fix issue

apps/edr-freight-api/src/modules/fuel/dto/create-fuel-purchase.dto.ts

@@ -1,4 +1,4 @@
-import { IsUUID, IsNumber, IsDateString, IsString, IsOptional, IsEnum } from 'class-validator';
+import { IsUUID, IsNumber, IsPositive, IsDateString, IsString, IsOptional, IsEnum } from 'class-validator';
 import { PaymentMethod } from '../entities/fuel-purchase.entity';
 
 export class CreateFuelPurchaseDto {
@@ -9,9 +9,11 @@ export class CreateFuelPurchaseDto {
   purchaseDate!: string;
 
   @IsNumber()
+  @IsPositive()
   liters!: number;
 
   @IsNumber()
+  @IsPositive()
   costPerLiter!: number;
 
   @IsOptional()

apps/edr-freight-api/src/modules/fuel/fuel.service.ts

@@ -1,4 +1,4 @@
-import { Injectable } from '@nestjs/common';
+import { ConflictException, Injectable } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { FuelRepository } from './fuel.repository';
@@ -15,6 +15,18 @@ export class FuelService {
   ) {}
 
   async recordFuelPurchase(dto: CreateFuelPurchaseDto): Promise<FuelPurchase> {
+    // Reject a re-submitted receipt for the same vehicle (double-entry guard).
+    if (dto.receiptNumber) {
+      const duplicate = await this.purchaseRepository.findOne({
+        where: { vehicleId: dto.vehicleId, receiptNumber: dto.receiptNumber },
+      });
+      if (duplicate) {
+        throw new ConflictException(
+          `A fuel purchase with receipt number ${dto.receiptNumber} already exists for this vehicle`,
+        );
+      }
+    }
+
     const totalCost = dto.liters * dto.costPerLiter;
 
     const purchase = this.purchaseRepository.create({