# backend/modules/task_management/serializers.py

from rest_framework import serializers
from .models import Task

class TaskSerializer(serializers.ModelSerializer):
    assigned_to_name = serializers.SerializerMethodField()
    work_order_label = serializers.SerializerMethodField()
    vehicle_registration = serializers.SerializerMethodField()

    class Meta:
        model = Task
        fields = [
            'id', 'title', 'description', 'status',
            'assigned_to', 'assigned_to_name',
            'vehicle', 'vehicle_registration',
            'work_order', 'work_order_label',
            'created_at',
        ]
        read_only_fields = ['id', 'created_at']

    def validate_title(self, value):
        """Primjer custom validacije: naziv ne smije biti prekratak."""
        if len(value) < 3:
            raise serializers.ValidationError("Naslov zadatka mora imati barem 3 znaka.")
        return value

    def validate(self, attrs):
        current = getattr(self, 'instance', None)
        status_value = attrs.get('status', getattr(current, 'status', 'aktivan'))
        work_order = attrs.get('work_order', getattr(current, 'work_order', None))
        vehicle = attrs.get('vehicle', getattr(current, 'vehicle', None))

        if current is None and not vehicle:
            raise serializers.ValidationError({
                'vehicle': "Dizalica je obavezna pri kreiranju taska."
            })

        if work_order and not vehicle:
            vehicle = work_order.vehicle
            attrs['vehicle'] = vehicle
        if work_order and vehicle and work_order.vehicle_id != vehicle.id:
            raise serializers.ValidationError({
                'work_order': "Putni nalog mora pripadati istoj dizalici kao task."
            })

        if status_value == 'neaktivan' and not work_order:
            raise serializers.ValidationError({
                'work_order': "Putni nalog je obavezan prije zatvaranja zadatka."
            })
        return attrs

    def get_work_order_label(self, obj):
        if not obj.work_order_id:
            return None
        return f"PN-{str(obj.work_order_id).split('-')[0].upper()}"

    def get_assigned_to_name(self, obj):
        if not obj.assigned_to_id:
            return None
        full_name = obj.assigned_to.get_full_name()
        if full_name:
            return full_name
        email = getattr(obj.assigned_to, 'email', None)
        if email:
            return email
        username = getattr(obj.assigned_to, 'username', None)
        if username:
            return username
        return str(obj.assigned_to_id)

    def get_vehicle_registration(self, obj):
        if not obj.vehicle_id:
            return None
        return obj.vehicle.registration_number