Add rice transplant planning feature

backend/apps/plans/views.py

@@ -2,8 +2,14 @@ from rest_framework import viewsets, status
 from rest_framework.decorators import action
 from rest_framework.response import Response
 from django.db.models import Sum
-from .models import Crop, Variety, Plan
-from .serializers import CropSerializer, VarietySerializer, PlanSerializer
+from .models import Crop, Variety, Plan, RiceTransplantPlan
+from .serializers import (
+    CropSerializer,
+    VarietySerializer,
+    PlanSerializer,
+    RiceTransplantPlanSerializer,
+    RiceTransplantPlanWriteSerializer,
+)
 from apps.fields.models import Field
 
 
@@ -130,3 +136,49 @@ class PlanViewSet(viewsets.ModelViewSet):
     def get_crops_with_varieties(self, request):
         crops = Crop.objects.prefetch_related('varieties').all()
         return Response(CropSerializer(crops, many=True).data)
+
+
+class RiceTransplantPlanViewSet(viewsets.ModelViewSet):
+    queryset = RiceTransplantPlan.objects.select_related(
+        'variety',
+        'variety__crop',
+    ).prefetch_related('entries', 'entries__field')
+
+    def get_queryset(self):
+        queryset = self.queryset
+        year = self.request.query_params.get('year')
+        if year:
+            queryset = queryset.filter(year=year)
+        return queryset
+
+    def get_serializer_class(self):
+        if self.action in ['create', 'update', 'partial_update']:
+            return RiceTransplantPlanWriteSerializer
+        return RiceTransplantPlanSerializer
+
+    @action(detail=False, methods=['get'])
+    def candidate_fields(self, request):
+        year = request.query_params.get('year')
+        variety_id = request.query_params.get('variety_id')
+        if not year or not variety_id:
+            return Response(
+                {'error': 'year と variety_id が必要です'},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        field_ids = Plan.objects.filter(
+            year=year,
+            variety_id=variety_id,
+        ).values_list('field_id', flat=True)
+        fields = Field.objects.filter(id__in=field_ids).order_by('display_order', 'id')
+        data = [
+            {
+                'id': field.id,
+                'name': field.name,
+                'area_tan': str(field.area_tan),
+                'area_m2': field.area_m2,
+                'group_name': field.group_name,
+            }
+            for field in fields
+        ]
+        return Response(data)