    copay_amount = models.DecimalField(
        max_digits=8,
        decimal_places=2,
        default=Decimal('0.00'),
        help_text='Patient copay amount'
    )
    insurance_amount = models.DecimalField(
        max_digits=10,
        decimal_places=2,
        default=Decimal('0.00'),
        help_text='Insurance payment amount'
    )
    
    # Patient Information
    patient_counseled = models.BooleanField(
        default=False,
        help_text='Patient was counseled'
    )
    counseling_notes = models.TextField(
        blank=True,
        null=True,
        help_text='Counseling notes'
    )
    
    # Refill Information
    is_refill = models.BooleanField(
        default=False,
        help_text='This is a refill'
    )
    refill_number = models.PositiveIntegerField(
        default=0,
        help_text='Refill number'
    )
    
    # Status
    status = models.CharField(
        max_length=20,
        choices=DispenseStatus.choices,
        default=DispenseStatus.DISPENSED,
        help_text='Dispense status'
    )
    
    # Pickup Information
    picked_up_by = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        help_text='Person who picked up medication'
    )
    pickup_datetime = models.DateTimeField(
        blank=True,
        null=True,
        help_text='Date and time of pickup'
    )
    identification_verified = models.BooleanField(
        default=False,
        help_text='Identification was verified'
    )
    
    # Quality Control
    quality_check_performed = models.BooleanField(
        default=False,
        help_text='Quality check performed'
    )
    quality_notes = models.TextField(
        blank=True,
        null=True,
        help_text='Quality control notes'
    )
    
    # Metadata
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        db_table = 'pharmacy_dispense_record'
        verbose_name = 'Dispense Record'
        verbose_name_plural = 'Dispense Records'
        ordering = ['-date_dispensed']
        indexes = [
            models.Index(fields=['prescription']),
            models.Index(fields=['inventory_stock']),
            models.Index(fields=['date_dispensed']),
            models.Index(fields=['dispensed_by']),
            models.Index(fields=['status']),
        ]
    
    def __str__(self):
        return f"{self.prescription.prescription_number} - {self.quantity_dispensed} units"
    
    def save(self, *args, **kwargs):
        """
        Calculate total price and update prescription status.
        """
        self.total_price = self.quantity_dispensed * self.unit_price
        
        # Update prescription quantity remaining
        if self.prescription:
            total_dispensed = self.prescription.dispense_records.aggregate(
                total=models.Sum('quantity_dispensed')
            )['total'] or 0
            
            if not self.pk:  # New dispense record
                total_dispensed += self.quantity_dispensed
            
            self.quantity_remaining = max(0, self.prescription.quantity_prescribed - total_dispensed)
            
            # Update prescription status
            if self.quantity_remaining == 0:
                self.prescription.status = 'COMPLETED'
            elif total_dispensed > 0:
                self.prescription.status = 'PARTIALLY_DISPENSED'
            else:
                self.prescription.status = 'DISPENSED'
            
            self.prescription.save()
        
        super().save(*args, **kwargs)
    
    @property
    def patient(self):
        """
        Get patient from prescription.
        """
        return self.prescription.patient
    
    @property
    def medication(self):
        """
        Get medication from inventory stock.
        """
        return self.inventory_stock.inventory_item.medication_inventory_items.first().medication


class MedicationAdministration(models.Model):
    """
    Medication Administration Record (MAR) for inpatient medication tracking.
    """

    class RouteGiven(models.TextChoices):
        PO = 'PO', 'Oral'
        IV = 'IV', 'Intravenous'
        IM = 'IM', 'Intramuscular'
        SC = 'SC', 'Subcutaneous'
        SL = 'SL', 'Sublingual'
        TOP = 'TOP', 'Topical'
        INH = 'INH', 'Inhalation'
        PR = 'PR', 'Rectal'
        PV = 'PV', 'Vaginal'
        NASAL = 'NASAL', 'Nasal'
        OPTH = 'OPTH', 'Ophthalmic'
        OTIC = 'OTIC', 'Otic'
        OTHER = 'OTHER', 'Other'

    class MedicationStatus(models.TextChoices):
        SCHEDULED = 'SCHEDULED', 'Scheduled'
        GIVEN = 'GIVEN', 'Given'
        NOT_GIVEN = 'NOT_GIVEN', 'Not Given'
        HELD = 'HELD', 'Held'
        REFUSED = 'REFUSED', 'Refused'
        OMITTED = 'OMITTED', 'Omitted'

    class ReasonNotGiven(models.TextChoices):
        PATIENT_REFUSED = 'PATIENT_REFUSED', 'Patient Refused'
        PATIENT_UNAVAILABLE = 'PATIENT_UNAVAILABLE', 'Patient Unavailable'
        MEDICATION_UNAVAILABLE = 'MEDICATION_UNAVAILABLE', 'Medication Unavailable'
        HELD_BY_PROVIDER = 'HELD_BY_PROVIDER', 'Held by Provider'
        PATIENT_NPO = 'PATIENT_NPO', 'Patient NPO'
        PATIENT_ASLEEP = 'PATIENT_ASLEEP', 'Patient Asleep'
        ADVERSE_REACTION = 'ADVERSE_REACTION', 'Adverse Reaction'
        OTHER = 'OTHER', 'Other'

    # Prescription relationship
    prescription = models.ForeignKey(
        Prescription,
        on_delete=models.CASCADE,
        related_name='administration_records',
        help_text='Related prescription'
    )
    
    # Patient and Encounter
    patient = models.ForeignKey(
        'patients.PatientProfile',
        on_delete=models.CASCADE,
        related_name='medication_administrations',
        help_text='Patient'
    )
    encounter = models.ForeignKey(
        'emr.Encounter',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='medication_administrations',
        help_text='Related encounter'
    )
    
    # Administration Information
    administration_id = models.UUIDField(
        default=uuid.uuid4,
        unique=True,
        editable=False,
        help_text='Unique administration identifier'
    )
    
    # Scheduled vs Actual
    scheduled_datetime = models.DateTimeField(
        help_text='Scheduled administration time'
    )
    actual_datetime = models.DateTimeField(
        blank=True,
        null=True,
        help_text='Actual administration time'
    )
    
    # Dosage
    dose_given = models.CharField(
        max_length=50,
        help_text='Dose given'
    )
    route_given = models.CharField(
        max_length=30,
        choices=RouteGiven.choices,
        help_text='Route of administration'
    )
    
    # Status
    status = models.CharField(
        max_length=20,
        choices=MedicationStatus.choices,
        default=MedicationStatus.SCHEDULED,
        help_text='Administration status'
    )
    
    # Staff
    administered_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='administered_medications',
        help_text='Nurse who administered medication'
    )
    witnessed_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='witnessed_administrations',
        help_text='Witness (for controlled substances)'
    )
    
    # Reason for Not Given
    reason_not_given = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        choices=ReasonNotGiven.choices,
        help_text='Reason medication was not given'
    )
    reason_notes = models.TextField(
        blank=True,
        null=True,
        help_text='Additional notes about reason'
    )
    
    # Patient Response
    patient_response = models.TextField(
        blank=True,
        null=True,
        help_text='Patient response to medication'
    )
    side_effects_observed = models.TextField(
        blank=True,
        null=True,
        help_text='Side effects observed'
    )
    
    # Site Information (for injections)
    injection_site = models.CharField(
        max_length=50,
        blank=True,
        null=True,
        help_text='Injection site'
    )
    site_condition = models.CharField(
        max_length=100,
        blank=True,
        null=True,
        help_text='Condition of injection site'
    )
    
    # Verification
    double_checked = models.BooleanField(
        default=False,
        help_text='Medication was double-checked'
    )
    double_checked_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='double_checked_administrations',
        help_text='Second nurse who verified medication'
    )
    
    # Metadata
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    class Meta:
        db_table = 'pharmacy_medication_administration'
        verbose_name = 'Medication Administration'
        verbose_name_plural = 'Medication Administrations'
        ordering = ['-scheduled_datetime']
        indexes = [
            models.Index(fields=['patient', 'scheduled_datetime']),
            models.Index(fields=['prescription']),
            models.Index(fields=['encounter']),
            models.Index(fields=['status']),
            models.Index(fields=['administered_by']),
        ]
    
    def __str__(self):
        return f"{self.patient.get_full_name()} - {self.prescription.medication.display_name} - {self.scheduled_datetime}"
    
    @property
    def is_overdue(self):
        """
        Check if administration is overdue.
        """
        if self.status == 'SCHEDULED':
            return timezone.now() > self.scheduled_datetime + timedelta(minutes=30)
        return False
    
    @property
    def medication(self):
        """
        Get medication from prescription.
        """
        return self.prescription.medication


class DrugInteraction(models.Model):
    """
    Drug interaction model for clinical decision support.
    """

    class Severity(models.TextChoices):
        MINOR = 'MINOR', 'Minor'
        MODERATE = 'MODERATE', 'Moderate'
        MAJOR = 'MAJOR', 'Major'
        CONTRAINDICATED = 'CONTRAINDICATED', 'Contraindicated'

    class InteractionType(models.TextChoices):
        PHARMACOKINETIC = 'PHARMACOKINETIC', 'Pharmacokinetic'
        PHARMACODYNAMIC = 'PHARMACODYNAMIC', 'Pharmacodynamic'
        ADDITIVE = 'ADDITIVE', 'Additive'
        SYNERGISTIC = 'SYNERGISTIC', 'Synergistic'
        ANTAGONISTIC = 'ANTAGONISTIC', 'Antagonistic'
        OTHER = 'OTHER', 'Other'

    class EvidenceLevel(models.TextChoices):
        ESTABLISHED = 'ESTABLISHED', 'Established'
        PROBABLE = 'PROBABLE', 'Probable'
        SUSPECTED = 'SUSPECTED', 'Suspected'
        POSSIBLE = 'POSSIBLE', 'Possible'
        UNLIKELY = 'UNLIKELY', 'Unlikely'

    # Tenant relationship
    tenant = models.ForeignKey(
        'core.Tenant',
        on_delete=models.CASCADE,
        related_name='drug_interactions',
        help_text='Organization tenant'
    )
    
    # Medications
    medication_1 = models.ForeignKey(
        Medication,
        on_delete=models.CASCADE,
        related_name='interactions_as_drug1',
        help_text='First medication'
    )
    medication_2 = models.ForeignKey(
        Medication,
        on_delete=models.CASCADE,
        related_name='interactions_as_drug2',
        help_text='Second medication'
    )
    
    # Interaction Information
    interaction_id = models.UUIDField(
        default=uuid.uuid4,
        unique=True,
        editable=False,
        help_text='Unique interaction identifier'
    )
    
    # Severity
    severity = models.CharField(
        max_length=20,
        choices=Severity.choices,
        help_text='Interaction severity'
    )
    
    # Interaction Details
    interaction_type = models.CharField(
        max_length=30,
        choices=InteractionType.choices,
        help_text='Type of interaction'
    )
    
    mechanism = models.TextField(
        help_text='Mechanism of interaction'
    )
    clinical_effect = models.TextField(
        help_text='Clinical effect of interaction'
    )
    
    # Management
    management_recommendations = models.TextField(
        help_text='Management recommendations'
    )
    monitoring_parameters = models.TextField(
        blank=True,
        null=True,
        help_text='Parameters to monitor'
    )
    
    # Evidence
    evidence_level = models.CharField(
        max_length=20,
        choices=EvidenceLevel.choices,
        help_text='Level of evidence'
    )
    
    # References
    references = models.TextField(
        blank=True,
        null=True,
        help_text='Literature references'
    )
    
    # Status
    is_active = models.BooleanField(
        default=True,
        help_text='Interaction is active'
    )
    
    # Metadata
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='created_drug_interactions',
        help_text='User who created the interaction record'
    )
    
    class Meta:
        db_table = 'pharmacy_drug_interaction'
        verbose_name = 'Drug Interaction'
        verbose_name_plural = 'Drug Interactions'
        ordering = ['-severity', 'medication_1__generic_name']
        indexes = [
            models.Index(fields=['tenant', 'is_active']),
            models.Index(fields=['medication_1']),
            models.Index(fields=['medication_2']),
            models.Index(fields=['severity']),
        ]
        unique_together = ['tenant', 'medication_1', 'medication_2']
    
    def __str__(self):
        return f"{self.medication_1.display_name} + {self.medication_2.display_name} ({self.severity})"
    
    @property
    def is_major_interaction(self):
        """
        Check if interaction is major or contraindicated.
        """
        return self.severity in ['MAJOR', 'CONTRAINDICATED']