implement getCampainById

src/prisma/prisma.service.ts

@@ -1,9 +1,13 @@
-import { Injectable, OnModuleInit } from '@nestjs/common';
+import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
 import { PrismaClient } from '@prisma/client';
 
 @Injectable()
-export class PrismaService extends PrismaClient implements OnModuleInit {
+export class PrismaService extends PrismaClient implements OnModuleInit, OnModuleDestroy {
   async onModuleInit() {
     await this.$connect();
   }
+
+  async onModuleDestroy() {
+    await this.$disconnect();
+  }
 }

src/resolvers/campaign.resolver.ts

@@ -1,8 +1,30 @@
-import { Resolver } from '@nestjs/graphql';
+import { Resolver, Query, Args } from '@nestjs/graphql';
 import { PrismaService } from 'src/prisma/prisma.service';
 import { Campaign } from './models/campaign.model';
+import { NotFoundException, BadRequestException } from '@nestjs/common';
 
 @Resolver(() => Campaign)
 export class CampaignResolver {
   constructor(private prismaService: PrismaService) {}
+
+  @Query(() => Campaign, { nullable: true })
+  async getCampaignById(@Args('id') id: number): Promise<Campaign | null> {
+    // Validate ID format (assuming UUID format)
+    //TODO: difine other ways to validate the id.
+    if (typeof id !== 'number') {
+      throw new BadRequestException('Invalid campaign ID format');
+    }
+
+    // Fetch campaign from database
+    const campaign = await this.prismaService.campaign.findUnique({
+      where: { id },
+    });
+
+    // Handle non-existent campaign
+    if (!campaign) {
+      throw new NotFoundException(`Campaign with ID ${id} not found`);
+    }
+
+    return campaign;
+  }
 }