chore: discount module

src/modules/invoices/DTO/apply-discount-invoice.dto.ts

@@ -0,0 +1,13 @@
+import { IsNotEmpty, IsString } from "class-validator";
+
+import { DiscountMessage } from "../../../common/enums/message.enum";
+
+export class ApplyDiscountDto {
+  @IsString({ message: DiscountMessage.INVOICE_ID_STRING })
+  @IsNotEmpty({ message: DiscountMessage.INVOICE_ID_REQUIRED })
+  invoiceId: string;
+
+  @IsString({ message: DiscountMessage.DISCOUNT_CODE_STRING })
+  @IsNotEmpty({ message: DiscountMessage.DISCOUNT_CODE_REQUIRED })
+  discountCode: string;
+}

src/modules/invoices/entities/invoice.entity.ts

@@ -5,6 +5,7 @@ import { Column, Entity, ManyToOne, OneToMany } from "typeorm";
 import { InvoiceItem } from "./invoice-item.entity";
 import { BaseEntity } from "../../../common/entities/base.entity";
 import { DecimalTransformer } from "../../../common/transformers/decimal.transformer";
+import { Discount } from "../../discounts/entities/discount.entity";
 import { User } from "../../users/entities/user.entity";
 import { InvoiceStatus } from "../enums/invoice-status.enum";
 
@@ -28,9 +29,14 @@ export class Invoice extends BaseEntity {
   @Column({ type: "int", default: 0 })
   tax: number;
 
+  //---------------------------------------------
+
   @OneToMany(() => InvoiceItem, (invoiceItem) => invoiceItem.invoice, { cascade: true })
   items: InvoiceItem[];
 
+  @ManyToOne(() => Discount, { nullable: true, onDelete: "SET NULL" })
+  discount: Discount;
+
   get isOverdue(): boolean {
     return this.status === InvoiceStatus.PENDING && new Date() > this.dueDate;
   }

src/modules/invoices/invoices.module.ts

@@ -6,10 +6,12 @@ import { Invoice } from "./entities/invoice.entity";
 import { InvoicesController } from "./invoices.controller";
 import { InvoicesService } from "./providers/invoices.service";
 import { InvoicesRepository } from "./repositories/invoices.repository";
+import { Discount } from "../discounts/entities/discount.entity";
+import { DiscountRepository } from "../discounts/repositories/discount.repository";
 
 @Module({
-  imports: [TypeOrmModule.forFeature([Invoice, InvoiceItem])],
-  providers: [InvoicesService, InvoicesRepository],
+  imports: [TypeOrmModule.forFeature([Invoice, InvoiceItem, Discount])],
+  providers: [InvoicesService, InvoicesRepository, DiscountRepository],
   controllers: [InvoicesController],
   exports: [InvoicesService],
 })

src/modules/invoices/providers/invoices.service.ts

@@ -4,9 +4,11 @@ import Decimal from "decimal.js";
 import { QueryRunner } from "typeorm";
 
 import { InvoiceMessage } from "../../../common/enums/message.enum";
+import { DiscountRepository } from "../../discounts/repositories/discount.repository";
 import { SubscriptionPlan } from "../../subscriptions/entities/subscription.entity";
 import { RoleEnum } from "../../users/enums/role.enum";
 import { PaginationUtils } from "../../utils/providers/pagination.utils";
+import { ApplyDiscountDto } from "../DTO/apply-discount-invoice.dto";
 import { CreateInvoiceDto } from "../DTO/create-invoice.dto";
 import { InvoicesSearchQueryDto, UserInvoicesSearchQueryDto } from "../DTO/invoices-search-query.dto";
 import { Invoice } from "../entities/invoice.entity";
@@ -18,9 +20,12 @@ import { InvoicesRepository } from "../repositories/invoices.repository";
 export class InvoicesService {
   constructor(
     private readonly invoiceRepository: InvoicesRepository,
+    private readonly discountRepository: DiscountRepository,
     // private readonly invoiceItemsRepository: InvoiceItemsRepository,
   ) {}
+
   ///********************************** */
+
   async createInvoiceAdmin(createDto: CreateInvoiceDto) {
     //
     const invoiceItems = createDto.items.map((item) => {
@@ -55,7 +60,9 @@ export class InvoicesService {
       invoice,
     };
   }
+
   ///********************************** */
+
   async createInvoiceForSubscription(userId: string, plan: SubscriptionPlan, dueDate: Date, queryRunner: QueryRunner) {
     const invoiceItems = [
       { name: plan.service.name, count: 1, unitPrice: plan.price, discount: 0, subscriptionPlan: plan, totalPrice: plan.price },
@@ -117,7 +124,9 @@ export class InvoicesService {
       paginate: true,
     };
   }
+
   //*********************************** */
+
   async getInvoiceById(invoiceId: string, role: RoleEnum, userId: string) {
     let invoice: Invoice | null;
 
@@ -139,7 +148,9 @@ export class InvoicesService {
       invoice,
     };
   }
+
   //*********************************** */
+
   async getUserInvoices(queryDto: UserInvoicesSearchQueryDto, userId: string) {
     const { limit, skip } = PaginationUtils(queryDto);
 
@@ -165,4 +176,56 @@ export class InvoicesService {
       paginate: true,
     };
   }
+
+  //*********************************** */
+
+  async applyDiscount(invoiceId: string, applyDiscountDto: ApplyDiscountDto) {
+    const invoice = await this.invoiceRepository.findOneBy({ id: invoiceId });
+    if (!invoice) throw new BadRequestException(InvoiceMessage.NOT_FOUND_BY_ID);
+
+    const discount = await this.discountRepository.findOne({
+      where: { code: applyDiscountDto.discountCode, isActive: true },
+      relations: ["subscriptionPlans", "users"],
+    });
+    if (!discount) {
+      throw new BadRequestException(`Discount with code ${applyDiscountDto.discountCode} not found or inactive`);
+    }
+
+    if (discount.subscriptionPlans && discount.subscriptionPlans.length > 0) {
+      const isApplicable = invoice.items.some((item) => {
+        const subscriptionPlan = item.subscriptionPlan;
+        if (!subscriptionPlan) return false;
+        return discount.subscriptionPlans.some((plan) => plan.id === subscriptionPlan.id);
+      });
+      if (!isApplicable) {
+        throw new BadRequestException("This discount is not applicable to any subscription plan in the invoice.");
+      }
+    }
+
+    if (discount.users && discount.users.length > 0) {
+      if (!invoice.user || !discount.users.some((user) => user.id === invoice.user.id)) {
+        throw new BadRequestException("This discount is not applicable for this user.");
+      }
+    }
+
+    invoice.discount = discount;
+    await this.invoiceRepository.save(invoice);
+
+    return { invoice };
+  }
+
+  async calculateFinalPrice(invoiceId: string): Promise<Decimal> {
+    const invoice = await this.invoiceRepository.findOneBy({ id: invoiceId });
+    if (!invoice) throw new BadRequestException(InvoiceMessage.NOT_FOUND_BY_ID);
+
+    let discountValue = new Decimal(0);
+    if (invoice.discount) {
+      if (invoice.discount.calculationType === "PERCENTAGE") {
+        discountValue = invoice.totalPrice.mul(invoice.discount.amount).div(100);
+      } else if (invoice.discount.calculationType === "FIXED") {
+        discountValue = new Decimal(invoice.discount.amount);
+      }
+    }
+    return invoice.totalPrice.minus(discountValue);
+  }
 }