feat(server): add model base (#9734)

packages/backend/server/src/models/index.ts

@@ -1,31 +1,71 @@
-import { Global, Injectable, Module } from '@nestjs/common';
+import {
+  ExistingProvider,
+  FactoryProvider,
+  Global,
+  Module,
+} from '@nestjs/common';
+import { ModuleRef } from '@nestjs/core';
 
+import { ApplyType } from '../base';
 import { FeatureModel } from './feature';
+import { MODELS_SYMBOL } from './provider';
 import { SessionModel } from './session';
 import { UserModel } from './user';
 import { VerificationTokenModel } from './verification-token';
 
-const models = [
-  UserModel,
-  SessionModel,
-  VerificationTokenModel,
-  FeatureModel,
-] as const;
+const MODELS = {
+  user: UserModel,
+  session: SessionModel,
+  verificationToken: VerificationTokenModel,
+  feature: FeatureModel,
+};
 
-@Injectable()
-export class Models {
-  constructor(
-    public readonly user: UserModel,
-    public readonly session: SessionModel,
-    public readonly verificationToken: VerificationTokenModel,
-    public readonly feature: FeatureModel
-  ) {}
-}
+type ModelsType = {
+  [K in keyof typeof MODELS]: InstanceType<(typeof MODELS)[K]>;
+};
+
+export class Models extends ApplyType<ModelsType>() {}
+
+const ModelsProvider: FactoryProvider = {
+  provide: Models,
+  useFactory: (ref: ModuleRef) => {
+    return new Proxy({} as any, {
+      get: (target, prop) => {
+        // cache
+        if (prop in target) {
+          return target[prop];
+        }
+
+        // find the model instance
+        // @ts-expect-error null detection happens right after
+        const Model = MODELS[prop];
+        if (!Model) {
+          return undefined;
+        }
+
+        const model = ref.get(Model);
+
+        if (!model) {
+          throw new Error(`Failed to initialize model ${Model.name}`);
+        }
+
+        target[prop] = model;
+        return model;
+      },
+    });
+  },
+  inject: [ModuleRef],
+};
+
+const ModelsSymbolProvider: ExistingProvider = {
+  provide: MODELS_SYMBOL,
+  useExisting: Models,
+};
 
 @Global()
 @Module({
-  providers: [...models, Models],
-  exports: [Models],
+  providers: [...Object.values(MODELS), ModelsProvider, ModelsSymbolProvider],
+  exports: [ModelsProvider],
 })
 export class ModelModules {}