refactor: 优化数据库连接管理与统一接入方式

- 优化数据库连接管理，直接使用获取数据库实例的函数并传入是否为无服务器环境的标识。
- 统一使用db中间件替代dbProvider，简化数据库连接处理并保持代码一致性。
- 添加数据库实例的单例获取机制并定义类型接口

apps/server/src/api/middlewares/db.ts

@@ -1,29 +1,13 @@
 import { os } from '@orpc/server'
-import { createDb } from '@/db'
+import { getDb } from '@/db'
 
 const IS_SERVERLESS = false // TODO: 这里需要优化
 
-let globalDb: ReturnType<typeof createDb> | null = null
-
-function getDb() {
-  if (IS_SERVERLESS) {
-    return createDb()
-  }
-
-  if (!globalDb) {
-    globalDb = createDb()
-  }
-
-  return globalDb
-}
-
-export const dbProvider = os.middleware(async ({ context, next }) => {
-  const db = getDb()
-
+export const db = os.middleware(async ({ context, next }) => {
   return next({
     context: {
       ...context,
-      db,
+      db: getDb(IS_SERVERLESS),
     },
   })
 })

apps/server/src/api/routers/todo.ts

@@ -1,20 +1,18 @@
 import { ORPCError } from '@orpc/server'
 import { eq } from 'drizzle-orm'
-import { dbProvider } from '@/api/middlewares'
+import { db } from '@/api/middlewares'
 import { os } from '@/api/server'
 import { todoTable } from '@/db/schema'
 
-export const list = os.todo.list
-  .use(dbProvider)
-  .handler(async ({ context }) => {
+export const list = os.todo.list.use(db).handler(async ({ context }) => {
   const todos = await context.db.query.todoTable.findMany({
     orderBy: (todos, { desc }) => [desc(todos.createdAt)],
   })
   return todos
-  })
+})
 
 export const create = os.todo.create
-  .use(dbProvider)
+  .use(db)
   .handler(async ({ context, input }) => {
     const [newTodo] = await context.db
       .insert(todoTable)
@@ -29,7 +27,7 @@ export const create = os.todo.create
   })
 
 export const update = os.todo.update
-  .use(dbProvider)
+  .use(db)
   .handler(async ({ context, input }) => {
     const [updatedTodo] = await context.db
       .update(todoTable)
@@ -45,7 +43,7 @@ export const update = os.todo.update
   })
 
 export const remove = os.todo.remove
-  .use(dbProvider)
+  .use(db)
   .handler(async ({ context, input }) => {
     await context.db.delete(todoTable).where(eq(todoTable.id, input.id))
   })

apps/server/src/db/index.ts

@@ -11,3 +11,18 @@ export function createDb() {
     schema,
   })
 }
+
+export type Db = ReturnType<typeof createDb>
+
+export const getDb = (() => {
+  let db: Db | null = null
+
+  return (serverless: boolean = false) => {
+    if (serverless) {
+      return createDb()
+    }
+
+    db ??= createDb()
+    return db
+  }
+})()