refactor: split the services to multiple service classes (#202)

packages/server/src/services/Purchases/Bills/GetBill.ts

@@ -0,0 +1,42 @@
+import { Inject, Service } from 'typedi';
+import HasTenancyService from '@/services/Tenancy/TenancyService';
+import { TransformerInjectable } from '@/lib/Transformer/TransformerInjectable';
+import { IBill } from '@/interfaces';
+import { BillsValidators } from './BillsValidators';
+import { PurchaseInvoiceTransformer } from './PurchaseInvoiceTransformer';
+
+@Service()
+export class GetBill {
+  @Inject()
+  private tenancy: HasTenancyService;
+
+  @Inject()
+  private transformer: TransformerInjectable;
+
+  @Inject()
+  private validators: BillsValidators;
+
+  /**
+   * Retrieve the given bill details with associated items entries.
+   * @param {Integer} billId - Specific bill.
+   * @returns {Promise<IBill>}
+   */
+  public async getBill(tenantId: number, billId: number): Promise<IBill> {
+    const { Bill } = this.tenancy.models(tenantId);
+
+    const bill = await Bill.query()
+      .findById(billId)
+      .withGraphFetched('vendor')
+      .withGraphFetched('entries.item')
+      .withGraphFetched('branch');
+
+    // Validates the bill existance.
+    this.validators.validateBillExistance(bill);
+
+    return this.transformer.transform(
+      tenantId,
+      bill,
+      new PurchaseInvoiceTransformer()
+    );
+  }
+}