from rest_framework import serializers
from ..models import (
    InventoryItem, InventoryStock, InventoryLocation,
    PurchaseOrder, PurchaseOrderItem, Supplier
)


class BaseSerializer(serializers.ModelSerializer):
    """Base serializer with common functionality"""
    
    class Meta:
        fields = ['id']
        read_only_fields = ['created_at', 'updated_at']


class SupplierSerializer(serializers.ModelSerializer):
    """Serializer for Supplier model"""
    
    class Meta:
        model = Supplier
        fields = [
            'supplier_id', 'name', 'contact_person', 'email', 'phone',
            'address', 'city', 'state', 'zip_code', 'country',
            'tax_id', 'payment_terms', 'credit_limit', 'is_active',
            'created_at', 'updated_at'
        ]
        read_only_fields = ['supplier_id', 'created_at', 'updated_at']


class InventoryLocationSerializer(serializers.ModelSerializer):
    """Serializer for InventoryLocation model"""
    
    class Meta:
        model = InventoryLocation
        fields = [
            'location_id', 'name', 'description', 'location_type',
            'building', 'floor', 'room', 'zone', 'capacity',
            'temperature_controlled', 'security_level', 'is_active',
            'created_at', 'updated_at'
        ]
        read_only_fields = ['location_id', 'created_at', 'updated_at']


class InventoryItemSerializer(serializers.ModelSerializer):
    """Serializer for InventoryItem model"""
    category_display = serializers.CharField(source='get_category_display', read_only=True)
    unit_display = serializers.CharField(source='get_unit_display', read_only=True)
    
    class Meta:
        model = InventoryItem
        fields = [
            'item_id', 'name', 'description', 'category', 'category_display',
            'sku', 'barcode', 'manufacturer', 'model_number',
            'unit', 'unit_display', 'unit_cost', 'reorder_level',
            'reorder_quantity', 'max_stock_level', 'is_active',
            'requires_expiry_tracking', 'requires_lot_tracking',
            'is_controlled_substance', 'storage_requirements',
            'created_at', 'updated_at'
        ]
        read_only_fields = ['item_id', 'created_at', 'updated_at']


class InventoryStockSerializer(serializers.ModelSerializer):
    """Serializer for InventoryStock model"""
    item_name = serializers.CharField(source='item.name', read_only=True)
    location_name = serializers.CharField(source='location.name', read_only=True)
    is_low_stock = serializers.BooleanField(read_only=True)
    is_expired = serializers.BooleanField(read_only=True)
    days_until_expiry = serializers.IntegerField(read_only=True)
    
    class Meta:
        model = InventoryStock
        fields = [
            'stock_id', 'item', 'item_name', 'location', 'location_name',
            'quantity_on_hand', 'quantity_allocated', 'quantity_available',
            'lot_number', 'expiration_date', 'unit_cost', 'total_cost',
            'last_counted', 'is_low_stock', 'is_expired', 'days_until_expiry',
            'created_at', 'updated_at'
        ]
        read_only_fields = [
            'stock_id', 'quantity_available', 'total_cost', 'is_low_stock',
            'is_expired', 'days_until_expiry', 'created_at', 'updated_at'
        ]


class PurchaseOrderSerializer(serializers.ModelSerializer):
    """Serializer for PurchaseOrder model"""
    supplier_name = serializers.CharField(source='supplier.name', read_only=True)
    status_display = serializers.CharField(source='get_status_display', read_only=True)
    created_by_name = serializers.CharField(source='created_by.get_full_name', read_only=True)
    
    class Meta:
        model = PurchaseOrder
        fields = [
            'order_id', 'order_number', 'supplier', 'supplier_name',
            'order_date', 'expected_delivery_date', 'actual_delivery_date',
            'status', 'status_display', 'total_amount', 'tax_amount',
            'shipping_cost', 'grand_total', 'notes', 'created_by',
            'created_by_name', 'created_at', 'updated_at'
        ]
        read_only_fields = [
            'order_id', 'order_number', 'total_amount', 'grand_total',
            'created_at', 'updated_at'
        ]


class PurchaseOrderItemSerializer(serializers.ModelSerializer):
    """Serializer for PurchaseOrderItem model"""
    item_name = serializers.CharField(source='item.name', read_only=True)
    item_sku = serializers.CharField(source='item.sku', read_only=True)
    line_total = serializers.DecimalField(max_digits=12, decimal_places=2, read_only=True)
    
    class Meta:
        model = PurchaseOrderItem
        fields = [
            'item_id', 'purchase_order', 'item', 'item_name', 'item_sku',
            'quantity_ordered', 'quantity_received', 'unit_cost',
            'line_total', 'notes', 'created_at', 'updated_at'
        ]
        read_only_fields = ['item_id', 'line_total', 'created_at', 'updated_at']


class InventoryStatsSerializer(serializers.Serializer):
    """Serializer for inventory statistics"""
    total_items = serializers.IntegerField()
    low_stock_items = serializers.IntegerField()
    expired_items = serializers.IntegerField()
    expiring_soon = serializers.IntegerField()
    total_value = serializers.DecimalField(max_digits=15, decimal_places=2)
    pending_orders = serializers.IntegerField()
    received_today = serializers.IntegerField()
    category_breakdown = serializers.DictField()
    location_utilization = serializers.DictField()


class StockAdjustmentSerializer(serializers.Serializer):
    """Serializer for stock adjustments"""
    stock_id = serializers.IntegerField()
    adjustment_type = serializers.ChoiceField(choices=['ADD', 'SUBTRACT', 'SET'])
    quantity = serializers.IntegerField()
    reason = serializers.CharField()
    notes = serializers.CharField(required=False, allow_blank=True)
    
    def validate_quantity(self, value):
        """Validate adjustment quantity"""
        if value <= 0:
            raise serializers.ValidationError("Quantity must be greater than 0.")
        return value


class StockTransferSerializer(serializers.Serializer):
    """Serializer for stock transfers"""
    from_stock_id = serializers.IntegerField()
    to_location_id = serializers.IntegerField()
    quantity = serializers.IntegerField()
    reason = serializers.CharField()
    notes = serializers.CharField(required=False, allow_blank=True)
    
    def validate_quantity(self, value):
        """Validate transfer quantity"""
        if value <= 0:
            raise serializers.ValidationError("Quantity must be greater than 0.")
        return value


class PurchaseOrderCreateSerializer(serializers.Serializer):
    """Serializer for creating purchase orders"""
    supplier_id = serializers.IntegerField()
    expected_delivery_date = serializers.DateField()
    items = serializers.ListField(
        child=serializers.DictField(),
        min_length=1
    )
    notes = serializers.CharField(required=False, allow_blank=True)
    
    def validate_items(self, value):
        """Validate purchase order items"""
        for item in value:
            if 'item_id' not in item or 'quantity' not in item or 'unit_cost' not in item:
                raise serializers.ValidationError(
                    "Each item must have item_id, quantity, and unit_cost."
                )
            if item['quantity'] <= 0:
                raise serializers.ValidationError("Item quantity must be greater than 0.")
            if item['unit_cost'] < 0:
                raise serializers.ValidationError("Unit cost cannot be negative.")
        return value


class ReceiveOrderSerializer(serializers.Serializer):
    """Serializer for receiving purchase orders"""
    order_id = serializers.IntegerField()
    items = serializers.ListField(
        child=serializers.DictField(),
        min_length=1
    )
    notes = serializers.CharField(required=False, allow_blank=True)
    
    def validate_items(self, value):
        """Validate received items"""
        for item in value:
            if 'item_id' not in item or 'quantity_received' not in item:
                raise serializers.ValidationError(
                    "Each item must have item_id and quantity_received."
                )
            if item['quantity_received'] < 0:
                raise serializers.ValidationError("Quantity received cannot be negative.")
        return value