"""
Process API ViewSet
"""
from rest_framework import viewsets, filters
from rest_framework.pagination import LimitOffsetPagination
from django_filters.rest_framework import DjangoFilterBackend
from django.db.models import Count
from stateflow import models
from stateflow.serializers import (
    ProcessListSerializer,
    ProcessDetailSerializer,
    ProcessCreateUpdateSerializer,
)


class ProcessViewSet(viewsets.ModelViewSet):
    """
    流程 CRUD 接口
    
    list: 获取流程列表
    retrieve: 获取流程详情（包含节点）
    create: 创建流程
    update: 更新流程
    partial_update: 部分更新流程
    destroy: 删除流程
    
    查询参数:
    - name: 按名称模糊查询
    - search: 全文搜索（名称和描述）
    - ordering: 排序字段，支持 id, name, node_count, created_at, updated_at
    """
    pagination_class = LimitOffsetPagination
    filter_backends = [DjangoFilterBackend, filters.SearchFilter, filters.OrderingFilter]
    filterset_fields = ['name']
    search_fields = ['name', 'description']
    ordering_fields = ['id', 'name', 'node_count', 'created_at', 'updated_at']
    ordering = ['-created_at']
    
    def get_serializer_class(self):
        """根据动作选择序列化器"""
        if self.action == 'list':
            return ProcessListSerializer
        elif self.action in ['create', 'update', 'partial_update']:
            return ProcessCreateUpdateSerializer
        else:  # retrieve
            return ProcessDetailSerializer
    
    def get_queryset(self):
        """优化查询"""
        queryset = models.Process.objects.all()
        
        if self.action == 'list':
            # list 时添加节点计数注解
            queryset = queryset.annotate(node_count=Count('process_nodes'))
        elif self.action == 'retrieve':
            # retrieve 时预加载节点和状态
            queryset = queryset.prefetch_related('process_nodes__state')
        
        return queryset