[NestJS] Milestone 2: ID Verification

kyc-nest/src/app.module.ts

@@ -3,6 +3,7 @@ import { AppController } from './app.controller';
 import { AppService } from './app.service';
 import { ProfileModule } from './profile/profile.module';
 import { TypeOrmModule } from '@nestjs/typeorm';
+import { KycModule } from './kyc/kyc.module';
 
 @Module({
   imports: [
@@ -13,6 +14,7 @@ import { TypeOrmModule } from '@nestjs/typeorm';
       synchronize: true,
     }),
     ProfileModule,
+    KycModule,
   ],
   controllers: [AppController],
   providers: [AppService],

kyc-nest/src/kyc/kyc.controller.ts

@@ -0,0 +1,13 @@
+import { Controller, Post, Body } from '@nestjs/common';
+import { KYCService } from './kyc.service';
+import { WebhookMessage } from './webhook-message.interface';
+
+@Controller('kyc')
+export class KYCController {
+  constructor(private readonly kycService: KYCService) {}
+
+  @Post('webhook')
+  async handleWebhook(@Body() message: WebhookMessage): Promise<void> {
+    await this.kycService.handleWebhook(message);
+  }
+}

kyc-nest/src/kyc/kyc.module.ts

@@ -0,0 +1,11 @@
+import { Module } from '@nestjs/common';
+import { KYCService } from './kyc.service';
+import { KYCController } from './kyc.controller';
+import { ProfileModule } from 'src/profile/profile.module';
+
+@Module({
+  imports: [ProfileModule],
+  providers: [KYCService],
+  controllers: [KYCController],
+})
+export class KycModule {}

kyc-nest/src/kyc/kyc.service.ts

@@ -0,0 +1,31 @@
+import { Injectable } from '@nestjs/common';
+import { WebhookMessage } from './webhook-message.interface';
+import { ProfileService } from '../profile/profile.service';
+
+@Injectable()
+export class KYCService {
+  constructor(private readonly profileService: ProfileService) {}
+
+  async handleWebhook(message: WebhookMessage): Promise<void> {
+    // In a real application, you should verify a signature of the message here
+    const userId = message.userId;
+
+    console.log('Received webhook message:', message);
+
+    if (message.result === 'success') {
+      await this.profileService.update(userId, {
+        kycStatus: 'KYCIDVerified',
+        idVerificationId: message.verificationId,
+        idVerifiedAt: message.timestamp,
+      });
+    } else if (message.result === 'rejected') {
+      await this.profileService.update(userId, {
+        kycStatus: 'KYCIDRejected',
+        idVerificationId: message.verificationId,
+        idRejectedAt: message.timestamp,
+      });
+    } else {
+      console.error('Unknown ID verification result:', message.result);
+    }
+  }
+}

kyc-nest/src/kyc/webhook-message.interface.ts

@@ -0,0 +1,30 @@
+/**
+ * Webhook message interface that is sent by the ID verification service. This service is simulated
+ * in this project, so it lacks a signature which is normally used to verify the authenticity of
+ * the request.
+ *
+ * Some examples of messages are:
+ *
+ * Successful verification:
+ *
+ * {
+ *  "userId": "5f9f1b9b-7b1e-4b9f-9f1b-9b7b1e4b9f9f",
+ *  "result": "success",
+ *  "verificationId": "5f9f1b9b-7b1e-4b9f-9f1b-9b7b1e4b9f9f",
+ *  "timestamp": "2020-01-01T00:00:00.000Z"
+ * }
+ *
+ * Rejected verification:
+ * {
+ *  "userId": "5f9f1b9b-7b1e-4b9f-9f1b-9b7b1e4b9f9f",
+ *  "result": "rejected",
+ *  "verificationId": "5f9f1b9b-7b1e-4b9f-9f1b-9b7b1e4b9f9f",
+ *  "timestamp": "2020-01-01T00:00:00.000Z"
+ * }
+ */
+export interface WebhookMessage {
+  userId: string;
+  result: 'success' | 'rejected';
+  verificationId: string;
+  timestamp: string;
+}

kyc-nest/src/profile/profile.entity.ts

@@ -1,6 +1,6 @@
 import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';
 
-export type KYCStatus = 'KYCPending';
+export type KYCStatus = 'KYCPending' | 'KYCIDVerified' | 'KYCIDRejected';
 
 @Entity()
 export class Profile {
@@ -42,4 +42,13 @@ export class Profile {
 
   @Column({ default: 'KYCPending' })
   kycStatus: KYCStatus;
+
+  @Column({ nullable: true })
+  idVerificationId?: string;
+
+  @Column({ nullable: true })
+  idVerifiedAt?: string;
+
+  @Column({ nullable: true })
+  idRejectedAt?: string;
 }

kyc-nest/src/profile/profile.module.ts

@@ -8,5 +8,6 @@ import { Profile } from './profile.entity';
   imports: [TypeOrmModule.forFeature([Profile])],
   controllers: [ProfileController],
   providers: [ProfileService],
+  exports: [ProfileService],
 })
 export class ProfileModule {}

kyc-nest/src/profile/profile.service.ts

@@ -20,6 +20,21 @@ export class ProfileService {
     return newProfile;
   }
 
+  async update(userId: string, profileData: Partial<Profile>): Promise<void> {
+    const profile = await this.findById(userId);
+
+    if (
+      profileData.kycStatus &&
+      !this.isValidTransition(profile.kycStatus, profileData.kycStatus)
+    ) {
+      throw new BadRequestException(
+        `Invalid status transition from '${profile.kycStatus}' to '${profileData.kycStatus}'`,
+      );
+    }
+
+    await this.profileRepository.update(userId, profileData);
+  }
+
   async findAll(): Promise<Profile[]> {
     return this.profileRepository.find();
   }
@@ -35,4 +50,17 @@ export class ProfileService {
     }
     return profile;
   }
+
+  private isValidTransition(
+    currentState: KYCStatus,
+    newState: KYCStatus,
+  ): boolean {
+    const allowedTransitions: Record<KYCStatus, Array<KYCStatus>> = {
+      KYCPending: ['KYCIDVerified', 'KYCIDRejected'],
+      KYCIDVerified: [],
+      KYCIDRejected: [],
+    };
+
+    return allowedTransitions[currentState]?.includes(newState);
+  }
 }