"""
DRF Serializers for Finance app.
"""

from rest_framework import serializers
from .models import Invoice, InvoiceLineItem, Payment, Service, Package, PackagePurchase, Payer
from core.serializers import PatientListSerializer


class ServiceSerializer(serializers.ModelSerializer):
    """Serializer for Service model."""
    
    clinic_name = serializers.CharField(source='clinic.name_en', read_only=True)
    
    class Meta:
        model = Service
        fields = [
            'id', 'code', 'name_en', 'name_ar',
            'clinic', 'clinic_name', 'base_price',
            'duration_minutes', 'is_active'
        ]
        read_only_fields = ['id']


class PackageSerializer(serializers.ModelSerializer):
    """Serializer for Package model."""
    
    services_display = serializers.SerializerMethodField()
    
    class Meta:
        model = Package
        fields = [
            'id', 'name_en', 'name_ar', 'services', 'services_display',
            'total_sessions', 'price', 'validity_days', 'is_active'
        ]
        read_only_fields = ['id']
    
    def get_services_display(self, obj):
        """Return list of service names."""
        return [service.name_en for service in obj.services.all()]


class PayerSerializer(serializers.ModelSerializer):
    """Serializer for Payer model."""
    
    patient_name = serializers.CharField(source='patient.get_full_name', read_only=True)
    type_display = serializers.CharField(source='get_type_display', read_only=True)
    
    class Meta:
        model = Payer
        fields = [
            'id', 'patient', 'patient_name', 'name',
            'type', 'type_display', 'policy_number',
            'coverage_percentage', 'is_active'
        ]
        read_only_fields = ['id']


class InvoiceLineItemSerializer(serializers.ModelSerializer):
    """Serializer for InvoiceLineItem model."""
    
    service_name = serializers.CharField(source='service.name_en', read_only=True)
    package_name = serializers.CharField(source='package.name_en', read_only=True)
    
    class Meta:
        model = InvoiceLineItem
        fields = [
            'id', 'service', 'service_name', 'package', 'package_name',
            'description', 'quantity', 'unit_price', 'total'
        ]
        read_only_fields = ['id', 'total']
    
    def validate(self, data):
        """Calculate total."""
        quantity = data.get('quantity', 1)
        unit_price = data.get('unit_price', 0)
        data['total'] = quantity * unit_price
        return data


class InvoiceListSerializer(serializers.ModelSerializer):
    """Lightweight serializer for invoice lists."""
    
    patient_name = serializers.CharField(source='patient.get_full_name', read_only=True)
    status_display = serializers.CharField(source='get_status_display', read_only=True)
    
    class Meta:
        model = Invoice
        fields = [
            'id', 'invoice_number', 'patient', 'patient_name',
            'issue_date', 'due_date', 'total',
            'status', 'status_display'
        ]
        read_only_fields = ['id', 'invoice_number']


class InvoiceDetailSerializer(serializers.ModelSerializer):
    """Detailed serializer for invoice detail views."""
    
    patient = PatientListSerializer(read_only=True)
    line_items = InvoiceLineItemSerializer(many=True, read_only=True)
    status_display = serializers.CharField(source='get_status_display', read_only=True)
    amount_paid = serializers.SerializerMethodField()
    amount_due = serializers.SerializerMethodField()
    
    class Meta:
        model = Invoice
        fields = [
            'id', 'invoice_number', 'patient', 'appointment',
            'issue_date', 'due_date',
            'subtotal', 'tax', 'discount', 'total',
            'status', 'status_display',
            'amount_paid', 'amount_due',
            'line_items', 'notes',
            'created_at', 'updated_at'
        ]
        read_only_fields = ['id', 'invoice_number', 'created_at', 'updated_at']
    
    def get_amount_paid(self, obj):
        """Calculate total amount paid."""
        return sum(payment.amount for payment in obj.payments.filter(status='COMPLETED'))
    
    def get_amount_due(self, obj):
        """Calculate amount due."""
        amount_paid = self.get_amount_paid(obj)
        return obj.total - amount_paid


class InvoiceCreateSerializer(serializers.ModelSerializer):
    """Serializer for creating invoices."""
    
    line_items = InvoiceLineItemSerializer(many=True)
    
    class Meta:
        model = Invoice
        fields = [
            'patient', 'appointment', 'issue_date', 'due_date',
            'subtotal', 'tax', 'discount', 'notes', 'line_items'
        ]
    
    def create(self, validated_data):
        """Create invoice with line items."""
        line_items_data = validated_data.pop('line_items')
        
        # Calculate total
        subtotal = validated_data.get('subtotal', 0)
        tax = validated_data.get('tax', 0)
        discount = validated_data.get('discount', 0)
        total = subtotal + tax - discount
        validated_data['total'] = total
        validated_data['status'] = 'DRAFT'
        
        invoice = Invoice.objects.create(**validated_data)
        
        # Create line items
        for item_data in line_items_data:
            InvoiceLineItem.objects.create(invoice=invoice, **item_data)
        
        return invoice


class PaymentSerializer(serializers.ModelSerializer):
    """Serializer for Payment model."""
    
    invoice_number = serializers.CharField(source='invoice.invoice_number', read_only=True)
    patient_name = serializers.CharField(source='invoice.patient.get_full_name', read_only=True)
    method_display = serializers.CharField(source='get_method_display', read_only=True)
    status_display = serializers.CharField(source='get_status_display', read_only=True)
    processed_by_name = serializers.CharField(source='processed_by.get_full_name', read_only=True)
    
    class Meta:
        model = Payment
        fields = [
            'id', 'invoice', 'invoice_number', 'patient_name',
            'payment_date', 'amount',
            'method', 'method_display',
            'transaction_id', 'reference',
            'status', 'status_display',
            'processed_by', 'processed_by_name',
            'created_at'
        ]
        read_only_fields = ['id', 'created_at']


class PackagePurchaseSerializer(serializers.ModelSerializer):
    """Serializer for PackagePurchase model."""
    
    patient_name = serializers.CharField(source='patient.get_full_name', read_only=True)
    package_name = serializers.CharField(source='package.name_en', read_only=True)
    invoice_number = serializers.CharField(source='invoice.invoice_number', read_only=True)
    
    class Meta:
        model = PackagePurchase
        fields = [
            'id', 'patient', 'patient_name',
            'package', 'package_name',
            'invoice', 'invoice_number',
            'purchase_date', 'expiry_date',
            'total_sessions', 'used_sessions', 'remaining_sessions',
            'is_active'
        ]
        read_only_fields = ['id', 'remaining_sessions']