fix: add editable work order travel expenses

Introduce a dedicated travel-expenses table for work orders so Broj sati, Količina dnevnica, and Iznos dnevnice can be reviewed and edited before PDF generation. The PDF now uses the stored travel-expenses values, with default HR rate and cache invalidation on updates.

backend/modules/fleet/serializers.py

@@ -14,6 +14,7 @@ from .models import (
     VehicleNotification,
     WorkOrder,
     WorkOrderAdditionalCostsTable,
+    WorkOrderTravelExpensesTable,
     WorkOrderPhoto,
     WorkOrderInvoice,
     VehicleServiceRecord,
@@ -501,6 +502,105 @@ class WorkOrderAdditionalCostsTableSerializer(serializers.ModelSerializer):
         return super().update(instance, validated_data)
 
 
+class WorkOrderTravelExpensesTableSerializer(serializers.ModelSerializer):
+    RATE_DEFAULTS = {
+        'HR': Decimal('30.00'),
+        'BIH': Decimal('50.00'),
+        'SI': Decimal('80.00'),
+        'CG': Decimal('50.00'),
+    }
+
+    class Meta:
+        model = WorkOrderTravelExpensesTable
+        fields = [
+            'id',
+            'work_order',
+            'broj_sati',
+            'kolicina_dnevnica',
+            'iznos_dnevnica',
+            'daily_rate_country',
+            'total_for_payout',
+            'created_at',
+            'updated_at',
+        ]
+        read_only_fields = ['id', 'total_for_payout', 'created_at', 'updated_at']
+
+    @staticmethod
+    def _parse_decimal(value):
+        if value in (None, ''):
+            return None
+        try:
+            normalized = str(value).strip().replace('€', '').replace(' ', '').replace(',', '.')
+            return Decimal(normalized)
+        except (InvalidOperation, ValueError, TypeError):
+            raise serializers.ValidationError('Neispravna decimalna vrijednost.')
+
+    def validate_daily_rate_country(self, value):
+        normalized = str(value or '').strip().upper()
+        if not normalized:
+            return WorkOrderTravelExpensesTable.DEFAULT_RATE_COUNTRY
+        valid_choices = {choice for choice, _label in WorkOrderTravelExpensesTable.RATE_CHOICES}
+        if normalized not in valid_choices:
+            raise serializers.ValidationError('Neispravna država dnevnice.')
+        return normalized
+
+    def validate(self, attrs):
+        instance = getattr(self, 'instance', None)
+        country = attrs.get(
+            'daily_rate_country',
+            getattr(instance, 'daily_rate_country', WorkOrderTravelExpensesTable.DEFAULT_RATE_COUNTRY),
+        )
+
+        if 'iznos_dnevnica' not in attrs or attrs.get('iznos_dnevnica') in (None, ''):
+            attrs['iznos_dnevnica'] = self.RATE_DEFAULTS.get(
+                country,
+                WorkOrderTravelExpensesTable.DEFAULT_RATE_AMOUNT,
+            )
+
+        if 'broj_sati' in attrs:
+            attrs['broj_sati'] = self._parse_decimal(attrs['broj_sati'])
+        if 'kolicina_dnevnica' in attrs:
+            attrs['kolicina_dnevnica'] = self._parse_decimal(attrs['kolicina_dnevnica'])
+        if 'iznos_dnevnica' in attrs:
+            attrs['iznos_dnevnica'] = self._parse_decimal(attrs['iznos_dnevnica'])
+
+        attrs['broj_sati'] = attrs.get(
+            'broj_sati',
+            getattr(instance, 'broj_sati', Decimal('0.00')),
+        ) or Decimal('0.00')
+        attrs['kolicina_dnevnica'] = attrs.get(
+            'kolicina_dnevnica',
+            getattr(instance, 'kolicina_dnevnica', Decimal('0.00')),
+        ) or Decimal('0.00')
+        attrs['iznos_dnevnica'] = attrs.get(
+            'iznos_dnevnica',
+            getattr(instance, 'iznos_dnevnica', self.RATE_DEFAULTS.get(country, WorkOrderTravelExpensesTable.DEFAULT_RATE_AMOUNT)),
+        ) or self.RATE_DEFAULTS.get(country, WorkOrderTravelExpensesTable.DEFAULT_RATE_AMOUNT)
+        attrs['daily_rate_country'] = country
+        return attrs
+
+    def _calculate_total_for_payout(self, validated_data):
+        quantity = validated_data.get('kolicina_dnevnica', Decimal('0.00'))
+        rate = validated_data.get('iznos_dnevnica', Decimal('0.00'))
+        if not isinstance(quantity, Decimal):
+            quantity = self._parse_decimal(quantity) or Decimal('0.00')
+        if not isinstance(rate, Decimal):
+            rate = self._parse_decimal(rate) or Decimal('0.00')
+        return (quantity * rate).quantize(Decimal('0.01'))
+
+    def create(self, validated_data):
+        validated_data['total_for_payout'] = self._calculate_total_for_payout(validated_data)
+        return super().create(validated_data)
+
+    def update(self, instance, validated_data):
+        merged = {
+            'kolicina_dnevnica': validated_data.get('kolicina_dnevnica', instance.kolicina_dnevnica),
+            'iznos_dnevnica': validated_data.get('iznos_dnevnica', instance.iznos_dnevnica),
+        }
+        validated_data['total_for_payout'] = self._calculate_total_for_payout(merged)
+        return super().update(instance, validated_data)
+
+
 class WorkOrderPhotoSerializer(serializers.ModelSerializer):
     class Meta:
         model = WorkOrderPhoto