Refs #654 -- API: Writable item endpoints (#676)

* MKBDIGI-184: Basic create added for API items endpoint

* MKBDIGI-184: Starting endpoint for GET /api/v1/organizers/(organizer)/events/(event)/items/(id)/variations/

* MKBDIGI-184: endpoint for GET /api/v1/organizers/(organizer)/events/(event)/items/(id)/variations/

* MKBDIGI-184: Completed endpoint for variations

* MKBDIGI-184: Added endpoint for addons

* MKBDIGI-184: Added Item validation

* MKBDIGI-184: Added check for order/cart positions on item variation destroy.

* MKBDIGI-184: Fixed check for order/cart positions on item variation destroy.

* MKBDIGI-184: Updated tests, validation for addons

* MKBDIGI-184: Documentation feedback corrections

* MKBDIGI-184: Added documentation for item add-ons

* MKBDIGI-184: Code formatting fixes

* MKBDIGI-184: Feedback fixes

* MKBDIGI-184: Updated tests for delete item

* MKBDIGI-184: Cleaned up tests

* MKBDIGI-184: Added additional test URLs

* MKBDIGI-184: Documentation fixes

* MKBDIGI-184: Fixed read-only fields/Documentation

* MKBDIGI-184: Documentation fixes

* MKBDIGI-184: Added helper for dict merge for 3.4 compatibility

* MKBDIGI-184: Validation updates

* MKBDIGI-184: Fixed permissions test error. Changed to HTTP 404 for POST to addons endpoint

* MKBDIGI-184: Implemented nested variations and add-ons for POST on the item endpoint.

src/pretix/api/serializers/item.py

@@ -1,5 +1,8 @@
 from decimal import Decimal
 
+from django.core.exceptions import ValidationError
+from django.db import transaction
+from django.utils.translation import ugettext_lazy as _
 from rest_framework import serializers
 
 from pretix.api.serializers.i18n import I18nAwareModelSerializer
@@ -16,11 +19,44 @@ class InlineItemVariationSerializer(I18nAwareModelSerializer):
                   'position', 'default_price', 'price')
 
 
+class ItemVariationSerializer(I18nAwareModelSerializer):
+    class Meta:
+        model = ItemVariation
+        fields = ('id', 'value', 'active', 'description',
+                  'position', 'default_price', 'price')
+
+
 class InlineItemAddOnSerializer(serializers.ModelSerializer):
     class Meta:
         model = ItemAddOn
         fields = ('addon_category', 'min_count', 'max_count',
-                  'position')
+                  'position', 'price_included')
+
+
+class ItemAddOnSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = ItemAddOn
+        fields = ('id', 'addon_category', 'min_count', 'max_count',
+                  'position', 'price_included')
+
+    def validate(self, data):
+        data = super().validate(data)
+
+        ItemAddOn.clean_max_min_count(data.get('max_count'), data.get('min_count'))
+
+        return data
+
+    def validate_min_count(self, value):
+        ItemAddOn.clean_min_count(value)
+        return value
+
+    def validate_max_count(self, value):
+        ItemAddOn.clean_max_count(value)
+        return value
+
+    def validate_addon_category(self, value):
+        ItemAddOn.clean_categories(self.context['event'], self.context['item'], self.instance, value)
+        return value
 
 
 class ItemTaxRateField(serializers.Field):
@@ -32,8 +68,8 @@ class ItemTaxRateField(serializers.Field):
 
 
 class ItemSerializer(I18nAwareModelSerializer):
-    addons = InlineItemAddOnSerializer(many=True)
-    variations = InlineItemVariationSerializer(many=True)
+    addons = InlineItemAddOnSerializer(many=True, required=False)
+    variations = InlineItemVariationSerializer(many=True, required=False)
     tax_rate = ItemTaxRateField(source='*', read_only=True)
 
     class Meta:
@@ -44,6 +80,55 @@ class ItemSerializer(I18nAwareModelSerializer):
                   'require_voucher', 'hide_without_voucher', 'allow_cancel',
                   'min_per_order', 'max_per_order', 'checkin_attention', 'has_variations',
                   'variations', 'addons')
+        read_only_fields = ('has_variations', 'picture')
+
+    def get_serializer_context(self):
+        return {"has_variations": self.kwargs['has_variations']}
+
+    def validate(self, data):
+        data = super().validate(data)
+
+        Item.clean_per_order(data.get('min_per_order'), data.get('max_per_order'))
+        Item.clean_available(data.get('available_from'), data.get('available_until'))
+
+        return data
+
+    def validate_category(self, value):
+        Item.clean_category(value, self.context['event'])
+        return value
+
+    def validate_tax_rule(self, value):
+        Item.clean_tax_rule(value, self.context['event'])
+        return value
+
+    def validate_variations(self, value):
+        if self.instance is not None:
+            raise ValidationError(_('Updating variations via PATCH/PUT is not supported. Please use the dedicated'
+                                    ' nested endpoint.'))
+        return value
+
+    def validate_addons(self, value):
+        if self.instance is not None:
+            raise ValidationError(_('Updating add-ons via PATCH/PUT is not supported. Please use the dedicated'
+                                    ' nested endpoint.'))
+        else:
+            for addon_data in value:
+                ItemAddOn.clean_categories(self.context['event'], None, self.instance, addon_data['addon_category'])
+                ItemAddOn.clean_min_count(addon_data['min_count'])
+                ItemAddOn.clean_max_count(addon_data['max_count'])
+                ItemAddOn.clean_max_min_count(addon_data['max_count'], addon_data['min_count'])
+        return value
+
+    @transaction.atomic
+    def create(self, validated_data):
+        variations_data = validated_data.pop('variations') if 'variations' in validated_data else {}
+        addons_data = validated_data.pop('addons') if 'addons' in validated_data else {}
+        item = Item.objects.create(**validated_data)
+        for variation_data in variations_data:
+            ItemVariation.objects.create(item=item, **variation_data)
+        for addon_data in addons_data:
+            ItemAddOn.objects.create(base_item=item, **addon_data)
+        return item
 
 
 class ItemCategorySerializer(I18nAwareModelSerializer):